SOLENOID OPERATED VALVE (SOV) TESTING

SOV testing solution by Val Controls

What is Solenoid Operated Valve (SOV) testing?

The purpose of SOV testing is to exercise the SOV without any movement of the complete valve system. Val Controls SOV testing solution allows the plant to stay in operation while the testing is being performed. Data from the test will be stored and trending of the SOV performance can be used for evaluation.

The advantage of Val Controls SOV testing solution is that the end-user can diagnose the valve while it is in use. Furthermore, the solution provides the possibility of comparing the current performance data with the optimal reference data.

The SOV testing will exercise the SOV, decreasing the risk of valve stiction and ultimately malfunction.

BENEFITS OF SOV TESTING

In many SIS applications, the solenoid valve remains energized in the open position during normal operation. (Note: This indirectly acknowledges energize to trip applications.) However, if the system detects overpressure or other dangerous conditions, the valve moves to the closed position, activating the ESD valve to stop the process flow.

Despite the solenoid valve's critical role in ensuring the safety of the facility, equipment and nearby personnel, the solenoid valve rarely gets used. In fact, it can remain in the same position for months or even years, increasing the risk that it will fail to close on command. Frequent testing and exercise of the SOV will reduce the amount of unplanned shutdowns and potenially dangerous failures leading to an overall improvement of safety and cost reduction.  

VAL CONTROLS SOV TESTING SOLUTION

Val Controls provides a solution which can be used in any environment as well as existing or new installations. The IDC24 controller can be used at new or existing installations, comes with pre-programmed software, making it very easy to install.

The SOV testing solution provided is a very cost efficient "insurance". The SOV is often neglected, yet being the most critical part in the system, the IDC24 will add an extra layer of protection for the SOV, by frequently exercising and monitoring it.  

The software provided by Val Controls, allows the end-user to monitor the SOV reaction time enabling you to project at which time the SOV needs replacement. This method of predictive maintenance reduces the number of unplanned shutdowns and increases the overall site safety.

Image: Predictive maintenance of the SOV reaction time

WHY SOV FAILURES OCCOUR

In a typical SOV, O-rings remain in direct contact with the chamber walls, creating a seal while the plunger is in motion. The plunger must first overcome the stiction between the O-rings and walls to move. If the valve is at rest for an extended period, the stiction increases beyond its normal level until the forces generated by the SOV coil can no longer overcome it, preventing the valve from closing properly. In addition, the presence of water or oil can cause a sticky residue inside the valve.

Image: The consequences of SOV inactivity

Common SOV issues

Valve stiction

Plunger stocked

Blocked or restricted solenoid valve exhaust (or QEV)

Sand/dust build-up, icing or insect nests

Damage to instrument piping

Supply pressure - too high or low

Slow reaction time

Unknown expected lifetime of SOV

PREVENTING SOV FAILURE

Risk of stiction increase incrementally over time, infrequent testing raises the probability of valve failure on demand (PDF). Even without changing the architecture of the valving, more frequent testing will reduce stiction, lowering the average PFD. In addition to the potentially life-threatening safety concerns, including risk of fires or explosions, solenoid valve failure is a condition that has vast productivity implications - especially if it leads to plant shutdown.

Image: How SOV exercise improves safety

ADDITIONAL RESOURCES