Operational characteristics of this pressure relief valve are directly affected by back pressure changes. For conventional safety relief valve, only the superimposed back pressure affects the opening characteristic and set pressure value, but the combined back pressure (superimposed backpressure plus built up backpressure) affects the blowdown characteristic and re-seat pressure value. A conventional pressure relief valve is not used when the built-up backpressure is greater than 10% of the set pressure at 10% overpressure. A higher maximum allowable built-up backpressure may be used for overpressure greater than 10%.
Advantages of conventional relief valves are reliability and versatility. These relief valves are most reliable when sized properly and can be used in a wide range of services.
Disadvantage of these relief valves is the effect of backpressure on the relieving pressure of valve and hence pressure accumulation in the protected equipment. Also for high built up backpressure values generated by higher pressure loss in the relief valve discharge line, chattering can occur in these relief valves.