Suggestions for sizing safety Relief Valves that prevents the interior pressure

A safety valve prevents the interior pressure of a boiler from rising to unsafe levels. Typical steam safety relief valves have a large spring that applies a downward force on a metal piston. If the pressure in a steam boiler rises high enough, it will overcome the force of the spring and the piston will lift, relieving the interior pressure. The design and size of a safety relief valve is extremely important for industrial process safety. This sizing refers to the minimum required orifice size inside the Air Valves. Guidance for sizing procedures and formulas can be found in the authoritative reference from the American Petroleum Institute (API), specifically the Recommended Practice 520.

1.Determine all of the credible overpressure scenarios for a steam boiler. This will be the basis for the sizing of the Forged Steel Valves. For example, in a natural gas boiler the gas burner could malfunction, causing excessive heat for boiling the water.


2.Determine the maximum steam generation capacity and the maximum pressure rating of the boiler. For example, assume the boiler has a maximum steam generation of 50,000 pounds per hour with a maximum pressure of 300 psi and a temperature of 422 degrees Fahrenheit.

3.Determine the minimum required orifice size of the valve using the formula from API 520. The formula is A = W/(C x Kd x P x Kb x Kc) x √(T x Z)/M where A is the orifice area in square inches, W is the steam generation, C is a steam coefficient equal to 330, P is the pressure, Kd, Kb and Kc are all constants equal to 1.0 in this case. T is the temperature of the steam, Z is the steam compressibility factor (assume it is 1.0) and M is the molecular weight of the steam, which is 18.01. This calculates out to be 2.44 square inches.