Safety valves are the unsung heroes of safe boiler operation. Perfecting the design of the safety valve (SRV) brought boilers from the dark ages of explosions to predictably safe operation. Modern SRVs are manufactured under the control of the American Society of Mechanical Engineers (ASME). Approved assemblers and repair facilities like The Valve Shop are authorized and approved by the ASME to make adjustments and stamp boiler safety valves with the “V” symbol, and for SRVs on unfired vessels, the “UV” symbol. The Valve Shop repairs SRVs under the control of the National Board of Boiler & Pressure Vessels Inspections and bear the “VR” symbol.
The major shortcoming of SRVs has been the lack of efficient ways to determine their operating status. Increasing the pressure of the boiler until the valve relieves is one method, but that can lead to over pressuring the boiler controls or the plant process equipment. Raising the lifting lever to see if the valve is relieving properly is another method, but that approach doesn’t provide any information about the point of relief. Neither method is ideal, because any time a valve relieves, there’s a risk that particles in the steam will collect — or that steam will cut the disc or seat, creating a leak in the valve. Until recently, the only way to accurately test SRVs has been to remove them from the boiler, send them offsite to a qualified “VR” valve shop for rebuilding, testing and resetting the pressure, then installing the valve back into place.
Electronic valve testing now allows qualified technicians to verify the set pressure of SRVs in-line, without having to shut down a system or unit. The automated valve electronic test unit is portable and easy to set up, made up of a laptop computer connected to a hydraulic lifting device, and it works like this: Valve data is entered into the computer, then the hydraulic lifting device raises the valve stem just short of the point of blowing; this procedure determines the set pressure of the valve. The advantages of this approach are enormous:
- Because the SRV is tested at operating pressure, the boiler doesn’t have to be taken offline unless the SRV fails the test.
- The cost of testing six to eight valves in the field is about the same as rebuilding one in the shop.
- Since the electronic valve tester does not lift the valve from its seat, reseating problems are not an issue.
- Data is collected in real time, and test results can be printed or emailed.
On top of all the operational advantages, electronic valve testing by The Valve Shop is recognized by most insurers as an acceptable alternative to sending valves off-site for testing. Valves that test unsuccessfully can be tagged for repair during a scheduled maintenance outage, which significantly reduces downtime and costly, unexpected repairs. Learn more about the electronic valve testing at The Valve Shop.