Design Guidelines for Stainless Steel in Piping Systems

DESIGN GUIDELINES FOR STAINLESS STEEL IN PIPING SYSTEMS

A DESIGNERS’ HANDBOOK SERIES NO 9024

Produced by Distributed by AMERICAN IRON NICKEL AND STEEL INSTITUTE INSTITUTE DESIGN GUIDELINES FOR STAINLESS STEEL IN PIPING SYSTEMS

A DESIGNERS’ HANDBOOK SERIES NO 9024

Originally, this handbook was published in 1980 by the Committee of Stainless Steel Producers, American Iron and Steel Institute. The Nickel Institute republished the handbook in 2020. Despite the age of this publication the information herein is considered to be generally valid. Material presented in the handbook has been prepared for the general information of the reader and should not be used or relied on for specific applications without first securing competent advice. The Nickel Institute, the American Iron and Steel Institute, their members, staff and consultants do not represent or warrant its suitability for any general or specific use and assume no liability or responsibility of any kind in connection with the information herein.

Nickel Institute [email protected] www.nickelinstitute.org DESIGN GUIDELINES FOR STAINLESS STEEL IN PIPING SYSTEMS

Introduction This publication presents information on the design, fabrication, installation and economy of stainless steel in piping systems. The guidelines presented contain Contents important information for piping specialists and design engineers that will save money, time and effort in the several diverse industries utilizing piping systems. Stainless steels are defined as iron-base alloys con- Introduction ...... 3 taining 10 percent or more chromium. They are en- The Selection of a Piping System ...... 6 gineering materials selected primarily for their excellent Stainless Steel in Piping Systems ...... 6 resistance to corrosion, their outstanding mechanical Advantages ...... 6 properties at either ambient, high, or low temperature, Limitations ...... 13 and their economy. The Economics of Stainless Steel Of the 57 stainless steels recognized as standard by in Piping Systems ...... 17 the American Iron and Steel Institute (AISI), those most Design Costs ...... 18 commonly used in piping systems are the austenitic Material Costs ...... 18 alloys represented by AISI Types 304, 304L, 316 and Fabrication Costs ...... 19 316L. The austenitic Types 309 and 310, containing Erection Costs ...... 19 considerably more chromium and nickel than Types 304 Applicable Standards ...... 19 and 316, are also widely used, but for piping exposed to The Design, Fabrication, and Erection elevated temperatures. The stabilized Types 321 and of Plant Piping Systems ...... 20 347 are also used, as are some commercially available Construction Phase...... 21 proprietary grades. Appendix A shows chemical Bibliography ...... 22 compositions and typical properties. (Table 1 lists all 57 Appendices ...... 23 AISI numbered stainless steels.)

3 Table 1 RELATIVE CORROSION RESISTANCE OF AISI STAINLESS STEELS Mild Atmospheric Chemical AISI Atmospheric TYPE UNS and Salt Industrial Marine Mild Oxidizing Reducing Number Number Fresh Water Water 201 (S20100) X X X X X 202 (S20200) X X X X X 205 (S20500) X X X X X 301 (S30100) X X X X X 302 (S30200) X X X X X 302B (S30215) X X X X X 303 (S30300) X X X 303 Se (S30323) X X X 304 (S30400) X X X X X 304L (S30403) X X X X X (S30430) X X X X X 304N (S30451) X X X X X 305 (S30500) X X X X X 308 (S30800) X X X X X 309 (S30900) X X X X X 309S (S30908) X X X X X 310 (S31000) X X X X X 310S (S31008) X X X X X 314 (S31400) X X X X X 316 (S31600) X X X X X X X 316F (S31620) X X X X X X X 316L (S31603) X X X X X X X 316N (S31651) X X X X X X X 317 (S31700) X X X X X X X 317L (S31703) X X X X X X 321 (S32100) X X X X X 329 (S32900) X X X X X X X 330 (N08330) X X X X X X X 347 (S34700) X X X X X 348 (S34800) X X X X X 384 (S38400) X X X X X 403 (S40300) X X 405 (S40500) X X 409 (S40900) X X 410 (S41000) X X 414 (S41400) X X 416 (S41600) X 416 Se (S41623) X 420 (S42000) X 420F (S42020) X 422 (S42200) X 429 (S42900) X X X X 430 (S43000) X X X X 430F (S43020) X X X 430F Se (S43023) X X X 431 (S43100) X X X X 434 (S43400) X X X X X 436 (S43600) X X X X X 440A (S44002) X X 440B (S44003) X 440C (S44004) X 442 (S44200) X X X X 446 (S44600) X X X X X (S13800) X X X X (S15500) X X X X X (S17400) X X X X X (S17700) X X X X X

The "X" notations indicate that a specific stainless steel type may be considered as resistant to the corrosive environment categories. This list is suggested as a guideline only and does not suggest or imply a warranty on the part of the American Iron and Steel Institute, the Committee of Stainless Steel Producers, or any of the member companies represented on the Committee. When selecting a stainless steel for any corrosive environment, it is always best to consult with a corrosion engineer and, if possible, conduct tests in the environment involved under actual operating conditions.

Source: STEEL PRODUCTS MANUAL, STAINLESS AND HEAT RE- SISTING STEELS, DECEMBER 1974, American Iron and Steel Institute, Washington, D. C.

4 º

Table 2 WHERE DIFFERENT GRADES ARE USED Environment Grades Environment Grades

Acids Stainless generally is not recommended except Aldehydes Type 304 is generally satisfactory. Hydrocloric acid when solutions are very dilute and at room tem- perature. Amines Type 316 is usually preferred to Type 304.

"Mixed acids" There is usually no appreciable attack on Type 304 Cellulose Type 304 is satisfactory for low temperatures, but or 316 as long as sufficient nitric acid is present. acetate Type 316 or Type 317 is needed for high tempera- tures. Nitric acid Type 304L or 430 is used. Citric, formic and Type 304 is generally acceptable at moderate tem- Phosphoric acid Type 304 is satisfactory for storing cold phosphoric tartaric acids peratures, but Type 316 is resistant to all concen- acid up to 85% and for handling concentrations up trations at temperatures up to boiling. to 5% in some unit processes of manufacture. Type 316 is more resistant and is generally used for Esters From the corrosion standpoint, esters are compar- storing and manufacture if the fluorine content is able with organic acids. not too high. Type 317 is somewhat more resistant than Type 316. At concentrations up-to 85%, the Fatty acids Up to about 300ºF (150ºC), Type 304 is resistant to metal temperature should not exceed 212ºF fats and fatty acids, but Type 316 is needed at 300 (100ºC) with Type 316 and slightly higher with Type to 500ºF (150 to 260ºC) and Type 317 at higher 317. Oxidizing ions inhibit attack and other temperatures. inhibitors such as arsenic may be added. Paint vehicles Type 316 may be needed if exact color and lack of Sulfuric acid Type 304 can be used at room temperature for contamination are important. concentrations over 80%. Type 316 can be used in contact with sulfuric acid up to 10% at termpera- Phthalic Type 316 is usually used for reactors, fractionating tures up to 120ºF (50ºC) if the solutions are anhydride columns, traps, baffles, caps and piping. aerated; the attack is greater in airfree solutions. Type 317 may be used at temperatures as high as Soaps Type 304 is used for parts such as spray towers, 150ºF (65ºC) with up to 5% concentration. The but Type 316 may be preferred for spray nozzles presence of other materials may markedly change and flake-drying belts to minimize offcolor product. the corrosion rate. As little as 500 to 2000 ppm of cupric ions make it possible to use Type 304 in hot Synthetic Type 316 is used for preheat, piping, pumps and solutions of moderate concentration. Other detergents reactors in catalytic hydrogenation of fatty acids to additives may have the opposite effect. give salts of sulfonated high molecular alcohols.

Sulfurous acid Type 304 may be subject to pitting, particularly if Tall oil (pulp and Type 304 has only limited usage in tall-oil distilla- some sulfuric acid is present. Type 316 is usable at paper industry) tion service. High-rosin-acid streams can be han- moderate concentrations and temperatures. dled by Type 316L with a minimum molybdenum content of 2.75%. Type 316 can also be used in the Bases Steels in the 300 series generally have good cor- more corrosive high-fatty-acid streams at tempera- Ammonium rosion resistance at virtually all concentrations and tures up to 475ºF (245ºC), but Type 317 will hydroxide, temperatures in weak bases, such as ammonium probably be required at higher temperatures. sodium hydroxide. In stronger bases, such as sodium hyd- hydroxide, roxide, there may be some attack, cracking or etch- Tar Tar distillation equipment is almost all Type 316 caustic solutions ing in more concentrated solutions and at higher because coal tar has a high chloride content. Type termperatures. Commercial purity caustic solutions 304 does not have adequate resistance to pitting. may contain chlorides, which will accentuate any attack and may cause pitting of Type 316 as well as Urea Type 316L is generally required. Type 304. Pharmaceuticals Type 316 is usually selected for all parts in contact with the product because of its inherent corrosion Organics Acetic acid is seldom pure in chemical plants but Acetic acid resistance and greater assurance of product purity. generally includes numerous and varied minor constituents. Type 304 is used for a wide variety of Elevated Generally speaking increased chromium content equipment including stills, base heaters, holding Temperatures increases oxidation resistance. Those alloys con- tanks, heat exchangers, pipelines, valves and taining 16 to 20% chromium such as Types 304 pumps for concentrations up to 99% at tempera- and 316 are generally useful in air to temperatures tures up to about 120ºF (50ºC). Type 304 is also of 1600 to 1700ºF (870 to 925ºC). Alloys such as satisfactory for contact with 100% acetic acid va- Types 309 and 310 with higher chromium and pors, and–if small amounts of turbidity or color nickel contents may extend this temperature range pickup can be tolerated–for room temperature to 1800 or 1900ºF (180 to 1035ºC). Exposure to storage of glacial acetic acid. Types 316 and 317 fluctuating temperatures or even mild environ- have the broadest range of usefulness, especially if ments such as carbon dioxide or water vapor may formic acid is also present or if solutions are result in significant increases in corrosion rates at unaerated. Type 316 is used for fractionating these temperatures. equipment, for 30 to 99% concentrations where Type 304 cannot be used, for storage vessels, Cryogenic Austenitic stainless steels exhibit good ductility and pumps and process equipment handling glacial Temperatures toughness at the most severe of cryogenic acetic acid, which would be discolored by Type temperatures - minus 423ºF (- 253ºC). Impact tests 304. Type 316 is likewise applicable for parts hav- show that Type 304 is very stable over long periods ing temperatures above 120ºF (50ºC), for dilute of exposure and does not exhibit any marked vapors and high pressures. Type 317 has some- degradation of toughness. Properly made welds what greater corrosion resistance than Type 316 also have excellent low-temperature properties. under severely corrosive conditions. None of the Austenitic grades cold worked to high strength stainless steels has adequate corrosion resistance levels are also suitable for low-temperature ser- to glacial acetic acid at the boiling temperature or at vice. Type 310 can be cold worked as much as superheated vapor temperatures. 85% and still exhibit a good notched-to-unnotched tensile ratio down to - 423ºF (- 253ºC).

