Control Valve Accessories

Hydraulically operated automatic control valves function through a network of pilot valves, sensing lines and actuating chambers that modulate the main valve position in response to system conditions. Each component in this pilot circuit plays a specific role in valve performance, and the condition of these components directly affects the accuracy, stability and reliability of the control function. Using genuine replacement parts and accessories is the most effective way to maintain control valve performance throughout its service life.

Pilot regulators are the heart of the control function. A pressure reducing pilot valve senses downstream pressure through a sensing line and adjusts the pilot flow to modulate the main valve opening. The accuracy of pressure control depends on the calibration and mechanical condition of the pilot spring and diaphragm. Worn or corroded pilot internals lead to unstable pressure control, hunting or a failure to maintain setpoint. Genuine pilot regulators are manufactured to the same tolerances as the original equipment and are calibrated before despatch.

Solenoid coils and pilot solenoids allow electrical control of the main valve. A normally open solenoid pilot allows the valve to close on power loss; a normally closed pilot holds the valve shut until energised. Solenoid coils are available in 12V DC, 24V DC, 110V AC and 230V AC to suit local power supply arrangements. Coil windings deteriorate over time in humid or chemically aggressive environments and replacement coils should be sourced to the original specification to maintain the valve's response time and power consumption.

Position indicators and limit switches provide visual and electronic indication of valve position. A mechanical position indicator mounted on the valve stem cover gives a local open/closed indication visible during routine inspection. Limit switches provide a remote signal to SCADA or building management systems and can be configured to trigger alarms on unexpected valve movement or failure to reach full travel.

Diaphragm assemblies are the most commonly replaced component in hydraulic control valves. The actuating diaphragm separates the control chamber from the pipeline and any failure of the diaphragm material allows uncontrolled equalisation of pressure and loss of control function. EPDM diaphragms are standard for clean water service; NBR diaphragms are used where the pipeline contains petroleum products or where water temperatures exceed 60 degrees Celsius.

AFC Valves Europe stocks genuine accessories and spare parts for the full range of hydraulically operated automatic control valves. We supply European water utilities, framework maintenance contractors and mechanical service companies. Our technical team can assist with fault diagnosis, part identification and maintenance planning.