Air Intake Systems

Application & Installation Guide

Air Intake Systems

LEBW4969-07

Contents

Air Intake Systems Foreword ...... 1 Air Cleaners ...... 2 Standard Air Cleaners ...... 2 Heavy-Duty Air Cleaners ...... 3 Precleaners ...... 3 Dual Element Air Cleaners ...... 3 Exhaust Ejector ...... 3 Oil-Bath Air Cleaners ...... 4 Remote Mounted Air Cleaners ...... 4 Customer Furnished Air Cleaners ...... 5 Air Cleaner Efficiency ...... 5 Air Cleaner Design Requirements ...... 6 Air Cleaner Dust Calculation ...... 6 Combustion Air Flow Requirements ...... 8 Air Intake Ducting ...... 9 General ...... 9 Marine Intake Air Piping Examples ...... 10 C175 Remote Mount Air Cleaner ...... 10 Air Inlet Adapters ...... 14 Connections to Inlet Adapters and Turbochargers ...... 14 Joining Two Turbochargers ...... 16 Turbocharger Loading ...... 17 Flex Connections ...... 18 Cleanliness During Installation ...... 18

Inlet Air Duct Insulation ...... 19 Air Intake Restriction ...... 19 Example ...... 20 Additional Considerations ...... 21 Service Indicators ...... 21 Trip Lock Device ...... 21 Differential Pressure Gauge ...... 21 Intake Air Silencers ...... 21 Air Inlet Shut Off ...... 21 Air Manifold Drain Valve ...... 22 Shielding ...... 22 Breakaway Joints ...... 22 Cold Conditions ...... 22 Air Cleaner Icing ...... 22 Boost Control ...... 23 Extreme Cold ...... 23 Considerations for Low Pressure Gas ...... 23 Controlling Air Temperature ...... 24 Gas-to-Air Heat Exchanger ...... 26 Reference Material ...... 27

Foreword This section of the Application and Installation Guide generally describes wide- ranging requirements and options for the Air Intake 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. Below is a listing of air intake system components for various Cat engines. Refer to the Price List for specific options and compatibility.

Air Intake Systems Application and Installation Guide

Air Intake Systems A well designed air intake system provides cool, clean air for combustion while minimizing inlet air pressure drop to the turbocharger. Normally, this can be accomplished by using engine-mounted air cleaners, but some applications require intake air to be brought in through ducts from outside the engine room. There may also be requirements for special filtration and ducting due to fumes, dust, airborne mists, ambient temperature or even altitude. These requirements should be carefully considered because the inlet restriction that accompanies increased filtration and ducting can cause the engine to be derated and turbocharger life reduced. The air inlet restriction limits shown in TMI must not be exceeded, especially for EPA certified engines, in order to ensure regulatory compliance. Air intake systems using ducted air from outside the engine room should be accessible for routine maintenance and inspection. The system should also be located away from exhaust stacks (including engine exhaust stack), vents or processes that might vent flammable vapors, large concentrations of dirt, chemicals, industrial waste, or any other material that would not allow for cool, clean air. In an optimal design, nominal air temperature around the inlet should be between 15° to 32°C (60° to 90°F). Inlet air temperatures should not exceed 45°C (113°F) for standard ratings. For all Cat engines, efficient engine combustion is based on the proper mass flow ratio of fuel and air. The ratio is mass-based and not volume-based. It is always important to remember this fact when considering the impact of installations with non-standard altitude and temperature. Also be sure to submit a special rating request for non-standard altitude and temperature applications so it can be evaluated by Caterpillar performance engineering. SECTION CONTENTS

Air Cleaners ...... 2 • Connections • Dust, Dirt & Debris • Insulation • Types of Air Cleaners • Intake Air Restriction • Customer Furnished Air Additional Considerations ... 20 Cleaners • Service Indicators Combustion Air Requirements • Silencers ...... 8 Air Intake Ducting ...... 9 • Shutoff Valve • General • Cold Weather Operation • System Design • Low Pressure Gas Engines • Inlet Adapters • Reference Material 25 • Turbocharger Loading

