Farris valve vs singer valve series#

Also, oversizing relief valves is not a good thing. Would it have been more conservative to choose the E valve? Yes but it was not correct to do so. The calculated ASME area became something like 0.144 sq. But to convert this to ASME, you just multiply 0.973 by 0.9 to give you a certified coefficient of 0.876. You see, the Farris ASME D is 0.15! Yes, we calculated the 0.13 using the Farris coefficient of discharge (0.973). But when the vendor came back, he said we can still use a D orifice. I can't remember the exact numbers but we calculated a required orifice of somewhere around 0.13 sq. Let me give you a real world situation involving a Farris valve. You would then choose the actual orifice based on that manufacturer's table for his ASME orifice sizes. The only difference will be is that if you use the certified coefficient in the equation, your answer will be the ASME orifice area. The equation to calculate area is exactly the same. All the relief valave vendors are now moving towards specifying their valves in terms of the ASME or actual orifice areas with the corresponding certified coefficient of discharge (which is nothing more than 0.9 times the effective coeficient of discharge). I would get out of the practice of using API effective orifices and the corresponding effective coefficient of discharge. The effective-area concept in API allows for selection of valve size independent of manufacturer. Effective areas calculated by use of API formualtions and its Kds will always result in selection of valves with certified capacities equal to or greater than required capacities. Rather he is obliged to produce a valve which will have a flow rate equal to or greater than that determined by the API formulation.Дў) API formulations use Kd=0.975 for gas & vapour service, for liquid service they use Kd=0.62 however, as said in point1 the effective areas and API assumed Kds are generally different from actual orifice areas and discharge coefficients that are used to determine certified valve capacities. The manufacturer is not required to produce a valve with bore area equal to effective area. This orifice area is used in API formulations to calculate valve flow rate. As an example the effective area of a J orifice is 1.287 sq.

Farris valve vs singer valve series#

These standard sizes are characterized by a series of fourteen standard letter orifices ranging from D through T. 1) API developed a series of inlet, orifice, outlet combinations for various flanged valve pressure classes which are utilized throughout the petroleum and hydrocarbon industry.