Source: STAINLESS STEEL AND THE CHEMICAL INDUSTRY, Climax Molybdenum Company, Greenwich, Connecticut, 1966.

5 ries of corrosive environments. Table 2 details more THE SELECTION specific environments in which various grades are used, and a list of useful references to aid in the selection of stainless steels is included on page 22. OF A PIPING When dealing with corrosive environments, the pip- ing system designer and specifier should take careful SYSTEM note of the fact that there are significant differences in corrosion resistance and strength among the various The most commonly used material for metal piping stainless alloys. If Type 304 is not suitable for a particu- lar environment there is no reason to rule out other systems is carbon steel. Where carbon steel pipe is stainless steels. There are stainless steels with higher satisfactory, it generally results in the most economical chromium and nickel contents or with other alloying system. The justification for the selection of a more elements that provide better resistance to corrosion expensive material, however, is usually either a longer than Type 304. For instance, the AISI-numbered stain- life because of reduced corrosion, or an improvement in less steels are not recognized as being outstanding product quality as a result of reduced contamination materials for use in seawater environments. There are, (corrosion). The selection of a more expensive material however, commercially available proprietary stainless may also be dictated by piping code material restriction, steels that have exhibited excellent resistance in sea- such as in those cases where operating conditions are above or below the range of working temperatures water environments. approved for carbon steel. A variety of materials, both metallic and nonmetallic, are available to fill the varied piping needs of industry. STRENGTH CHARACTERISTICS Each of these materials has its own particular attributes that justify its use in certain applications and they each A very important consideration in evaluating various have limitations. A check-list has been developed (Ap- pipe system materials is strength. The mechanical pendix B) listing some of the factors which should be properties of stainless steels yield a number of important weighed in making a decision on the relative merits of advantages over nonmetallic pipe systems. alternative pipe materials. These include, among other High-Temperature Characteristics. The austenitic important considerations, pressure and temperature stainless steels are unique in that they combine high- limitations, supporting structure requirements, chemical temperature strength and oxidation resistance. Appli- resistance, protection from exposure to fire, thermal cations at 1000ºF are common and some applications expansion, piping code restrictions, safeguarding re- utilizing stainless steels operate at temperatures ap- quirements, tracing, vacuum collapse and insulation. proaching 1900ºF. Figure 1 gives a broad concept of the hot strength advantages of the austenitic stainless steels in com- parison with other materials. The stress values for Type 304 seamless pipe compared with a low-alloy chrome STAINLESS STEEL molybdenum steel pipe shown in Table 3 illustrate an important reason why austenitic stainless steels are IN PIPING preferred over other alloys for steam service at temper- atures over 1050ºF. (Many companies use Type 316 for high-temperature steam service.) SYSTEMS The most common criteria currently used in the United States for the design of hot piping are found in The role of stainless steel in piping systems can be ANSI B31.3.* This code prescribes minimum require- defined by outlining its advantages and disadvantages ments for piping systems subject to pressure or vacuum, as a piping material. over a range of temperatures up to 1500ºF. The basic allowable stress for a particular material at a particular temperature is based on several criteria, any of which may govern. In accordance with the Code, this basic allowable stress shall not exceed the lowest of the Advantages following: CORROSION RESISTANCE 1. One third of the material's minimum tensile strength at room temperature. 2. One third of the material's minimum tensile Stainless steels possess broad resistance to a wide strength at design temperature. variety of corrosives from fresh water to strong nitric 3. Two thirds of the material's minimum yield acid. This corrosion resistance generally allows the use strength at room temperature. of light-weight construction with Schedule 5S or 10S 4. Two thirds of the material's minimum yield piping. strength at the design temperature. While full discussion of corrosion resistance in spe- cific media is beyond the scope of this publication, *ANSI B 31.3. American National Standards Institute Code for Chem- Table 1 lists the relative corrosion resistance of the 57 ical Plant and Petroleum Refinery Piping, published by the American AISI-numbered stainless steels in seven broad catego- Society of Mechanical Engineers, 1976.

6 Table 3 ALLOWABLE STRESS AT MAXIMUM METAL TEMPERATURE

ºF 900 950 1000 1050 1100 1150 1200 ºC 482 510 538 566 593 621 649 Type ksi MPa ksi MPa ksi MPa ksi MPa ksi MPa ksi MPa ksi MPa 304 10.0 68.9 9.8 67.2 9.5 65.2 9.0 62.1 8.3 56.9 6.9 47.6 5.5 37.9 2¼Cr-1 Mo 13.1 90.3 11.0 75.8 7.8 53.8 5.8 40.0 4.2 29.0 3.0 20.7 2.0 13.8

Source: Stainless Steel Industry Data

5. The average stress for a creep rate of 0.01 percent most severe of cryogenic temperatures. Table 4 shows per 1,000 hours. mechanical properties of some of these materials at 6. 67 percent of the average stress for rupture at the cryogenic temperatures. end of 100,000 hours. In contrast, thermoplastics, fiberglass reinforced 7. 80 percent of the minimum stress for rupture at the plastic (FRP), and plastic-lined carbon steel have a end of 100,000 hours. much narrower range of temperatures at which their performance is acceptable. According to ANSI B31.3 An exception to the fourth criterion above is that for the suggested temperature limits for thermoplastic pipe austenitic stainless steels (generally the 300 series) is from -30ºF to 210ºF, depending upon the specific and for some of the nickel alloys, when used at temper- material. The temperature limits for reinforced ther- atures below 1100ºF, the limit may be as high as 90 mosetting resins are from -20ºF to 300ºF. For percent of the minimum yield strength at the design thermoplastics used as linings, the range is from 0ºF to temperature. However, this high allowable stress is not 500ºF, again depending upon the specific material. recommended for flanged, gasketed joints or other ap- Design Considerations. Because of excellent plications where a slight deformation could cause leak- strength characteristics, stainless steel piping can age. withstand higher pressures, or a full vacuum, over a An excellent discussion of this subject is in an article wide temperature range–which, in turn, means a by J.D. Dawson, "Designing High-Temperature Piping." greater degree of safety. For example, austenitic (CHEMICAL ENGINEERING, April 9, 1979.) stainless steels provide satisfactory service from low Low-Temperature Characteristics. At the other ex- cryogenic temperatures to temperatures of 1800ºF and treme, austenitic stainless steels are among the few above. Strength and toughness are especially impor- materials that retain their toughness and ductility at the tant for pipe systems handling hot acid solutions, other

Table 4 TYPICAL MECHANICAL PROPERTIES OF STAINLESS STEELS AT CRYOGENIC TEMPERATURES

Yield Elongation Tensile AISI Test Strength in Izod Impact Strength Type Temperature 0.2% Offset 2" ºF ºC ksi MPa ksi MPa % ft. lbs. J 304 - 40 - 40 34 234 155 1,069 47 110 149 - 80 - 62 34 234 170 1,172 39 110 149 -320 -196 39 269 221 1,524 40 110 149 -423 -252 50 344 243 1,675 40 110 149

310 - 40 - 40 39 269 95 655 57 110 149 - 80 - 62 40 276 100 689 55 110 149 -320 -196 74 510 152 1,048 54 85 115 -423 -252 108 745 176 1,213 56

316 - 40 - 40 41 283 104 717 59 110 149 - 80 - 62 44 303 118 814 57 110 149 -320 -196 75 517 185 1,276 59 -423 -252 84 579 210 1,448 52

347 - 40 - 40 44 303 117 807 63 110 149 - 80 - 62 45 310 130 896 57 110 149 -320 -196 47 324 200 1,379 43 95 129 -423 -252 55 379 228 1,572 39 60 81

410 - 40 - 40 90 621 122 841 23 25 34 - 80 - 62 94 648 128 883 22 25 34 -320 -196 148 1,020 158 1,089 10 5 7

430 - 40 - 40 41 283 76 524 36 10 14 - 80 - 62 44 303 81 558 36 8 11 -320 -196 87 607 92 634 2 2 3

Source: Stainless Steel Industry Data

7 hazardous liquids, or compressed gases (which in Table 5 large systems contain a substantial concentration of THICKNESS FOR STAINLESS STEEL PIPE DESIGNED potential energy). Flanged joints in nonmetallic sys- TO WITHSTAND FULL 30 in. H.G. VACUUM tems are more susceptible to gasketing and leakage problems due to their low modulus of elasticity. In lined Where vibration exists, the thickness should be increased and/or reinforcing rings added. pipe, vacuum service often leads to liner buckling. (Table 5 shows the thickness for stainless steel pipe Size Gauge U.S. Standard Thickness 1 14 0.078 designed to withstand a full vacuum of 30 inches of 1½ 14 0.078 mercury.) 2 14 0.078 Because of their excellent high-temperature charac- 3 14 0.078 teristics, stainless steel piping systems are readily 4 14 0.078 steam jacketed, and they have a greater tolerance for 6 14 0.078 steam tracing than the nonmetallic or lined systems. 8 14 0.078 10 12 0.109 Steam tracing of lined pipe may lead to buckling of the 12 12 0.109 liner. (Care should be exercised in steam tracing any 14 11 0.125 metallic pipe system to prevent hot spots, which could 16 11 0.125 cause accelerated corrosion.) 18 11 0.125 Also relative to the use of pipe systems at high or low 20 3/16 0.1875 3 temperatures, are the thermal expansion characteris- 22 /16 0.1875 24 3/16 0.1875 tics of the materials. The coefficient of thermal expan- 26 3/16 0.1875 28 3/16 0.1875 30 ¼ 0.250 32 ¼ 0.250 34 ¼ 0.250 Figure 1 36 ¼ 0.250 HOT STRENGTH CHARACTERISTICS Note: Standard rolled angle face rings may be used for reinforcing rings. (Dimensions are given in inches) Source: SUGGESTED STANDARDS FOR STAINLESS STEEL PIP- ING FOR THE PULP AND PAPER INDUSTRY, Tappi En- gineering Conference, November 1968, Houston, Texas

sion of stainless steels is much closer to that of carbon steel than that of plastic materials. Lined metallic piping systems have been known to fail because of the differ- ence in expansion between the pipe and its lining. In contrast to the excellent performance characteris- tics of stainless steel pipe systems exposed to elevated temperature (either internally or externally), special provisions are required to protect nonmetallic pipe sys- tems. These provisions are frequently in the form of thermal insulation, shields or process controls to protect against excessive heat or thermal shock, and/or armor guards or barricades for protection against mechanical abuse. In the event of a fire, a stainless steel piping system is more resistant than a plastic system, as it is neither flammable nor readily melted. Also, heat can seriously affect nonmetallic systems. High strength means fewer and less complicated supporting structures. Generally speaking, in a metallic piping system a minimum of two supports is used for each length of pipe for practical handling during instal- lation and removal, and valves are usually supported by the pipe system itself. In contrast, nonmetallic sys- tems use more supports, plus additional supports for each valve. For outside pipe runs, the supporting struc- tures for nonmetallic systems are more substantial and more expensive.

