Exhaust Systems

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APPLICATION AND INSTALLATION GUIDE

EXHAUST SYSTEMS

Contents

Exhaust Systems ...... 1

System Components ...... 2

Exhaust Manifold ...... 2

Dry Manifolds...... 2

Watercooled Manifolds ...... 2

Air Shielded Watercooled Manifolds ...... 3

Heat Shielding ...... 3

Blankets (Soft Manifold Shields) ...... 3

Hard Wrap (Hard Manifold Shields)...... 4

Guards and Shields ...... 4

Turbochargers ...... 4

Wastegate ...... 4

Flexible Exhaust Connections ...... 5

Flexible Metal Hose and Bellows ...... 5

Slip Joints...... 6

Silencer ...... 8

Silencer Rating ...... 8

Silencer Selection ...... 8

Exhaust System Piping ...... 10

Exhaust System Design ...... 10

Exhaust Thimbles...... 12

Exhaust Pipe Insulation...... 12

Water Ingress Prevention ...... 13

Exhaust System Backpressure ...... 13

Measuring Backpressure ...... 14

Calculating Backpressure ...... 16

Equivalent Length of Straight Pipe...... 16

Combined Exhaust Systems ...... 16

Pipe Support Considerations...... 17

Thermal Growth...... 17

Turbocharger Loading...... 17

Loading Calculations ...... 17

Vertical Exhaust...... 18

Horizontal Exhaust ...... 18

Vibration Transmission ...... 20

Exhaust Discharge ...... 20

Common Exhaust Stack...... 20

Power Module or Drop-Over Enclosure...... 21

Cleanliness During Installation ...... 23

Slobber or Wet Stacking ...... 23

Exhaust Systems for Specific Applications...... 24

Marine Dry Exhaust System ...... 24

Marine Exhaust Ejector Automatic Ventilation System ...... 24

Duct Design Guidelines...... 24

Marine Wet Exhaust System ...... 30

Exhaust Risers...... 31

Water Lift Silencers...... 31

Wave Action and Wet Exhaust Systems ...... 32

Surge Chamber...... 33

Valve in Exhaust Discharge ...... 34

Hose vs. Rigid Exhaust Pipe ...... 34

Location of Exhaust Discharge Opening ...... 34

Valves in Exhaust Water Cooling Lines ...... 34

Foreword This section of the Application and Installation Guide generally describes wide-ranging requirements and options for the Exhaust System on Cat® engines listed on the cover of this section. Additional engine systems, components and dynamics are addressed in other sections of this Application and Installation Guide. Engine-specific information and data are available from a variety of sources. Refer to the Introduction section of this guide for additional references. Systems and components described in this guide may not be available or applicable for every engine. The listing below indicates which exhaust component designs are utilized by each Cat engine model. Refer to the Price List for specific options and compatibility.

 =Standard  =Optional - =Not Available 3126B C7 C-9 C9 C-10/C-12 C11/C13 3406E C-15/C-16 C15/C18 3412E C27/C32 3500 C175 3600 G3300/G3400 G3500 G3600

Dry Manifolds               -   Watercooled Manifolds - - - -  -   -  -  - -   - Air Shielded Watercooled ------  - Manifolds Soft † Shields ------ -  - -  Hard Shields - - - - -      -    -  - Exhaust Silencers                 

† Soft shield covers turbocharger but not manifolds.

Information contained in this publication may be considered confidential. Discretion is recommended when distributing. Materials and specifications are subject to change without notice.

CAT, CATERPILLAR, their respective logos, “Caterpillar Yellow” and the POWER EDGE trade dress, as well as corporate and product identity used herein, are trademarks of Caterpillar and may not be used without permission.

Application and Installation Guide Exhaust Systems

Exhaust Systems Well-designed exhaust systems collect exhaust gases from engine cylinders and discharge them as quickly and silently as possible. Primary system design considerations include:  Minimizing resistance to gas flow (back pressure) and keeping it within the limits specified for the particular engine model and rating to provide maximum efficiency.  Reducing exhaust noise emission to meet local regulations and application requirements.  Providing adequate clearance between exhaust system components and engine components, machine structures, engine bays, enclosures and building structures to reduce the impact of high exhaust temperatures on such items.  Ensuring the system does not overstress engine components such as turbochargers and manifolds with excess weight. Overstressing can shorten the life of engine components.  Ensuring the exhaust system components are able to reject heat energy as intended by the original design. “Dry” turbochargers and manifolds should not be wrapped or shielded without Cat components or Caterpillar approval.

SECTION CONTENTS

System Components ...... 2  Slobbering  Manifolds Exhaust Systems  Heat Shielding for Specific Applications...... 23  Turbochargers  Marine Dry Exhaust  Connections  Ejector Automatic Ventilation  Silencers  Duct Design Exhaust System Piping ...... 9  System Design  Marine Wet Exhaust  Pipe Support Considerations  Water Lift Silencers  Exhaust Discharge  Wave Action on Wet Exhaust  Thimbles  Hose vs. Pipe  Water Ingress  Discharge Opening  Backpressure

 Cleanliness

System Components

The main components of an Dry Manifolds exhaust system include, but are not Dry manifolds are the preferred limited to, the exhaust manifold, manifold design. They are cost turbocharger, wastegate, piping and effective and by providing the the silencer. The individual maximum possible exhaust energy components and their function are to the turbocharger, they offer the explained below. highest overall efficiency. Dry Exhaust Manifold manifolds, however, also radiate the Engine exhaust manifolds collect most heat and reach the highest exhaust gases from each cylinder surface temperatures. and channel them into an exhaust Some applications require low outlet. The manifold is designed to manifold surface temperatures. give minimum backpressure and For example, the Mining Safety turbulence. Cat products utilize dry, and Health Agency (MSHA), the watercooled and air shielded Atmospheres Explosibles (ATEX) watercooled (ASWC) manifold directive and marine societies require designs, based on application and that engine surface temperatures design requirements. Refer to remain below 200°C (400°F) for Figure 1 for manifold configurations. certain mines. Heat shields and blankets are available for some Cat products to meet lower surface temperature requirements. A few marine products offer optional watercooled manifolds. Gas engines run with a higher exhaust temperature compared to diesel engines. Due to these high exhaust temperatures, some models utilize watercooled or air shielded watercooled manifolds. Watercooled Manifolds Passages within watercooled manifolds allow engine jacket coolant to flow around the manifold

removing heat otherwise carried by Figure 1 exhaust gases. Surface temperatures of watercooled manifolds are considerably lower than those of dry manifolds, however heat rejection to

