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Natural Gas Line Sizing using General Pressure Drop Equation

Line sizing is a part of every engineering activity. Although it is not major part, line sizing is required when we prepare piping and instrumentation diagram. In this post, I want to share you how to do natural gas line sizing (actually the method is applicable for all kind of gases).

I usually use process simulator when it came to natural gas line sizing. Long time ago, I tried to size manually. But the result is not the same as from simulator. But, I tried again and yesterday I got a satisfied results.

Natural gas line sizing calculated in this post will be from manual calculation and from process simulator. API RP 14E is used as reference.

Based on API RP 14E, single-phase gas lines should be sized so that the resulting end pressure is high enough to satisfy the requirements of the next piece of equipment. So, the point is the end pressure. The velocity is also a noise problem if it exceeds 60 ft/s. However the velocity of 60 ft/s should not be interpreted as an absolute criteria. Higher velocities are acceptable when pipe routing, valve choice and placement are done to minimize or isolate noise.

API RP 14E mentioned several approach to calculate pressure drop, but in this post I will use general pressure drop equation

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Pipe Size Selection and Several Criteria of Pipe Size

Someone in my office asked me if there is a criteria for pipe size selection, in other words, pipe sizing criteria. One basic document that every process engineer produce in the beginning of engineering stage is process design basisIn the document, pipe size criteria shall be stated clearly.

I have involved in at least two engineering projects. Those two projects have different pipe size criteria. Which one is correct? (more…)