Intelligent partial stroke test system eliminates costly spurious trips

Since 2000, Metso has offered Neles ValvGuard(TM), an intelligent solenoid valve with PST capability. Metso was the first SIL3 (safety integrity level) certified intelligent partial stroke device supplier. Metso's Neles ValvGuard is technically most advanced solution in the market with widespread installed base; top class intelligent safety solenoid with partial stroke testing features for emergency shutdown and venting valves.

By truly knowing the condition of the valves at any given time enables the operators and management to have a full picture of how to best mitigate risks. To continuously address customer concerns, Metso has now further enhanced its ValvGuard offering by launching an intelligent PST solution called VG9PST. This latest Metso development further reduces the risk for spurious trips with ValvGuard solution especially when a customer uses an external solenoid valve, minimizing the risk of consequent unwanted and costly plant shutdown.

"Our mission is to bring sustainable valve solutions to the market which maximize the plant uptime. The valves in a petrochemical or refinery process must withstand significantly demanding process conditions. Due to largest pneumatic capacity in the market, Neles ValvGuard works perfectly also with the biggest emergency shut-down valves and thus improving plant safety in a best possible way," summarizes Janne Laaksonen, Product Manager, Metso.

The new device offers additional safety by disabling all the testing and calibration if the input signal from the DCS falls below certain levels.

Another benefit of the new solution for the end user comes from simplified installation, since a solenoid valve is used for the fail-safe action and the VG9PST is used purely for testing purposes. Furthermore, the pneumatic capacity of the device allows valve operation without any external volume boosters. Also, the largest selection of integrated limit switches in the market eliminate the need for tandem mounted solution.

Neles ValvGuard(TM) VG9PST technical features

Neles ValvGuard VG9PST is designed to perform only the partial stroke test. The fail-safe action is carried out by a separate solenoid valve.

The ATEX & IECEx-certified VG9PST is available with HART communication and is powered from a distributed control system by an analog 4.20 mA signal, which is key to the solution. As 4 mA is considered to be the normal state, no signal change can stroke the valve. Even an electric failure or cable break cannot create a trip.

To visually distinguish the new VG9PST from Metso's standard Neles ValvGuard, this device has a green cover instead of a familiar red one. Having the "green" solution in place, operators can confidently perform all necessary testing and be knowledgeable of a valve's condition. This eliminates any risk for the plant's operation that may result in high costs and wasted resources.