Ultrasonic Pressure Relief Valve Testing

Ultrasonic inspection may replace interior inspection in some cases.

When a relief valve opens to release excess pressure, the valve may not close properly. In steam valves, this can cause the valve to vibrate or allow microscopic amounts of steam or vapor to escape. Ultrasonic testing detects this passage.

Using the Ultrasonic Test

The stethoscope of the ultrasonic instrument should be placed against the valve, near the orifice. The procedure should be repeated on downstream pipes. This reveals leaks. A hand-held infrared thermometer can be used to confirm the ultrasonic device by detecting temperature differences.

Inspection Intervals

The U.S. Department of Energy (DOE) provides guidelines for the interval of ultrasonic inspections based on such factors as high or low pressure and steam or water heating applications. Inspection intervals may be increased at the discretion of the inspector as long as guidelines for such substances as corrosive materials are followed.

Remote Monitoring

In cases where a vessel under pressure is in a remote location, acoustic devices such as ultrasonic equipment can be used in conjunction with wireless transmissions to monitor facilities. This method reduces the cost incurred by sending inspectors to the site.

References

• Gorelick: Ultrasonic Testing Tips for Steam Traps and Valves
• U.S. Department of Energy: Pressure Vessel and Relief Valve Inspection Frequency Table
• International Society of Automation: Valve Monitoring System Can Offer Operational Benefits

Resources

• SPM Flow Inc.: Emergency Relief Valve