Bendix Commercial Vehicle Systems BA-921 User Manual

BENDIX® BA-921® COMPRESSOR: STANDARD AND CLOSED ROOM

SD-01-690

"STANDARD" AND "CLOSED ROOM" VERSIONS

This service data sheet covers two versions of the Bendix® BA-921® compressor. The ﬁ rst version was originally released in 2002 and will be referred to as the “Standard” compressor in this Service Data sheet. The Standard compressor was offered on Caterpillar ACERT Medium and Heavy duty engines, and the DDC S60 EGR (2002-06) engine. These installations required an externally-mounted inlet check valve (ICV) on the air inlet side of the compressor. Depending on whether the air induction system was naturally aspirated or turbocharged dictated whether or not additional hardware was required along with the ICV (See Figure 6, page 3 and Section 1 of "Air Induction", on page 6).

The second version was originally released in 2007 and will be referred to as the “Closed Room” compressor in this service data sheet. This compressor is only permitted to be naturally aspirated – use of engine turbocharger as an air source is not allowed. This compressor eliminates the need for an externally mounted inlet check valve (ICV) on the air inlet side of the compressor (See Figure 6, page 3).

Refer to Figure 2 below to see the visual differences between the two BA-921® compressor heads. Other differences between the two versions will be referenced throughout this Service Data sheet.

DESCRIPTION

The function of the air compressor is to provide and maintain air under pressure to operate devices in air brake systems. The Bendix® BA-921® compressor is a single-cylinder reciprocating compressor with a rated displacement of

15.8 cubic feet per minute at 1250 RPM. The compressor consists of a water-cooled cylinder

head assembly and an integral air-cooled crankcase assembly.

The cylinder head assembly is made up of the cylinder head, cooling plate and valve plate assembly and uses

Cylinder

Head

Valve Plate

Assembly

FIGURE 1 - BENDIX

(STANDARD VERSION SHOWN)

BA-921® COMPRESSOR

Safety

Valve

Cooling

Plate

Crankcase

two sealing gaskets. Depending on the application, the cylinder head and cooling plate may be aluminum or cast iron. The cylinder head contains air and water ports as well as an unloader assembly. A cooling plate is located between the cylinder head and valve plate assemblies and assists in cooling.

The valve plate assembly consists of brazed steel plates which have valve openings and passages for air and engine coolant to ﬂ ow into and out of the cylinder head.

Standard:

Aluminum Cylinder Head With 4 Bolts

FIGURE 2 - BENDIX® BA-921® COMPRESSOR: STANDARD AND CLOSED ROOM VERSIONS

Standard:

Cast Iron Cylinder Head With 4 Bolts

Closed Room:

Aluminum Cylinder Head With 6 Bolts

Splash

Shield

Unloader

Cover

Unloader

Piston

Discharge

Reed

Valves (2)

Piston

Rod

Coolant Ports

(3 total)

Air

Intake

Cooling

Plate

Crankshaft

Coolant Ports

(3 total)

Discharge

Reed

Valves (2)

Unloader

Cover

Unloader

Piston

Cooling

Plate

Piston

Rod

Crankshaft

Crankcase

Cover

FIGURE 3 - BENDIX® BA-921® COMPRESSOR (CUT-AWAY) (STANDARD AND CLOSED ROOM)

The compressor's discharge valves are part of the valve plate assembly. The inlet reed valve/gasket is installed between the valve plate assembly and the top of the

Compressor Model,

Customer Piece Number,

Bendix Piece Number and

Serial Number shown here

Closed RoomStandard

crankcase. The cast iron crankcase houses the piston assembly,

connecting rod, crankshaft and related bearings. All Bendix® BA-921® compressors are equipped with a

safety valve to protect the compressor head in the event

FIGURE 4 - CRANKCASE BASE COVER

is stamped with information identifying the compressor model, customer piece number, Bendix piece number and serial number. See Figures 1 and 4.

of, for example, a discharge line blockage downstream of the compressor. Excessive air pressure will cause the safety valve to unseat, release air pressure and give an audible alert to the operator. The safety valve is installed in the cylinder head safety valve port, directly connected to the cylinder head discharge port.

The crankcase cover located at the bottom of the crankcase

OPERATION

The compressor is driven by the vehicle's engine and functions continuously while the engine is in operation. Actual compression of air is controlled by the compressor unloading mechanism operating in conjunction with a governor.

