Troubleshooting Tips
High Pressure
or
Control Valve Failure
Explanation
The purpose of the CONTROL VALVE FAILURE, or HIGH PRESSURE alarm is to prevent damage to mainlines, valves, and components such as bubblers, drip lines, filters, etc., due to a malfunctioning pressure reducing control valve. The definition of a pressure reducing control valve is:
Valve maintains a constant downstream pressure regardless of flow rate or inlet pressure.
Remember one interesting fact about reducing valves. When a problem occurs on a pilot operated pressure reducing valve, the most likely result will be that the valve goes wide open allowing a higher pressure downstream than what is intended. In other words, pressure reducing valves tend to fail wide open.
Pressure Reducing Control Valve Problems
a. Clogged pilot system filter.
b. High side pilot system ball valve closed or partially closed.
c. Metering orifice adjusted to a position that is too restrictive.
d. Leaking main body diaphragm.
e. Speed control adjusted incorrectly.
f. Incorrectly adjusted pressure regulating pilot.
g. Failed check valves in the pilot system.
h. Any leaks, clogs, restrictions, etc. in the pilot system.
Other Possible Causes
1. Are any field valves closing extremely fast? An extremely fast closing valve can cause a very fast pressure rise in the mainline, faster than the pressure control valve can respond to, and thereby cause this alarm. This type of event would be more likely if the fast closing valve were close to the pump station, but this does not have to be the case however.
2. If the station discharge butterfly valve is closed too quickly the pressure control valve will definitely not be able to respond fast enough and cause this condition. Butterfly valves should always be closed slowly. This valve can be closed fast enough so that the pressure control valve cannot respond fast enough to prevent a pressure rise.
