The Real Problem With DAF Truck Air Processing Units

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Over the past two years we have seen a considerable increase in warranty claims with regard to the Air Processing Units or Air Dryer Units fitted to DAF trucks in the UK.
Most of these claims appear to be in respect of the larger DAFs, namely the CF85 and the XF95, however any DAF truck fitted with these Air Processing Units seem to be susceptible to a claim.
Most of the warranty claims that have been submitted to us have been rejected due to severe contamination, namely oil deposits from the Air Compressor which is the major cause of failure with these units.
In an attempt to combat this problem the vehicle manufacturer has recommended that the Air Dryer unit be relocated along with other modifications, depending on the vehicle model to accommodate a larger Air Dryer Filter.
The old filter part number is 1391510 and it is to be replaced by 1681575.
This filter, not only reduces moisture going in to the air system but also filters any oil vapour thus reducing contamination.
In my opinion this is unpractical, costly to the vehicle owner and does not address the real problem which ultimately lies with the Air Compressor.
There will always be some oil vapour however excessive oil will still get through particularly when operators fail to change the filters regularly enough.
When a DAF Truck requires a replacement Air Processing Unit the Main Dealer or parts supplier should request that the old unit be returned and inspected for excessive contamination, however this could be deemed to be acceptable if the unit had been in service for a number of years and that any build up of carbon had been slowly progressive.
The Air Dryer's silencer, generally is a good indicator as to whether there is excess oil passing into the air system, a light dusting that is matt in appearance is considered normal whereas thick shiny deposits would be considered abnormal.
It is also worth pointing out that whenever we have supplied both the Air Dryer and Air Compressor together no problems were experienced thereafter.
Other operators have accepted that their DAFs have quirks, this being one, and that if the Air Dryer filters are changed regularly, problems rarely occur.
All Parts suppliers have an obligation to inform Customers of the potential problems of not ensuring that the Air Compressor is of satisfactory condition and that all delivery pipes into the Air Dryer are clean and free of any obstruction.
This also covers the Supplier should a future warranty claim be made.
Unfortunately the cost of replacing the Air Compressor and Air Dryer is such that many operators will choose to ignore the cause (Air Compressor) and replace the problem (Air Dryer) and while a temporary fix is achieved it is only a matter of time before the replaced unit is causing problems and so the warranty process begins.
Therefore the questions are: Is it a badly designed unit in the first place? Is the Operator carrying out the necessary checks and regular servicing? Are the Air Tanks being drained regularly? Are the Vehicle manufacturers and the Air Brake manufacturers singing from the same hymn sheet or is there a difference of opinion?
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