I’ve often written about how digital valve controllers improve control valve performance and ongoing maintenance. But how about on-off valves?
In this Valve World Americas featured story, How Digitized On-Off Valves Improve Operations, Emerson’s Riyaz Ali explains how the:
…data provided by smart on-off valves can be used to increase uptime, reduce maintenance costs, and improve safety.
Riyaz opens the article by highlighting some examples where on-off valves can be found.
Automated on-off valves are typically used for starting and stopping batch processes, routing process fluids to different locations, emptying and filling tanks, backwashing and blow-back of filters, loading and unloading, engaging automated safety shutdown functions, and other applications. These valves are usually referred to as final control elements.
Smart valve technologies enable many ways to improve operations, from remote monitoring to predictive maintenance. Before intelligent, microprocessor-based valve technology:
…on-off valves were automated with a separate solenoid valve, two feedback limit switches indicating an open or closed position, and in some cases a position transmitter. The common challenge with the feedback limit switches and position transmitters was their significant alignment and mounting issues.
Some common problems with on-off valves over time include:
Actuator failure.
Insufficient shut-off pressure for actuator operation.
Increased packing friction.
Packing leaks.
Valve body connection issues, such as shaft wind up, backlash, and stiction.
Spring failure.
Trim failure.
Insufficient torque.
Motor overloading.
Problems related to excess temperatures and pressures.
Valves with digital controllers, such as the Bettis XTE digital electric actuator or a Fisher valve with the FIELDVUE DVC6200 digital valve controller and ValveLink software:
…can be used to mitigate or eliminate many of the common issues… These smart devices can be used with sliding stem, rotary, quarter-turn, and other types of on-off valves. The actuator can be single- or double-acting, with direct or reverse action.
With this onboard intelligence, many of the problems above can be predicted, with the diagnostics being analyzed in DCMLink software for conditions such as:
Valve seat integrity.
Erratic valve performance.
Worn valve components.
Actuator problems.
Overall integrity of valve assembly.
Friction data, from which packing condition can be inferred.
Leakage in the pressurized pneumatic path to the actuator. Valve sticking.
Incorrect bench settings for diaphragm or piston actuator springs.
Buildup of process fluid material on a shaft.
Seizure of the shaft.
Fracturing of valve shafts or stems.
Actuator stem/shaft bending.
Corroded bearings.
Actuator spring rates.
Broken springs on the actuator.
Springs setting permanently in one position.
Dented spring return actuators, which do not allow valve travel.
Ball seal breakaway friction.
Slow air exhaust.
Blocked air exhaust paths.
Read the article for more on the on-off valve actuator diagnostics, how they function, detect faults early, enable predictive maintenance practices, remote troubleshooting, performance optimization, and data-driven decision-making. Visit the Actuators section on Emerson.com for more on these and other smart devices to help you improve operational performance and maintenance practices.