Air Cleaners Dirt and debris are the major source air supply during air cleaner service. A of engine wear. For this reason, air vertically mounted air cleaner with a cleaners are necessary to remove dirt bottom-mounted engine supply pipe is and debris from the incoming air. Any particularly vulnerable to this moving engine part may be subjected occurrence. A filter design to accelerated wear when dirt is incorporating a secondary or “safety” contained in the inlet air. Since the air element which remains undisturbed intake is one of the primary locations during primary filter change should be where dirt may enter an engine, used. Its higher initial cost is offset by frequent replacement of air cleaners its contribution to longer engine life. may be needed. Standard Air Cleaners Dirt and debris is introduced into the The standard air cleaner on most intake air ducting through: Cat engines uses a high-efficiency, dry • Residual materials from initial paper element packaged in a low fabrication and assembly of the restriction, weather resistant housing. intake air ducts. They remove 99.5% of AC fine dust • Filter changes. and are designed to minimize dust entrance during filter changes. Some Leaks in the ducting system. • newer models use a PowerCore air • Intake air flow. cleaner featuring a special nanofiber Engine wear tests have shown that element design. These cleaners dust particles under 1 micron (0.00004 achieve the filtration goals with lower in.) size have little effect on the restriction to air flow than engine. 99.5% of this dust will pass out the dry paper element design. through the engine exhaust. On most engine models, these Dust particles 1 to 10 microns air cleaners are engine mounted, (0.00004 to 0.0004 inch) in size has a however, on some engines the air measurable effect on engine life. Inlet cleaners are supplied loose for remote air dust particles larger than bearing oil mounting. See Remote Mounted Air film thicknesses will seriously affect Cleaners later in this section. Refer to bearing and piston ring life. the engine price lists for availability of air cleaner options on specific engine Well designed air cleaners are the most efficient way of assuring that only models. clean air enters the engine and harmful particles are not distributed through the engine systems. The efficiency of dry-type filters is not affected by installation orientation. However, special care should be used in arranging the filter housing and piping to ensure that dirt retained in the filter housing is not inadvertently dumped into the engine

Exhaust Ejector Heavy-Duty Air Cleaners In extremely dusty environments Heavy-duty air cleaners provide the where dust and other particles cause same protection as standard filters but air cleaners to plug up quickly, an allow extension of filter change improved precleaner has been periods. Depending on the engine air- designed. It is an integral part of an flow rate and filter type, service exhaust aspirated air cleaner system periods may be extended six to seven and will extend the service life of the times that of standard air cleaners. air cleaner elements. Depending on specific design, dual Using a louvered body design, the element air cleaners may also be precleaner has a very high separator categorized as heavy duty air efficiency. It will separate and remove cleaners. over 90% of the dirt and chaff from the Precleaners incoming air stream. Precleaners are an available option on some Cat engines, which, when Example of Precleaner, Air Cleaner added to the standard air cleaner, can and Exhaust Ejector extend filter service periods. The precleaner imparts a swirl to the air, centrifuging out a major percentage of the dirt particles which may be collected in a reservoir or exhausted out on either a continuous or an intermittent basis. A flow restriction of 0.25 to 1.5 kPa (1 to 6 in. H2O) is imposed by the precleaner, but it can prolong the life of the filter by three to seven times. Any application in an environment with heavy dust and debris is recommended to use a precleaner. Dual Element Air Cleaners Dual element air cleaners can be used to provide additional protection for the engine. This arrangement uses two elements mounted in series. The secondary filter remains in place while the primary filter is serviced. Figure 1 A dual element configuration differs from a double element configuration it that the two elements are used in parallel.

Dual element air cleaners are also available with a precleaning stage.

Remote Mounted Air Cleaners For the G3500C/E and 3600/G3600 The air comes into the precleaner gensets, the air cleaner enclosure is where the dirt and chaff is removed only offered as shipped loose for from the air. With a slight vacuum, the remote mounting. For the G3500H dirt is sucked directly through the gensets, the air cleaner enclosure can muffler into the exhaust flow and does be ordered as shipped loose for no harm to the engine. Refer to remote mounting if desired. They are Figure 1. furnished as shipped loose items, and The remaining dust in the air is then must be remote mounted and plumbed removed by the air cleaner before it by the customer. Air cleaner systems, enters the turbo. and their support structures, should With this system, consideration must never be mounted on the engine be made regarding the location of exit block, or any engine component. The of the exhaust and the surroundings, engines are not designed to support as there may be particles in the engine this extra weight and engine vibrations exhaust. will be transmitted to the structure and piping. The air cleaner housings may Oil-Bath Air Cleaners be wall, floor, or roof mounted with the Oil-bath air cleaners, while inlet facing downward, or they can be sometimes required to meet customer oriented for horizontal entry, but specifications, are not recommended modifications are required to support by Caterpillar. the elements. At best their efficiency is 95% Two element (double) and three as compared to 99.5% for dry-type element (triple) air cleaner housings filters. Their relative ease of service are available. Unlike the dual element and insensitivity to water are arrangement, air flow through these advantages easily outweighed elements is in parallel. by disadvantages, such as: The double and triple air cleaner • Lower efficiency housings have optional precleaners • Low ambient temperature limits, and soot filters, to extend element life low oil level, high restriction at in severe applications. Examples of low air flow (such as at low idle), remote air cleaner housings are shown and installed tilt angle may lessen in Figure 2 and Figure 3. efficiency further. • Oil carry-over, which is the oil becoming airborne in the air intake system whether resulting from overfilling or increased air flow, can seriously affect turbocharger and engine life, and may actually become an engine fuel.

