Twelve fields, and what each omission costs downstream
An enquiry reading '6 inch 300# WN flanges, ASTM A105, quantity 40' can be priced by any supplier and satisfied by several materially different products. Each missing field transfers a decision from the specification to whoever is quoting.
An enquiry that reads "6 inch 300# WN flanges, ASTM A105, quantity 40" will get quoted. Several suppliers will quote it, the prices will differ, and the differences will be assumed to be commercial. Often they are not. They are different products.
Every field below that an enquiry leaves out is a decision that moves from the specification to whoever is preparing the quote. Sometimes their assumption matches the intent. When it does not, the discovery point is goods-inward at best, and hydrotest at worst.
1. Standard and edition. ASME B16.5 and EN 1092-1 are not interchangeable, and a project that lists both without saying which applies where will receive both. Dimension standard governs bolt circle, bolt hole count and facing geometry — the things that decide whether two flanges physically mate.
2. Size and class. Nominal size and pressure class, in the units of the governing standard. A Class 300 and a PN 50 are not the same flange.
3. Attachment type. Weld neck, slip-on, socket weld, lap joint, threaded or blind. This is a service decision before it is a cost decision: weld neck for cyclic and severe duty because the tapered hub carries bending back into the pipe; socket weld only at 4 in and under; slip-on where the service is genuinely general.
4. Facing. Flat face, raised face, ring-type joint, tongue and groove, or male and female. RTJ appears from Class 600 upward. ASME B31.3 does not permit facings of different type to be bolted together, so this field has to be right on both sides of every joint, not just on the line item being bought.
5. Facing finish. A separate field from the facing itself. Raised and flat faces to ASME B16.5 carry a serrated concentric finish of 125–250 AARH. RTJ groove side walls are held to a much tighter 1.6 µm Ra. A gasket selected for one finish and seated against another is a leak that will not be diagnosed quickly.
6. Bore, for weld neck flanges. The bore must match the mating pipe's inside diameter, which means the enquiry has to state the pipe schedule. A weld neck flange bored for Schedule 40 welded to Schedule 80 pipe leaves an internal step — a stress raiser, a turbulence source, and on some services a corrosion site. This is the field most often left out, and the one most expensive to correct because it is only visible after the joint is welded.
7. Material specification and grade. ASTM A105 is a specification; it is not the only decision. Low-temperature service, austenitic and duplex grades, and clad or overlaid faces all follow from process conditions the enquiry should carry.
8. Sour service requirements. If the service is sour, NACE MR0175 / ISO 15156 compliance is a manufacturing and heat-treatment constraint, not a certificate to be added afterwards. It has to be in the enquiry.
9. Supply condition and heat treatment. Normalised, quenched and tempered, solution annealed — as the material specification and the service require.
10. NDE scope. Which examinations, to which acceptance criteria, on what proportion of the order. "As per standard" is not a scope, because the product standard and the project specification frequently differ, and the difference is exactly what is being bought.
11. Certificate type. EN 10204 2.2, 3.1 or 3.2, with the validating party and notification period named if 3.2 is required. See 3.1 or 3.2: what a material certificate actually proves — specifying 3.2 without a witness point in the ITP is the most common documentation failure on any package.
12. Marking, preservation and packing. Hard stamping versus low-stress marking, what the marking must contain, face protection, preservation for the transit and storage duration actually expected, and the packing standard. Machined sealing faces that arrive damaged are not a quality problem at the mill. They are a specification gap in the enquiry.
The purpose of the list is not completeness for its own sake. It is that each field maps to a specific downstream failure:
| Field left open | Where it surfaces |
|---|---|
| Facing | At fit-up, when two facings will not mate |
| Facing finish | At hydrotest, as a joint that will not seal |
| Bore | After welding, as an internal step |
| Sour service | At material review, unrecoverable without remanufacture |
| NDE scope | At documentation review, as a re-test or a concession |
| Certificate type | At despatch, as a 3.1 where 3.2 was expected |
| Preservation | At goods-inward, as damaged sealing faces |
Every one of those is more expensive than the ten minutes it takes to close the field at enquiry stage.
Most projects already own the answers. They are in the piping material specification, the line list and the project inspection requirements — they simply are not transcribed into the enquiry, because the enquiry is treated as a commercial document rather than a technical one.
Aligning an enquiry to the specification before it goes out is unglamorous work, and it is most of what determines whether a supply package lands cleanly. It is also the point at which a supplier can add or destroy value, which is why Engic reviews requirements against the applicable standards before pricing rather than after award.
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