Crankcase

Cover

Caterpillar

C7, C9

Engines

FIGURE 5 - TYPICAL COMPRESSOR DRIVE FLANGES

Caterpillar

HD Acert

Engines

Detroit

Diesel S60

Standard Compressors use an Inlet Check Valve

(ICV), or alternately, an ICV plus a reservoir,

in the air inlet line depending on the application

Air

Discharge

Port

Air Inlet

Port

Discharge

Valve

Closed

Unloader

Port

Governor

Unloader Port

Governor Reservoir

Port

Compressor

Closed Room Compressor Typical System

Governor

Unloader Port

Governor Reservoir

Port

Compressor

FIGURE 6 - STANDARD AND CLOSED ROOM BA-921® COMPRESSOR CHARGING SYSTEMS

Air Dryer

Supply Reservoir

Air Dryer

Supply Reservoir

Cooling

Plate Valve

Plate

Piston Moving Down

FIGURE 7A - OPERATION - LOADED (INTAKE). (SIMILAR FOR ALL COMPRESSORS - STANDARD COMPRESSOR SHOWN)

Discharge

Valve Open

Air

Discharge

Port

Air Inlet

Port

Unloader

Piston

Down &

Seated

Inlet Valve Open

Unloader

Port

AIR INTAKE (LOADED)

Just as the piston begins the down stroke, (a position known as top dead center, or TDC), the vacuum created in the cylinder bore above the piston causes the inlet reed valve to ﬂ ex open. Atmospheric air (in naturally aspirated applications) or pressurized air (in turbocharged applications) ﬂ ows through the open inlet valve and ﬁ lls the cylinder bore above the piston. See Figure 7A.

AIR COMPRESSION (LOADED)

When the piston reaches the bottom of the stroke, (a position known as bottom dead center, or BDC), the inlet reed valve closes. Air above the piston is trapped by the closed inlet reed valve and is compressed as the piston moves upwards. When air in the cylinder bore reaches a pressure greater than that of the system pressure, the discharge reed valves open and allow air to ﬂ ow into the discharge line and air brake system.

At the same time air ﬂ ows into the hollow center of the unloader piston through an opening in the end of the piston. Compressed air acts on the interior surfaces of the unloader piston and, along with the unloader piston spring, holds the unloader piston in the down position, against its seat on the valve plate. See Figure 7B.

Cooling

Plate

Valve Plate

Inlet

Valve

Closed

Piston Moving Up

FIGURE 7B - OPERATION - LOADED (COMPRESSION) (SIMILAR FOR ALL COMPRESSORS - STANDARD COMPRESSOR SHOWN)

Unloader

Piston

Down &

Seated

Cooling

Plate Valve

Plate

Air Inlet Port

Air From Governor Unloader

Port

Unloader

Piston Up &

Unseated

Air From Governor Unloader

Port

Closed

Room

Unloader

Piston Up &

Unseated

Air in Pistons Shuttles Back and Forth from the

Piston to the Cylinder Head and Inlet Port During

Unloaded Mode

FIGURE 8 - OPERATION - UNLOADED (STANDARD)

NON-COMPRESSION OF AIR (UNLOADED)

Section 1: For Standard Compressor. See Figure 8.

When air pressure in the supply reservoir reaches the cutout setting of the governor, the governor delivers system air to the compressor unloader port. Air entering the unloader port acts on the unloader piston causing the piston to move upwards, away from its seat on the valve plate assembly. When the unloader piston is unseated an air passageway is opened between the cylinder bore and the air inlet cavity in the cylinder head.

As the piston moves from bottom dead center (BDC) to top dead center (TDC) air in the cylinder bore ﬂ ows past the unseated unloader piston, into the cylinder head inlet cavity and out the inlet port. T o prevent the air from ﬂ owing back into the engine air induction system, an inlet check valve (ICV) is installed upstream of the air compressor inlet port. The location of the device and the way it is plumbed into the compressor air induction system is unique to the speciﬁ c engine and the type of air induction (naturally aspirated or boosted air) the compressor uses. These air induction systems will be explained in further detail in the “Air Induction” section on page 4. On the piston down stroke (TDC to BDC) air ﬂ ows in the reverse direction, from the inlet cavity past the unseated unloader piston and inlet reed valve, and into the cylinder bore.

Air in Pistons Shuttles Back and Forth from the

Piston to the Closed Room

FIGURE 9 - OPERATION - UNLOADED (CLOSED ROOM)

Section 2: For Closed Room Compressor. See Figure 9. When air pressure in the supply reservoir reaches the

cutout setting of the governor, the governor delivers system air to the compressor unloader port. Air entering the unloader port acts on the unloader piston causing the piston to move away from its seat on the valve plate assembly. When the unloader piston is unseated, an air passageway is opened between the cylinder bore and a secondary compartment or “closed room” in the interior of the cylinder head.