Double Element Housing Dirty or improper filters can restrict intake air flow. Differential pressure readings should be used to signal needed filter changes. Caution: Under no circumstances should the engine be operated without air cleaners. If the air cleaner enclosure(s) are outside in the weather, a protective shield is recommended to prevent rain from being pulled into the cleaners/precleaners. Figure 2 Customer Furnished Air Cleaners

Air Cleaner Efficiency Double Element Housing with Customer furnished air cleaner 3 Precleaners selection should be based upon the following air cleaner efficiency test: A satisfactory air cleaner must meet the International Organization of Standardization’s requirement of the ISO 5011 dust test. The filter should have 99.5% minimum efficiency as calculated following test code with additions and exceptions as follows: • Air flow corrected to m3/min at 99.9 kPa pressure and 32.2°C (ft3/min at 29.6 in. Hg Figure 3 pressure and 90°F). • Use sonic dust feeder. For marine and offshore • Dust quantity determined by light- applications, where remote mounted duty class. air cleaners may be located in a • Filter to be dried and weighed in salt water environment, epoxy an oven at 93°C to 107°C (200°F coated housings are available. Refer to 225°F) before and after test. to Figure 4 and Figure 5 in the Use AC fine dust. next section for typical marine • arrangements for remote mounted air cleaners.

AC fine dust is defined as follows: V x d x (1 - e) x 60 D = Particle Size n % Total Weight (microns) 0 – 5 39 ± 2 Where: 6 –10 18 ± 3 D = Specific dust consumption 11 – 20 16 ± 3 in mg/hr/cylinder 21 – 40 18 ± 3 V = Intake air flow in cu ft/min (cfm). 41 – 80 9 ± 3 d = Dust concentration in mg/cu ft (Estimated dust concentration 99.5% filtration of the AC fine dust for residential and offshore has been determined to be a practical applications is 0.001 to combination of the kind of dirt likely 0.002 in mg/cu ft. Estimate encountered in service, and will result industrial and inland waterway in an air cleaner efficiency expected to applications at 0.002 to give optimum engine wear life. 0.05 in mg/cu ft.) Air Cleaner Design e = Average air cleaner efficiency Requirements (always < 1.0) (estimated efficiency of paper elements = Following the above procedure will 0.99, & estimated efficiency of establish sufficient control on the filter non-paper elements = 0.95) media filtering ability of the tested air cleaner, but there are other design n = Number of engine cylinders (6, variables needing further control. 8, 12 or 16) • Choose filters supplied by Example A manufacturers that can best A 3606 Engine operating at provide quality control. 900 rpm in an EPG application with non-paper elements. • Design filters to be resistant to damage at initial assembly V = 5554 CFM or during cleaning. If end seal d = 0.02 mg/cu ft and filter media are subject e = 0.95 to damage, dust leakage into the engine can result. n = 6 Air Cleaner Dust Calculation 5554 x 0.02 x (1 – 0.95) x 60 D = 3600/G3600 engines must not ingest 6 more than 34.5 mg/hr/cylinder of dust at rated power to achieve acceptable Example A equates to a dust engine life. Air cleaners offered by consumption of 55.54 mg/hr/ Caterpillar are designed to this cylinder. Since the engine must requirement. Customer provided not ingest more than 34.5 mg/hr/ air cleaners must also meet this cylinder of dust for acceptable engine requirement or reduced engine life will life, this air cleaner system result. Specific dust consumption for is unacceptable. various engines, air cleaners, and environments can be calculated using the following formula.

Example B Using the same engine but with paper air cleaner elements that offer approximately 0.99 efficiency (e = 0.99).

5554 x 0.02 x (1 – 0.99) x 60 D = 6

Example B equates to a dust consumption of 11.1 mg/hr/cylinder. This air cleaner system will provide acceptable engine life.

