Drain valve are used to drain liquids from lines, valves, vessels and tanks. They can be part of a valve, used with a bleed ring or just flanged to equipment.
Drain Valve Considerations
Drain valves are generally installed on the bottom of the pipe, 90-degrees off of horizontal. However, in services that are sandy or where there is particulate in the system, consider installing the valve 60-degrees off of horizontal. This may help mitigate the effects of particulate plugging.
Sizing of the drain valve should take the following into account:
- How large does the valve need to be to effectively drain the line? The smaller the valve, the lower the flow rate through the valve and longer it will take to drain. For example, using a 1/4" valve on a line that is hundreds of feet long, is likely a poor decision.
- Is the process hazardous and does it require a vacuum truck connection? If the process cannot be discharged directly on to the ground, there should be provisions installed to capture the fluid into a receptacle.
- Is a vent valve needed? A vent valve upstream of the drain valve will allow for faster discharge through the drain valve.
- Is the process sandy or does it have particulate in the process? Often times, if operations personnel open the drain and it is plugged, they will try to knock the plug out with a piece of welding rod. Consider using a larger drain valve and shorter nipple to assist the operator. When it makes sense, consider the use of a filter upstream of the drain valve to remove the particulate.