No Loop Or Do Not Pocket in terms of pipelines - are they same meaning? in that case why used in different occasions? Pls. clarify.

"Do not pocket" means that the vapor can condense and perhaps fill the vapor line with liquid if it is not level or sloping toward the next piece of equipment.  An example would be if the line drops to a lower level then rises thus forming a loop that could fill with liquid; like the surge control(controlvalve) return lines on the HP compressors at the last offshore platform where I once worked.

No loop applies on floating platforms where an expansion loop at trim can create a pocket. It's unusual for it to be a problem but when it is trying to prove that you can still vent through the line is a major head-ache!

In Jet A1 systems water can separate out. In some aircraft with aluminium fuel tanks bacteria living in this water excrete acids that cause pin hole leaks. Thus it is common for all piping to the filter coalescers to totally drain. Hence no pockets, sloping lines etc. Even changes between sch 5s and 10s piping have the internal welds ground out to prevent pockets of water.

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