©2013 Caterpillar Page 2 All rights reserved. Application and Installation Guide Exhaust Systems the jacket water is increased by 20 installation type, environment and to 40 percent. This increase requires legislative requirements. Guards a larger capacity cooling system. may also be an effective means of Watercooled manifolds also reduce providing protection. Shields that are exhaust heat energy delivered to the designed and supplied by Caterpillar turbocharger. This requires the use are fit for this purpose. Any of an appropriately matched customer fitted shields must be turbocharger for maximum carefully designed and applied to efficiency. The turbocharger used on ensure that damage to the engine dry manifold applications may not be does not result. Wraps and shields, suitable for use on watercooled especially those not provided by applications. Caterpillar, must be cautious of increasing component skin Air Shielded Watercooled Manifolds temperature. Significant airflow Air shielded watercooled manifolds around the shield can help reduce (ASWC) make use of an insulating increases in component skin air cavity between the exhaust temperature. manifold and the water shield. Engine water circulates around the Blankets (Soft Manifold Shields) air shield but does not come into Blankets are made of an insulating direct contact with the inner layer of material with a thermal cloth manifold. This reduces the necessary outer layer. Most blankets will be jacket water cooling load and held in place with stainless steel maintains higher exhaust energy springs or wire which will be laced available to the turbocharger. over the blankets. Blankets will isolate both heat and noise. Heat Shielding Caterpillar does not recommend Note: Installing non-approved shields use of blankets on exhaust or softwrap can cause exhaust manifolds, turbochargers or other system damage. Damage from non- engine components. The use of approved components will not be manifold blankets often results in subject to Quality and Workmanship premature failure of exhaust warranty without approval from manifold components. Exceptions Caterpillar. If lower exhaust skin may be made if the insulation is temperatures are necessary, further supplied and approved for a evaluation of displacement and particular application by Caterpillar; rating (A-E) choices should be for these products, Caterpillar uses considered. exhaust and turbocharger Heat shielding may be used as a components that are made from means of shielding hot surfaces and materials capable of withstanding protecting components or operators higher temperatures. Cat engines from excessive heat. The use of that use wraps and shields are heat shields depends on many developed to a lower exhaust gas factors including, but not limited to, temperature limit.

Hard Wrap (Hard Manifold Shields) output by converting some of the Hard wrap is often used on the energy in the exhaust gas stream engine itself, for example in the vee into energy in the inlet system in the between cylinder banks. The hard form of raised inlet pressure (boost). wrap consists of three layers; a This raised inlet pressure forces thermal sheet, a blanket of fiberglass more air into the engine cylinders, and sheet of bendable metal. It is allowing more fuel to be burned and installed with the thermal sheet thus resulting in higher power facing the hot surface but not output. touching it. The air layer in between works as an insulator. Holes for bolts can be drilled in the metal sheet, making it easy to install or remove. Guards and Shields Guards and shields are usually made using perforated sheet metal. They are installed with an air gap between the shield and the hot Figure 2 surface. With adequate airflow around the engine, the heat transfer from iron to air will lower the Refer to Figure 2. Hot exhaust temperature of the shield gases exit the cylinder and enter the considerably. turbine side of the turbocharger. The CAUTION: All heat shielding, turbine blades and the compressor whether blankets, hard wrap or blades share a common shaft. guards and shields should be The exhaust gases drive the designed in such a way that critical turbine blades which in turn drive engine components, such as the compressor blades on the air manifolds and turbochargers, do not intake side. This high speed rotation reach critical temperatures, as this compresses the intake air to provide may lead to premature failure. more oxygen for combustion. Turbocharger turbine housings and Wastegate non-water cooled turbine housings Turbochargers equipped with a should not be wrapped. In some wastegate can efficiently operate in cases, Caterpillar designed and a much broader range of altitudes approved heat shielding/wrap is and ambient conditions. The available for specific engine models wastegate opens at a predetermined and ratings. pressure and vents some of the Turbochargers exhaust flow away from the Turbochargers are employed to turbocharger. The reduced exhaust achieve higher specific engine power flow slows the turbocharger to avoid

©2013 Caterpillar Page 4 All rights reserved. Application and Installation Guide Exhaust Systems overspeed and excessive boost Flexible connections should be pressure. installed as close as possible to the On some natural gas engines, the engine exhaust outlet. A flexible wastegate may be manually adjusted exhaust connection has three for site conditions to optimize the primary functions. throttle position for efficiency or  To isolate the weight of the improved response. exhaust piping from the engine. Note: The exhaust flow by-passing The amount of weight which the two turbochargers of a G3600 the exhaust outlet for each vee engine via the wastegate are engine model can withstand plumbed together and exit on one varies. exhaust outlet. Therefore, if  To relieve exhaust components measuring exhaust flow, you will of excessive vibrational fatigue notice an uneven exhaust gas flow stresses. through the two exhaust outlets  To allow relative shifting of when the wastegate is open. exhaust components. This has Typically, the right side flow will be numerous causes. It may result 15% higher than the left side. from expansion and contraction CAUTION: Tampering with the boost due to temperature changes, by line to the wastegate will raise creep processes that take place aftercooler heat rejection, increase throughout the life of any turbocharger speed and peak engine structure, or by torque cylinder pressure. This will reactions. negatively affect engine reliability, The weight of the exhaust piping durability, stability, emissions and and supports should not be overall performance. supported by the engine block or Flexible Exhaust Connections engine components. Never attach structures supporting the weight of The exhaust piping system must the exhaust piping directly to the be isolated from the engine with engine block or engine components. flexible connections, designed for The engines are not designed to zero leakage and flexible in all support his extra weight and engine directions. Two types of flexible vibrations will be transmitted to the connections are normally used a structure and piping. flexible metal hose type and a bellows type. A typical piping layout with flexible connections is shown in Figure 3. Flexible Metal Hose and Bellows Flexible metal hose is commonly Flexible pipe connections, when used for exhaust systems with a insulated, must expand and contract diameter of 150 mm (6 in) and freely within the insulation. This smaller. Bellows are typically used generally requires a soft material or for exhaust systems with a diameter insulated sleeve to encase the of 200 mm (8 in) and larger. connection.

