Effective discharge area

A= effective discharge area, in square inches (from manufacturers standard orifice areas). 

API 520 Definition A nominal or computed area used with an effective discharge coefficient to calculate the minimum required reheving capacity for a pressure relief valve per the preliminary sizing equations contained in API Standard 526. API Standard 526 provides effective discharge area for a range of sizes in terms of letter designations D through T. 

Orifice area See effective discharge area (Figure 3.5). API has determined standard orifice areas from D to T, each with a corresponding orifice size (in2 or cm2) (See Section 4.2.3). 

When an SRV is sized for viscous liquid service, it is suggested that it would be sized first as for a non-viscous type application in order to obtain a preliminary required effective discharge area (A). From the manufacturer s standard effective orifice sizes, select the next larger orifice size and calculate the Reynolds number, Re, per the following formula ... 

A = Effective discharge area (in2, from manufacturers standard orifice... 

Ti = back-pressure ratio, estimated at relieving pressure, Pa/P . A = required effective discharge area, mm. ... 

Effective discharge area. For botir scenario 1 and scenario 2, the effective discharge area is estimated by using Equation 4.91. 

A = required effective discharge area (Equation 4.91) = 4,071.3 mm Required orifice = P... 

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