As the piston moves from bottom dead center (BDC) to top dead center (TDC) air in the cylinder bore ﬂ ows past the unseated unloader piston, into the “closed room”. The size of the closed room is sufﬁ cient to accept the compressed air provided by the compressor piston without creating excessive air pressure in the “closed room”. On the piston down stroke (TDC to BDC) air ﬂ ows in the reverse direction, from the “closed room” past the unseated unloader piston and inlet reed valve, and into the cylinder bore. Note: For optimum performance, it is recommended that the air dryer is equipped with “turbo cut-off”.

Head

Bolt (4)

Discharge

Port

Governor

Connection

Unloader

Cover

Coolant In or Out

CYLINDER HEAD PORT IDENTIFICATION

The cylinder head connection ports are identiﬁ ed with cast in numerals as follows:

AIR IN 0 Compressed AIR OUT 2 Coolant IN or OUT 9 Governor Control 4

FIGURE 10 - STANDARD BENDIX® BA-921® COMPRESSOR CYLINDER HEAD

Head

Bolt (6)

Inlet

Port

Coolant In or Out

CYLINDER HEAD PORT IDENTIFICATION

The cylinder head connection ports are identiﬁ ed with cast in numerals as follows:

AIR IN 0 Compressed AIR OUT 2 Coolant IN or OUT 9 Governor Control 4

Discharge

Safety Valve

Discharge

Safety Valve

Discharge

Port

Coolant In or Out

(One or other not used)

Inlet Port

Coolant In

or Out

(One or other not

used)

Governor

Connection

Unloader

Cover

LUBRICATION

The vehicle's engine provides a continuous supply of oil to the compressor. Oil is routed from the engine to the compressor's oil inlet. An oil passage in the crankshaft routes pressurized oil to the precision sleeve main bearings and to the connecting rod bearings. Spray lubrication of the cylinder bores, connecting rod wrist pin bushings, and ball type main bearings is obtained as oil is forced out around the crankshaft journals by engine oil pressure. Oil then falls to the bottom of the compressor crankcase and is returned to the engine through drain holes in the compressor mounting ﬂ ange.

Standard Compressor Lubrication for Caterpillar C11 and C13 engine applications

Bendix

BA-921® compressor - for Caterpillar C11 and C13 engine installations only - use an "oil jet" that sprays oil under the piston for purposes of cooling. This oil jet is part of a special crankcase cover that is used only on the BA-921® compressor for CAT C11 and C13 engine installations (see Figure 17).

This design slightly alters the ﬂ ow of oil for lubrication. The oil supply line from the engine is directly connected to the back side of the special crankcase over. The oil ﬂ ows in parallel through a passageway in the crankcase cover and through the oil jet to spray oil under pressure up onto the underneath of the piston for cooling. At the same time, oil ﬂ ows out of the opposite end of the special crankcase cover, through a ﬁ tting and a metal tube and second ﬁ tting into the oil supply port of the compressor. At this point oil ﬂ ows in a similar manner as in the ﬁ rst paragraph of this section.

COOLING

Bendix® BA-921® compressors are cooled by air ﬂ owing through the engine compartment as it passes the compressor's cast-in cooling ﬁ ns and by the ﬂ ow of engine coolant through the cylinder head. Coolant supplied by the engine cooling system passes through connecting lines into the cylinder head and passes through internal passages in the cylinder head, cooling plate and valve plate assembly and returns to the engine. Figures 10 and 1 1 illustrate the various approved coolant ﬂ ow connections. Proper cooling is important in minimizing discharge air temperatures - see the tabulated technical data on page 18 of this manual for speciﬁ c requirements.

FIGURE 11 - CLOSED ROOM BENDIX® BA-921® COMPRESSOR CYLINDER HEAD

Inlet

AFr

Por

nlet

Inlet Check Valve

FIGURE 12 - EXAMPLE OF CATERPILLAR (ACERT ENGINE) C7/C9 COMPRESSOR AIR INDUCTION SYSTEM (TURBOCHARGED)

nlet

Expansion Tank

nlet

ir Supply

rom Engin

Air Suppl

From Engin

CATERPILLAR

Caterpillar HD ACERT engines (C11, C13, C15 and C18) and MD ACER T engines (C7 and C9) are typically equipped with Bendix

BA-921® compressors. These engines provide pressurized (turbocharged) air to the compressor's inlet port. Caterpillar recommends the use of an inlet check valve in the air induction system to prevent the air from the compressor being forced back into the engine air induction system when the compressor is operating in the "unloaded" condition (not building air). Because the compressor induction system is turbocharged, an additional air volume is required between the compressor inlet port and the inlet check valve to prevent excessive air pressure at the compressor inlet in the unloaded mode. Figures 12 and 13 show examples of the different air induction systems used by Caterpillar to perform this function.

