Does a self-operated control valve actually need a pressure gauge?

• Facilitating On-site Commissioning and Setting: The setpoint of a self-operated control valve (such as downstream pressure) is adjusted by modifying the spring preload. With a pressure gauge installed downstream, operators can observe pressure changes directly and in real-time, allowing them to precisely and conveniently adjust the valve to the desired control pressure. Therefore, the pressure gauge should be located close to the pressure sensing point to ensure the setpoint accurately reflects the actual sensed pressure and to facilitate easy observation.
• Monitoring Operational Status: By observing the readings of the upstream and downstream pressure gauges, operators can intuitively determine whether the control valve is functioning normally. For example, they can assess whether the valve is operating stably near the setpoint or if there are abnormal pressure fluctuations.
• Assisting in Fault Diagnosis: When system pressure anomalies occur, the difference between upstream and downstream gauge readings serves as a crucial basis for troubleshooting. For instance, consistently high downstream pressure might indicate a poor valve seal or a setpoint drift, while abnormal upstream pressure fluctuations could suggest issues with upstream equipment or piping. The real-time data provided by the gauges helps maintenance personnel quickly pinpoint the problem.
• Enhancing Operational Safety: During commissioning and maintenance, operators can use the pressure gauges to verify that pipeline pressure has been relieved to a safe level, thereby avoiding the risks associated with working on pressurized systems. Furthermore, during operation, pressure gauges provide real-time system pressure readings, facilitating the timely detection of hazardous conditions—such as overpressure—thereby ensuring the safety of both equipment and personnel. If pressure gauges are not installed on the pipelines upstream and downstream of the self-operated regulating valve, the gauge integrated into the valve body itself becomes even more critical.

As shown in the figure below, the absence of pressure gauges on the self-operated regulating valve and its associated upstream and downstream piping creates significant inconvenience for on-site inspections and commissioning. Figure: Self-operated regulating valve without upstream or downstream pressure gauges. Some enterprises have already addressed this issue; for instance, the technical specifications for instrument selection and design at certain large-scale domestic coal-chemical enterprises explicitly require that self-operated regulating valves utilize flanged connections and be equipped with both sensing-line and pressure-regulating pressure gauges. Figure: Self-operated regulating valve equipped with sensing-line and pressure-regulating pressure gauges. It should be noted that for pilot-operated self-operated regulating valves (such as the nitrogen supply valves in nitrogen blanketing systems), a filter equipped with a pressure gauge should be installed upstream of the pilot valve. Figure: Nitrogen supply valve for a nitrogen blanketing system.

To facilitate on-site observation, the adjustment of setpoints, and the monitoring of upstream and downstream pressures, it is recommended that pressure gauges be included as an optional feature during the design and selection process, based on specific operating conditions and requirements. Equipping a self-operated regulating valve with pressure gauges effectively integrates commissioning tools, monitoring instruments, and safety features into a single unit. This enables on-site personnel to perform setup, monitoring, and diagnostic tasks locally, instantly, and intuitively, serving as a crucial measure to ensure the precise, safe, and reliable operation of the valve.