EASE OF FABRICATION General comparison of the hot-strength characteristics of austenitic, martensitic and ferritic stainless steels with those of low-carbon unal- loyed steel and semi-austenitic precipitation and transformation- The excellent ductility of the austenitic stainless hardening steels. steels enables extensive forming operations. Forming

8 of Van Stone flanges and pipe bending, for example, Table 6 offer economies that are unavailable with other less- REPRESENTATIVE PRESSURE RATING FOR ductile materials. VAN STONE FLANGED TYPES 304L and 316L

Temp. ºF Schedule 10S Schedule 40S Van Stone Flanging 100 275 psi 300 psi 200 240 psi 300 psi Van Stone flanging involves roll flaring of the pipe 300 210 psi 300 psi 400 180 psi 300 psi end to form a lap perpendicular to the pipe axis. Using a 500 150 psi 300 psi lap joint back-up flange, or a slip-on flange with the inner 600 130 psi 300 psi corner between the flange face and bore slightly cham- 650 120 psi 300 psi fered, offers one of the best methods of providing a Ratings are based on the following: flanged connection. The advantages, compared to a 1. Stresses used are not more than ½ allowed by ASME code. weld-neck flange, are readily apparent: 2. Use of standard slip-on flanges per ASA B16.5. Reliability–This is a machine operation with precise 3. Where lightweight back-up flanges are used, the bolt circle bolt size and bore diameter should be per ASA B16.5. In this case the rating tooling. Each lap is virtually identical. of stub and back-up assembly is limited by the capabilities of the Speed–Always faster than welding. back-up flange. Ease of Installation–Since the back-up flange is free 4. These ratings allow for normally encountered bending moments due to thermal cycling. Where such conditions are severe and a piping to rotate, there is never a problem of bolt-hole align- flexibility analysis is made, stresses due to bending moment should ment with the mating flange. be limited to a stress range of 20,000 psi (±10,000) in the wall No Need for Expensive Flange–Back-up flanges adjacent to the lap. have a mechanical function, which does not require Source: PIPE FABRICATION, SGL Piping Systems, a division of SGL Industries, Inc., Newport, Delaware corrosion resistance. A forged steel or ductile iron back-up flange may be used with stainless steel pipe. Cost–Fast fabrication, elimination of welds, fast in- stallation, and inexpensive flanges add up to sub- is the fact that close-radius bends match standard stantial cost savings. forged steel long-radius elbows per USAS B16.9; 4-inch Stainless steel welded and full-finished pipe man- iron pipe size (IPS), for example, is bent on a 6-inch ufactured in accordance with standard specification radius while 2-inch IPS pipe is bent on a 3-inch radius. ASTM A312 is preferred for flanging Type 304 or 316 Close-radius bending may be used interchangeably with (plus low-carbon grades) in ½ to 12-inch diameters in forged elbows in any piping system with no revision in Schedules 5S, 10S, and 40S. Table 6 shows represen- layout. tative pressure rating data for Van Stone flanged Types Bends of 1 to 180 degrees are possible. Table 8 304 and 316, while Table 7 shows typical Van Stone lap provides guidelines for maximizing the use of bending, geometries. Figures 2 and 3 show typical examples. and Figures 4 and 5 show typical applications. Bending is used generally for sizes up to 4 inches in diameter. Bending of larger sizes is possible with special equip- Pipe Bending ment. For example, in some shops fabricating piping systems for nuclear power plants, 34-inch diameter The piping designer can achieve significant cost sav- pipe with a 4-inch wall thickness is being successfully ings by specifying close-radius bending of stainless bent utilizing induction heating of the bend area. This steel wherever possible in the piping system. Important type of bending results in lower welding and fitting

Table 7 VAN STONE LAP GEOMETRIES Flange Type IPS LAP OD Schedules Schedules Serrated (in inches) (in inches) 5S/10S 40S/80S Face ½ 13/8 SO LJ A ¾ 111/16 SO LJ A 1 2 SO LJ A 1¼ 2½ SO LJ A 1½ 27/8 SO LJ A 2 35/8 SO LJ A 2½ 41/8 SO LJ A 3 5 SO LJ A 4 63/16 SO LJ A 6 8½ SO LJ A 8 105/8 SO LJ A 10 12¾ SO LJ NA 12 15 SO LJ NA

SO–Slip-On; LJ–Lap Joint; A-Available; NA–Not Available Back-up flanges may be forged steel or ductile iron, flat face or raised face.

Source: PIPE FABRICATION, SGL Piping Systems, a division of SGL Industries, Inc., Newport, Delaware

9 Figure 2 Figure 3 Typical example of a Van Stone flange. The flange, The flared end of the pipe or tube can be smooth, or it can which can be of a noncorrosion resistant material, is be flared with a serrated face, as shown here. The slipped over the end of the pipe and then the end is serrations are formed by the flaring tool and are "rolled" flared by an operation that resembles spinning. in, not machined.

Table 8 CLOSE RADIUS BENDING TABLES

Min. Center-to-Center and Center-to-Face Dimensions to allow adequate clamping. (Dimensions in inches)

90°Bends 45°Bends Pipe Radius A B C D E F Size R ½ 1½ 5½ 7½ 7 45/8 65/8 5¼ ¾ 11/8 51/8 7½ 6¼ 49/16 6¾ 5 1 1½ 5½ 8 7 45/8 73/8 5¼ 1½ 2¼ 8 9 10¼ 611/16 77/8 7¼ 2 3 11 9 14 9¼ 73/8 10½ 3 41/8 13½ 12 18 107/8 9½ 12¾ 3½ 5¼ 14¼ 13 19½ 11¾ 10 133/8 4 6 16¾ 14 22¾ 13¼ 10½ 15¾

A or D–Plain or Beveled End B or E–Flanged End C or F–Center to Center

Source: PIPE FABRICATION, SGL Piping Systems, a division of SGL Industries, Inc., Newport, Delaware

10 Figure 4 This is a "pancake" heating coil of 1½inch Type 304 stainless steel pipe, 40 feet in diameter. The detail (inset) shows how 180 degree bends were made to the centerline spacing. By bending, the fabricator eliminated one weld per return, significantly reducing the cost as compared to conventional U-bend fittings. costs. In any piping system, the need for fewer welds translates into a significant reduction of in-service in- spections and nondestructive examination require- ments. The repair or replacement of a stainless steel section can be easily and quickly accomplished while other materials often require involved repair procedures with significant downtime. For example, special fixtures are required with lined pipe to form the liner over a flange face.

AVAILABILITY

Stainless steel pipe and tubing are available as either Figure 5 welded or seamless products. CONVENTIONAL CONSTRUCTION Welded pipe is ordinarily preferred to seamless pipe Requires seven welds and four purchased fittings. for chemical plant piping because it is more eco- FLARED LAPS AND BENT CONSTRUCTION Requires nomical. The greater uniformity of wall is beneficial in one weld and no purchased fittings. (Branch is made performing the fabricating operations of short radius with a saddle weld.)

11 Table 9 PIPE SIZES AND WEIGHTS-304, 304L, 309, 310, 316 and 316L

Nominal Nominal Schedule 5S Schedule 10S Schedule 40S Schedule 80S IPS OD Wall Weight Wall Weight Wall Weight Wall Weight inches inches inches pounds/foot inches pound/foot inches pounds/foot inches pounds/foot 1/8 0.405 0.049 0.1880 0.068 0.2470 0.095 0.3175 ¼ 0.540 0.065 0.3328 0.088 0.4287 0.119 0.5401 3/8 0.675 0.065 0.4274 0.091 0.5729 0.126 0.7457

½ 0.840 0.065 0.5430 0.083 0.6773 0.109 0.8589 0.147 1.098 ¾ 1.050 0.065 0.6902 0.083 0.8652 0.113 1.141 0.154 1.487 1 1.315 0.065 0.8759 0.109 1.417 0.133 1.695 0.179 2.192

1¼ 1.600 0.065 1.117 0.109 1.822 0.140 2.294 0.191 3.025 1½ 1.900 0.065 1.286 0.109 2.104 0.145 2.743 0.200 3.665 2 2.375 0.065 1.619 0.109 2.662 0.154 3.687 0.218 5.069

2½ 2.875 0.083 2.498 0.120 3.564 0.203 5.847 0.276 7.733 3 3.500 0.083 3.057 0.120 4.372 0.216 7.647 0.300 10.35 3½ 4.000 0.083 3.505 0.120 5.019 0.226 9.194 0.318 12.62

4 4.500 0.083 3.952 0.120 5.666 0.237 10.89 0.337 15.12 5 5.563 0.109 6.409 0.134 7.842 0.258 14.75 0.375 20.97 6 6.625 0.109 7.856 0.134 9.376 0.280 19.15 0.432 28.84

8 8.625 0.109 10.01 0.148 13.52 0.322 28.82 0.500 43.79 10 10.750 0.134 15.34 0.165 18.83 0.365 40.86 0.500 55.25 12 12.750 0.156 21.18 0.180 24.39 0.375 50.03 0.500 66.03

14 14.000 0.156 23.28 0.188 27.99 16 16.000 0.165 28.17 0.188 32.05 18 18.000 0.165 31.72 0.188 36.10

20 20.000 0.188 40.15 0.218 45.49 22 22.000 0.188 44.21 0.218 51.19 24 24.000 0.218 55.89 0.250 64.01 30 30.000 0.250 80.18 0.312 99.85 Source: Stainless Steel Industry Data bending and forming flared laps. of different methods. If the application involves a sterile On the other hand, seamless pipe is accorded a environment, they are readily sterilized. higher allowable hoop stress without special examina- tion than is welded pipe, and heavier wall thicknesses are more readily available in seamless pipe, which ABRASION RESISTANCE would be required for some high-pressure applica- tions. The code for chemical plant and petroleum piping, Stainless steels possess good abrasion resistance ANSI B31.3, permits use of the same stresses for for handling slurries. welded pipe as those used for seamless pipe, provided the longitudinal seam weld has passed the requisite 100 percent radiographic examination. HEAT TRANSFER Both pipe and the necessary fittings of stainless steel conforming to ASTM and ANSI standards are readily A metallic piping system has distinct advantages available from a number of sources. Table 9 shows pipe over nonmetallic systems if heat transfer is important.

sizes, wall thicknesses and weights of Types 304, 304L, Table 10 provides data on the conductivity and overall 309, 310, 316, and 316L stainless steels. heat transfer coefficients of various metals.

PROTECTIVE COATINGS ECONOMY Protective coatings are usually not required due to the inherent corrosion resistance of stainless steel. When all costs are considered, stainless steel piping However, sometimes coatings are applied to the exterior systems often win out over other materials. This is es- of pipe for color coding or for protection against chloride pecially true if advantage is taken of the mechanical attack from wet insulation. properties and corrosion resistance of stainless steel which allow light-weight construction. For instance, Schedule 5S, Type 304 stainless steel approaches EASE OF CLEANING Schedule 40 carbon steel in installed cost, and it is certainly more economical than Schedule 80 carbon Stainless steels can be readily cleaned by a number steel.