CATERPILLAR C7/C9 ENGINES

The Bendix® BA-921® compressor in the C7/C9 air induction system (see Figure 12) receives its air from the engine's intake manifold (turbocharged). During the pumping condition (loaded mode), the air ﬂ ows from the engine intake manifold through the inlet check valve and inlet line to the compressor inlet port. During the non-pumping condition (unloaded mode), the compressor cylinder pushes air back out of the inlet port to the inlet check valve. The ICV prevents the air from traveling beyond this point. Because the air is boosted (under pressure), it is important that the compressor inlet line is of sufﬁ cient length, strength and volume to minimize the build-up of air pressure in the inlet system. The air shuttles back and forth between the compressor cylinder bore and the ICV during this phase of the compressor operation.

Inlet Check Valve

FIGURE 13 - EXAMPLE CATERPILLAR (HD ACERT ENGINE) C11/C13/C15/C18 COMPRESSOR AIR INDUCTION SYSTEM (TURBOCHARGED)

AIR INDUCTION

Section 1: For Standard Compressors.

GENERAL

The Standard Bendix® BA-921® air compressor can be used both with air induction systems that are naturally aspirated (atmospheric air) and pressurized (turbocharged). The following section covers Caterpillar and Detroit Diesel engine air induction arrangements. See Figure 5, for typical ﬂ anges used.

Inlet

Check

Valve

FIGURE 14 - EXAMPLE OF DETROIT DIESEL (EGR) S60 COMPRESSOR AIR INDUCTION SYSTEM (NATURALLY ASPIRATED)

Inlet Por

CATERPILLAR C11, C13, C15 AND C18 ENGINES

PREVENTATIVE MAINTENANCE

The Bendix® BA-921® compressor in the C11, C13, C15, and C18 air induction systems (see Figure 13) receives its air from the engine's intake manifold (turbocharged). During the pumping condition (loaded mode), the air ﬂ ows from the engine intake manifold through the inlet check valve, expansion tank and inlet line to the compressor inlet port. During the non-pumping condition (unloaded mode), the compressor cylinder pushes air back out of the inlet port into the expansion tank. The ICV (at the end of the expansion tank) prevents the air from traveling beyond this point. Because the air is boosted (under pressure), it is important that the compressor inlet line is of sufﬁ cient length, strength and volume to minimize the build-up of air pressure in the inlet system. The air shuttles back and forth between the compressor cylinder bore and the expansion tank during this phase of the compressor operation.

DETROIT DIESEL

The Detroit Diesel Series 60 (EGR) engine is equipped with the Bendix® BA-921® compressor and uses naturally aspirated air induction system. Detroit Diesel recommends the use of an inlet check valve in the air induction system to prevent the air from the compressor cylinder bore from being forced back into the engine air induction system when the compressor is in the unloaded mode (non-pumping condition). A ﬂ exible high-pressure hose is installed between the inlet check valve and the compressor inlet ﬁ tting. This hose can be of various lengths to accommodate the distance between the compressor and inlet check valve. See Figure 14.

During operation, non-pressurized air from the engine's air source is routed to the compressor from a point between the engine air ﬁ lter and the non-pressure side of the turbocharger. When the compressor is building air (loaded mode), the air ﬂ ows from the engine intake tube, through the inlet check valve into the inlet port of the compressor. When the compressor is not building air (unloaded mode), the compressor pushes the air back out the compressor during the cylinder upstroke towards the inlet check valve. The ICV prevents the air from traveling beyond this point. The air shuttles back and forth between the compressor cylinder bore and the ICV during this phase of the compressor operation.

AIR INDUCTION

Section 2: For Closed Room Compressors.

Bendix Closed Room BA-921 only permitted to be naturally aspirated – use of engine turbocharger as an air source is not allowed. See Figure 6 on page 3 for an example of a naturally aspirated air induction system.

NOTE: DO NOT install an inlet check valve (ICV) on air induction systems where a closed room compressor is used.

air compressors are

Regularly scheduled maintenance is the single most important factor in maintaining the air brake charging system. Refer to Table A in the T roubleshooting section on page 21, for a guide to various considerations that must be given to maintenance of the compressor and other related charging system components.

Important Note: Review the warranty policy before performing any intrusive maintenance procedures. An extended warranty may be voided if intrusive maintenance is performed during this period.

EVERY 6 MONTHS, 1800 OPERATING HOURS OR AFTER EACH 50,000, MILES WHICHEVER OCCURS FIRST, PERFORM THE FOLLOWING INSPECTIONS AND TESTS.

AIR INDUCTION

The Bendix® BA-921® compressor is designed for connection to the vacuum side of the engine’s air induction system and the pressure side (turbocharged) of the engine’s air induction system.

