SD-01-700 BENDIX® BA-922® COMPRESSOR DESCRIPTION The function of the air compressor is to provide and maintain air under pressure to operate devices in the air brake systems. The Bendix® BA-922® compressor is a two cylinder, reciprocating compressor with a rated displacement of 31.6 cubic feet per minute at 1250 RPM. The compressor consists of a water-cooled cylinder head, cooling plate, valve plate assembly, and an integral air cooled crankcase and cylinder block.
Caterpillar® Detroit Diesel® FIGURE 3 - TYPICAL COMPRESSOR DRIVE FLANGES AIR INTAKE (LOADED) During the piston down stroke, a vacuum is created in the cylinder bore above the piston. The vacuum causes the inlet reed valve to flex open. Atmospheric air flows through the open inlet valve and fills the cylinder bore above the piston. Detroit Diesel® John Deere® cavity and into the other cylinder. A small amount of air moves out of the inlet port.
COOLING Air Discharge Port Air Inlet Port Discharge Valve Open Unloader Port Valve Plate Unloader Piston Down & Seated Inlet Valve Closed Piston Moving Up FIGURE 6 - OPERATION - LOADED (COMPRESSION) LUBRICATION The vehicle's engine provides a continuous supply of oil to the compressor. Oil is routed from the engine to the compressor oil inlet. An oil passage in the crankshaft conducts pressurized oil to precision sleeve main bearings and to the connecting rod bearings.
A supply of clean air is one of the single most important factors in compressor preventative maintenance. Since the Bendix® BA-922® compressor receives supply air from the engine air filter, periodic maintenance of the engine air filter is necessary. Head Bolt (6) Discharge Safety Valve Unloader Covers Coolant In or Out Inspect the compressor intake adapter, and the connecting hoses each time engine air cleaner maintenance is performed. 1. Inspect the intake hose adapters for physical damage.
IMPORTANT NOTE Replacement air governors must have a minimum cut-in pressure of 105 psi. The cut-in pressure is the lowest system pressure registered in the gauges before the compressor resumes compressing air. Note: When comparing build-up times, be sure to make an allowance for any air system modifications which could cause longer times, such as adding air components or reservoirs. Always check for air system leakage.
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 above, before making a determination that compressor performance has been lost. 2.
1 2 3 4 5 6 7 10 8 9 Cylinder Head 11 Cooling Plate 11 Valve Plate Assembly 12 Crankcase & Cylinder Block 13 14 Item 1 21 31 41 51 Qty. 2 1 1 1 1 Description Unloader Cover Cap Screw Unloader Cover Unloader Cap Gasket Unloader Balance Piston Spring Crankcase Cover Item 61 71 81 91 10 Qty.
4. Remove the discharge and inlet fittings, if applicable, and note their position on the compressor to aid in reassembly. Note: If a cylinder head maintenance kit is being installed, stop here and proceed to PREPARATION FOR DISASSEMBLY. If replacing the compressor continue. 5. Remove any supporting bracketing attached to the compressor and note their positions on the compressor to aid in reassembly. 6. Remove the flange mounting bolts and remove the compressor from the vehicle. 7.
INSPECTION OF PARTS CYLINDER HEAD & VALVE PLATE 1. Carefully inspect the cylinder head gasket surfaces for deep gouges and nicks. If detected, the compressor must be replaced. 2. Carefully inspect the valve plate assembly gasket surfaces for deep gouges and nicks. Pay particular attention to the metal gasket surface. A metal gasket (12) is used between the valve plate assembly and the cylinder block. This surface must be smooth and free of all but the most minor scratching.
9. Install the balance piston spring (5) in the unloader piston (7), then install the small diameter of the balance piston (4) through the center of the spring. 5, 11 10. Install the unloader cover gasket (3) on the cylinder head making certain the unloader vent passage and both screw holes align. 8, 14 1, 15 7,13 11. Position the unloader cover (2) on top of the balance piston (4) making certain the stamped logo is visible. 12.