12 collect and become stagnant. The material being utilized in the formation of a cre- Limitations vice need not be metallic. Scale, wood, plastics, rub- ber, glass, concrete, asbestos, wax, and living or- CORROSIVE ENVIRONMENTS ganisms have all been reported to cause crevice corro- sion. Once attack begins within the crevice, its prog- No piping material is resistant to all corrosive media. ress may be very rapid. The stainless steels containing Stainless steels have a few limitations (or precautions) molybdenum are more resistant to this type of attack which must be considered in the design of a piping and are often used to minimize the problem. Not- system. For instance, unsatisfactory service may result withstanding, the best solution to crevice corrosion is a from use of stainless steels in strongly reducing envi- design that eliminates as many crevices as possible. ronments, depending on concentration and tempera- Stress-corrosion cracking is caused by the com- ture. Likewise, problems may be encountered with bined effects of tensile stress and corrosion. Many alloy stainless steels exposed to high-chloride environ- systems have been known to experience stress- ments. Precautions must also be taken to avoid corro- corrosion cracking–for example, brass in ammonia, sive attack on the exterior of the pipe by chlorides carbon steel in nitrate solutions, titanium in methanol, leached from pipe insulation. Chlorides may cause pit- aluminum in sea water, and gold in acetic acid. Some ting, crevice corrosion or stress-corrosion cracking. stainless steels (i.e. the austenitic grades) are suscep- Materials engineers familiar with these types of corro- tible to stress-corrosion cracking in chloride and caustic sive attack can avoid problems with stainless steels by environments. selecting the proper grade and by taking proper pre- It is necessary for tensile stress, chlorides in solution ventive measures, such as avoiding environments and elevated temperature all to be present for stress- known to corrode stainless steels, by eliminating cre- corrosion cracking to occur in stainless steel. Wet-dry or vices, by providing for regular cleaning to remove de- heat transfer conditions, which promote the concen- posits or by using silicate inhibited insulation. tration of chlorides, are particularly aggressive with The types of corrosive attack which are more likely respect to initiating stress-corrosion cracking. A typical to be of concern in utilizing stainless steels are: pitting, problem area is under pipe insulation. If the insulation crevice attack, stress-corrosion cracking, and inter- becomes wet, chlorides in the insulation can leach out granular corrosion. and concentrate on the metal surface as a result of Pitting occurs when the protective oxide film on stain- alternate wetting and drying. The problem with insula- less steel breaks down in small isolated spots. Halide tion can be prevented by using a silicate-inhibited insu- ions are most often responsible for this type of attack. lation. Once started, the attack may propogate because of While the mechanism of. stress-corrosion cracking is differences in electric potential between the large area of not fully understood, laboratory tests and service expe- passive surface vs. the small active pitted area. rience have resulted in methods to minimize the prob- Pitting is avoided in many environments by using lem. For instance, Type 329 (an austenitic-ferritic stain- Type 316 or 317 or other stainless steels containing less containing 25-30 percent chromium, 3-6 percent higher levels of chromium and molybdenum. nickel, and 1-2 percent molybdenum) exhibits superior Crevice corrosion results from local differences in resistance to chloride stress-corrosion cracking; plus it oxygen concentration associated with deposits on the has a general corrosion and pitting resistance similar to metal surface, gaskets, lap joints, or crevices under Type 316. Recent studies indicate that Type 317 with bolt or rivet heads where small amounts of liquid can 3.5 percent (minimum) molybdenum has excellent re-

Table 10 EFFECT OF METAL CONDUCTIVITY ON "U" VALVES Film Coefficients Thermal Conductivity "U" Value Btu/hr/ft2/F of Metal Btu/hr/ft2/F/in. Btu/hr/ft2/F Application Material (W/m2•K) (W/m•K) (W/m2 •K)

ho hi Heating Copper 300 (1704) 1000 (5678) 2680 (387) 299 (1300) water with Aluminum 300 (1704) 1000 (5678) 1570 (226) 228 (1295) saturated Carbon Steel 300 (1704) 1000 (5678) 460 (66) 223 (1266) steam Stainless Steel 300 (1704) 1000 (5678) 105 (15) 198 (1124) Heating Copper 5 (28) 1000 (5678) 2680 (387) 4.98 (28) air with Aluminum 5 (28) 1000 (5678) 570 (226) 4.97 (28) saturated Carbon Steel 5 (28) 1000 (5678) 460 (66) 4.97 (28) steam Stainless Steel 5 (28) 1000 (5678) 105 (15) 4.96 (28)

Where ho = outside fluid film heat-transfer coefficient

hi = inside fluid film heat-transfer coefficient Stainless steel is 300 Series Type

Source: Tranter Mfg. Inc.

13 sistance. Several proprietary austenitic stainless steels HIGH-TEMPERATURE ENVIRONMENTS with higher nickel content also have shown resistance to stress cracking in hot chloride environments. Stainless steels are generally selected, first, on the The ferritic stainless steels, which are very resistant basis of their resistance to corrosion and, second, on to stress-corrosion cracking, should also be considered the basis of their mechanical properties. As the tem- when the potential exists for this type of corrosion. peratures of operating environments increase, however, Intergranular corrosion. When austenitic stainless elevated temperature properties quickly become the steels are heated or cooled through the temperature primary concern. The stainless steels are most ver- range of about 800-1650ºF, the chromium along grain satile in their ability to meet the requirements of high- boundaries tends to combine with carbon to form temperature service. chromium carbides. The carbide precipitation causes a There are three primary design factors that depletion of chromium and the lowering of corrosion engineers consider when choosing materials for service resistance in areas adjacent to the grain boundary. This at elevated temperature. These design factors are: phenomenon, known as sensitization, is time and tem- 1. Service life (corrosion resistance and mechanical perature dependent. properties) Sensitization may result from slow cooling from an- 2. Allowable deformation nealing temperatures, stress-relieving in the sensitiza- 3. Environment. tion range, or welding. Due to the longer time at tem- Service life–For a given type of steel at a specific perature of annealing or stress-relieving, it is possible thickness, the expected service life depends on the that the entire piece of material will be sensitized. Weld- maximum temperature to which it is exposed plus the ing, on the other hand, may cause sensitization of a maximum stresses to which it is subjected; also narrow band adjacent to but slightly removed from the whether service is at a constant temperature or intermit- weld in the region known as the heat-affected-zone tent high temperature, plus corrosion resistance. (HAZ). For a prolonged anticipated service life, such as 20 Intergranular corrosion depends upon the mag- years, plain carbon steels are usually limited to a maxi- nitude of the sensitization and the aggressiveness of mum operating temperature of 750ºF; the ½ percent the environment to which the sensitized material is ex- molybdenum alloy steels to approximately 850ºF; and posed. Many environments do not cause intergranular the stainless steels to considerably higher tempera- corrosion in sensitized austenitic stainless steels. For tures depending upon the type used and the nature of example, glacial acetic acid at room temperature or the environment. It is important to recognize that for fresh clean water do not; strong nitric acids do. (High high-temperature service, strength at temperature is purity water, however, such as used in primary circuits related to time at temperature. of nuclear reactors can be aggressive to sensitized Allowable deformation–Another factor to consider stainless steels.) in designing for high-temperature service is the amount Carbide precipitation and subsequent intergranular of deformation that can be permitted during the antici- corrosion in austenitic stainless steels have been thor- pated service life. This factor determines which of two oughly investigated; the causes are understood and high-temperature strength properties should be given methods of prevention have been devised. These priority; creep or creep-rupture (sometimes called methods include: stress-rupture). If the component is small and/or the 1. Use of welded stainless steel pipe in the annealed tolerances very close (such as in turbine blades) creep condition (post-weld annealing). is regarded as the overriding factor. But if the compo- 2. Selection of the low-carbon (0.030 percent maxi- nent is large and capable of accommodating greater mum) stainless steels when welding is involved. deformation, such as shell-and-tube heat exchangers, Low-carbon grades are Types 304L, 316L, and the creep rupture strength is the usual basis for selec- 317L. The less carbon available to combine with tion. Where considerable deformation is permitted, it is the chromium, the less likely is carbide precipita- well to know the anticipated time to rupture, so parts tion to occur. However, the low-carbon grades can be scheduled for replacement before failure oc- may become sensitized at extremely long expo- curs. sures to temperatures in the sensitization range. It is also useful to know whether or not service at 3. Selection of a stabilized grade, such as Type 321 elevated temperature is cyclic or continuous. Cyclic (titanium stabilized) or Type 347 (columbium operation may lead to failure by fatigue or loss of metal stabilized). The stabilization provided by titanium due to flaking of the oxide scale prior to the expected and columbium is based upon the greater affinity creep-rupture time. that they have for carbon than does chromium. Environment–The effect of exposure of a material to media can be a very complex subject. Elevated tem- peratures tend to increase corrosive action, heat trans- Columbium stabilization is preferred because its fer may affect corrosivity, thermal cycling can increase carbides are more readily retained in welds and it is metal wastage through spalling of protective scale on easier to add in the steelmaking process. However, the the metal surface, and metal temperature probably will use of columbium stabilized steel requires additional not be the same as the environment to which it is ex- care in welding. posed. Generally, if oxidation or other forms of scaling A low-carbon grade is usually specified for welding are expected to be severe, a greater cross-sectional fabrication, while a stabilized grade is usually specified area–beyond that indicated by mechanical-property when the component is to be used at elevated tempera- requirements–is usually specified. Problems like this ture.

