Valve modification programme
reduces downtime and costs of BS EN 378 testing
A leading refrigeration and temperature cooling specialist has developed a modification programme which reduces both the downtime and costs associated with BS EN 378 compliance.
ICS Temperature Control (ICS) has successfully completed a number of Dual Port Relief Valve (DPRV) retrofits across a wide range of industries, ensuring compliance with the standard and with insurance requirements. BS EN 378 requires that the liquid carrying parts of a refrigeration system can be isolated from the rest of the system, or that there must be a minimum of one pressure relief device mounted on, or in the proximity of, the pressure vessel or the part of the system which it is to protect.
Brent Hall, Technical Manager at ICS explains how the programme works. "Refrigeration systems operate at relatively high pressures. Even when idle, the internal pressure can often be in excess of ten bars. This in itself is not considered to be dangerous; the components, vessels and pipe systems are designed and tested for pressures far higher than these. "Problems arise when the liquid-carrying vessel is isolated, its temperature rises for any reason, and its pressure rises as a result. Manual isolation is not always necessary. When stopped, most compressors act as a non-return valve; the refrigerant liquid and vapour between the compressor and the liquid line solenoid valve are trapped in that part of the system. Therefore, there is a clear need for a safety pressure relief valve to ensure that any excessive rise in the refrigerant vapour pressure is safely relieved."
According to Hall, the safety relief valve is a unique and essential component of any medium and large refrigeration system and the system user/operator must be confident that it will serve its design purpose and function properly and at the correct pressure. The current BS EN 378 standard requires relief valves to be tested every five years, yet Hall asserts that visual examinations should be undertaken with each maintenance of 'F-gas' inspection, which checks for all hydrofluorocarbon (HFC) refrigerants. "When we carry out F-gas inspections, we check the seal, that the discharge cover is in place, that there is no debris or water lodged in the discharge tube or pipe, and the relief stream is clear," explains Hall. Safety valves are often installed directly into the vessel/pipe system they are protecting without isolation. This makes removal for testing a time consuming and costly operation, requiring the equipment to be out of action for longer than necessary, potentially up to 24 hours. ICS's modification programme converts single valve installations to ones where there are two safety relief valves on a dual changeover valve manifold. This arrangement enables one valve to be taken out of circuit and tested with no machine or plant downtime.
"During a recent example, we tested and replaced DPRVs for an IT and telecommunications company," Hall illustrates. "We had to remove the liquid refrigerant to access and then replace the relief valves to fit with their insurance requirements. This ensured that future testing would not require refrigerant removal. "The installation of the DPRV enabled a significant reduction in downtime on future five year checks, and has reduced costs whilst maintaining system integrity and safety."