TORQUE SPECIFICATIONS Assembly Torques in inch pounds (in. Ibs.) M8x1.25-6g Cylinder Head .......... 265-292 In. Lbs. (30-33 Nm) M5x0.75-6g Unloader Cap ................... 62-71 In. Lbs. (7-8 Nm) M8x1.25-6g Governor Adapter .... 195-213 In. Lbs. (22-24 Nm) M8x1.25-6g Rear End Cover........ 195-213 In. Lbs. (22-24 Nm) M6x1.00-6g Crankcase Cover ........... 62-71 In. Lbs. (7-8 Nm) M20x2.50-6g Crankshaft Nut 1858-2567 In. Lbs. (210-290 Nm) Inlet Port Fittings 1 3/16"-12 UN-2B ..........................
Introduction to the Air Brake Charging System Powered by the vehicle engine, the air compressor builds the air pressure for the air brake system. The air compressor is typically cooled by the engine coolant system and lubricated by the engine oil supply.
Table A: Maintenance Schedule and Usage Guidelines Regularly scheduled maintenance is the single most important factor in maintaining the air brake charging system. Vehicle Used for: No. of Axles Column 1 Column 2 Typical Compressors Spec'd Discharge Line (See footnote 7) I.D. Length 1/2 in. 6 ft. Column 3 Recommended Air Dryer Cartridge Replacement1 Column 4 Recommended Reservoir Drain Schedule2 Column 5 Acceptable Reservoir Oil Contents3 at Regular Drain Interval e.g.
Air Brake Charging System Troubleshooting Look for: How to use this guide: Find the symptom(s) that you see, then move to the right to find the possible causes (“What it may indicate”) and remedies (“What you should do”). Review the warranty policy before performing any intrusive compressor maintenance. Unloader or cylinder head gasket replacement and resealing of the bottom cover plate are usually permitted under warranty. Follow all standard safety procedures when performing any maintenance.
Symptom: What it may indicate: What you should do: 2.0 Oil on the Outside of the Compressor Engine and/or other accessories leaking onto compressor. Find the source and repair. Return the vehicle to service. 2.1 Oil leaking at compressor / engine connections: (a) Leak at the front or rear (fuel pump, etc.) mounting flange. Repair or replace as necessary. If the mounting bolt torques are low, replace the gasket. (b) Leak at air inlet fitting. Replace the fitting gasket.
Symptom: What it may indicate: 4.0 Oil in Supply or Service Reservoir (air dryer installed) (If a maintained Bendix PuraGuard® system filter or Bendix® PuraGuard QC™ oil coalescing filter is installed, call 1-800-AIR-BRAKE (1-800-247-2725) and speak to a Tech Team member.) ® What you should do: Maintenance (a) If air brake charging system maintenance has not been performed.
Symptom: 4.0 Oil in Supply or Service Reservoir* (air dryer installed) (continued) What it may indicate: What you should do: Temperature (e) Air compressor discharge and/or air dryer inlet temperature too high. Check temperature as outlined in Test 3 on page 24. If temperatures are normal go to 4.0(h). Inspect coolant line. Replace as necessary (I.D. is 1/2"). (f) Insufficient coolant flow. Inspect the coolant lines for kinks and restrictions and fittings for restrictions.
Symptom: 4.0 Oil in Supply or Service Reservoir* (air dryer installed) (continued) What it may indicate: What you should do: Other (cont.) (i) Poorly filtered inlet air (poor air quality to compressor). Check for leaking, damaged or defective compressor air inlet components (e.g. induction line, fittings, gaskets, filter bodies, etc.). Repair inlet components as needed. Note: Dirt ingestion will damage compressor and is not covered under warranty. Inspect the engine air cleaner.
Symptom: What it may indicate: What you should do: 6.0 Excessive oil consumption in engine. A problem with engine or other engine accessory. See engine service manual. 7.0 Oil present at air dryer cartridge during maintenance. Air brake charging system is functioning normally. The engine service manual has more information. Oil shown leaking from an air dryer cartridge. Air dryers remove water and oil from the air brake charging system. A small amount of oil is normal.
Symptom: What it may indicate: 9.0 Air brake charging system seems slow to build pressure. (continued) (f) Restricted discharge line. (f) Dash gauges. Kinked discharge line shown. Engine Oil Quality Inadequate oil change intervals, the formulation of the oil and/or the quality of oil filter used can all lead to poor oil quality. These can increase the rate at which carbon builds up in the discharge line. Bendix recommends oil soot (solids) be maintained at less than 3%.