Typical Exhaust Piping With Flexible Connection

Figure 3

The flexible connections should be should be soft enough to prevent pre-stretched during installation to transmission of vibration beyond allow for expected thermal growth. the connection. Four small straps can be tack-welded The installation limitations of between the two end flanges to hold Caterpillar supplied flexible exhaust the engine exhaust flexible fittings are shown in the table connections or bellows in a rigid below. For maximum durability, position during exhaust piping allow the bellows to operate as installation. This will prevent the close as possible to its free state. bellows from being installed in a flexed condition. Attach a warning Slip Joints tag to the bellows noting that the Slip joints are another method of weld straps must be removed prior handling the expansion and contraction of exhaust systems. to starting the engine. Slip joints are designed to have Any flexible connector must have controlled leakage when the system good fatigue resistance. It should is cold. When the engine starts and give acceptable service life while the exhaust pipes warm up, the withstanding vibratory stress and it joints will expand and make a gas-

©2013 Caterpillar Page 6 All rights reserved. Application and Installation Guide Exhaust Systems tight fit. The slip joints are flexible in joints due to disadvantages such only one direction and require good as leaking exhaust fumes, exhaust support on each side. slobber and the inability of the joint to flex in more than one direction. However, Caterpillar does not normally recommend the use of slip

Installation Limits of Flexible Exhaust Fittings – Flexible Metal Hose-Type

A B C Hose Maximum Offset Maximum Compression Maximum Extension Diameter Between Flanges From Free Length From Free Length mm in. mm in. mm in. 4 & 5 in. 25.4 1.0 6.25 .25 6.25 2.5 6 in. 38.1 1.5 6.25 .25 6.25 2.5

Installation Limits of Flexible Exhaust Fittings - Bellows-Type

A B** C Bellows Maximum Offset Minimum Acceptable Maximum Extension Diameter Between Flanges Convolution Gap From Free Length mm in. mm in. mm in. 6 in. 1.00 0.04 2.27 0.089 2.00 0.08 8 & 12 in. 19.05 0.75 3.07 0.121 25.40 1.00 10 in. 15.00 0.59 25.40/1.00*** 1.00/0.35*** 14 in. 19.05 0.75 7.97 0.314 25.40 1.00

18 in. 22.86 0.90 7.87 0.310 44.45 1.75 ** Critical Dimensions: DO NOT allow gaps in convolutions to be less than value indicated anywhere on part! *** Maximum allowable COMPRESSION from free length

Spring Rate for Flexible Fittings - Bellows-Type Spring Rate Diameter kN/m lb/in. 6 in. 140.0 799

8 in. 29.7 170

12 in. 33.9 194

14 in. 68.5 391 18 in. 19.3 110

Figure 4

Silencer terms commonly used to describe Exhaust noise is one of the the different ratings. principal noise sources of any engine  Level 1 Silencer System installation. The purpose of the “Residential” — Suitable for silencer is to reduce the noise of the industrial areas where back- exhaust before it is released to the ground noise level is relatively atmosphere. high or for remote areas where Exhaust noise arises from the partly muffled noise is intermittent release of high pressure permissible. exhaust gas from the engine  Level 2 Silencer System cylinders, causing strong gas “Critical” — Reduces exhaust pressure fluctuations in the exhaust noise to an acceptable level in system. This leads not only to localities where moderately discharge noise at the exhaust outlet, effective silencing is required — but also to noise radiation from such as semi-residential areas exhaust pipe and silencer surfaces. A where moderate background well designed and matched exhaust noise is always present. system will significantly reduce noise  Level 3 Silencer System from these sources. The silencer “Supercritical” — Provides makes a major contribution to maximum silencing for exhaust noise reduction. residential, hospital, school, Excessive noise is objectionable in hotel, store, apartment building most applications. The required and other areas where degree of silencing depends on background noise level is low factors such as the application type, and generator set noise must be whether it is stationary or mobile and kept to a minimum. whether there are any legal Silencer Selection regulations regarding noise emission. The silencer is generally the largest For example, excessive noise is single contributor to exhaust back- objectionable in a hospital or pressure. Therefore, required noise residential area but may well be reduction and permissible back- acceptable at an isolated pumping pressure must be considered when station. selecting a silencer. Application type, Silencer Rating available space, cost and appearance Silencers are typically rated may also need to be taken into according to their degree of account. silencing. Industrial silencer (sound To select a silencer, use silencer reduction up to 12-18 dB), supplier data, corrected for outlet Residential silencer (sound reduction temperature and velocity, to up to 18-25 dB), Critical silencer determine the silencer size and type (sound reduction up to 25-35 dB), that satisfies noise reduction criteria and Hospital silencer (sound reduction up to 32-42 dB) are the

©2013 Caterpillar Page 8 All rights reserved. Application and Installation Guide Exhaust Systems with an acceptable maximum pressure drop. After calculating pressure loss, it may be necessary to check a second silencer, or a different pipe size, before an optimum combination is achieved. Silencer design is a highly specialized art. Responsibility for the details of design and construction should be assigned to the silencer manufacturer.

