need of information

[Anonymous]

sir,

this is prakash from india. i'm an student in the final year of mechanical Engineering.
I am doing a live project under railway wagon workshop here. i'm the leader of my project team.
The task we were allotted is a major one and i need some help from u if it is possible, i hope u can be helpful in guiding me to complete my project.

the problem is as follows:

here in the workshop, the distributor valves of different wagons are detached, cleaned and tested in the air brake system unit whether they are functioning properly or not. There is a tolerance limit given to the workers here that out of 100 distributor valves(DV) some 10 DVs can be left unrepaired, ie 10 out 100 DVs which contain some minor repairs can be overlooked which do not have major effect on application of brakes.

The train that leaves the workshop after getting repaired
moves to the main station which is some 20 kms away from here. Further the DVs are checked there and to the surprise of the workers there, some of those 10 dvs( out of 100) which were reported as having minor troubles seems to be working properly and the dvs that are certified alright by the workshop started giving troubles. Same is the case happening at other workshops as well and the staff cannot find what was really happening. There are no major atmospheric differences at these areas and the problem seems to be a mystery.

This is a challenging task and i was asked to find the reason for it. I will be thankful to if u suggest me any reasons for this. Ofcourse I am doing my own work for this. Only your answer will be a guide to me.

thanking you sir
yours sincerely
prakash

[jchnhtfd]

There are better guys than me on this forum to answer that, Prakash -- but my first guess would be dirt. Those buggers are prone to hanging up on tiny bits of crud in the brake pipes -- which then get blown out on the next application and you can't find the problem. Step one? Clean everything so well you can eat off it, and keep it that way...

Are there filters on the lines?

And, by the way, are we talking vacuum or air here?

[mudchicken]

Talk to the people at the AAR Test Center (AAR/TTC) at Pueblo, Colorado.....www.AAR.org and www.AAR.com

AAR = Association of American Railroads

[kenneo]

Jamie -- would it matter? I think that this problem would be worse in a vac system than a preasure system.

If it is a vac system, perhaps British Rail could assist. Actually, any European system could advise and which country would depend on what languages our questioners speak.

[jchnhtfd]

Eric -- wouldn't matter a bit whether it was vacuum or air, so far as getting things like dirt hung up in a valve and giving trouble -- though I'd agree that it would seem to me that the problem would be worse with a vacuum system. Would make a difference in one way, though, perhaps (although what I know about vacuum systems would fit into a very small hat) -- maybe atmospheric dirt would matter more, and train line dirt less?