A wrong flange costs far more than the material: the line waits, the crew stands idle and the schedule slips. These five mistakes are the ones we see most often on enquiry lists.
1. Not stating the standard
"6 inch 150# flange" can point to two different standards. ASME B16.5 and EN 1092-1 differ in bolt circle and bolt count, so the part will not fit its mate. Above 24 inches, the B16.47 Series A versus Series B distinction comes in as well.
2. Omitting the pipe schedule
The hub bore of a weld neck flange is machined to the pipe wall thickness. Without the schedule the maker assumes, and a SCH 80 hub on SCH 40 pipe leaves a wall mismatch that inspection rejects.
3. Skipping the face type
RF, FF and RTJ need different gaskets and do not mate with each other. Bolting an RF flange to cast iron equipment risks cracking. If the specification calls for a particular surface finish, state that too.
4. Leaving the certificate level open
The difference between EN 10204 3.1 and 3.2 is not just paperwork; 3.2 requires independent inspection and extends lead time. Requested after the order, it means re-inspection or new production.
5. Ordering gaskets and studs separately
A flange does not work alone. Gasket type follows the face, and stud length follows flange and gasket thickness. Items ordered separately end up mismatched on site, and the difference matters most where blind flanges, isolation sets and blinding plates are used.
What a good enquiry line looks like
- *ASME B16.5, 6", 300#, RF, WN, to suit SCH 40 pipe, ASTM A105, EN 10204 3.1 — 8 pcs. Gasket: spiral wound 316L/graphite with inner and outer ring. Studs and nuts: A193 B7 / A194 2H, xylan coated, as a set.*
Send your list at this level of detail: enquiry form.
FAQ
What happens if the standard is not stated?
The maker assumes one, and because ASME and EN bolt circles differ, the part will not fit the mating flange.
Can the certificate level be changed later?
Moving from 3.1 to 3.2 requires independent inspection, so the part is re-inspected and the schedule slips.
Why order as a set?
Gasket type and stud length are determined together with the flange dimensions, which removes the risk of mismatch.
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