A supply of clean air is one of the single most important factors in compressor preventive maintenance. Since the air supply for BA-921® compressor and engine is the engine air cleaner, periodic maintenance of the engine air ﬁ lter is necessary.

Inspect the compressor air induction system each time engine air cleaner maintenance is performed.

1. Inspect the intake hose adapters for physical damage. Make certain to check the adapters at both ends of the intake hose or tubing.

2. Inspect the intake hose clamps and tighten them if needed.

3. Inspect the intake hose or line for signs of drying, cracking, chafing and ruptures and replace if necessary.

4. Verify that the compressor inlet ﬁ tting is tight (check torque).

5. Any metal tubes should also be tight (torqued properly) to the mating ﬁ tting. Inspect the metal tubes for any cracks or breaks and replace if necessary.

6. If an expansion tank is present (turbocharged air induction systems only), inspect for any cracks and replace if necessary.

COMPRESSOR COOLING

Inspect the compressor discharge port, inlet cavity and discharge line for evidence of restrictions and carbon buildup. If more than 1/16" of carbon is found, thoroughly clean or replace the affected parts. In some case, carbon

buildup indicates inadequate cooling. Closely inspect the compressor cooling system. Check all compressor coolant lines for kinks and restrictions to ﬂ ow. Minimum coolant line size is 3/8" I.D. Check coolant lines for internal clogging from rust scale. If coolant lines appear suspicious, check the coolant ﬂ ow and compare to the tabulated technical data present in the back of this manual. Carefully inspect the air induction system for restrictions.

LUBRICATION

Caterpillar Engine Installations.

Check the external oil supply line for kinks, bends, or restrictions to ﬂ ow. Supply lines must be a minimum of 3/16” I.D. Refer to the tabulated technical data in the back of this manual for oil pressure minimum values.

Check the exterior of the compressor for the presence of oil seepage and refer to the TROUBLESHOOTING section for appropriate tests and corrective action.

Detroit Diesel S60 Installations

On Detroit Diesel Series 60 engine installations, the compressor utilizes an internal oil feed design. Check the exterior of the compressor for the presence of oil seepage and refer to the TROUBLESHOOTING section for appropriate tests and corrective action. Refer to the tabulated technical data in the back of this manual for oil pressure minimum values.

OIL PASSING

All reciprocating compressors pass a minimal amount of oil. Air dyers will remove the majority of oil before it can enter the air brake system. For particularly oil sensitive systems, the Bendix® PuraGuard® system can be use in conjunction with a Bendix® air dryer.

If compressor oil passing is suspected, refer to the TROUBLESHOOTING section (starting on page A-1) for the symptoms and corrective action to be taken. In addition, Bendix has developed the “Bendix Air System Inspection Cup” or BASIC™ kit to help substantiate suspected excessive oil passing. The steps to be followed when using the BASIC™ kit are presented in APPENDIX B, on page A-16.

COMPRESSOR DRIVE

Check for noisy compressor operation, which could indicate excessive drive component wear. Adjust and/or replace as necessary. Check all compressor mounting bolts and retighten evenly if necessary. Check for leakage and proper unloader mechanism operation. Repair or replace parts as necessary.

COMPRESSOR UNLOADER & GOVERNOR

Test and inspect the compressor and governor unloader system for proper operation and pressure setting.

1. Check for leakage at the unloader port. Replace leaking or worn o-rings.

2. Make certain the unloader system lines are connected as illustrated in Figure 6.

3. Cycle the compressor through the loaded and unloaded cycle several times. Make certain that the governor cuts-in (compressor resumes compressing air) at a minimum of 105 psi (cut-out should be approximately 15 - 20 psi greater than cut-in pressure). Adjust or replace the governor as required.

4. Note that the compressor cycles to the loaded and unloaded conditions promptly. If prompt action is not noted, repair or replace the governor and/or repair the compressor unloader.

IMPORTANT NOTE

Replacement air governors must have a minimum cut-in pressure of 100 psi. The cut-in pressure is the lowest system pressure registered in the gauges before the compressor resumes compressing air.

Compressors with no signal line to the unloader port should have a vent cap (e.g. Bendix part number 222797) installed in the port. Under no circumstances should the port be plugged or left open.

SERVICE TESTS

GENERAL

The following compressor operating and leakage tests need not be performed on a regular basis. These tests should be performed when it is suspected that leakage is substantially affecting compressor buildup performance, or when it is suspected that the compressor is “cycling” between the loaded (pumping) and unloaded (non-pumping) modes due to unloader leakage.

See Figure 10

for Port Details.

