BENDIX TCH-001-045 Manuel D’Utilisation
An absence of water and/or oil after the second draining indicates the compressor and all compressor support
systems are operating properly. Continue to perform reservoir draining on a regular basis as outlined in Table A.
systems are operating properly. Continue to perform reservoir draining on a regular basis as outlined in Table A.
Step 2: External Influences
At this point it should have been established through observations made in Step 1 that conditions exist causing
excessive oil passing. This does not indicate that immediate removal of the compressor is necessary or that the
compressor is the root cause for this issue. Removal of the compressor at this point usually leads to the
replacement of several compressors over a period of time without resolution of the issue.
At this point it should have been established through observations made in Step 1 that conditions exist causing
excessive oil passing. This does not indicate that immediate removal of the compressor is necessary or that the
compressor is the root cause for this issue. Removal of the compressor at this point usually leads to the
replacement of several compressors over a period of time without resolution of the issue.
The support systems, which control and contribute to the compressor operation must be examined. There are
many external influences, which can affect compressor oil passing. The influences can be grouped into
subcategorizes as follows:
many external influences, which can affect compressor oil passing. The influences can be grouped into
subcategorizes as follows:
• Vehicle operation
• Engine operation
• Compressor inlet air supply system
• Compressor coolant supply system
• Compressor oil supply and return system
Proceed to Step 3.
Step 3: Vehicle Operation
Vehicle operation is the driving factor for compressor performance and influences all of the systems that control
and contribute to compressor operation.
Check vehicle system leakage. Vehicle system leakage should not exceed industry standards of 1 psi (6.9 kPa)
pressure drop per minute without brakes applied and 3 psi (20.7 kPa) pressure drop per minute with brakes
applied. If leakage is excessive, check for system leaks and repair.
After determining that the system leakage meets industry standards the compressor duty cycle must be
established. Duty cycle is the percent of time the compressor is loaded during a period of operation. As duty cycle
increases, the amount of oil passed into the system increases.
Example:
If two compressors, which pass the same amount of oil when operated at the same duty cycle, are placed on two
vehicles which are identical except for duty cycle, the compressor on the vehicle with the greater duty cycle
would pass more oil into the system. The amount of effluent purged from the dryer would be greater on the
vehicle with the greater duty cycle. Thus the relative amount of oil at the purge of the dryer is not only an
indication of the level of oil passed by the compressor but also the duty cycle of the compressor.
Compressors that operate with duty cycles of 25% or less will have an expected life equal to the normal warranty
period. As duty cycles extend beyond 25% the expected life will decrease.
It is recommended that the compressor duty cycle should not exceed 25% and the average charge period should
not exceed 90 seconds to ensure the normal life of the compressor and dryer. By keeping the charge time at or
below 90 seconds the compressor operating temperature is lower reducing oil consumption, carbon formation,
and discharge temperatures. By keeping discharge temperatures lower the dryer’s ability to remove oil and
moisture is increased.
Once the duty cycle is established review Table A for the vehicle application and make sure that the compressor
and air dryer combination installed on the vehicle match those recommended based on duty cycle. If the vehicle is
not properly equipped a change of the compressor and/or air dryer maybe necessary.
If the duty cycle exceeds the recommended 25%, two options are available:
• Reduce the amount of demand by redesigning the air system.
Proceed to Step 3.
Step 3: Vehicle Operation
Vehicle operation is the driving factor for compressor performance and influences all of the systems that control
and contribute to compressor operation.
Check vehicle system leakage. Vehicle system leakage should not exceed industry standards of 1 psi (6.9 kPa)
pressure drop per minute without brakes applied and 3 psi (20.7 kPa) pressure drop per minute with brakes
applied. If leakage is excessive, check for system leaks and repair.
After determining that the system leakage meets industry standards the compressor duty cycle must be
established. Duty cycle is the percent of time the compressor is loaded during a period of operation. As duty cycle
increases, the amount of oil passed into the system increases.
Example:
If two compressors, which pass the same amount of oil when operated at the same duty cycle, are placed on two
vehicles which are identical except for duty cycle, the compressor on the vehicle with the greater duty cycle
would pass more oil into the system. The amount of effluent purged from the dryer would be greater on the
vehicle with the greater duty cycle. Thus the relative amount of oil at the purge of the dryer is not only an
indication of the level of oil passed by the compressor but also the duty cycle of the compressor.
Compressors that operate with duty cycles of 25% or less will have an expected life equal to the normal warranty
period. As duty cycles extend beyond 25% the expected life will decrease.
It is recommended that the compressor duty cycle should not exceed 25% and the average charge period should
not exceed 90 seconds to ensure the normal life of the compressor and dryer. By keeping the charge time at or
below 90 seconds the compressor operating temperature is lower reducing oil consumption, carbon formation,
and discharge temperatures. By keeping discharge temperatures lower the dryer’s ability to remove oil and
moisture is increased.
Once the duty cycle is established review Table A for the vehicle application and make sure that the compressor
and air dryer combination installed on the vehicle match those recommended based on duty cycle. If the vehicle is
not properly equipped a change of the compressor and/or air dryer maybe necessary.
If the duty cycle exceeds the recommended 25%, two options are available:
• Reduce the amount of demand by redesigning the air system.