A three-way valve on the panel can be installed to bypass the high- and low-pressure pilots and the sand probes while sensors are being tested, calibrated, or replaced. For safety reasons, it should be very evident from a distance that the bypass valve has been switched by the use of panel-mounted indicators. Many facilities require an alarm when bypass switches are used. Sometimes individual bypass valves for each of the three sensors are used.
A test connection in the field should be provided for checking the pressure sensors. Individual barstock root valves and test valves are normally used. When oil quality allows the pressure pilots to be panel-mounted, then the test connection can be panel-mounted also.
Needle valves in the supply gas and hydraulic oil tubing runs should be provided to allow components to be replaced without requiring that an individual wellhead or all the wellheads be shut down. Some of the components which may require replacement are as follows:
• Pressure regulators
• Pressure gages
• Hydraulic pumps and their regulators