Combustion Air Flow Requirements

Combustion air flow requirements SR = Density of air at reference will vary, depending on the specific conditions (kg/m3), (lb/ft3). engine model and rating. Specific air (Density of air = 1.292 kg/Nm3 flow data for Cat engines is given in (0.074 lb/ft3)) 3 both volumetric [m /min (cfm)] and mass [kg/hr (lb/hr)] flow terms, at standard reference conditions. To convert both mass airflow and volumetric air flow from reference Reference conditions for conditions to site conditions, use the temperature and pressure are used to following formulas: provide a basis for consistent measure TS of combustion air quantities. However, MR x = MS different parts of the world subscribe to TR different standards, thus it is important to note that the metric and English TS QR x = QS conditions are not equivalent. TR Caterpillar practice is to use ISO 8528 “normal” conditions of 25°C (77°F) and Where: 101.3 kPaa (14.7 psia) when providing M = Mass flow at reference values in metric units, and ASME SAE R conditions (kg/hr), (lb/hr). J1349 “standard” conditions of 25°C (77°F) and 101.3 kPaa (14.7 psia) MS = Mass flow at site conditions when providing values in English units. (kg/hr), (lb/hr). To convert from mass airflow to QR = Air flow at reference conditions 3 volumetric airflow at reference (m /min), (cfm). conditions, use the following formula: QS = Air flow at site conditions 3 MR (m /min), (cfm). = QR SR TR = Air temperature at reference conditions (°K), (°R).

Where: TS = Air temperature at site MR = Mass air flow at reference conditions (°K), (°R). conditions (kg/hr), (lb/hr) °K = °C + 273. QR = Volumetric air flow at reference °R = °F + 460. conditions (m3/min), (cfm)

Air Intake Ducting isolate vibrations, segments of the General piping should consist of flexible rubber When ducting is necessary to obtain fittings. These are designed for use on cooler or cleaner air, the filters should diesel engine air intake systems and remain on the engine to prevent are commercially available. These harmful dirt from leaking into the fittings include hump hose connectors engine through ducting joints. When and reducers, rubber elbows and a air cleaners must be remote-mounted variety of special shapes. it is extremely important that all joints Wire-reinforced flexible hose should be air tight to prevent ingestion of dirt. not be used. Most material available is When designing air intake ducting, susceptible to damage from abrasion consideration must be given to and abuse and is very difficult to seal appropriate routing, duct support and effectively at the clamping points system restriction, especially on the unless special ends are provided on larger engines, where overhead the hose. cranes are used to service the Inlet ducting should be designed to engines. Proper support for duct work withstand a minimum vacuum of 12.5 adjacent to the engine is critical, so kPa, (50 in. H O), which is also the that its weight is not borne by the 2 structural capability of the Cat air turbocharger or other engine-mounted cleaner filter element. components. Piping diameter should be equal to Locate the air piping away from the or larger than the air cleaner vicinity of the exhaust piping so that inlet/outlet and the engine air inlet. A the air provided to the engine is as rough guide for pipe size selection is cool as possible. Air temperature to to keep maximum air velocity in the the air inlet should be no more than piping to 10 m/s (2,000 fpm). Higher 11°C (20°F) above ambient air velocities will cause high noise levels temperature. Inlet air temperature and excessive flow restrictions. Refer should not exceed 45°C (113°F) to the Air Intake Restriction section for for standard ratings. guidance in determining required Avoid abrupt transitions in the intake intake duct sizing. ducting to provide the smoothest All piping must be designed and possible air flow path. When supported to meet any local seismic unavoidable, transitions should be requirements that may be in force. made as far upstream of the turbocharger as possible. Keep total The ducting should be of seamless duct head loss (restriction) below 0.5 or welded seam piping to minimize the kPa (2 in. H2O) for maximum filter life. flow restriction. The ducting should Any additional restriction will reduce also be constructed of materials filter life. suitable for local environmental conditions such as offshore or marine To allow for minor misalignment due applications. to manufacturing tolerances, engine- to-enclosure relative movement and

