Valves that leak internally can lead to major losses of valuable product, or unintended transfer of process constituents, in some cases seriously elevating process risks. Evaluating the condition of in-service valves that process fluids is difficult. Diagnostic methods that require valve movements often cannot be utilized while the plant is in operation and this affects on how future maintenance or valve replacement scopes are being planned. As a result, operators often fall into the situation where a good valve is being taken off for maintenance that is not necessary required, or no maintenance is planned at all for a bad valve.

VELD System survey deploys acoustic emission (AE) technology to accurately locate noise sources. Suspect valve diagnoses are checked using AE analyses of data from a 2-channel acoustic emission data processor. Validation involves recording and analysing AE data from sensors placed upstream and downstream of the suspect valve. Frequency spectrum (FFT curves) and differential signal intensity traces (dB vs. time) are used to isolate suspect valves from process background acoustic sources.

Simultaneous time domain analyses of sound emissions from both sensors in the target frequency range and associated matching of noise signals enables the exact location of the source of passing valve noise.

Having found and accurately located and verified passing valves, order of magnitude estimates are provided, based on proprietary leak estimation algorithms combined with validated valve acoustic emission signal properties and valve design parameters to provide a relative indication of the passing leak magnitude.

• Use of V.E.L.D system to determine valve seat leakage helps operators to:
• Prevent unplanned shutdowns and maintain consistent product output.
• Minimize the need for valve tear downs during plant shutdowns.
• Learn about valve maintenance problems before they become critical.
• Avoid unnecessary maintenance on valves that have minimal trim damage.