A good specification for a valve or fastener names the design standard, size, pressure rating or strength grade, materials, finish, tests, certificates, marking and packing. Anything you leave out, the supplier will decide for you.
Write it once, attach it to every enquiry and purchase order, and use the same version when you inspect the goods.
For a valve
- Type and design standard, such as a gate valve to API 600 or a ball valve to API 608. See valve standards: API, ANSI and DIN.
- Size, pressure class or PN rating, and the temperature range.
- End connections, such as flanged to ASME B16.5 with a raised face, butt-weld or threaded, and the face-to-face standard.
- Body, bonnet, trim, seat, stem, gasket and packing materials, each with its material standard.
- Operation, such as lever, gearbox or actuator, and any actuator mounting standard.
- Service fluid and any special conditions, such as sour service, fire-safe design or low fugitive emissions.
- Pressure tests and the test standard, such as API 598, and whether they will be witnessed.
- Paint system and colour, and any internal coating.
- Marking on the body and nameplate, including size, rating, material, heat number and serial number.
For a fastener
- Type and dimension standard, such as a hex bolt to ISO 4014 or ISO 4017.
- Thread size, pitch, length and thread length, plus thread tolerance class.
- Property class or grade, such as 8.8 to ISO 898-1, A4-80 to ISO 3506 or B7 to ASTM A193. See fastener grades and standards.
- Matching nut and washer standards and grades, if supplied as sets.
- Coating, its standard and minimum thickness, the passivation type and the salt spray hours required.
- Baking after plating for high-strength bolts, to reduce the risk of hydrogen embrittlement.
- Head marking requirements, including grade mark and maker's mark.
- Lot size and the tests required per lot, such as hardness, tensile and proof load.
Certificates and documents
State the certificate type you need. Many buyers ask for an EN 10204 type 3.1 material certificate, explained in what EN 10204 3.1 means. Ask for test reports to link to the heat number or lot number on the goods.
For valves in regulated service, list any approvals you need, such as Pressure Equipment Directive conformity for the EU. Confirm the legal requirements with your regulator or a notified body.
Inspection, packing and labels
- State the inspection stages, the sampling plan and who will inspect.
- State the packing method, such as end caps on valves, VCI bags and ISPM-15 pallets.
- State the label contents and barcodes required on each carton and pallet.
- State that no change to material, process or subcontractor is allowed without your written approval.
Next step
We help you turn your requirements into a clear specification, then check samples and lots against it. Book a free sourcing review to get started.