Beaded pipe ends at hose joints are and scale from accumulating. recommended. Sealing surfaces Stainless steel ducting should be should be round, smooth and free of treated in the same manner. Flanged burrs or sharp edges that can cut the connections with gaskets are preferred hose. The tubing should have over threaded connections. Fasteners sufficient strength to withstand hose such as rivets should not be used. clamping forces. Either T-bolt type or Unsupported weight on clamp-type SAE type F hose clamps that provide joints should not exceed 1.3 kg a 360° seal should be used. High (3 lb). quality clamps must be used. Double clamps are recommended on Marine Intake Air Piping connections downstream of the air Examples cleaner. Figure 4 shows a 3600 marine PVC piping has a number of application configured to use a remote benefits. It is light-weight, provides a mounted air cleaner and outside air for good seal without the chance of weld combustion. An intake air heater may slag coming loose and will not rust. be required for cold weather operation. However, it is not well suited for high Figure 5 shows a 3600 marine or low temperature environments. It application configured to use a remote can lose much of its strength when mounted air cleaner and engine room subjected to temperatures of 150C air for combustion. (300F) or above. It can also become brittle and shatter at low temperatures. C175 Remote Mount Air If using PVC pipe, use at least Cleaner schedule Figure 5A shows a C175 application 40 pipe and check that it meets local to use a remote mounted air cleaner regulations for the area classification. and outside air for combustion. An If ferrous material is necessary, intake air heater may be required for it must be properly cleaned after cold weather operation. fabrication and treated to prevent rust

Remote Mounted Air Cleaner with Outside Air Intake

Figure 4

Figure 4A

Remote Mounted Air Cleaner with Engine Room Air Intake

Figure 5

Figure 5A

Air Inlet Adapters Connections to Inlet Adapters and Caterpillar offers various air inlet Turbochargers adapters for connecting to The piping connected to the turbocharger air inlets. The adapters turbocharger inlet should be designed are part of the system to provide an to ensure that air is flowing in a efficient transition from the engine straight, uniform direction into the room intake air ducting to the engine turbocharger compressor. This turbocharger. Adapters are typically is typically achieved by installing a shipped loose and include gaskets and straight section of pipe, equal in length mounting hardware. to at least two or three times pipe diameter, to the inlet. This CAUTION: Turbocharger performance arrangement reduces the possibility of may be adversely affected if premature compressor wheel failure appropriate air intake components are due to pulsations created by air not used (they are designed to provide striking the compressor wheel at an the proper air flow pattern ahead of the angle. Transitional ducting turbocharger). immediately preceding the straight section of pipe should consider the following guidelines:

• The duct between the straight transition from round to pipe and elbow cannot have rectangular cross section. protruding edges. • An accelerated flow is • The bend can be designed as a expected to occur in the bend. circular arc or with sections of The flow area (F) should be: mitered pipe with rectangular or F1 > 1.5 x F2, as shown in round flow cross sections, or as Figure 6.

Turbocharger Vertical Inlet Design Options

Figure 6

Inlet Pipe Design Joining Two Turbochargers

Figure 7

Joining Two Turbochargers The transitions used to combine When ductwork feeding two multiple ducts must also follow typical turbochargers is combined to form design standards described a single duct, a steadying zone must in this guide. Ducts should have be provided after the dividing joint; as smooth transitions and not cause shown in Figure 7. The steadying disturbance in the air flow. Piping zone B must be a minimum of designs that use a Tee, as shown 5 times the pipe diameter: in Figure 8, should not be used to connect multiple ducts. B > 5 x Dh1

The flow area is:

F0 = 1.0 ÷ 2.0 x F1

The transitions from Sections 0-0 to 1-1 and from 1-1 to 2-2 will have many circular or rectangular variations due to turbocharger hardware and Figure 8 installation site design. Regardless of the transition selected, the steadying zone must be provided.

Turbocharger Loading The maximum allowable When remote-mounted air cleaners turbocharger load will vary, depending are used, turbocharger loading from on the engine model, the weight of the air inlet components the inlet adapter and the adapter becomes a concern. The orientation. In the example below, turbochargers are not designed to Figure 10, the 90° inlet adapter can be support any additional weight beyond rotated in 30° increments. standard factory attachments. When Turbochargers for 3600/G3600 possible, make the flexible connection engines are designed to withstand directly to the turbocharger air inlet, as a maximum moment of 294 N•m shown in Figure 9. All duct work to (217 ft-lb). Figure 10 shows how the that point along with the air cleaner moment can be calculated. and its support structures, should not Models that provide a mounting be directly mounted to the engine bracket for the turbocharger inlet adapter, such as the C15, can support up to 11.3 kg (25 lb) of duct weight.