Exhaust System Piping The function of the exhaust piping however; the exhaust piping should is to convey the exhaust gases from never be supported directly by the the engine exhaust outlet to the engine block or engine components. silencer and other exhaust system Allowances should be made for components, terminating at the system movement and vibration system outlet. Piping is a key feature isolation by using suitable flexible in overall exhaust system layout. components such as rubber dampers or springs. Exhaust System Design Piping must be designed with The physical characteristics of the engine service in mind. In many engine room or engine bay will cases, an overhead crane will be determine the exhaust system used to service the heavier engine layout. Exhaust piping should be components on the larger engines. designed to minimize the exhaust backpressure while keeping engine The following recommendations serviceability in mind. The exhaust should be followed when designing piping should be securely supported an exhaust piping system.

Typical Silencer Details

Figure 5

The minimum requirements for the  Install metal thimble guards for design of the exhaust system should exhaust piping passing through be to contain explosions that could be wooden walls or roofs. The encountered during the operation of thimble guards should be the engine. Caterpillar recommends 305 mm (12 in) greater in the use of explosion relief valves on diameter than the exhaust pipes, all gas engines, particularly for the see Figure 5. larger size engines due to the high  When exhaust stacks are used, fuel volumes. Explosion relief valves extend them upward and away should be located as close to the from the engine room to avoid engine as possible (typically at piping heat, fumes and odors. elbows) to minimize any potential exhaust system damage in the event  Locate the exhaust pipe outlets of an exhaust explosion. Additional away from the air intake system. pressure relief valves can be used Engine air cleaners, turbochargers prior to the muffler, catalytic and aftercoolers contaminated converter, or heat recovery equipment with exhaust products can induce to add additional protection for these premature failures. devices. Explosion relief valves are  Avoid routing exhaust piping fitted on the exhaust pipe to relieve close to fuel pumps, fuel lines, pressure in a safe manner and must fuel filters, fuel tanks and other be vented to a safe area. (Reference combustible materials. local codes.) Explosion relief valves  Exhaust pipe outlets cut at 30° can be purchased from aftermarket to 45° angles, rather than suppliers. 90° angles, will reduce exhaust  All piping should be installed with gas turbulence and noise. Refer a minimum clearance of 229 mm to Figure 6. (9 in) from combustible materials.  Exhaust outlets should be  The exhaust piping must be arranged to keep water from properly supported, especially entering the piping system. Rain adjacent to the engine, so that its caps forced open by exhaust weight is not borne by the engine pressure will accomplish this; or the turbocharger. This is however, they will also introduce discussed in more detail later in additional backpressure into the this section. system and should be carefully  Exhaust piping should be sized evaluated. according to the maximum  Paint or other materials should backpressure limit for the engine. not be applied directly on or near  Where appropriate, heat radiation the engine exhaust system or may be reduced by covering the installation exhaust piping unless off-engine exhaust piping with rated for high temperature suitable, high temperature applications. insulation.

Pipe Design Joining Two Turbochargers

Figure 6

The exhaust system can in order to provide mechanical and accumulate a considerable amount thermal isolation. Single sleeve of condensed moisture. For example, thimbles must have diameters at gas engines burning natural gas least 305 mm (12 in) larger than the create one pound of water for each exhaust pipe. Double thimbles 10 ft3 of natural gas burned. For this (inner and outer sleeve) should have reason, long runs of exhaust piping outside diameters at least 152 mm require traps to drain moisture. (6 in) larger than the exhaust pipe. Traps should be installed at the Exhaust Pipe Insulation lowest point of the line, near the No exposed parts of the exhaust exhaust outlet, to prevent rain water system should be near wood or other from reaching the engine. Exhaust combustible material. Exhaust piping lines should be sloped away from inside the engine room or machinery engine, toward the trap, so space (and the silencer, if mounted condensation will properly drain, see inside) should be covered with suitable Figure 3 in the previous section. insulation materials to protect Exhaust Thimbles personnel and to reduce room Exhaust thimbles, as illustrated in temperature. A sufficient layer of Figure 5, are fabrications used for suitable insulating material surrounding wall or ceiling penetrations. The the piping and silencer and retained by thimble provides a separation of the a stainless steel or aluminum sheath exhaust pipe from walls or ceilings, may substantially reduce heat radiation

©2013 Caterpillar Page 12 All rights reserved. Application and Installation Guide Exhaust Systems to the room from the exhaust system. Slots are cut into the exhaust An additional benefit of the insulation pipe to allow rain/spray to drain is that it provides sound attenuation to harmlessly. The edges of each reduce noise in the room. slot are deformed as shown in the Water Ingress Prevention previous graphic. The engine side Exhaust system outlets must be of the slot is bent inward and the provided with an appropriate means downstream side of the slot is bent of preventing snow, rainwater or sea outward. No more than a 60° arc spray from entering the engine of the pipe circumference should be slotted in this way. through the exhaust piping. This can be accomplished by several For applications where none of the methods, but must be given careful above methods is possible, it may be consideration. The selected method necessary to fit some form of rain can impose significant restrictions cap to the end of the vertical pipe that must be taken into account when section. This method can provide a calculating system backpressure. positive means of water ingress One simple method, used primarily prevention, but not without imposing with horizontal exhaust pipes, is to a significant backpressure restriction. angle cut the end of the pipe as shown in Figure 3, Figure 5 and Exhaust System Backpressure Figure 7. Excessive exhaust restriction can A common method used with adversely affect performance, vertical exhaust pipes is to angle the resulting in reduced power and pipe at 45 or 90 from vertical increased fuel consumption, exhaust using an appropriate elbow, then temperatures and emissions. It will angle cutting the pipe end as also reduce exhaust valve and previously described. turbocharger life. It is imperative Another feature that may be used that exhaust backpressure is kept in conjunction with either of the within specified limits for those above methods are Rain/Spray Slots engines subject to emissions as shown in Figure 6. legislation. When designing an exhaust system, the design target for backpressure should be half the maximum allowable system backpressure. To ensure compliance, exhaust system backpressure must be verified to be within the Caterpillar EPA declared maximum value for the engine configuration and rating. Values can be found in Figure 7 the “Systems Data” listed in the Cat Technical Marketing Information (TMI) system.

