I was wondering if you can help me; what exactly is the difference between the lug and wafer type butterfly valves and when are these specified? I can't seem to find a clear definition of each.

As seen from Scandinavia we have the same problem of definitions, both in the Scandinavian and the English language as you have.

- One of the reasons is the misuse and mixup of the meaning of the words 'flange' and 'wafer' and 'lug' in specifications and different context. Most often you have to add some extra wording or explanation to be sure of what you are talking about.

There are three different main types of centric BFL valves(Forged Steel Valves) housing form with this short building length in my opinion:

1. Wafer: To be mounted between flanges, without any flange on the valve itself of any type or ears with threads for bolts.

Note: could be supplied with a set (Normally two or four) 'ears' as open holes with a minimum af material, larger than bolt diameter to help facilitate placement when mounting and dismounting.

Theese ears are sometimes given the name half-lug (type valves), a mixup in my opinion as they have nothing to do with type 2. The mixup is not less as half-lug often is misabbreviated to 'lug'.

2. Lugged (with threaded holes) centric valves. Also called full lug or mono-flange. A lugged type will have threaded holes for normally all bolts. The mixup comes as the mono-flange valve could also have a 'brim' with unthreaded holes, and as full-lug often are shortened to lug, or used to describe unthreaded holes.

3. U-profile flange. With two flanges, one on each side with open holes. Limitation as the flanges normally will have a too limited space between flanges for anything but bolts entered from outside through both flanges and nut mounted on opposite side of pipeline flange.

This type is often misused to offer or use a cheaper valve if a description craves a 'flanged valve' without further additions - but meant to describe the longer building length (as forinstance often given in double-eccentric valves) with flanges so far apart that a separate set of bolts can be used for both flanges. Bolts entered from valveside of valve flanges and out, if needed.

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