I'm having a hard time picturing the plastic "trap" you describe. It sounds more to me that it may be an oiler that was installed in line with an air/electric valve to operate an air ram or other device on the old sweeper bed. I've seen the air rams on belly dumps set up similar to that. Most air driers I've seen on trucks are of steel construction and are plumbed between the compressor and the tanks.


Joe McNeel

http://mcneelnet.com/~jmcneel/59.html