Backpressure includes restrictions Some engine installations are due to pipe size, silencer, system already equipped with a fitting in the configuration, rain cap and other exhaust discharge for measuring exhaust-related components. backpressure. If the system is not Excessive backpressure is commonly equipped with such a fitting, use the caused by one or more of the following guidelines, Figure 8 and following factors: Figure 9 to locate and install a  Exhaust pipe diameter too pressure tap. small.  Locate the pressure tap in a  Excessive number of sharp straight length of exhaust pipe bends in the system. as close to the turbocharger  Exhaust pipe too long. as possible.  Silencer resistance too high.  Locate the tap three pipe Engines with a vee cylinder diameters from any upstream configuration should be designed pipe transition. so the exhaust piping gives equal  Locate the tap two pipe backpressure to each bank. diameters from any Measuring Backpressure downstream pipe transition. Exhaust backpressure is measured For example, in a 100 mm (4 in) as the engine is operating under full diameter pipe, the tapping would be rated load and speed conditions. placed no closer than 300 mm Either a water manometer or a (12 in) downstream of a bend or gauge measuring inches of water section change. may be used.

Preferred Pressure Tap Location & Installation

Figure 8 The pressure tapping can be made by using a 1/8 NPT “half coupling” welded or brazed to the desired location on the exhaust pipe. After the coupling is attached, a 3.05 mm (0.12 in) diameter hole is drilled through the exhaust pipe wall. Any burrs on the inside of the pipe wall should be removed so that the gas flow is not disturbed. The gauge or gauge hose can then be attached to the half coupling. The tip of the probe should be cut parallel to the exhaust gas flow. Figure 9

Calculating Backpressure Equivalent Length of Straight Pipe Backpressure is calculated by: To obtain equivalent length of straight pipe for various elbows: L x S x Q2 x 3.6 x 106 P (kPa) = + PS D5 33D Standard Elbow L = X elbow radius = pipe diameter L x S x Q2 P (in. H2O) = + PS 187 x D5 20D Long Elbow L = X radius = 1.5 diameter Where: 15D P = Back pressure (kPa), (in. H2O) L = 45° elbow X psi = 0.0361 x in. water column kPa = 0.00981 x mm water column 66D L = square elbow L = Total Equivalent Length of X

pipe (m) (ft) Where X = 1000 mm or 12 in. Q = Exhaust gas flow (m3/min), (cfm) As shown by the equations, if 90° elbows are required, long radius D = Inside diameter of pipe (mm), elbows with a radius of 1.5 times (in.) the pipe diameter helps to lower 3 3 S = Density of gas (kg/m ), (lb/ft ) resistance. Ps = Pressure drop of Combined Exhaust Systems silencer/raincap (kPa), Although economically tempting, a (in. H2O) common exhaust system for multiple Useful conversion factors: installations is not acceptable. psi = 0.0361 x in. of water column Combined exhaust systems with psi = 0.00142 x mm of water boilers or other engines allow column exhaust gases to be forced into engines not operating. Water vapor psi = 0.491 x in. of mercury created during combustion will column condense in cold engines and quickly kPa = 0.0098 x mm of water causes engine damage. Duct valves column separating engine exhausts is also kPa = 0.25 x in. of water column discouraged. High temperatures kPa = 3.386 x in. of mercury warp valve seats causing leakage. column Exhaust draft fans have been kPa = 0.145 psi applied successfully in combined exhaust ducts, but most operate only whenever exhaust is present. To prevent turbocharger windmilling (without lubrication), draft fans

©2013 Caterpillar Page 16 All rights reserved. Application and Installation Guide Exhaust Systems should not be operable when the Supports should also be located to engine is shut down. The exhaust allow expansion away from the system of non-running engines must engine. Supports can reduce strains be closed and vented. or distortions to connected 3600 vee engines have two equipment and can allow component exhaust outlets, one for each bank. removal without additional support. Combining these together with a Flexible pipe connection, when Y-type fabrication, while possible, insulated, must expand and contract may result in unequal thermal freely within the insulation. This growth and backpressure from one generally requires a soft material bank to the other. This unequal or insulated sleeve to encase the growth can put unwanted loading connection. onto the turbocharger mounting or Turbocharger Loading the flex bellows. The unequal Careful consideration must be backpressure can adversely affect given to the load external piping may the operation and performance of induce on the turbocharger. To the engine. If the exhaust outlets are minimize the load carried by the joined, these problems can be turbocharger housing, a bellows minimized by providing a flexible should be placed as close as connection on each leg and by possible to the turbocharger outlet keeping each leg equal in length. and downstream exhaust piping Pipe Support Considerations should be self supporting. The thermal growth of horizontal piping Thermal Growth connected to the turbocharger Thermal growth of exhaust piping exhaust must also be accounted for must be taken into account in order in the design. to avoid excessive load on Maximum allowable vertical load supporting structures. and bending moment limits are Steel exhaust pipe expands provided for each engine model. 1.13 mm/m (0.0076 in/ft) for each Consult the Technical Information 100°C (100°F) rise of exhaust Appendix for the appropriate temperature. This amounts to information. 16.5 mm (0.65 in) expansion for For 3600/G3600 series engines, each 3.05 m (10 ft) of pipe from the Caterpillar supplied bellows and 35° to 510°C (100° to 950°F). adapter, or elbow and bellows Piping systems must be designed options, account for the maximum so thermal growth expands away allowable loading on the from the engine. turbocharger. All other external A restraint member may be used to piping must be self-supporting. keep the ends of a long pipe run Loading Calculations fixed in place, forcing all thermal The following example illustrates growth towards the expansion the type of calculation used to joints.

