Long weld-neck flanges are primarily used on vessels, the extended neck makes up a normal nozzle projection, as apposed to using a normal weld-neck flange and having to weld on an additional small pup-piece to achieve the "normal" projection length. From the factory, long weld-neck flange come with, so to butt-weld them in the field (or shop) a 37.5 Deg. bevel will have to be applied …which is going add to time and the expensive of using them. So you might want to point that out client and make sure they understand what they are asking for! ...However "IF" your order of these flanges was large enough, you might get the factory custom bevel these flanges ...surprising what you can get if enough money is involved!FYI ...there are 3 different types of long weld neck flanges, they range from "LWN", "HB", & "EB" ...these last two are for vessel use only, only the "LWN" style would be suitable "" you were going to use them. www.lyncoflange.com/customer/lyf ... _600_E.htm (for Class 600)
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