Safety valve testing
The most common test method for safety valves and relief valves is bench testing performed in a workshop. Such tests are typically carried out in conjunction with a strip down, inspection and overhaul. This requires the valve to be removed from operation and transferred to a workshop. ESD provide full on‑site or off‑site (return to our workshops) safety valve maintenance, overhaul, testing and calibration services.Dismounting safety valves from their operational location can be a time consuming. risky and expensive operation. The ESD Online Test system provides the capability to test safety and relief valves in‑situ, without the onerous requirement to remove the valve from the system or shut the system down. In-situ testing of this form, as part of a carefully planned and monitored test and maintenance regime which also includes periodic strip down, inspection and overhaul, can provide a highly cost effective means of managing safety valve and relief valve inventories.
The ESD Online Test system offers the important capacity of testing in actual operating conditions. This provides added confidence in the protection afforded by the safety valve. It also supports the optimization/minimization of maintenance downtime through ESD operated condition monitoring of safety valves in service.
Features of the Online Test system
The ESD Online Test system is a unique advanced in‑situ Safety Valve test system. Some of the advantages of the system are:
- Objective, accurate and reproducible evaluation of safety valve set pressure. . Tests can be “hot”, i.e. in‑situ with medium pressure acting on the safety valve, or “cold”. i.e. on or off site with no medium pressure acting on the safety valve.
- Highly accurate transducers (0.1% accuracy class) are used to measure force and lift.
- Fully automatic test and control of test, the test takes place without human operator intervention. . Pre‑programmed computer controlled test cycle.
- Pre‑programmed safety limits are sensed and managed automatically during the test cycle in order to prevent damage and to provide fail‑safe operation.
- An integrated pressure transducer can be used to provide the most accurate measurement of actual system pressure at the time of the test and as the test evolves.
- ESD Online Test equipment is ATEX approved for operation in potentially explosive atmospheres (EEx ia UC T6).
- Lift limitation is pre‑established and provided to minimise the risk of valve damage or a full lift safety valves popping open during in‑situ test. The computer controlled preprogrammed test eliminates the chance that the inherent vagaries of a human operator manually controlling the lift might result in the safety valve lifting.
- Ability to provide power driven closure of safety valve should the valve pop open during test.
- Equipment and procedures designed to enhance operational Health and Safety.
- The safety valve test method using the Online Test system is widely approved, for instance, by Lloyds Register of Shipping SAFED and the Insurance Industry.
- Set pressure reseat and full lift tests available.
- Fully reproducible and objective footprint/benchmark tests for valve health monitoring.
What is the Online Test measuring
The ESD Online Test system measures the force required to initiate separation of the disk from the valve seat. This force divided by the effective disk area of the valve gives the equivalent pressure at which the disk lifts away from the seat. This compares with the set pressure as normally measured with a bench test or leak test.
Where required, full lift tests or defined lift tests can also be carried out to provide more extensive evaluation of the function and condition of the valve.
Hot testing in situ
Hot in situ testing involves lifting the disk of the valve very slightly away from the seat while the valve is in service and exposed to the fluid pressure. This form of testing offers many operational, safety and cost advantages. The ESD Online Test system has sophisticated features to control the testing process safely and accurately.
Testing can also be carried out without system pressure. This can be carried out in situ or in our service centre or workshops. The set pressure can be adjusted after repairs have been carried out.
A ‘Footprint’ or calibration test on the valve can be carried out before
installation: then future tests can be compared and verified against this
calibration test to monitor the condition of the valve. ESD can provide a full maintenance service to support these tests.
Resetting set pressure in situ
The ESD Online Test system can be used to reset the set pressure of safety valves in situ arid in service.
Specialist test rigs
ESD have an extensive range of specialist in situ test rigs for the most demanding requirements, including:
• Ultra high power rigs capable of full lift testing the largest of safety valves;
• Micro rigs for the smallest and most delicate of safety valves
• Special rigs for torsion bar safety valve, and:
• Specialist test rigs for pilot operated safety valves.
Set pressure test and calibration
Pressure testing or calibrating the set pressure of a safety valve can be an intermediate operation between periodic strip down, inspection and overhaul. The valve is dismounted from its operating position and tested or calibrated using a test bench. This can be carried out in our workshop or on site using the portable ESD (QuicktesterTM) system. In many circumstance dismounting the valve for testing can be impractical or expensive, in which case the solution is to use the ESD Online Test in situ testing system.
The ESD Condition Rating”‘ technology provides for the true calibration of safety valves, only through such true calibration can the effective and safe operation of the safety valve be ensured.
Safety valve calibration and condition measurement
ESD Condition Rating”‘ measures safetv valve condition and calibration. It can be used before and after overhaul to provide confidence that a safety valve is calibrated to perform to specification and to quantify, the quality of the refurbishment work, also it can be used on a safety valve in service to provide condition or health monitoring.
While the ESD Online Test provides an excellent determination of the set pressure of a safety valve when installed in line arid in service, ESD Condition Rating”‘ ‘1 goes far beyond this.
In Condition Rating”,’, ESD have a quick and simple computerized test that measures both the calibration and the mechanical condition of a safety valve. So now, for the first time, there is a scientific and objective means of evaluating any degradation in the condition of a safety valve and whether it can continue to perform correctly in operation.
The ESD Condition Rating”‘ technology provides for the true calibration of safety valves.
The ESD Condition Rating’ technology also enables the condition of a safety valve to be measured in situ and while it is still in operation. ESD Condition Rating”‘ provides objective metricated health monitoring over time with measurement of whether a valve requires overhaul, thus eliminating the unnecessary cost and risks of removing and overhauling valves purely by date. It thus provides an objective predictive methodology for risk based assessment to aid in safety, reliability and maintenance planning as well as diagnostic condition analysis of the internal mechanical components of a safety valve.
The ESD Condition Rating” parameter is a percentage value ranging upwards from the perfection value of zero. It provides an extremelysensitive scale of safety valve status or health covering the quality of sealing surfaces as well as alignment and freedom of action of mechanical parts. From the point of view of function, a Condition Rating”‘ value of 10 will indicate that the valve will not even start to open inside an accumulation of 10%. Thus, at this Condition Rating 11 the valve cannot be considered to be fit for service even though it may have passed a conventional set pressure bench test; it will not meet the accumulation requirements and may not afford the correct level of protection required by the system design parameters. Therefore 9 is the limiting Condition RatingT value for safety valves subject to a 10% accumulation requirement.
Safety Valve inventory databases
An ESD safety valve inventory management database forms a complete electronic record for plant safety valve inventory and maintenance information.
The ESD overhaul report and test certificate records all the necessary information including the ESD Condition Rating”‘, it can be supplied in hard or soft copy.