determine vertical load and bending Horizontal Exhaust moment at the engine exhaust outlet W = Adapter Weight due to the weight of the adapter J = Elbow Adapter Weight mounted directly to the exhaust outlet. I = ½ Bellows Weight Figure 10 shows measurement With Cat Hardware: points for the various distances W = 2.9 kg (6.4 lb) when calculating the forces and I = 0.6 kg (1.4 lb) moments on the turbocharger. J = 4.8 kg (10.7 lb) This example assumes a Gas h1 = 0 3516 with single exhaust outlet. h2 = 100 mm (3.9 in) Vertical Exhaust h3 = 580 mm (22.8 in) W = Adapter Weight I = 1/2 Bellows Weight Forces: FW = 28 N (6.4 lb) g = gravity = 9.82 m/s (32.2 ft) FI = 6 N (1.4 lb) With Cat Hardware: FJ = F x g = 4.8 x 9.82 = W = 2.9 kg (6.4 lb) 47 N (10.7 lb) I = 0.6 kg (1.4 lb) Sum of Vertical Forces Forces: FV = FW + FI + FJ = FW = W x g = 2.9 x 9.82 = 28 + 6 + 47 = 28 N (6.4 lb) 81 N (18.5 lb) FI= I x g = 0.6 x 9.82 = Sum of Moments 6 N (1.4 lb) M = (h1 x FW) + (h2 x FI) + (h3 x FJ) = Sum of Vertical Forces: (0 x 28) + (.100 x 6) + (.580 x 47) = FV = FW + FI = 28 + 6 = 27.9 N•m (20.8 ft-lb) 34 N (7.8 lb) Since for this particular engine Sum of Moments: model FV < 111 N (25 lb) and M < M = (h1 x FW) + (h2 x FI) = 120 N•m (89.5 ft-lb), the exhaust (0 x 28) + (0 x b) = system meets the load and moment 0 N•m (ft-lb) requirements. Since for this particular engine model FV < 111 N (25 lb) and M < 120 N•m (89.5 ft-lb), the exhaust system meets the load and moment requirements.

Vertical and Horizontal Exhaust

Figure 10

Vibration Transmission This can occur when air, Piping connected to stationary significantly above ambient, is engines requires isolation, drawn through radiator equipped particularly when resilient mounts cooling systems. Figure 12 through are used. Without isolation, pipes Figure 16 show typical exhaust can transmit vibrations long piping systems that are arranged to distances. Isolator pipe supports avoid recirculation. should have springs to attenuate low frequencies and rubber or cork to Common Exhaust Stack minimize high frequency The exhaust can be directed into a transmissions. special stack that also serves as the outlet for radiator discharge air and may be sound-insulated. In such instances the radiator discharge air enters below the exhaust gas inlet so that the rising radiator air tends to cool exhaust system components within the stack. Refer to the following two graphics. Figure 11 The silencer may be located within the stack or in the room with its tail pipe extending through the stack To prevent build up of resonant and then outward. Air guide vanes pipe vibrations, support long piping should be installed in the stack to runs at unequal distances as shown turn radiator discharge airflow in Figure 11. upward and to reduce radiator fan air flow restriction. Alternatively the Exhaust Discharge sound insulation lining may have a Exhaust outlets, whether via an curved contour to direct air flow exhaust pipe or stack, must be upward. designed to ensure that engine exhaust is discharged in such a An exhaust stack will remain manner that exhaust gas will not cooler and cleaner if the engine recirculate and be drawn back into exhaust is contained within the the engine’s environment. Engine air exhaust piping throughout its run cleaners, turbochargers and through the stack. If the exhaust aftercoolers may become pipe terminates short of the stack contaminated with spent combustion outlet, the discharged ventilation air products such as hydrocarbons and will tend to cool the exhaust stack soot. This contamination can lead to downstream of the point where it various modes of failure. mixes with the exhaust gases. Recirculation of hot exhaust gas can also adversely affect the ambient capability of the installation.

Power Module or Drop-Over Enclosure For a generator set enclosed in a power module or drop-over enclosure, the exhaust and radiator discharges should flow together, either above or below the enclosure without a stack. This arrangement, as shown in Figure 14 and Figure 15, will prevent the recirculation of exhaust gases Figure 12 back into the module or enclosure. Sometimes, for this purpose, the radiator can be mounted horizontally Figure 12 is an example of a and the fan driven by an electric horizontally mounted exhaust motor to discharge air vertically. silencer with the exhaust pipe and Note that the suction fan radiator air utilizing a common stack. arrangement in Figure 16 does not provide adequate cooling air to the generator. A separate source of generator cooling air is required for this configuration.

Figure 13

Figure 13 is an example of a vertically mounted exhaust silencer with the exhaust pipe and radiator air utilizing a common stack.

Typical Power Module or Drop-Over Enclosure Exhaust System with Internal Silencer

Figure 14

Typical Power Module or Drop-Over Enclosure Exhaust System with External Silencer

Figure 15

Cleanliness During Installation Engines are designed to operate at During exhaust system assembly, loaded conditions. Extended engine all openings on the turbocharger operation at no load or lightly loaded should be covered with an conditions (less than 15% load) identifiable blanking plate to prevent reduce the sealing capability of some debris from falling into the integral engine components, even turbocharger. The Cat shipping when the engine is new. cover can be used for this purpose. If slobber occurs, external signs of This can be installed directly onto slobber will be evident, unless the the turbine housing outlet. A exhaust system is completely warning tag should also be attached sealed. to the plate or cover indicating that Exhaust slobber is not usually it must be removed prior to engine harmful to the engine, but the starting. Refer to Caterpillar Flushing results can be unsightly and and Pickling Guidelines for pipe objectionable. cleanliness. If extended idle or light load Slobber or Wet Stacking periods of engine operation are Exhaust slobber is the black oily mandatory, the objectionable effect fluid that can leak from exhaust of the engine slobber can be avoided system joints. It consists of fuel by loading the engine to at least and/or oil mixed with soot from the 30% load for approximately ten inside of the exhaust system. minutes every four hours. This will Oil leakage may be a result of remove any fluids that have worn valve guides, piston rings or accumulated in the exhaust turbocharger seals. Fuel leakage manifold. To minimize exhaust usually occurs with combustion slobber, it is important that the problems. engine is correctly sized for each application.

