millemille
Member
- Joined
- 28 Jul 2011
- Messages
- 353
I am surprised that the Low Main Reservoir Protection system operated to initiate an Emergency brake application as a result of WSP activity. Low Main Reservoir protection is primarily intended to stop the train in the event that the compressed air supply is no longer available. I would expect the compressor/s to be able to provide sufficient air for WSP activity.
Not quite , the main reservoir low pressure protection kicks in to ensure that there is still enough pressure left to ensure that the train can come to a stand with full brake effort from the train's maximum speed. Prolonged WSP activity on all vehicles uses a lot of air, generally about as quickly as compressor/compressors can produce it AND then you've probably got a sander merrily blasting away consuming even more air.
The problem is worse on DMU's because the compressor output is generally engine rpm related and when a DMU is braking engine rpm is low so compressor output is low.
When we design sander systems it is one of the factors to consider; will the train's air system support prolonged WSP activity AND sander activity AND warning horn sounding (because it is not unreasonable to assume that a prolonged slide may result in the warning horn needing sounding) AND normal "hotel" air consumption like toilets being flushed*.....
*and before anyone pipes up, not the one for the driver as they sh*t themselves as they slide past red signals....