14 cannot be solved by laboratory analysis. They require Carburization observation of test specimens in actual operating envi- ronments in pilot plants or full-size units. Carburization is the diffusion of carbon into a metal. It A brief discussion of the corrosion behavior of stain- can be carried to such a degree as to form high-carbon less steels in various high-temperature environments alloys with low ductility and impact strength at ambient follows: temperature. The chromium carbides thus formed are prone to rapid oxidation under oxidizing conditions. The virtual disappearance of the metal carbides leaves Oxidation deep holes. Such an extension of carburization, which is relatively uncommon, is known as metal dusting. Carburization can be caused by continuous over- In noncyclic-temperature service, the oxidation re- heating of a metal in the presence of hydrocarbon sistance (or scaling resistance) of stainless steels de- pends on chromium content. Stainless steels with less gases, carbon monoxide, coke, or molten metals con- than 18 percent chromium (ferritic grades primarily) are taining dissolved carbon. limited to temperatures below 1500ºF. Those containing Laboratory and field experience indicate that the rate 18 to 20 percent chromium are useful to temperatures of of carburization is affected by chromium content. 1800ºF, while adequate resistance to scaling at tem- peratures up to 2000ºF requires a chromium content of at least 25 percent, such as Types 309, 310, or 446. Hydrogen Attack

Atomic hydrogen, which results from a corrosion reaction or the dissociation of molecular hydrogen, can Sulfidation diffuse rapidly through the steel lattice to voids, imper- fections, or low-angle grain boundaries. The diffusing Sulfur attack is second only to air oxidation in fre- atoms accumulate and combine to form molecular hyd- quency of occurrence in many industries, and it is of rogen or, at high temperature, react with carbon to form even greater consequence because deterioration is methane. The larger hydrogen or methane molecules likely to be more severe. Like oxidation, sulfidation pro- are trapped, and the subsequent pressure buildup re- ceeds by converting metal to scale, which may be sults in blisters or laminations (hydrogen damage) protective except that metal sulfides melt at lower tem- and/or degradation of ductility (hydrogen embrittle- peratures than comparable oxides, and diffusion ment). Eventually the steel cracks and may become through a molten corrosion product is much faster than unsuitable for continued use. through a solid corrosion product. Also, sulfides are less In low-temperature environments, carbon or low- likely to form tenacious, continuous protective films. alloy steels are usually suitable, but for temperatures Fusion and lack of adherence can result in accelerated above 800ºF and at high pressures (about 10,000 psi) corrosion. the austenitic stainless steels have sufficient chromium As with oxidation, resistance to sulfidation relates to to impart good resistance to hydrogen attack. chromium content. Unalloyed iron will be converted rather rapidly to iron sulfide scale, but when alloyed with Ammonia and Nitrogen chromium, sulfidation resistance is enhanced. Silicon also affords some protection against sulfidation. In addition to the usual factors of time, temperature, Most metals and alloys are inert towards molecular and concentration, sulfidation depends upon the form nitrogen at elevated temperature. However, atomic ni- in which the sulfur exists. Of particular interest is the trogen will react with and penetrate many steels, pro- effect of sulfur vapor, sulfur dioxide, hydrogen sulfide, ducing hard, brittle nitride surface layers. and flue gases. The behavior of stainless steels in ammonia depends For example, it is extremely difficult to generalize on temperature, pressure, gas concentration, and about corrosion rates in flue and processes gases, chromium and nickel contents. Results from service since gas composition and temperature may vary con- tests have demonstrated that corrosion rates for siderably within the same process unit. Combustion straight-chromium stainless steels are greater than gases normally contain sulfur compounds; sulfur dioxide those for the chromium-nickel grades. (See publication is present as an oxidizing gas along with carbon "Stainless Steels for Ammonia Production" by the dioxide, nitrogen, carbon monoxide, and excess oxygen. Committee of Stainless Steel Producers.) Protective oxides are generally formed, and depending on exact conditions, the corrosion rate may be approximately the same as in air or slightly greater. The Halogens resistance of stainless steels to normal combustion gases is improved by increasing chromium content. Austenitic stainless steels are severely attacked by Reducing flue gases contain varying amounts of hyd- halogen gases at elevated temperatures. Fluorine is rogen sulfide, hydrogen, carbon monoxide, carbon more corrosive than chlorine, and the upper tempera- dioxide and nitrogen. The corrosion rates encountered in ture limits for dry gases are approximately 480ºF and these environments are sensitive to hydrogen sulfide 600ºF, respectively, for the high chromium-nickel content and temperature, and satisfactory material grades. Wet chlorine gas containing 0.4 percent water selection often necessitates service tests. is more corrosive than dry chlorine up to about 700ºF.

15 Liquid Metals Other low-melting metals–Molten metals and alloys Liquid-metal corrosion differs from aqueous and such as aluminum, zinc, antimony, bismuth, cadmium, gaseous corrosion since it depends primarily on the tin, lead-bismuth, and lead-bismuth-tin are generally solubility of the solid metal in the liquid metal instead of corrosive to stainless steels. on electro-chemical forces. Although chemical reactions Molten salts–Molten salts may corrode metals ac- may play an important role in liquid-metal corrosion, cording to the reaction processes described for liquid- mass transfer mechanisms are the most significant. metal corrosion, namely, simple solution, temperature The resistance of austenitic stainless steels to vari- and concentration gradient mass transfer, and impurity ous liquid metals cannot be generalized, so some of the reactions. Corrosion may also occur by direct chemical low-melting metals and alloys are discussed separately: reaction, or a combination of corrosion and the reaction Sodium and sodium-potassium alloys–The austeni- processes. Most information available concerns the tic stainless steels have been used extensively to contain corrosive nature of heat treating salts or salt mixtures. sodium and sodium-potassium alloys (NaK). They are not Stainless steels high in nickel and low in chromium, susceptible to mass transfer up to 1000ºF, and the rate of such as Type 330, are usually selected for chloride salt transfer remains within moderate levels up to 1600ºF. containments. Molten sodium may cause severe carburization of For low-temperature heat treating (300 to 1100ºF) stainless steels if it becomes contaminated by car- mixtures of potassium nitrate and sodium nitrate are fre- bonaceous material. For example, carburization has quently used. While cast iron or steel are serviceable for occurred from the storage of the liquid metal under temperatures below 800ºF, the austenitic stainless kerosene. steels show excellent resistance at the upper service Lead–Mass transfer will be experienced to varying temperatures. degrees with any of the common engineering alloys Molten cyanide salt baths are used widely to exposed to molten lead under dynamic conditions. In surface-harden mild or low-alloy steels by the formation addition, lead is an active corrodent in static systems. of a carburized, nitrided, or carbonitrided layer on the Lead has a comparatively high solubility for a number of surface. Since a chemical reaction is an essential part metals, and therefore simple solution attack may result of the process, these salts are more corrosive than the in serious deterioration even in the absence of mass salts used purely as heat transfer media. As discussed transfer. Further, lead absorbs oxygen readily and may earlier, chromium inhibits carburization but promotes cause rapid oxidation of susceptible alloys, particularly nitriding. Nickel, however, inhibits both reactions, at the interface in an open pot where oxygen contami- therefore, stainless steels with low chromium and high nation is high. In some instances when the lead bath nickel–Type 330 for example–are used in this service. has been maintained in a reduced state by the introduc- tion of a hydrocarbon, carburization of stainless steel containers has resulted. COEFFICIENT OF THERMAL EXPANSION

The coefficient of thermal expansion of austenitic

Table 11 PHYSICAL PROPERTIES OF TYPICAL PIPING STAINLESS STEELS (ANNEALED)

Type 304 Type 316 Type 309 Type 310 Modulus of Elasticity in Tension psi x 106 (GPa) 28.0 (193) 28 (193) 29 (200) 30 (207) Modulus of Elasticity in Torsion psi x 106 (GPa) 12.5 (86.2) Density, Ibs/in3(kg/m3) 0.29 (8060) 0.29 (8060) 0.29 (8060) 0.29 (8060) Specific Heat, Btu/Ib/F (J/kg•K) 32-212ºF (0-100ºC) 0.12 (503) 0.12 (503) 0.12 (503) 0.12 (503) Thermal Conductivity, Btu/hr/ft/ft/F (Jkg•K) 212ºF (100ºC) 9.4 (0.113) 9.4 (0.113) 8.0 (0.096) 8.0 (0.096) 932ºF (500ºC) 12.4 (0.149) Mean Coefficient of Thermal Expansion x10-6/ºF (x1 0-6/ºC) 32-212ºF (0-100ºC) 9.6 (17.3) 8.9 (16.0) 8.3 (15.0) 8.8 (15.9) 32-600ºF (0-315ºC) 9.9 (17.9) 9.0 (16.2) 9.3 (16.6) 9.0 (16.2) 32-1000ºF (0-538ºC) 10.2 (18.4) 9.7 (17.5) 9.6 (17.2) 9.4 (17.0) 32-1200ºF (0-648ºC) 10.4 (18.8) 10.3 (18.6) 10.0 (18.0) 9.7 (17.5) 32-1500ºF (0-815ºC) - - 11.1 (20.0) 32-1800ºF (0-982ºC) - - - - 11.5 (20.6) 10.6 (19.1) Melting Point Range ºF 2550 to 2650 2550 2650 2650 (ºC) (1398 to 1454) (1398) (1454) (1454)

Source: Stainless Steel Industry Data

16 stainless steels is approximately 1½ times that of carbon Piping system designers should avoid the inclination steel. The design of a stainless steel pipe system must allow to base selection on general comparisons which have for this by providing more flexibility. Coefficients of thermal been published in the literature. While many of these expansion and other characteristic physical properties are comparisons appear complete with a large amount of given in Table 11. data, they are often based on one specific installation. Furthermore, the installation on which the study is based is usually tailored to take advantage of one par- PROPER IDENTIFICATION ticular material, and the data are often not valid for other specific installations. For example, it has been the experience of many Although stainless pipe is shipped from the mill with companies in the chemical and pulp and paper indus- proper identification, this identification is sometimes tries that the two materials most often vying for a particu- damaged during fabrication and handling. Carelessness lar piping installation are FRP and stainless steel. An in maintaining alloy identification can lead to the economic study conducted by one manufacturer of installation and use of the wrong alloy, which in turn nonmetallic piping (J. Yamartino, Dow Chemical Com- often results in unexpected and premature pipe failure. pany, "Installed Cost of Corrosion-Resistant Piping– If the material has lost its identification, qualitative tests 1978," CHEMICAL ENGINEERING, November 20, 1978) can and should be made. Unfortunately, field tests gives the advantage to FRP. cannot distinguish among some grades of stainless In order for FRP and stainless steel to be considered steel, so when in doubt, consult a stainless steel for the same installation, the service has to be corrosive supplier. enough to warrant going to stainless steel; and the temperature and pressure requirements must be low enough to be within the range of FRP pipe. Fur- thermore, there have been many other studies of other THE installations in which the installed cost gives the advan- tage to stainless steel. To illustrate, consider the follow- ECONOMIES OF ing study, which was made in 1972. STAINLESS STEEL STAINLESS STEEL IN VERSUS REINFORCED PLASTIC

PIPING SYSTEMS A cost comparison between stainless steel and two types of reinforced plastic for a scrubber water piping For any proposed piping installation, the design en- system at Copper Cliff, Ontario, was made by an inde- gineer will quickly narrow down a long list of available pendent engineering firm. The study indicates that piping materials to one or more that satisfy chemical, stainless steel, in normal wall thickness of Schedules temperature, and pressure requirements. More often 10S and 40S, was competitive with the best reinforced than not, stainless steels emerge as the obvious and epoxy and polyester piping systems on an installed- uncontested choice, in which case design efforts are cost basis. The cost comparison is given in Table 12. then directed toward achieving maximum economies. Dollar figures are Canadian and equivalent to .98 U.S. This includes "fine tuning" the piping layout to reduce dollars. its complexity as much as possible, choosing the Most of the stainless steel considered in the study proper stainless steel composition to avoid ''over was more expensive than Type 304; 53.8 percent of the specifying," and selecting efficient and economical total length of piping was Type 316L, 27.4 percent was fabrication and installation methods, such as shop fab- Type 304L and 9.3 percent was Type 316 and only the rication utilizing Van Stone flanging and close-radius remaining 9.5 percent was Type 304. bending. Machine-made, reinforced epoxy pipe was not Occasionally, situations arise when two or more pipe made in Canada and had to be imported from the U.S. materials appear suitable from an engineering stand- Therefore, the material cost for this system included a point, so the designer wants to base his final selection 17½ percent duty plus a small brokerage charge on an economic study. In large companies with well amounting to a total of $7,890. The hand-layed-up staffed engineering and construction departments, such polyester system was made in Canada and no duty studies are often programmed for computer analysis was included in the estimate. with much of the cost data available from previous Several grades of machine-made, reinforced epoxy projects. For small companies or applications for which piping systems were available. This estimate was based there is no previous experience, a new study is con- upon one of the better grades with the best chemical ducted. This can be a complex problem, because the resistance and a rating of 150-350 psig. (depending on costs of systems of different materials depend on many size) and a temperature rating of 250-300ºF. factors, such as system complexity, pipe sizes, availa- The system consisted of a total of 2,747 feet of piping bility of building steel for support, capability of available and 565 fittings which varied in size from one-inch to pipe fabricating facilities, etc. 14-inch as shown in Table 13.