Figure 9

Maximum Loads for Turbocharger Intake

Figure 10

Flex Connections Cleanliness During Installation Flexible connections are required to The air intake ducting must be isolate engine vibration and noise from cleaned of all debris. Fabricated the ducting system. The connections ducting, utilizing fasteners such should be configured for maximum as rivets, should not be used. The allowable offset and compression to ducting should be made of material prevent early failure and excess forces such that prolonged operation will not on the turbocharger and air inlet result in debris coming loose components. The flexible connection and entering the turbocharger. should be as close to the engine as practical and installed in such a way to An identifiable blanking plate should not induce stress on the ducting system. be installed ahead of the turbocharger The flex engagement with the air intake to prevent debris from entering during duct should be a minimum of 50 mm (2 initial installation of the unit. The plate in.) and a maximum of 200 mm (8 in.). should have a warning tag indicating it Care must be used to prevent exhaust has to be removed prior to starting the piping heat from deteriorating rubber flex engine. The Caterpillar supplied connections. shipping cover can be used for this purpose.

Provisions should be made to connection. For remote mounted air inspect the ducting for cleanliness just cleaners, the following formulas can prior to initial start up. If the piping is be used to calculate duct restriction. not clean, it must be cleaned before the engine is started at L x S x Q2 x 3.6 x 106 commissioning. This may require P(kPa) = 5 removal of the piping from its installed D position. L x S x Q2 P(in. H 0) = Inlet Air Duct Insulation 2 187 x D5 Insulation may be needed on the intake ducting for remote mounted air Where: cleaners. Insulation reduces P = Restriction (kPa), (in. H2O) turbocharger noise emitted into psi = 0.0361 x in. water column the engine room and will minimize pre- kPa = 6.3246 x mm water column heating of intake air. L = Total equivalent length of pipe, Air Intake Restriction measured in (m), (ft) Excessive vacuum on the inlet side Q = Inlet air flow, measured in of the turbocharger (or the air inlet on (m3/min), (cfm). - (found in TMI naturally aspirated engines) can result or performance book, and in reduced engine power capability corrected for site conditions and degrade engine performance. when necessary) Air intake restriction is also an D = Inside diameter of pipe, emissions critical parameter declared to measured in (mm), (inches) obtain EPA non-road certification. If the duct is rectangular, as shown Therefore, the air intake system’s total in Figure 11: restriction (including dirty filters, duct work, vents, silencers, etc.) is limited Then: depending on engine model, rating and 2 x a x b D = air configuration. The air intake a+b restriction limits for Cat engines can be found in the Technical Information Appendix or TMI. In order to maximize air filter life, it is important to keep total duct restriction below 0.5 kPa (2 in. H2O). Every additional restriction caused by the air Figure 11 inlet system subtracts from air filter life. Maximum filter life is partially dependent 3 3 on the absolute pressure differential S = Density of air kg/m (lb/ft ) between the turbocharger compressor 352.5 S(kg/m3) = inlet and atmosphere. Air Temperature + 273°C Inlet air restriction includes the 39.6 pressure losses between the air S(lb/ft3) = cleaner and the engine air inlet Air Temperature + 460°F

3000 mm + 2(33 x 20 x Use the following formulas to obtain L 152.4) 152.4 + equivalent lengths of straight pipe for = 1000 1000 mm various elbows. mm Standard Elbow 33D L = 16.1 m L = (radius = diameter) X

Long Radius Elbow 20D 120 in+ 2(33 x L = (radius = 1.5 diameter) X L = 6) + 20 x 6 12 in 12 in 45° Elbow 15D L = 53 ft (radius = 1.5 diameter) L = X

Next, calculate the density of Square Elbow 66D the air. (radius = 1.5 diameter) L = X 352.5 S = 55 + 273°C Where: S = 1.075 kg/m3 x = 1000 mm (12 in.) As shown above, if 90° bends are 39.6 S = required, long radius elbows, with 131 + 460°F a radius of 1.5 times the pipe S = 0.067 lb/ft3 diameter, offer lower resistance than standard elbows. Lastly, insert the previous results into Example the duct restriction formula and Below is an example of an air intake calculate. duct restriction calculation. 16.1 x 1.075 x 36.72 x 3.6 x 106 A 3412 packaged genset has an inlet P = 5 air flow of 36.7 m3/min 152 (1292 cfm) with duct configuration P = 1.02 kPa or 104 mm H2O consisting of 3 m (10 ft) of straight length duct along with 2 standard 53 x 0.067 x 12922 elbows and a long radius elbow. The P = 187 x 65 pipe has a diameter of 152.4 mm (6 in) and the temperature of the P = 0.147 psi or 4.07 in H2O air is 55°C (131°F). Total duct restriction should be First calculate the total equivalent below 0.5 kPa (2 in. H2O). The duct length of the ducting. restriction in this example is above the desired value, and therefore this duct configuration is unacceptable.

