ValveWatch® - Application Detection

Application Detection

* For ball valves and slab gate valves with a sealed cavity, operator can automatically test for seal leaks while the valve is open and flowing. This important function eliminates the need to close the valve to perform a leak test.

Case Studies

Blocked Solenoid Exhaust
Partially blocked exhaust ports can significantly increase valve closing time. With ValveWatch^®, measurements taken from the actuator pressure sensor during a valve stroke can identify this problem. This example shows a signature from a valve with a blocked exhaust port compared to several signatures from a normal valve. The blocked exhaust caused an increase in stroke time of 500% for this valve. Left undetected, this problem can compromise the performance of critical systems such as ESD systems.

Bent Valve Stem
Bent valve stems can significantly accelerate packing wear. With ValveWatch^®, data taken from the strain gauge during a valve stroke can identify when this problem is occurring. This example shows a signature taken from a gate valve with a bent stem. As the valve strokes open, the bend in the stem causes a rapid increase in the thrust required to partially open the valve, followed by a rapid decrease to normal thrust required to complete the stroke. This hump in the thrust signature is an indication of a bent valve stem, and left undetected may result in external valve leaks.

Excessive Breakout Torque
Excessive breakout torque can eventually result in valves seizing. This example shows strain gauge signatures taken over four strokes of an offshore shutdown valve. The first three signatures display the significant increase in torque required to open the valve. The excessive torque is also apparent in the running load throughout the full stroke. The final signature was taken after the operator serviced the valve to bring it within normal specification. Left undetected, this valve could have seized without warning and compromised the safety of the facility and its workers.

Actuator Pressure Leak
Air leaking from the actuator may prevent the actuator from overcoming its spring pressure. The result is a valve that does not open completely. This example shows signatures taken from two valves using the actuator pressure sensor. The top signature depicts a normally opening valve, while the lower signature depicts a valve that fails to stroke fully open when the actuator is charged. Without monitoring, actuators may leak air for extended periods before this problem is identified.

Excessive Friction
Excessive friction can be the result of several damaging issues inside the valve, including internal corrosion, deposit formation, or over-tightened packing. This example shows strain gauge signatures taken from two valves during a full open stroke. The bottom signature shows a normally operating valve with a smooth strain signal throughout the valve stroke. The top signature shows a jerking motion as the valve moves fully open. Often invisible from outside the valve, the rapid peaks and valleys in the strain signal are the first signs of excessive friction and a potentially damaging valve problem.