Exhaust Systems for Specific Applications Some engine applications face minimize vibration more installation challenges than transmission. others. Marine installations, for  The exhaust pipe is provided instance, are afforded very little with a drainage system to space and require considerable collect and remove any water protection from water entering that may get into the piping. the exhaust system. The information that follows Marine Exhaust Ejector addresses some of these challenges Automatic Ventilation System and can be applicable to marine- A relatively simple system utilizing based as well as some land based an engine’s exhaust for ventilating installations. an engine room can be arranged with most dry exhaust systems. Marine Dry Exhaust System Ductwork can be installed around The marine dry exhaust system, in the engine exhaust piping in such a general, is similar to a typical land- way that the exhaust flow creates a based exhaust system and will be vacuum that is utilized to draw the subject to the same exhaust system hot air out of the upper part of the design considerations as already engine room. This method has been discussed in this section. used successfully in marine Figure 16 shows a typical marine applications with small engine rooms exhaust system installation that and minimal ventilation addresses these design requirements. considerations: An exhaust ejector system may  The exhaust piping is draw out a quantity of ventilating air supported directly above the approximately equal to the flow of engine exhaust outlet, so that exhaust gas. Figure 17, Figure 18 the weight of the exhaust and Figure 19 show variations of piping is not directly this design. supported by the engine or Note: To make an exhaust ejector turbocharger. system successful, air must be  The exhaust piping is run in allowed to enter the engine room a simple and direct manner, freely. with a minimum number of bends, in order to minimize Duct Design Guidelines system backpressure. To determine duct area, a useful rule of thumb is:  Intermediate section of piping 2 is supported with a spring Use 10 cm of duct cross sectional hanger to allow for movement area per engine kilowatt and not due to thermal growth and to more than three right angle bends.

Use 1.25 in2 of duct cross exhaust stack following the mixture sectional area per engine can seriously affect the system’s horsepower and no more than performance. three right angle bends. Furthermore, the exhaust stack will If more right angle bends are remain cooler and cleaner if the required, increase the pipe diameter engine exhaust is contained within by one pipe size. the exhaust piping throughout its run For best results, the intake air through the stack. The discharged openings should discharge cool air ventilation air will tend to cool the into the engine room near the floor exhaust stack upstream of the point level. After the intake air has been where it is mixed with the exhaust heated by contact with hot surfaces gases. in the engine room, draw the Exhaust ejectors are most effective ventilating air out from a point on vessels with only one propulsion directly over the engines, near the engine. On multiple engine engine room overhead. installations, if one engine is Place the ejector in the exhaust operated at reduced load, the ejector system just prior to the exhaust’s air flow for the engine with reduced discharge to atmosphere to avoid load may reverse, pulling exhaust backpressure on the mixture of gas from the more heavily loaded exhaust gas and hot air through any engine into the engine room. length of stack. Any bends in the

Typical Marine Dry Exhaust System

Figure 16

Sample Exhaust Ejector System

Figure 17

Sample Exhaust Ejector System

Figure 18

Sample Exhaust Ejector System

Figure 19

Marine Wet Exhaust System boat at or slightly below the vessels Wet exhaust systems mix the waterline. exhaust gases with the sea water With a relatively small elevation discharged from the sea water side difference between the engine’s of the engine’s jacket water heat exhaust discharge elbow and the exchanger. See Figure 20 for an vessels waterline, it is difficult to example of a wet exhaust system. design a system which will always Wet exhaust piping may be cool prevent water from entering the enough to be made of uninsulated engine through the exhaust system. fiberglass reinforced plastic (FRP) or While a number of proprietary rubber. exhaust components are available to help avoid this problem, the most Moisture of exhaust gases and common generic methods are seawater is discharged from the exhaust risers and water lift silencers.

Wet Exhaust System using Dry Exhaust Elbows at Engine Exhaust Discharge

Figure 20

1. Turbocharger Heat Shield 6. Exhaust Hose 2. Flexible Pipe Connection 7. Connecting Exhaust Pipe 3. Elbow (Centerline bend radius must be greater 8. Discharge Pipe than or equal to the diameter of the pipe) 9. Surge Pipe 4. Insulation (Must not restrict flexibility of flexible 10. Raw Water Discharge Connection pipe connection) 11. Support from overhead structure 5. Elbow (Minimum 15° with water discharge ring)

Exhaust Risers Do not attempt to carry the weight One way to minimize the of the risers from the boat’s possibility of water entering the overhead or deck structure. The engine from backflow in the wet risers will vibrate and move with the exhaust system is to have a steep engine-transmission. The risers must downward slope on the exhaust be supported independently from the piping, downstream of the engine. hull to avoid transmitting those Refer to Figure 21. vibrations into the boat’s structure and passenger compartments. A flexible connection must be used between the riser and the hull mounted exhaust pipe to allow for the engine transmission movement during operation. Except for a few small engines, exhaust risers are not available from Caterpillar. See fabricators of custom exhaust components for exhaust risers. Figure 21 Water Lift Silencers Exhaust risers are pipes that Another way to minimize the elevate the exhaust gases, allowing possibility of water entering the a steeper slope in the downstream engine from backflow in the wet piping. exhaust system is by using a water lift silencer. See Figure 22 for an The risers must be insulated or example of a water lift silencer. water-jacketed to protect personnel in the engine compartment from the Water lift silencers are small, high temperatures of the exhaust sealed tanks, mounted to the deck gas in the riser. The seawater is not in the engine compartment. The injected into the exhaust gases until tanks have two connections, an inlet downstream of the top of the riser, connection and an outlet connection. so the upward-sloping portion of the An additional small drain connection riser is dangerously hot if not in the bottom is often provided. The insulated or water-jacketed. inlet enters the tank through the top or side. The weight of locally fabricated risers (not provided by Caterpillar) The tubing of the inlet connection must be supported from the engine does not extend past the tank walls. and marine transmission. Refer to The tubing of the outlet connection the Technical Data Sheet for max enters the tank walls through the static bending moment on the top and extends to the bottom of exhaust connection. the tank, where it terminates on an angle.