Additional Considerations

Service Indicators Intake Air Silencers Vacuum sensing devices designed A Cat air intake filter/silencer is to indicate the need for air cleaner available for use with 3600 diesel servicing are commercially available engines. It cannot be used with G3600 and when added to the air intake gas engines due to turbocharger orientation. system, serve a vital function. There are two types of sensing devices, both recommended for use. Service indicators are installed directly into the intake air ducting and sense the pressure differential between the air in the intake ducting and the air outside the ducting. It must be noted that in installations using outside air for combustion, engine room pressure and outside, or atmospheric, pressure is not always the same. The indicator must be installed so that it senses the air in the intake duct on one side and the air Figure 12 from where it was drawn on the other. The filter/silencer provides good air Trip Lock Device filtration, but it should only be used in The trip lock device indicates that the a clean engine room environment air cleaner condition is either (filtered air). The customer is satisfactory or in need of service. responsible for ensuring the engine When in need of service, it typically room air is suitably filtered. will have a red display. This type of Unless specifically designed for such mechanism uses a spring-loaded a purpose, intake air silencers should diaphragm to measure the pressure be remote mounted from the differential between the clean and dirty turbocharger inlet as shown in side of the air cleaner. The trip or Figure 12. latching type is preferred and available on most engine price lists. Air Inlet Shut Off Differential Pressure Gauge Air inlet shut-off is a feature specific The direct reading differential gauge to the diesel engine air intake system. indicates the actual pressure It provides a positive means of differential across the intake air filter. stopping the combustion process in One end of the gauge is connected to the event of an emergency shutdown the air inlet duct and the other end to a by stopping the flow of combustion air. straight length of pipe immediately This is not recommended for gas upstream of the turbocharger. engines, as they have the ability to

©2015 Caterpillar All rights reserved. Page 21 Application and Installation Guide Air Intake Systems positively stop the combustion process Precleaners and prescreeners by controlling the source of ignition. incorporated into the intake cap design The air inlet shut-off feature is are also available. They can be used standard on 3600 diesel engines and where special conditions prevail or to available on many other Cat diesel increase the air cleaner service life. engines. It is normally used when an These devices can remove 70% to engine will be operating in a potentially 80% of airborne dirt. combustible environment. This feature Breakaway Joints can be actuated manually or A breakaway joint may be used on a electronically, but is for emergency cab or hood to tilt away from the use in case of engine overspeed only, engine compartment for accessibility not for normal engine shutdown. and servicing of the engine. Half of the Air Manifold Drain Valve rubber seal flange remains on the An air manifold drain valve is engine air intake and the other half is available for the 3600 diesel engine secured to the enclosure or hood. family, consisting of an automatic float If carefully designed and used only valve that drains the condensate from upstream of the air cleaner, the engine air manifold. The C175 breakaway joints may be used. offers a manual ball type air manifold Note: Never use breakaway joints drain valve as an option. Otherwise, between the air cleaner and engine. draining must be facilitated by removing the standard plugs from the When breakaway joints are required, aftercooler outlet lines.This feature is chose a joint designed recommended for use in applications for lifetime sealing under the most where high humidity is expected and severe conditions and needing limited the possibility exists for the air inlet or no maintenance. manifold temperature to drop below Cold Conditions the atmospheric dew point. Refer to Caterpillar Service Publication Air Cleaner Icing SEBD9317 and SEBU8100 for more Air cleaner icing can occur in information on this subject. saturated air environments when the dew point of the ambient air is near Shielding freezing. Small disturbances to the air The air inlet should be shielded such as velocity and pressure changes against direct entrance of rain or snow. at the air cleaner inlet reduce the The most common practice is to moisture-holding capacity of the air. provide a cap or inlet hood which This results in moisture condensation incorporates a course screen to keep and ice crystal formation. The ice out large objects. This cap should be buildup reduces the airflow area and designed to keep air flow restriction to increases the pressure differential a minimum. Some users have across the air cleaner. Eventually, a designed a front air intake which plateau is reached where the pressure provides a direct air inlet and an differential remains constant even internal means of achieving water though ice buildup may continue. separation. Power loss and increased fuel