1 Head Cap Screws (4)

(include washers)

4 Unloader Cover

5 Unloader Cover Gasket

™

12 ST-4

Safety Valve

13 Cylinder Head

2 Unloader Cover Cap Screws (2)

3 Unloader Cover Splash Shield

6 Unloader Balance Piston

7 O-Ring

8 Spring

9 O-Ring 10 Unloader Piston

11 O-Ring

14 Head Gasket

Alignment

(2)

Bushings

15 Cooling

Plate

Kit Notes: Kit 1: Cylinder Head Gasket

Kit (5008558)

Kit 2: Unloader Kit (5008557) Kit 3: Governor Adapter Kit

(5008561) Kit 4: Cylinder Head Assembly Kit (K023600, K023601)

Other:

Crankcase Compressor Seal Kit (5008559) Unique Engine Seal Kits are available, for Cat C7/C9 Engine, Cat C11/C13/C15/C18 Engines, and DDC Series 60 Engines

Item Qty. Description

1 4 Head Cap Screws - (Kit 4) 2 2 Unloader Cover Cap Screws - (Kit 4) 3 1 Unloader Cover Splash Shield - (Kit 4) 4 1 Unloader Cover - (Kits 2 & 4) 5 1 Unloader Cap Gasket - (Kits 2 & 4) 6 1 Unloader Balance Piston - (Kits 2 & 4) 7 1 O-Ring - (Kits 2 & 4) 8 1 Spring - (Kits 2 & 4) 9 1 O-Ring - (Kits 2 & 4) 10 1 Unloader Piston - (Kits 2 & 4) 11 1 O-Ring - (Kits 2 & 4) 12 1 ST-4™ Safety Valve - (Kit 4) 13 1 Cylinder Head - (Kit 4) 14 2 Head Gaskets - (Kits 1 & 4) 15 1 Cooling Plate - (Kit 4) 16 1 Valve Plate Assembly - (Kit 4) 17 1 Inlet Reed Valve/Gasket - (Kits 1 & 4) 18 1 Piston 19 1 Connecting Rod 20 1 Sleeve Bearing 21 1 Crankcase 22 1 Crankshaft

17 Inlet Reed Valve/

Gasket

18 Piston

20 Bearing

Sleeve

21 Crankcase

27 Bottom Cover

Gasket

28 Crankcase

Cover

Item Qty. Description

23 1 Rear Bearing 24 1 O-Ring 25 1 Rear End Cover 26 4 Cap Screws 27 1 Bottom Cover Gasket 28 1 Crankcase Cover 29 4 Cap Screws 30 2 Governor Gasket - (Kits 3 & 4) 31 1 Governor Adapter - (Kits 3 & 4) 32 2 Bolt with Washer - (Kits 3 & 4)

FIGURE 15 – BA-921® STANDARD COMPRESSOR EXPLODED VIEW

19 Connecting

Rod

Crankcase

Alignment

Pins

22 Crankshaft

29 Cap

Screws (4)

16 Valve Plate

Assembly

Governor

Gasket (2)

23 Rear Bearing

24 O-Ring

Governor

Adapter

32 Bolt

with

Washer

(2)

25 Rear End

Cover

26 Cap

Screws (4)

12 ST-4™ Safety Valve

1 Head Cap Screws (6)

(include washers)

2 Unloader Cover Cap Screws (2)

See Figure 11 for

Port Details.

14 Head Gasket

13 Cylinder Head

(2)

16 Valve Plate

17 Inlet Reed Valve/

Gasket

4 Unloader Cover

5 Unloader Cover Gasket

6 Unloader Balance Piston

7 O-Ring

8 Spring

9 O-Ring 10 Unloader Piston

11 O-Ring

15 Cooling Plate

Alignment

Bushings

Assembly

Crankcase

Alignment

Pins

Kit Notes: Kit 1: Cylinder Head Gasket

Kit (K022563)

Kit 2: Unloader Kit (5008557) Kit 3: Governor Adapter Kit

(5008561)

Item Qty. Description

1 4 Head Cap Screws 2 2 Unloader Cover Cap Screws 3 1 Unloader Cover Splash Shield 4 1 Unloader Cover 5 1 Unloader Cap Gasket - (Kit 2) 6 1 Unloader Balance Piston - (Kit 2) 7 1 O-Ring - (Kit 2) 8 1 Spring - (Kit 2) 9 1 O-Ring - (Kit 2) 10 1 Unloader Piston - (Kit 2) 11 1 O-Ring - (Kit 2) 12 1 ST-4 13 1 Cylinder Head 14 2 Head Gaskets - (Kit 1) 15 1 Cooling Plate 16 1 Valve Plate Assembly 17 1 Inlet Reed Valve/Gasket - (Kit 1) 18 1 Piston 19 1 Connecting Rod 20 1 Bearing 21 1 Crankcase 22 1 Crankshaft (see Fig. 15)

