Discussion on the installation requirements for the combination of safety valves and burst disc safety devices
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Dear experts: In Figure 1 of Section 5.1 of standard GBT38599, it is specified that a rupture disc assembly should be installed in front of the safety valve. The installation distance between the rupture disc and the safety valve is required to be less than 5 times the inner diameter of the pipeline. I would like to ask you all: where does this value of 5D come from?
According to the standard GB/T 38599 \"Guidelines for the Application of Safety Valves and Burst Disc Safety Devices\", the installation distance for a burst disc assembly connected in series before the safety valve inlet is required to be within 5 times the pipe diameter (5D). This requirement is generally based on international industry practices as well as recommendations from relevant international standards and codes. Examples include: 1. API RP 520 (American Petroleum Institute standard specification); 2. ASME BPVC (American Society of Mechanical Engineers code for boilers and pressure vessels); 3. Internationally recognized engineering installation practices. In particular, standards such as API 520 and ASME specify installation guidelines stating that the pipe length should not exceed 5 pipe diameters (D). The purpose of this parameter is to reduce the pressure drop loss after the rupture disc opens, ensuring that the safety valve operates promptly and effectively. Currently, the domestic standard GB/T 38599 is typically formulated by referring to requirements of foreign standards such as API 520 and combining them with practical engineering experience. Therefore, this “5D” value is essentially a convention recognized across the industry; there is no specific theoretical formula behind it, as it results more from practical experience. .