Outside diameter of wafer valves

[kzjh]

I am looking for clarification regarding the requirement for a clearance or overlap between the outside diameter of a wafer check valve and the diameter between bolts (which in ASME B16.34 is described as the "circumference of a circle inscribed through the inner tangent points to the flange bolt holes".
I have looked at the following standards but couldn't find what I was looking for: API 594, ASME B16.5, ASME B16.10 and ASME B16.37.
In the past I have purchased a wafer dual plate #600 DN 350 (14")to ASME B16.5. Outside diameter of the valve was 492 mm and diameter between bolts as per ASME B16.5 is 489 mm(PCD=20.75" - Bolt holes diameter =1 1/2 " gives 19.25"= 489 mm). That would mean a 3 mm overlap.
Now I need a valve DN 600 and a supplier offered a valve with and outside diameter of 690mm. Diameter between bolts would be 723mm for the relevant standard. That clearance seems really high.

Does someone know where is specified either of the two following:
a) Outside diameter of wafer check valves (and I guess the issue would be the same for butterfly or other wafer type valves)
b) Minimum / maximum overlap or clearance between outside diameter of a wafer valve and the diameter between bolts.

Thanks,

 

[gerhardl]

In my (European) experience but also with US standards this is not exactly specified in any standard, but I could be mistaken.

Making descriptions for open bids, we always made following inlusions: suitable for mounting between flanges (and bolting for)...(pressure class and flange form where given full short description, but with no bolt measurement details), building length between flanges to be specified. Full mounting measurements and description to be included.

Another thing is that the 'standard descriptions': 'wafer', 'lug' and 'semilug' also are unprecise, and that a wafer check valve in itself will vary in quality, construction and Cv, and operational specification. (Another construction all over could be better for function and lifetime than the original).

I would myself have focused on quality and functional description within the correct operational details and let the fitting into pipeline be given by the general description, ensuring that the valve neck did not steal away use of standard bolts, and that the valve had full pressure standard.

The measurements given by you could be ok if the valve is constructed for the flanges, but care must be taken when centering the valve under mounting. Semilug? (Ears for placement (unthreaded) for positioning under mounting?)

 

[katmar]

I haven't seen a standard for wafer valve diameters, and I was under the impression that manufacturers attempted to design to a diameter that would fit into US or European flanges. I have seen slotted lugs, and also non-lugged but with tapered "ears" (like cams) that center the valve as it is rotated about the pipe axis and the ears (cams) engage the bolts. These made me think that they were deliberately designed to suit multiple standards.

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[gerhardl]

..katmar,

you are right about the tapered ears / cams on some, but this is used only be a few, and often 'high quality' producers, and most often for lower dimensions, say up to 10 inches (250mm) and limited in pressure classes, most often up to 40 bar for the smallest, else PN25 or PN16 and 10 for larger if EN standard).

Above DN300 (12 inches) for wafer check is often more limited in commercial varity and standard versions (produced in smaller series).

Other members: please correct me or supply if I am 'off the track'.

 

[kzjh]

Thanks for this information.
My specific case was a pure wafer with no lugs, or ears/cams. The reason I was interested in this particular valve is that it was available quickly, and it isn't that easy to find a DN 600 valve quickly.
I have spoken to the supplier again and yes he advised this was probably a bit of trouble for installation although common practice -one solution can be to use some packers. I understand it is easier to install a valve which outside diameter is the same as the diameter between bolts

Just one correction on what I wrote in my previous post: on the previous case I had, I wrote there was a 3mm overlap, actually there was not, because the measurement I gave were between bolt holes, not between bolts themselves. For the example I gave, diameter between bolts is actually 492 mm, which is exactly the valve outside diameter.
All comments welcome,

 

[gerhardl]

OK! What type of valve are you replacing? Have you checked performance suitabillity of the one you are evaluating installing?

 

[kzjh]

To gerhardl, not replacing a valve, this is just a valve we need for a temporary connection, that will be used 2 to 3 months.