Can needle valves be used in opposite direction?
You may not find the specific information for Needle Valves but the reason is the same as for a Globe Valves.
Some Globe Valve manufacturers advise NOT installing a Globe Valve backwards because in the closed position the higher pressure fluid is on the top (or stem side) of the disc. This has the High pressure fluid (or Gas) against the Packing (around the Stem) and will cause leaks faster/sooner than when installed in the conventional manner.
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