Adequate drainage points with Compressed air drain traps should be provided in a compressed air distribution network. Water entrained in compressed air not only damages the equipments at the user end, it also develops leaks in the compressed air network.
Although in an ideal system all cooling and condensing should be carried out before the air leaves the receiver, often not achieved in practice. It is in fact impossible where after-coolers are not fitted in the network. The whole of the compressed air mains therefore becomes additional cooling surface and the amount of condensing which takes place depends on the efficiency of moisture extraction before the air leaves the receiver and the temperature in the mains itself.
If the moisture is not separated from the air, this moisture will enter the air consuming equipments at the user end such as blowguns, pneumatic actuators, etc. In pneumatic actuators of valves, this water very often damages the diaphragm of the actuator thus damaging the valve and hampering the process. Also the water in the compressed air mains erodes and corrodes the piping, leading to the development of leaks in the network.
Thus care must be taken in the layout of the mains so that adequate provision is provided in the compressed air network for evacuation of the condensed water. One of such measures is to ensure adequate fall is provided for the drainage points. While the general layout of the building will dictate the best position for drainage points, in general the mains should be given a fall of at least 1m in 100m in the direction of the air flow and the distance between the drain points should not exceed 30m. Additionally at these drain points compressed air drain traps should be provided. Similar in functioning to steam traps, compressed air drain traps drain the condensed water while holding back the compressed air in the network.