©2015 Caterpillar Page 22 All rights reserved. Air Intake Systems Application and Installation Guide consumption will result during these gas engines that do not have air-fuel periods. ratio control. Several techniques may be used to overcome air cleaner icing. One solution is to heat the intake air slightly. It is not necessary to heat the air above freezing. The air requires only enough heat to be above the dew point. Heat can be supplied to the air cleaner housing by ducting engine room air. Heated air from the exhaust piping or muffler, or electrical heating tape may also be used. Boost Control A boost control valve is available for the 3600 diesel engine family for use in extremely cold ambient conditions, 0°C (32°F). The valve is used to limit the air inlet manifold pressure during low air temperature conditions to maintain acceptable cylinder pressure. Waste gated C280 engines do not require the use of boost control valves. The wastegates serve the same purpose as the boost control valve and will effectively mitigate high cylinder pressures. Extreme Cold Heated engine room air may be required (for starting purposes only) in applications at very cold ambient temperatures, -25°C (-13°F). This assumes combustion air is being drawn from outside the engine building, and the engine is preconditioned with pre-heaters for metal, water and oil temperatures of 0°C (32°F). Admitting engine room air must be done without the possibility of allowing dirt or debris into the air inlet system of the engine. Considerations for Low Pressure Gas Take special care when designing the air intake system for low-pressure

Carburetors used in Cat gas engines To maintain a 2.0 g NOx /bhp-hr meter fuel into incoming air on a level, VAT must not exceed 5.5°C volume-for-volume basis. If the density (10°F). of either the air or the gas changes relative to the other, the air-fuel ratio of the engine will change, affecting emission levels and the detonation margin. For example, if a G3516 Low Emissions engine with an 11:1 compression ratio and 32°C (90°F) A/C is adjusted to produce 2 g NOx at full load, the percent of O2 in the exhaust must be set to 8%, which results in an air-fuel ratio of 14.75 on a volume-for-volume basis. If the engine is adjusted when the incoming air is 10°C (50°F) and the incoming gas is 21°C (70°F), then:

∆T1 = 10°C - 21°C = -11°C (∆T1 = 50°F - 70°F = -20°F) Figure 13 If the air temperature is later High pressure gas engines are not increased to 32°C (90°F) and the gas affected by these changes to the same temperature remained constant, then: extent as low pressure gas engines. ∆T2 = 32°C - 21°C = 11°C This is because the supply gas (∆T2 = 90°F - 70°F = 20°F) temperature remains relatively The Variation in Air Temperature constant at most installations and the (VAT) would then become: thermostatically controlled aftercooler V∆T = |-11°C - 11°C)| = 22°C maintains a fairly constant air (V∆T = |-20°F - 20°F| = 40°F) temperature to the carburetor. Since these two temperatures are not The density of the air would then subject to large changes, the air-fuel decrease, resulting in a lower air-fuel ratio remains relatively constant. ratio of 13.67. The lower air-fuel ratio There are two primary methods of would result in reducing the percent O2 in the exhaust to 6.5%. The graph in controlling VAT, controlling the air temperature and using a gas-to-air Figure 13 shows how NOx changes as heat exchanger. a function of percent O2 in the exhaust. The increased air Controlling Air Temperature temperature in our example would One method of controlling air supply increase the NOx emissions to 8.8 g temperature is to regulate the engine NOx /bhp-hr, which is an increase of room temperature. However, this 440%. approach is not recommended. It is difficult to regulate an engine room to a temperature that is both comfortable

©2015 Caterpillar Page 24 All rights reserved. Air Intake Systems Application and Installation Guide to work in and high enough to provide running, will not maintain the air-fuel a constant air temperature to the ratio while the doors are open. engine. For example, an installation The preferred method is to use duct expecting a 32°C (90°F) ambient work to supply a temperature temperature, will need to regulate the regulated air supply to the engine. See engine room to about 38°C (100°F) at Figure 14. This system uses jacket all times. Also, engine rooms having water to heat the air to the large service doors that, at times, must temperature set by the thermostat. be left open while the engines are

Ducting with Temperature Regulator

Figure 14

If one intake system is used to entering the gas regulator. The supply temperature controlled air to pressure drop across the heat multiple engines, provisions must be exchanger at full load must be added made to ensure that heated water is to the minimum gas supply pressure sent to the heat exchanger when required by the engine. Design the engines are running. If engine jacket heat exchanger to minimize both gas water is used, the engine that the and air flow pressure drop while still water is taken from must be running providing enough heat transfer so that when any of the other engines are VAT stays within the given limits. operating. Gas-to-Air Heat Exchanger If the use of duct work is not practical for a given installation, another option is to install a gas-to-air heat exchanger, shown in Figure 15. If done correctly, this system will prevent temperature changes in the gas or the air from affecting the air-fuel ratio. Design the system so the gas flows through the heat exchanger before Figure 15

Reference Material The following information is provided as an additional reference to subjects discussed in this guide. SEBD9317 Engine News 2003/01/01. SEBU8100 C175 Series Generator Set

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