17 Screwed fittings (150 lb) were specified for the stain- Erection Costs less steel 1½ inch and under, and butt-welded fittings Pipe Supports were specified for the larger sizes. Where welding was Pipe Erection required the low-carbon grade was utilized. Testing On the basis of this cost comparison, the stainless Incidental Work steel system was chosen because it was more eco- nomical than either a machine-made epoxy system or a hand-layed-up polyester system. There would have been an even greater cost differential if an all- lightweight stainless steel system could have been Design Costs used. If the installation were to be installed in the United Either models or piping arrangement drawings are States, the epoxy system would have been more com- required on any major scope of piping work. They serve petitive but still higher priced ($128,650 vs $128,100 for the same purpose, namely to route pipe runs between the installed stainless steel). the pieces of equipment they are connecting. The re- It should be stressed that every installation has to be quirements will be the same for all the piping materials considered separately, and there are a number of con- being compared; i.e. stainless steel, FRP, or plastic- siderations to take into account. A quick check of piping lined carbon steel. costs alone is likely to indicate a definite cost advan- Pipe support design and detail sketching are interre- tage for reinforced plastic. There are, however, factors lated. They will be dependent on the kind of piping favoring lightweight, thin-wall stainless steel piping that installed. For example, FRP piping requires the most should be considered. For example, the cost figures for support, including separate supports at each valve and stainless steel cited in this example could be consid- other special considerations covered in the manufac- erably less if Van Stone lapped joints were used and if turers design manuals. (Note: Thermoplastic pipe sys- bending were substituted for many of the elbows in the tems would require more support than FRP.) The pre- smaller diameter pipe. ferred routing of the three systems being compared may It soon becomes apparent that each system must be differ somewhat to take advantage of the most estimated in considerable detail to reach a trustworthy economical layout to suit fabrication or the use of cost comparison. standard pieces. Plastic lined steel pipe can generally A comparative estimate should reflect a comparison follow the route of stainless steel pipe although the cost of costs for each of the following elements (their in- and availability of standard or special fittings may be- dividual significance is reviewed in the following text): come a problem. It should also be noted that the Design Costs smaller sizes of pipe valves and fittings are not avail- Models able for FRP or plastic-lined steel systems. Piping Arrangement Drawings Detail Sketching Pipe Support Design Material Costs Pipe Material Costs Fittings Valves It is common practice to purchase FRP and plastic- Supporting Structures lined steel pipe prefabricated. Stainless steel pipe and Miscellaneous Material fittings can be purchased and shop fabricated into a Fabrication Costs piping system locally at the construction site. For small Field Fabrication projects it may be more economical to purchase the Shop Fabrication pipe prefabricated. These alternatives are discussed Purchase of Fabricated Pipe under Shop Fabrication.

Table 12 COST COMPARISON FOR GLASS-REINFORCED PLASTIC PIPING SYSTEMS VS STAINLESS STEEL IN CANADIAN CHEMICAL PLANTa

Estimated Cost, Canadian Dollarsb System Material Labor Total Machine-made, glass reinforced epoxy (high quality) $53,090c $83,450 $136,540

HLU Glass reinforced polyester made in accordance with Canadian Government Specifications Board Standard 41-GP-22 (for 125 psig, 0 - 100ºF) $58,422 $83,450 $141,872

Types 304, 304L, 316 and 316L Stainless steel– Schedule 40S for 1½ in. piping and below, Schedule 10S for 2 in. piping and over $56,930 $71,170 $128,100

(a) Estimates by independent engineering firm. (c) System has to be imported into Canada from U.S. and is subject to (b) Canadian dollar floating at time of estimate–exchange rate, duty of 17½% plus brokerage charge. This comes to $7,890; $1.00 U.S. equal to $.98 Canadian. therefore, cost in U.S. would be $45,200 for material, $128,650 for total, times .98.)

18 Table 13 suit the fabricating methods available. As an example, PIPING BREAKDOWN FOR ESTIMATE savings can be effected in a combination by routing the AISI Size Quantity Number pipe so that there is space for machine access to pro- Type Schedule (inches) (feet) of Fittings vide for the bending and lapping operations. 304 40S 1½ 115 18 For small piping projects that must be carried out 304 40S 1 145 73 with a minimum of shop facilities, purchase of 304L 10S 8 300 30 304L 10S 6 98 32 prefabricated pipe should be evaluated. Custom 304L 10S 4 40 4 fabricating shops are available with the capability of 304L 10S 3 195 70 short radius bending and flare-lapping stainless steel 304L 10S 2 120 33 pipe. 316 40S 1 255 79 316L 10S 14 70 7 Stainless steel pipe has an advantage over competi- 316L 10S 12 60 6 tive materials since last minute field modifications can 316L 10S 10 65 16 utilize conventional fittings and welding methods, 316L 10S 8 227 45 whereas FRP or plastic-lined pipe generally require 316L 10S 6 382 66 316L 10S 4 245 42 special fittings as well as special techniques and tool- 316L 10S 3 155 24 ing. In the case of plastic-lined steel pipe, this means 316L 10S 2½ 15 2 liner flaring tooling for the various sizes. In the case of 316L 10S 2 160 18 an FRP system, it may mean tooling suited to forming the proprietary joint arrangement of the particular pipe manufacturer.

Fittings are generally high-cost items in FRP systems. They are frequently an even greater cost item in plastic-lined steel systems. The material cost for these Erection Costs systems increases much more rapidly with increasing Somewhat higher erection costs might be expected complexity than does the cost of a stainless steel sys- with FRP due to more frequent support than that re- tem. FRP and plastic-lined valves are likewise much quired for stainless steel pipe. In the case of plastic- more expensive than stainless steel valves. The mate- lined steel pipe, there are usually more erection joint rial requirements for supporting structures will usually flanges to be bolted up, resulting in a direct cost in- be somewhat greater for FRP and plastic-lined steel crease. than for a stainless steel system. Testing is required for all piping systems. Some FRP The requirements for miscellaneous materials, such manufacturers advocate the practice of test-pressure as paint, will vary according to the system. FRP may application and release for 5 to 10 pressure cycles in require an ultra-violet resistant paint coat, while plastic- order to assure integrity of the system. This recommen- lined steel pipe and flanges will require painting. The dation represents an added cost consideration com- steel backup flanges on the stainless steel system will pared to stainless steel or plastic-lined steel where a require corrosion protection by painting (an alternative one-cycle test is usually adequate. is galvanizing). Also, the supports should be painted, Incidental erection labor is, of course, required for while bolting is sometimes galvanized. painting, insulation, etc., already discussed under mis- Generally, FRP does not require insulation because cellaneous materials. the plastic is, in itself, a good insulator. However, some In conclusion, it is obvious that comparing the costs insulation may be required for ambient heat or fire pro- of corrosion-resistant systems of various materials is a tection of the FRP pipe. complex problem. Very few overall conclusions can be reached. There is no known shortcut solution. The as- sumptions used for a general comparison may or may not be valid for a particular system. A detailed analysis Fabrication Costs of the specific installation is the only reliable cost guide. Field fabrication of pipe at the point of installation is extremely inefficient. Estimates of labor for field fabrica- tion are often 50 percent higher than for the identical APPLICABLE work done under shop conditions. The concentration of work in a shop may also increase the shop work load sufficiently to justify improved shop facilities. For STANDARDS example, the addition of equipment to make flared Van Stone laps may reduce fabricating labor 15 percent and eliminate the cost of stub ends. The addition of modern AISI short-radius bending facilities may reduce fabricating labor another 20 percent in addition to eliminating the The American Iron and Steel Institute recognizes 57 purchase of elbows. In both cases, savings in labor stainless steels as standard, and indicates their chemi- results from the elimination of the welds at the fittings, cal composition limits. A table of the AISI stainless steel two in the case of the elbow and one in the case of the grades most commonly used for piping and their corre- stub end. sponding UNS numbers, typical properties and appli- Economies can often be effected by detailing pipe to cable ASTM specifications are included in Appendix A.

19 ASTM SPECIFICATION SUMMARY

The American Society for Testing and Materials covers The characteristics of distinct piping systems may be AISI grades and proprietary grades of stainless steel in recapped by pipe codes for reference and possible use their specifications. They also add a number of other for piping fluids not yet identified. See Appendix E. requirements, such as dimensional tolerances, heat treatment, mechanical property requirements, etc. and THE PROCESS PIPING DIAGRAM in this way are more definitive and restrictive. This is a type of flow diagram. All significant pipe lines ASME complete with valves and equipment are assigned line numbers and shown. Sizes are based on flow require- Piping may be considered to fall under the fired or ments. Information on piping system specifications, in- unfired pressure vessel codes of the American Society sulation, tracing, etc. is added as it is developed. See of Mechanical Engineers. These codes are used for Appendix F. design. Allowable design stresses for code piping are defined in the codes. SELECTION OF MATERIALS OF CONSTRUCTION

ANSI Usually this step occurs simultaneously with the preparation of the index of fluids and gases, although it The American National Standards Institute has prepared may be delayed until a cost analysis can be made. Cost codes for pressure piping. These fall under the several comparisons, reliability predictions, corrosion allow- sections of B31 listed in Appendix C. ANSI B31.3 was ances and product contamination must be given con- written specifically for chemical plants and petroleum sideration. refineries.

