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API 615 Gate Valve Stem Orientation

API 615 Gate Valve Stem Orientation

API 615 Gate Valve Stem Orientation

(OP)
Clause 5.1.1.6 of API RP 615 cautions that gate valves larger than 8" in any position other than vertical can result in the disc getting hung up against the inside body guides. API 598 specifies leakage test with stem vertical. But, in process plant piping, it is very difficult to adhere to the API recommendation. What are the technical requirements to be specified while ordering new valves which are suitable for operation in all orientations?
Thanks in advance for valuable inputs in the forum.

RE: API 615 Gate Valve Stem Orientation

-mbk899,
You wrote: "What are the technical requirements to be specified while ordering new valves which are suitable for operation in all orientations?"

- If you are buying a single valve for an unusual orientation you are better of just defining the orientation the valve is to be placed in. Otherwise you will potentially incur a lot of extra costs.

- If you are buying many different valve sizes in bulk (large numbers) for a new process plant you should not try to customize Technical Requirements for only one valve or a few valves. If you did ask for one 8" valve to have something special but you are buying 100 8" valves you will have trouble making sure that 'Special" valve is installed in the proper place.

Sometimes its possible to do all the right things and still get bad results

RE: API 615 Gate Valve Stem Orientation


My experience is that for some valvebrands and some applications, orientation of the valve is of less importance.

For other brands/types and fluids/applications this is on the other hand very critical.

Selection of a best possilble constructed brand (when type is already selected) is essential, if a 'non optimal' orientation of a valve can not be avoided.

Generally some producers give limits, for instance not to exceed vertical position up more than 30 degrees either side.

I have however seen a lot of valves (but perhaps not in your branch) mounted horizontally, and in practically all other positions.

Problems with other than optimal orientation often comes from residues assembling in pockets (not optimal inner construction), or residues on parts tearing sealings, stemsealings, seatsealing and guides. Weight and forces not constructed or dimensioned for skew weight will add to the problems.

I have also often seen valves stuck alone or in combination with above because of too large horizontal or skew weight on the valve itself caused by unsufficent separate support of pipeline and valve.

Suggested checkpoints: Technical details on applications, control of pipeline construction and valve placement, pipeline and valve support, checking and control of makers limitations for orientation, check of inner construction, sealing and guiding quality and support for closing members, as few residual pockets as possible (will vary from maker to maker), construction of support and guiding of stem and force transfer to closing member (as little leverage from stem to closing member as possible), solid inner construction, manufacturors comment. Note: This might lead to a valve quality not cheapest in price, but far much better to withstand the actual conditions when mounted 'non normal'.

(......[smile] if there is a problem ensuring that a marked valve, else equal to a (seemingly) identical lot, is placed at a designated tagged place, the project might have other problems than valve selection, at least in my part of the world............)

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