Typical Water Lift Silencer the highest system elevation must allow for a 25.4 m/sec (5000 ft/min) flow velocity of the exhaust-gas- and-water droplet mixture, with the engine running at rated load and speed. If this velocity is not maintained, the water droplets will not remain in suspension. The water will be forced out of the reservoir of the water lift muffler as a solid slug of water. This Figure 22 will cause the exhaust back pressure to be the same as a column of water As the mixture of seawater and the height of the upward sloping exhaust gas enters the tank from the muffler discharge piping. inlet connection, the water level rises in the tank. As the water level If the velocity in the upward rises, the water surface gradually sloping muffler discharge piping reduces the gas flow area entering is kept above 25.4 m/sec the discharge pipe. The reduced area (5000 ft/min), then the exhaust for gas flow causes a great increase backpressure will be much lower. in gas velocity. The high speed of Wave Action and Wet Exhaust the gases, entering the outlet pipe, Systems finely divides the water. The finely While the previously discussed divided water is transported to the methods will help prevent water highest elevation of the exhaust piping as a mist of water droplets. from entering the engine through the exhaust system in normal If good design practice is not circumstances, wave action can followed, the engines exhaust pose additional problems. Waves, backpressure limit is easily striking the hull’s exhaust opening, exceeded. can force water up into the exhaust The vertical (upward sloping) system. If the waves are severe, or portion of piping immediately if the exhaust system design allows, downstream of a water lift muffler the water can reach the engine. must be designed as a pneumatic Early turbocharger failure or piston conveyer, using high exhaust gas seizure may result. velocities to lift finely divided There are a number of ways the droplets of the sea water to a point kinetic energy of waves entering the from which the gas/water mixture engine’s exhaust system can be can be safely allowed to drain to the harmlessly dissipated. thru-hull fitting. The traditional method of The diameter of the piping preventing water from entering an between the water lift muffler and idle engine is to locate the engine far

©2013 Caterpillar Page 32 All rights reserved. Application and Installation Guide Exhaust Systems enough above the water line that of wave energy dissipation, the breaking waves do not reach the lower the elevation difference height of the exhaust elbow. While required. the relative elevation of the engine  In no case should the elevation to the water line is fixed and difference between the water unchangeable, it is possible to line and the highest point in the design an exhaust system that exhaust piping be less than protects the engine from ingesting 560 mm (22 in.). water. Surge Chamber Features of such an exhaust A surge chamber is a branch of the system include: exhaust piping, near the engine that  Sufficient elevation difference has one end closed off, as shown as between the water line and the Item 3 in Figure 23. When a wave of highest point in the exhaust water enters the exhaust pipe and piping to prevent even small moves toward the engine, the air amounts of water from reaching trapped in front of the wave will be the engine. compressed into the surge chamber.  Some method of dissipating the The cushion of compressed air in the kinetic energy of the waves as surge chamber will force almost all they enter the exhaust piping. waves back out. The more effective the method

Typical Wet Exhaust System with Engine Mounted Above Water Line

Figure 23

1. Water-cooled Exhaust Elbow – sea water cools 3. Backwater Surge Chamber – prevents sea water elbow, then discharges into exhaust pipe through surging into engine exhaust from oncoming waves peripheral slot at end of elbow. when vessel is at rest. 2. Rubber Exhaust Hose Flexible Connection – must 4. Exhaust Pipe - should have slight downward be oil and heat resistant. gradient toward discharge end. 5. End Cover Plate – removable for inspection and cleanout purposes.

Valve in Exhaust Discharge and deck area exposed to the A valve located where the exhaust eventual discoloration. piping exits the hull can keep waves The best exhaust system to from entering the exhaust piping minimize smoke and noise is to when the engine is not running. locate the exhaust exit under the The valve mechanism should not water. These systems must also include any components that rely on have a small above the water line sliding contact to maintain flexibility. path for the exhaust for when the This type of action has proven boat is not moving. Care must be troublesome in an atmosphere of salt taken when designing underwater water and exhaust gas. A flexible exhaust systems to keep the strip of one of the chemically inert backpressure within limits. plastics can provide hinge action. Valves in Exhaust Water Cooling Hose vs. Rigid Exhaust Pipe Lines The weight and heat of the water Never use shutoffs or valves of and exhaust gases can cause non- any kind in the lines supplying rigid exhaust piping to sag or cooling water to the water-cooled deform, leaving low spots between exhaust fittings. pipe supports. The cooling water that is injected If the slope of the piping is too into the exhaust gas stream must shallow, water will collect in the not be interrupted, for any reason, low spots and reduce the flow of while the engine is running. Without exhaust gas. This will lead to a dependable supply of cooling excessive exhaust backpressure, water, the high temperature of the smoke, high exhaust temperatures, exhaust gases will cause severe and and in severe cases, premature rapid deterioration of plastic or engine failures. rubber exhaust pipe, with potentially disastrous consequences. Hose and other non-rigid piping must be evenly supported over its entire length. Location of Exhaust Discharge Opening All diesel engines will eventually discharge some smoke through their exhaust systems. Perhaps not when they are new, but certainly near the end of their useful time before overhaul. Locating exhaust discharge openings as far aft as possible and on the sides of the vessel, if above the water line, will minimize the hull