Symptom: 10.0 Air charging system doesn’t build air. What it may indicate: (a) Governor malfunction*. Go to Test 4 on page 25. (b) Restricted discharge line. See 9.0(f). (c) Air dryer heater malfunction: exhaust port frozen open. Replace air dryer heater. (d) Compressor malfunction. Replace the compressor only after making certain the preceding conditions do not exist.
Symptom: 12.0 Air dryer safety valve releases air. Air dryer safety valve What it may indicate: (a) Restriction between air dryer and reservoir. Inspect delivery lines to reservoir for restrictions and repair as needed. (b) Air dryer safety valve malfunction. Verify relief pressure is at vehicle or component manufacturer specifications. Replace if defective. (c) Air dryer maintenance not performed. See Maintenance Schedule and Usage Guidelines (Table A, column 3, on page 13).
16.0 Compressor leaks air Testing for leaks with soap solution. 17.0 Compressor leaks coolant 18.0 Noisy compressor (Multi-cylinder compressors only) What it may indicate: What you should do: (a) Compressor leaks air at connections or ports. Check for leaking, damaged or defective compressor fittings, gaskets, etc. Repair or replace as necessary. (b) Compressor unloader mechanism malfunction. Go to Test 6 on page 25. (c) Damaged compressor head gasket(s).
Tests Test 1: Excessive Oil Leakage at the Head Gasket Exterior leaks at the head gasket are not a sign that oil is being passed into the air charging system. Oil weepage at the head gasket does not prevent the compressor from building air. Look for Weepage Observe the amount of weepage from the head gasket.
Tests (continued) Test 4: Governor Malfunction 1. Inspect control lines to and from the governor for restrictions (e.g. collapsed or kinked). Repair as necessary. 2. Using a calibrated external gauge in the supply reservoir, service reservoir, or reservoir port of the D-2® governor, verify cut-in and cut-out pressures are within vehicle OEM specification. 3. If the governor is malfunctioning, replace it. Test 5: Governor Control Line 1.
Appendix A: Information about the BASIC Test Kit (Bendix P/N 5013711) Service writer records info - including the number of days since all air tanks were drained - and fills out symptom checklist. Technician inspects items. days Bendix® Air System Inspection Cup (BASIC) Test Information START BASIC TEST Park vehicle on LEVEL ground. Chock wheels, drain air from system. Drain contents of ALL air tanks into BASIC™ cup Is there less than one unit of liquid? Vehicle OK. Return vehicle to service.
Appendix A continued: Information about the BASIC Test Kit (Bendix P/N 5013711) ® Filling in the Checklist for the Bendix Air System Inspection Cup (BASIC) Test Note: Follow all standard safety precautions. For vehicles using a desiccant air dryer.
Appendix A continued: Information about the BASIC Test Kit (Bendix P/N 5013711) ® Filling in the Checklist for the Bendix Air System Inspection Cup (BASIC) Test Note: Follow all standard safety precautions. For vehicles using a desiccant air dryer. 2. Record amount of oil found: _________ days _________ units If number of days is: 30-60 days (high air use) or 30-90 days (low air use) Otherwise . . . (if the number of days is unknown, or outside the limits above) 3.
Appendix B Technical Bulletin Bulletin No.
Appendix B: Continued Bulletin No.: TCH-008-021 Effective Date: 3/5/2010 Page: 2 of 2 System Leakage Check the air brake system for excessive air leakage using the Bendix “Dual System Air Brake Test and Check List” (BW1279). Excessive system leakage causes the compressor to “pump” more air and also reduce the life of the air dryer desiccant cartridge. Reservoir Draining (System without an Air Dryer) Routine reservoir draining is the most basic step in reducing the possibility of freeze-up.
Appendix B: Continued Technical Bulletin Bulletin No.: TCH-008-022 Subject: Additional Effective Date: 1/1/1994 Page: 1 of 1 Cold Weather Operation Tips for the Air Brake System Last year we published Bulletin PRO-08-21 which provided some guidelines for “winterizing” a vehicle air brake system. Here are some additional suggestions for making cold weather vehicle operation just a little more bearable.
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