DEVELOPMENT OF PIPING THE DESIGN, SYSTEM SPECIFICATIONS Utilizing the size requirements from the process pip- FABRICATION ing diagram (Appendix F) the wall thickness, and hence the pipe schedule, is calculated from temperature, AND ERECTION pressure and corrosion allowances. Gasket materials, fittings, joints, fabrication techniques, valves, weld testing, and cleaning requirements are then de- OF PLANT termined. Allowable stresses are available in the appli- PIPING SYSTEMS cable ANSI B31 Codes (Appendix C). THE PROCESS MODEL The following sequence indicates the natural devel- opment of the selection and design of a piping system. A scale model of the proposed installation is fre- The discussion is provided by Addison Hempstead. The quently made, which is useful for many purposes such sequence is similar to that in use by some of the major as: chemical companies. 1. Visualizing equipment arrangement to assure space for operating access and maintenance. INDEX OF FLUIDS AND GASES 2. Planning installation of the facilities. 3. Avoiding interferences. It is appropriate to begin with an alphabetical list of 4. Pipe sketching and takeoff of construction mate- the products and services that will require piping sys- rials. tems (Appendix D is a hypothetical listing which serves 5. Operator training. as a basis for discussion in this section). The piping The detail of the model depends on its complexity material, maximum operating pressures and tempera- and the specific design. Models usually include all tures and other pertinent information are tabulated for significant pipelines with their valves and flanged joint each item. If sizes or operating conditions cover a locations. broad range for a given service, it may be desirable to Final models are usually scaled ¾ inch equals one assign two or more pipe codes to most effectively foot, although a preliminary study model is sometimes satisfy the requirements (Example: Items 1 and 8, Ap- made at a scale of 3/8 inch equals one foot. pendix D). When a line carrying any one of these ser- PIPING FLEXIBILITY ANALYSIS vices is added to a piping diagram, the proper pipe code can be selected from this list. This procedure provides for an orderly assignment of piping specifi- ANSI B31.3, The Code for Chemical Plant and Petro- cations, and it may be maintained as a standard for leum Refinery Piping, requires that piping systems shall reuse on future installations having the same service. have sufficient flexibility to prevent thermal expansion or This will save design time otherwise required to rede- contraction or movements of pipe supports and ter- velop the pipe code requirements. minals from causing: Failure of piping or supports from

20 overstress or fatigue, leakage at joints, or detrimental goes from the shop to the field for erection, it should be stresses or distortions in piping or in connected pumps, sent complete with all of the valves, bolts, nuts, hangers turbines, valves, etc. and gaskets. A formal analysis of piping flexibility is not always If possible, steam tracing and insulation should be required to meet code requirements. For details the applied before the piping leaves the shop. The im- reader is referred to the ANSI B31 Codes. provements in productivity and quality come both from the better facilities that can be made available at a shop ESTIMATING and from the conveniences in material availability and better working conditions. Pipe should follow a rudi- At this point in the development of design informa- mentary production line thru the shop. tion, it is usually possible for an experienced estimator It should be noted that stainless steels are generally to develop an estimate to any degree of detail required. more easily fabricated (for repair or replacement) in the Organizations with highly developed estimating data field as compared with other piping materials. often can calculate average costs based on a typical Welding–There are four principal processes for fu- pipe line run, which is then multiplied by a simple count sion welding stainless steels. They are: of the number of pipelines. This provides an estimate on 1. Shielded Metal Arc Welding (SMAW), using a broad scope. However, in order to accurately compare coated electrodes. costs of alternate pipeline materials, it may be 2. Gas Tungsten Arc Welding (GTAW or TIG), necessary to calculate the costs of individual elements, using an inert gas (such as argon) to protect the such as pipe, fittings, valves, hangers, etc., which may weld zone from the atmosphere. then be built up into a detail estimate of a single pipe 3. Gas Metal Arc Welding (GMAW or MIG), also an line. inert gas shielded process. 4. Submerged Arc Welding (SAW), which is seldom PRELIMINARY COMMENTS AND used on piping except for heavy sections. APPROVALS In the submerged arc process shielding is provided by a granulated flux covering the weld area and welding electrode. Automated or semi-automated welding It is appropriate at this point to review the model, the equipment is available. Table 14 shows time study data index of fluids and gases, the specifications for the for GTAW welding of eight sizes of stainless steel pipe. piping systems, corrosion data, system safety under Bending–Modern "push" bending equipment is emergency conditions, maintainability of the piping, available that will accomplish bends at conventional experience with the operation of similar facilities etc., Long Radius (bend radius = 1½ x nominal pipe diam- among the interested parties. This is the "last chance" eter) radii with wall thinning of 20 percent or less. This to make changes without incurring major cost penal- operation eliminates the cost of the purchased elbow ties. and the two welds required for its installation, with sav- PIPING SKETCHES ings up to approximately 35 percent realized in some sizes. Flared (Van Stone) laps–The ANSI B31 Series of pipe Isometric pipe sketches are prepared from a combi- codes permits the use of laps formed by flaring the end nation of the model and equipment arrangement data of the pipe in most applications. (ANSI B31.3-76 that provide precise connection locations. These paragraph 306.4.2). Flared laps can be formed with sketches and the requisite material takeoff may be either a smooth or modified spiral finish depending on drawn manually or computer generated. Computer the type of roller used for flaring. This technique elimi- generated sketches are generally more accurate. nates the cost of a purchased stub end and the weld Computer programs are available that also generate required for its installation. shop (traveller) cards providing exact cut lengths for each piece of pipe as well as shop routing for any bending or end preparation (laps, flanges, bevels or ERECTION threading). To maintain the pattern of labor effectiveness, pipe erection in the field should follow a production se- Construction Phase quence. When a line has been received complete in the field, it can be erected most efficiently by first installing FABRICATION the hangers, followed by sequential erection of the pipe and bolting up the flanges. Efficient tools, such as rachet wrenches, are a labor-saving investment. Spe- General considerations–Craft labor is more effi- cialized crews may be utilized for the various opera- cient working in a shop than at the pipe installation site. tions where the scope of the job warrants, such as a For economy, productivity and quality, any large vol- crew for hangers, one for pipe erection, one for testing, ume of pipe, as a general rule, should be shop fabri- etc. cated. The shop, to be efficient, should have suitable modern equipment and it must have some effective production control system. Material should not be re- TESTING leased to the shop for fabrication until all the material required for a line or other unit has been assembled. Testing requirements are usually prescribed by the Since labor is usually more than half the cost of a piping specifications. Shop testing of individual fabricated system, it must be used efficiently. When a pipe line sections followed by testing the erected pipe may 21 prove economical. It is generally permissible to make a An excellent presentation of a method for establish- preliminary air test at not more than 25 psig prior to ing nondestructive examination (NDE) levels for fluid making a final hydrostatic test. This preliminary air test services in chemical plants and refineries is in an arti- is useful in locating major leaks before the system is cle, ''A Quantitative Method for Determining NDE filled with a fluid that must be drained before the leak Levels" by R. Getz. (HEATING/PIPING/AIR CONDI- can be corrected. TIONING, August 1979.)

Table 14 TIME STUDY DATA FOR WELDING THREE SIZES OF STAINLESS STEEL PIPEa

Time, hrb,c Pipe size, in. 1 1¼ & 1½ 2 2½ 3 4 6 8 Time required to make one butt weld Schedule 5S 0.067 0.083 0.083 0.1 0.1 0.112 0.166 0.333 Schedule 10S 0.1 0.1 0.133 0.166 0.2 0.232 0.333 0.5 Schedule 40S 0.25 0.3 0.333 0.415 0.415 0.5 0.75 1.166

Time required to align, tack, and weld one 90 deg elbow Schedule 5S 0.465 0.5 0.5 0.535 0.535 0.57 0.675 1.0 Schedule 10S 0.57 0.57 0.6 0.665 0.735 0.8 1.8 1.333 Schedule 40S 0.866 0.93 1.0 1.1 1.16 1.333 2.0 2.5

Time required to align, tack, and weld one 45 deg elbow Schedule 5S 0.666 0.666 0.666 0.7 0.7 0.73 0.89 1.166 Schedule 10S 0.735 0.75 0.75 0.83 0.9 1.0 1.166 1.75 Schedule 40S 1.0 1.0 1.166 1.333 1.333 1.5 2.1 2.65

Time required to align, tack and weld one tee Schedule 5S 1.0 1.1 1.25 1.33 1.5 1.5 1.75 2.0 Schedule 10S 1.5 1.5 1.5 1.5 1.65 1.65 2.0 3.5 Schedule 40S 2.0 2.0 2.0 2.25 2.25 2.5 3.5 4.0

Time required to align, tack and weld one slip-on flange Schedule 5S 0.166 0.166 0.25 0.333 0.333 0.42 0.5 0.75 Schedule 10S 0.166 0.166 0.3 0.42 0.42 0.5 0.666 0.75 Schedule 40S 0.25 0.3 0.33 0.5 0.5 0.58 0.835 1.25

Time required to align, tack and weld one butt-weld flange Schedule 5S 0.25 0.25 0.33 0.33 0.42 0.5 0.6 0.835 Schedule 10S 0.333 0.333 0.5 0.5 0.5 0.666 0.75 1.0 Schedule 40S 0.42 0.42 0.666 0.666 0.75 0.835 1.0 1.333

a All values are based on gas tungsten-arc welding of austenitic stainless b Add 10 minutes to each fabrication (tee, elbow, pipe joint, etc.) for steel, using 3/32 and 1/8 in. diam filler metals, where required. purging, if a purge is required. c These times do not include cutting and beveling. Source: H. A. Sosnin, "The Joining of Light-Wall Stainless Steel Piping," WELDING JOURNAL, October 1967. BIBLIOGRAPHY April 1978, Committee of Stainless Steel Produc- ers, American Iron and Steel Institute, Washington, 1. "Design Guidelines for the Selection and Use of D.C. Stainless Steel," April 1977, Committee of Stainless 7. "The Role of Stainless Steels in Desalination," April Steel Producers, American Iron and Steel Institute, 1974, Committee of Stainless Steel Producers, Washington, D.C. American Iron and Steel Institute, Washington, 2. "High Temperature Characteristics of Stainless D.C. Steels," April 1979, Committee of Stainless Steel 8. "Stainless Steels: Effective Corrosion Control in Producers, American Iron and Steel Institute, Water and Waste-Water Treatment Plants," March Washington, D.C. 1974, Committee of Stainless Steel Producers, 3. "Welding of Stainless Steels and Other Joining American Iron and Steel Institute, Washington, Methods," April 1979, Committee of Stainless Steel D.C. Producers, American Iron and Steel Institute, 9. "Stainless Steels in Ammonia Production," Washington, D.C. November 1978, Committee of Stainless Steel 4. "The Role of Stainless Steels in Petroleum Refining," Producers, American Iron and Steel Institute, April 1977, Committee of Stainless Steel Producers, Washington, D.C. American Iron and Steel Institute, Washington, D.C. 10."Stainless Steels for Acetic Acid Service," April 5. "Effective Use of Stainless Steels in FGD Scrubber 1977, Committee of Stainless Steel Producers, Systems," April 1978, Committee of Stainless Steel American Iron and Steel Institute, Washington, Producers, American Iron and Steel Institute, D.C. Washington, D.C. 11.''Joining of Light Wall Stainless Steel Piping," 6. "Stainless Steels for Pumps, Valves and Fittings," WELDING JOURNAL, October 1967 22 APPENDIX A CHEMICAL COMPOSITIONS AND TYPICAL PROPERTIES OF STAINLESS STEELS COMMONLY USED IN PIPING SYSTEMS Chemical Analysis, % Mechanical Properties of Solution (Single Values are Maximums Except as Noted) Annealed Material at Room Temperature Corresponding ASTM Spec’s

