API 602 forged valves: scope and specification guide

What API 602 covers

API publishes Standard 602 for gate, globe and check valves through DN 100 (NPS 4) for the petroleum and natural-gas industries. It is a product standard for compact steel valves. Ball valves are outside that title and are normally specified against a ball-valve standard such as API 608 together with the applicable piping and project requirements.

The size ceiling is not a purchasing recommendation. A valve inside the nominal size range still needs a construction covered by the selected edition. The purchase order should identify the edition and any project amendments instead of relying on the words “API 602 type”.

Standards to specify alongside API 602

A product-standard reference does not by itself fix every interface or service limit. ASME B16.34 supplies a widely used basis for valve pressure-temperature ratings and covers materials, dimensions, examination, testing and marking within its scope. Flange details are commonly taken from ASME B16.5, butt-weld preparation from ASME B16.25 and NPT threads from ASME B1.20.1. The governing piping code and the owner’s valve specification remain part of the purchase basis.

Testing is another separate line item. If API 598 is required, write it into the requisition together with any supplementary low-pressure closure, high-pressure closure, fugitive-emission or witness requirements. “Tested to API” is too vague for inspection planning.

• Product standard and edition: API 602
• Pressure-temperature and valve design basis: state the applicable standard and edition
• End-connection standard: state flange, weld-end or thread basis
• Inspection and pressure testing: state standard, acceptance criteria and witness points
• Project overlay: piping class, corrosion allowance, NACE/ISO requirements, documentation and tagging

The minimum purchase description

A usable description identifies the valve before it lists optional documentation. Start with family, pattern and flow function. Then state NPS or DN, pressure class, end connection and bore where relevant. Follow with body, bonnet, closure member, seat, stem, packing and bolting materials. Finish with operating conditions, test standard, certificate scope and quantity.

For globe and check valves, pattern matters. A T-pattern globe valve and a Y-pattern globe valve are not interchangeable from a pressure-drop or envelope standpoint. A piston check and a swing check also respond differently to orientation and flow. Leaving the pattern open can produce technically different quotations under the same API 602 heading.

Conformity, certification and the API Monogram are different claims

A manufacturer can design and document a valve against a standard without holding an API Monogram licence for that product at that facility. Conversely, an API licence is tied to an audited organisation, facility and licensed scope. The Monogram may be applied only under the programme rules.

Do not request “API approved” as a catch-all. State whether the project requires design conformity, a manufacturer’s declaration, an API Monogram from a currently licensed facility, or a named third-party certificate. If the Monogram is mandatory, verify the facility and status in API’s official composite list before order placement.

Items that still require engineering review

API 602 does not select a valve for the process. The purchaser still owns the service definition: fluid composition, solids, phase, design and operating conditions, differential pressure, cycling rate, required shut-off, installation orientation and external loads.

Low temperature, sour service, oxygen service, cryogenic duty, severe throttling and hazardous emissions all need explicit review. A familiar body grade or trim number is not evidence that the assembled valve is suitable for those duties.