FURMANITE has developed and patented a system that saves time and costs by enabling safety and relief valves to be tested while plant continues to operate normally.
Furmanite's Trevitest system avoids the need to remove valves from the process line for bench testing in the workshop. Instead, testing is done on-line at normal operating pressures and temperatures, without interrupting plant production (hot testing).
Trevitest can test most safety and relief valves used in steam, air, gas, process and water systems, including conventional spring-type valves, torsion bar valves, and pilot-operated valves. A specially-certified version can be used even in the most hazardous conditions.
The Trevitest system applies a force to the valve spindle to overcome the valve's spring tension through a set of mechanics mounted on the valve. Using a hydraulic power pack, and an electronic force transducer linked to a portable computer, the system traces force applied. An acoustic transducer confirms the point of lift and flow through the valve.
A date-marked certified print-out of valve performance is produced, allowing set pressure, spring adjustment and valve displacement to be determined, and an indication gained of the effect of the nozzle ring, guide ring, and reseat pressure.
Test results are accurate, within 1% of the set pressure when the valve is tested on-line. From the recorded trace the technician can recognise passing valves, sluggish valves, valves with long blow down and valves with long simmers. The results and print-outs provide an auditable history trail and comprehensive valve test diagnostic record.
The equipment's light weight and modular design make it easy to use under variable plant conditions, as well as to integrate with other specialist diagnostic equipment that may be required in user-specific applications.
A version certified for hazardous environments is also available. The system contains computer and data acquisition hardware in a pressurised, purged enclosure, with transducers connected via zener barriers. This prevents potential ignition source exists outside the enclosure, allowing safe use in volatile and flammable environments.
Trevitest hot testing can minimise fuel costs. It required no interruption to plant production while testing is underway, and minimises time required to commission the plant after shutdown.
Time and costs are also saved by diagnosing valves requiring maintenance prior to shutdown, so only those valves requiring overhaul need be removed from the line, and welded-in valves can be adjusted without removal from the line.
Trevitest permits multiple tests and re-settings of the valve within a short timescale, and, because the test is undertaken at normal operating temperature, no temperature compensation to set pressure is required. The risk of damage such as valve seat erosion or water starvation in boiler tubes is also low.
The Trevitest system can also be used for cold-testing, when there is no line pressure or with the valve removed from the line. This can be useful for pre-commissioning of valves on new plant.