™

Safety Valve

20 Bearing

Item Qty. Description

23 1 Rear Bearing (see Fig. 15) 24 1 O-Ring (see Fig. 15) 25 1 Rear End Cover (see Fig. 15) 26 4 Cap Screws (see Fig. 15) 27 1 Bottom Cover Gasket 28 1 Crankcase Cover 29 4 Cap Screws 30 2 Governor Gasket - (Kit 3) 31 1 Governor Adapter - (Kit 3) 32 2 Bolt with Washer - (Kit 3)

FIGURE 16 – BA-921® CLOSED ROOM COMPRESSOR EXPLODED VIEW.

27 Bottom Cover

Gasket

28 Crankcase

Cover

29 Cap

Screws (4)

21 Crankcase

Gasket (2)

Governor

Adapter

32 Bolt

with

Washer

(2)

IN SERVICE OPERATING TESTS

CYLINDER HEAD

Compressor Performance: Build-up Test

This test is performed with the vehicle parked and the engine operating at maximum recommended governed speed. Fully charge the air system to governor cut out (air dryer purges). Pump the service brake pedal to lower the system air pressure below 80 psi using the dash gauges. As the air pressure builds back up, measure the time from when the dash gauge passes 85 psi to the time it passes 100 psi. The time should not exceed 40 seconds. If the vehicle exceeds 40 seconds, test for (and ﬁ x) any air leaks, and then re- test the compressor performance. If the vehicle does not pass the test the second time, use the Advanced Troubleshooting Guide for Air Brake Compressors, starting on page A-1 of this document to assist your investigation of the cause(s).

Note: All new vehicles are certiﬁ ed using the FMVSS 121 test (paragraph S5.1.1) by the vehicle manufacturer, however the above test is a useful guide for in-service vehicles.

Optional Comparative Performance Check

It may be useful to also conduct the above test with the engine running at high idle (instead of maximum governed speed), and record the time taken to raise the system pressure a selected range (for example, from 90 to 120 psi, or from 100 to 120 psi, etc.) and record it in the vehicle’s maintenance ﬁ les. Subsequent build-up times throughout the vehicle’s service life can then be compared to the ﬁ rst one recorded. (Note: the 40 second guide in the test above does not apply to this build-up time.) If the performance degrades signiﬁ cantly over time, you may use the Advanced Troubleshooting Guide for Air Brake Compressors, starting on page A-1 of this document, to assist investigation of the cause(s).

Note: When comparing build-up times, be sure to make an allowance for any air system modiﬁ cations which would cause longer times, such as adding air components or reservoirs. Always check for air system leakage.

LEAKAGE TESTS

See the standard Air Brake System and Accessory Leakage test on Page A-14 (Test 2).

Note: Leakage in the air supply system (components before the supply reservoir - such as the governor, air dryer , reservoir drain cocks, safety valve and check valves) will not be registered on the vehicle dash gauges and must be tested separately. Refer to the various maintenance manuals for individual component leakage tests and the Bendix “Test and Checklist” published in the Air Brake System Handbook (BW5057) and on the back of the Dual Circuit Brake System Troubleshooting Card (BW1396).

Check for cylinder head gasket air leakage.

1. With the engine running, lower air system pressure to 60 psi and apply a soap solution around the cylinder head. Check the gasket between the cylinder head and valve plate assembly and the inlet reed valve/gasket between the valve plate assembly and crankcase for air leakage.

2. No leakage is permitted. If leakage is detected replace the compressor or repair the cylinder head using a genuine Bendix maintenance kit available from an authorized Bendix parts outlet.

INLET, DISCHARGE & UNLOADER

In order to test the inlet and discharge valves and the unloader piston, it is necessary to have shop air pressure and an assortment of ﬁ ttings. A soap solution is also required.

1. With the engine shut off, drain ALL air pressure from the vehicle.

2. Disconnect the inlet and discharge lines and remove the governor or its line or adapter ﬁ tting.

3. Apply 120-130 psi shop air pressure to the unloader port and soap the inlet port. Leakage at the inlet port should not exceed 50 sccm.

4. Apply 120-130 psi shop air pressure to the discharge port and then apply and release air pressure to the inlet port. Soap the inlet port and note that leakage at the inlet port does not exceed 20 sccm.

If excessive leakage is noted in Tests 3 or 4, replace or repair the compressor using genuine Bendix replacements or maintenance kits available from any authorized Bendix parts outlet.

While it is possible to test for inlet, discharge, and unloader piston leakage, it may not be practical to do so. Inlet and discharge valve leakage can generally be detected by longer compressor build-up and recovery times. Compare current compressor build-up times with the last several recorded times. Make certain to test for air system leakage, as described under In Service Operating Tests, before making a determination that performance has been lost.

