we have problem with selfdrain valves on air reservoir, as they sound exteremly some times or doeson't sound at all i want to know is it something about it that we dont know for example how to install properly or using one filter befor them , and if other railroades have same problem like us and how they solve it ?
What type of valve do you have ? There is two type of self-drain valves (or spitter valves) well known in the industry. The Salem 686 (see link)
http://www.grahamwhite.com/main/product ... P1=1&P2=-1
or the Sarco trap. The Sarco is a steam condensation trap that have been introduce in the railway industry like a virus.. It doesn't work properly on any locomotive.
The Salem 686 is well design and works well as long as you manually drain the reservoirs at least twice a week and the system (reservoir slope, compressor intake filter etc..) is in good working order.
Since self-drain valve operate with the presence of liquid in the air (water and/or oil) the more liquid is accumulated in the reservoir more often the valve operate and the longer it stays open.
Higher is the humidity in the air, more water will condensate in the reservoir too.
The reservoir has to be installed with a slope toward the drain valve. If the slope is reversed or too small, water accumulates on the opposite side of the valve and flows rapidly toward the valve when locomotive level changes (drain valves become the lowest point) or during deceleration (braking). In such case the valve become crazy and spits all the time.
Those valve are also very sensitive to contabination (rust, scale etc..)
Keeping the air compressor intake filter in good condition hepls too.
Claude