Yield Elongation For Piping Components ** AISI Tensile Strength in 2"

Type Strength (Offset 0.2%) (50.80mm) Pipe & AISI (UNS) Cr Ni C Mn Si Mo P S Other ksi MPa ksi MPa % Tubing Fittings Forgings Castings Characteristics TYPE 304 18.0- 8.0- 0.08 2.0 1.0 – 0.045 0.03 85 586 35 241 50 A312 A403 A182 A296 The most commonly used 304 (S30400) 20.0 10.5 A409 A351 stainless piping material 304L 18.0- 8.0- 0.03 2.0 1.0 – 0.045 0.03 78 538 34 234 55 A312 A403 A182 A296 Lower carbon than Type 304 304L (S30403) 20.0 12.0 A409 A351 reduces potential for carbide precipitation during welding 309 22.0- 12.0- 0.20 2.0 1.0 – 0.045 0.03 90 621 45 310 45 A312 A403 A182 A296 For high temperature 309 (S30900) 24.0 15.0 A409 A351 applications 309S 22.0- 12.0- 0.08 2.0 1.0 – 0.045 0.03 90 621 45 310 45 A312 403 A182 A296 Low carbon modification of 309S (S30908) 24.0 15.0 A409 A351 Type 309 reduces potential for carbide precipitation 310* 24.0- 19.0- 0.25 2.0 1.5 – 0.045 0.03 95 655 45 328 45 A312 A403 A182 A296 Better high temperature 310 (S31000) 26.0 22.0 A409 A351 resistance than Type 309 but more prone to welding

problems 310S* 24.0- 19.0- 0.08 2.0 1.5 – 0.045 0.03 95 655 45 328 45 A312 A403 A182 A296 Low carbon modification of 310S (S31008) 26-0 22.0 A409 A351 Type 310 reduces potential for carbide precipitation 316 16.0- 10.0- 0.08 2.0 1.0 2.0-3.0 0.045 0.03 85 586 35 241 50 A312 A403 A182 A296 Molybdenum increases 316 (S31600) 18.0 14.0 A409 A351 corrosion resistance of this alloy compared to

Type 304 316L 16.0- 10.0- 0.03 2.0 1.0 2.0-3.0 0.045 0.030 80 552 35 241 55 A312 A403 A182 A296 Lower carbon than Type 316 316L (S31603) 18.0 14.0 A409 A351 reduces potential for carbide precipitation during welding 321 17.0- 9.0- 0.08 2.0 1.0 – 0.045 0.030 Ti, 5xC 84 586 35 241 50 A312 A403 A182 A246 Stabilized for service in 321 (S32100) 19.0 12.0 min. A409 A351 800-1600F range 347 17.0- 9.0- 0.08 2.0 1.0 – 0.045 0.030 Cb+ta, 85 586 35 241 45 A312 A403 A182 A296 Similar to Type 321 347 (S34700) 19.0 13.0 10xC min. A409 A351

* Composition of Type 310 and 310S pipe and tubing varies slightly from AISI values shown. See ASTM A312.

** Composition and Mechanical Properties may vary from those shown, see the ASTM Spec for actual values. Due to space limitations, only the most common ASTM Specs have been listed.

23 APPENDIX B

Useful Guides In Making A Selection Of Material For A Piping System

I. General Considerations F. Branches and taps can be provided without spe- cial fittings at a minimum cost. A. Consider the safety inherent in stainless steel G. Requires fewer supports. compared to alternative materials by virtue of its 1. Requires less support for runs. A minimum of properties, methods of joining and history of ser- two supports are often provided for each vice, reliability. length of pipe for practical handling in instal- 1. Does the fluid have hazardous properties lation and removal. that need special consideration? 2. Valves are generally supported by the piping 2. What quantity of fluid could be released by a in a metallic pipe system. Special valve piping failure? support is usually required in most non- 3. What would be the effect on the environ- metallic piping systems. ment? H. Thermal expansion of stainless steel is greater 4. What potential exists for personnel expo- than that of carbon steel but considerably less sure? than that of most nonmetallic piping materials. B. Would special provisions be required to protect Lined metallic piping systems sometimes fail be- plastic or reinforced thermo-setting resin pipe cause of the difference in the expansion of the against possible failures such as: thermal insula- pipe and liner. tion, shields or process controls to protect from I. A metallic system offers greater safety for com- excessive heat or thermal shock; armor, guards, pressed air or gas service applications. This is barricades or other protection from mechanical especially true for larger systems with a substan- abuse? tial amount of potential energy stored in the com- C. Is a metallic system preferred tofacilitate ground- pressed gas. ing static charges? J. Carbon and low-alloy steels are generally more D. How important is continuity of service? susceptible to corrosion than stainless steels, 1. What are the relative reliabilities of the pipe, leading to reduced life and potential contamination fittings, and joints of the alternative system of the product. materials under consideration? K. The maximum and minimum temperatures for E. Is insulation an adequate precaution to protect carbon and low-alloy steel and nonmetallic piping piping against failure under fire exposure? systems are limited compared to stainless steels. F. Are the thread sealant, packing, gasket material, See the B31. Piping Codes for limitations. etc., compatable with the fluid being handled? L. Is the pipe material compatible with the fluid being handled? II. Metallic Pipe 1. Consider the possibility of embrittlement A. Ability of stainless steel pipe to withstand higher when handling strong caustic fluids in carbon and lower temperatures than plastic, reinforced or low-alloy steel. thermo-setting resin, or plastic-lined carbon steel 2. Consider the increased possibility of hyd- pipe. rogen damage under some conditions when B. Ability to withstand full vacuum over a wide tem- carbon or low-alloy steel piping material is perature range. exposed to hydrogen or aqueous acid C. Greater tolerance for steam tracing than non- solution. The austenitic stainless steels re- metallic or lined systems. sist hydrogen effects. D. Readily steam jacketed. M. Stainless steel pipe has excellent resistance to E. Minimum of flanged joints required. most atmospheric corrosion. Does not require 1. Reduces cost of piping. painting or other protection from sunlight, oxygen 2. Reduces leakage potential and maintenance or ultraviolet exposure, as is the case with some cost. nonmetallic materials.

24 III. Nonmetallic Pipe H. Flanged joints of nonmetallic materials are sus- A. Principal Classes ceptible to gasketing and leakage problems due 1. Thermo-plastic to the low modulus of elasticity of the flanges. 2. Reinforced thermo-setting resin I. Nonmetallic lines generally require more closely 3. Special materials, (ceramic, asbestos- spaced supports and guiding than metallic pip- cement, glass, impregnated graphite) gen- ing. This may necessitate supplementary inter- erally are limited to very specialized appli- mediate steel structures. cations. J. Valves generally require independent support. B. The applications of thermo-plastic pipe are se- verely limited by service temperature consid- IV. Lined Metallic Pipe erations. A. Linings are available of materials resistant to C. Thermo-plastics are excluded from use in flamm- most chemical environments. able liquid service above ground by the B31.3 B. Fittings are required for all branches and taps. Code. All pipe joints are flanged. D. Nonmetallic pipe is not susceptible to electrolytic C. Less support is required than for nonmetallic corrosion. pipe, particularly in smaller sizes. Valves gen- E. Nonmetallic pipe may be permeable by toxic erally do not require independent support. materials. D. Steam tracing or vacuum service may result in 1. Internal to external permeation. liner buckling. 2. External to internal (buried lines in contami- E. Thermal cycling may cause liner to crack at nated soil). flanges. F. Nonmetallics are very resistant to corrosion in F. Lined flanged fittings are required at all some classes of fluids such as non-oxidizing branches, taps and changes in direction. These acids and chlorides. added flange joints increase both the cost and G. Nonmetallic pipe may require insulation or other potential for leakage. provisions for protection from any potential fire G. Field or shop fabrication requires special fixtures exposure. for forming the liner over the flange face.

APPENDIX C Status of ANSI B31 Code for Pressure Piping Standard Number and Designation Scope and Application Remarks B31.1.0 Power Piping For all piping in steam generating stations. *

B31.2 Fuel Gas Piping For fuel gas for steam generating stations * and industrial buildings.

B31.3 Chemical Plant and For all piping within the property limits of * Petroleum Refinery facilities engaged in the processing or Piping handling of chemical, petroleum, or related products unless specifically excluded by the code.

B31.4 Oil Transportation For liquid crude or refined products in * Piping cross-country pipe lines.

B31.5 Refrigeration Piping For refrigeration piping in packaged units * and commercial or public buildings.

B31.7 Nuclear Power Piping For fluids whose loss from system could Withdrawn; see Section cause radiation hazard to plant personnel or 3, ASME Boiler & PV general public. Code

B31.8 Gas Transmission For gases in cross-country pipe lines as well * and Distribution as for city distribution lines. Systems

* Addenda are issued at intervals between publication of complete editions. Information on the latest issues can be obtained from the American Society of Mechanical Engineers, New York, NY

25 APPENDIX D Index of Fluids and Gases Max. Operating

Product Condition Test Pipe or Degrees Press. Basic Code Item Service PSIG ºF ºC PSIG Material Number Remarks 1 Air, Plant 150 375 190 Copper P14 ¾" and smaller 150 300 148 Steel P13 On-Off valve-B120 for Galv. ½"–2"; G92JH for 3"

2 Oil, Lubrication 150 300 148 304 SST P10 Tubing

3 Process Piping 175 350 176 304 SST P16A

4 Steam Tracers, 1000 600 315 304 SST P10 Tubing Acid Exposure

5 Steam, 50 PSIG & 50 300 148 Steel P18 Lower

6 Water, 120 220 104 Steel P11 Use X11A Aboveground, Ball Valve

7 Water, 50 300 148 Steel P19 Condensate

8 Water, 150 376 190 304 SST P16 Demineralized 1400 200 93 304 SST P17

9 Water, Process 150 500 260 Steel P12 A.G. 3" & Larger 220 150 65 Steel P12A

10 Water, Process, 150 375 190 304 SST P16 Hot

11 Water, Process 150 150 65 Cast Iron P15 Underground Cement Lined

APPENDIX E Pipe Code Summary Max. Operating Condition Pipe Degrees Code Basic Number PSIG ºF ºC Material Remarks

P10 1000 600 316 304 SST Tubing P11 125 220 104 Steel P12 150 500 260 Steel P12A 220 150 65 Steel P13 175 330 148 Steel-Galvanized P14 150 375 190 Copper P15 150 150 65 Cast Iron Cement Lined P16 150 375 190 304 SST P16A 175 350 176 304 SST P17 1500 250 120 304 SST P18 75 350 176 Steel P19 100 340 171 Steel

26

APPENDIX F Typical Process Piping Diagram

Line Numbers (a) Numbers allotted 1-99 (b) Last number used 7 (c) Numbers canceled 1

(a) Record Numbers allotted to this diagram in this block. (b) Record last number used in this block. (c) Record canceled numbers of those allotted in this block.

Valve

Line Number and Direction of Flow

27