Unloader leakage is generally exhibited by excessive compressor cycling between the loaded and unloaded condition.

1. With service and supply system leakage below the maximum allowable limits and the vehicle parked, bring system pressure to governor cut-out and allow the engine to idle.

2. The compressor should remain unloaded for a minimum of 5-10 minutes. If compressor cycling occurs more frequently and service and supply system leakage is within tolerance replace the compressor or repair the compressor unloader system using a genuine Bendix maintenance kit available from authorized Bendix parts outlets.

COMPRESSOR REMOVAL & DISASSEMBLY

GENERAL

The following disassembly and assembly procedure is presented for reference purposes and presupposes that a rebuild or repair of the compressor is being undertaken. Several maintenance kits are available and the instructions provided with these parts and kits should be followed in lieu of the instructions presented here.

MAINTENANCE KITS & SERVICE PARTS

Since the compressors have a different head and crankcase design, be sure to only use replacement parts speciﬁ cally applicable.

Note: In particular, the heads and head gaskets are not interchangeable between the two compressors covered in this document.

Section 1: Standard Compressor

Cylinder Head Gasket Kit ....................................................... 5008558

Unloader Kit ...........................................................................5008557

Governor Adapter Kit .............................................................5008561

Compressor Seal Kit (crankcase) ...........................................5008559

Components and kits for Caterpillar Engines

CAT C7/C9 Cylinder Head Assembly Kit ...............................K023601

CAT C11/C13/C15/C18 Cylinder Head Assembly Kit ............K023600

CAT C7/C9 Inlet Check Valve .................................................801580

CAT C11/C13/C15/C18 Inlet Check Valve ...............................801592

CAT C7/C9 Engine Seal Kit....................................................5012367

CAT C11/C13/C15/C18 Engine Seal Kit .................................5012369

CAT ST-4™ Discharge Safety Valve (7/8"-14 thrd.) ...................801116

Components and kits for DDC Engines

DDC Inlet Check Valve ............................................................802192

DDC Series 60 Engine Seal Kit .............................................. 5012371

™

DDC ST-4

Section 2: Closed Room Compressor

Cylinder Head Gasket Kit .......................................................K022563

Unloader Kit ...........................................................................5008557

Governor Adapter Kit .............................................................5008561

DDC Series 60 Engine Seal Kit .............................................. 5012371

DDC ST-4

All components shown in Figures 15 and 16 with a key number are available in kits and/or as individual service parts.

Discharge Safety Valve (M16-1.5 thrd.) .................800534

™

Discharge Safety Valve (M16-1.5 thrd.) .................800534

IMPORTANT! PLEASE READ AND FOLLOW THESE INSTRUCTIONS TO AVOID PERSONAL INJURY OR DEATH:

When working on or around a vehicle, the following general precautions should be observed at all times:

1. Park the vehicle on a level surface, apply the parking brakes, and always block the wheels. Always wear safety glasses. Where speciﬁ cally directed, the parking brakes may have to be released, and/or spring brakes caged, and this will require that the vehicle be prevented from moving by other means for the duration of these tests/procedures.

2. Stop the engine and remove ignition key when working under or around the vehicle. When working in the engine compartment, the engine should be shut off and the ignition key should be removed. Where circumstances require that the engine be in operation, EXTREME CAUTION should be used to prevent personal injury resulting from contact with moving, rotating, leaking, heated or electrically charged components.

3. Do not attempt to install, remove, disassemble or assemble a component until you have read and thoroughly understand the recommended procedures. Use only the proper tools and observe all precautions pertaining to use of those tools.

4. If the work is being performed on the vehicle’s air brake system, or any auxiliary pressurized air systems, make certain to drain the air pressure from all reservoirs before beginning ANY work on the vehicle. If the vehicle is equipped with an AD-IS air dryer system or a dryer reservoir module, be sure to drain the purge reservoir.

5. Following the vehicle manufacturer’s recommended procedures, deactivate the electrical system in a manner that safely removes all electrical power from the vehicle.

6. Never exceed manufacturer’s recommended pressures.

7. Never connect or disconnect a hose or line containing pressure; it may whip. Never remove a component or plug unless you are certain all system pressure has been depleted.

8. Use only genuine Bendix® replacement parts, components and kits. Replacement hardware, tubing, hose, ﬁ ttings, etc. must be of equivalent size, type and strength as original equipment and be designed speciﬁ cally for such applications and systems.

9. Components with stripped threads or damaged parts should be replaced rather than repaired. Do not attempt repairs requiring machining or welding

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