In any oil refinery, gas trunk line, steam power plant, desalination train or chemical process, the industrial valves on the P&ID are the components that actually decide whether the system runs, shuts down, isolates, regulates or protects itself. Selecting the wrong valve — or specifying it without aligning to the right flange, pipe and fitting — is one of the most common causes of project delay, leakage and unplanned shutdown. This guide is written from the buyer's side: how to read the seven main valve families, which API / ASME / ISO standard applies, which materials hold up in which service, and how to source them as a single, traceable bundled package from a mill-direct partner such as EZ STEEL INDUSTRIAL.

1. The Seven Valve Families You Will See on Every Project RFQ

Before you get into pressure class and trim material, decide which function the valve performs. The seven families below cover more than 95% of all industrial valve line items on a typical EPC RFQ.

When you are sourcing a piping package, every one of these families will arrive with a different face-to-face dimension, a different end connection, and a different bolt pattern. That is why the pipe flanges and the valve bodies must be ordered together — not as two unrelated line items.

2. Which API / ASME / ISO Standard Applies — And Why It Matters at RFQ

Most RFQ rejections in our 30 years of industrial supply have come from the buyer quoting the wrong standard. The four families below cover the bulk of refinery, pipeline, power and chemical-service valve specifications.

2.1 API (American Petroleum Institute)

• API 600 — Bolted bonnet steel gate valves for refinery and high-temperature service.
• API 602 — Compact gate, globe and check valves for small-bore lines.
• API 6D — Pipeline valves (gate, ball, check) for trunk-line and offshore.
• API 6A — Wellhead and Christmas tree equipment.
• API 598 — Mandatory valve inspection and testing reference.

2.2 ASME (Mechanical design and dimensions)

• ASME B16.34 — Pressure-temperature ratings for steel valves.
• ASME B16.10 — Face-to-face and end-to-end dimensions (critical for interchangeability with adjacent pipe fittings).
• ASME B16.5 / B16.47 — Flange dimensions for matching steel flanges.

2.3 ISO, MSS, NACE, EN

• ISO 14313 — Equivalent to API 6D for international EPC tenders.
• ISO 10434 — Bolted bonnet steel gate valves (ISO equivalent of API 600).
• MSS SP-61 — Hydrostatic shell test methodology.
• NACE MR0175 / MR0103 — Mandatory for sour (H₂S) service valves.
• EN 593 — Butterfly valves for European projects.

3. Match the Body and Trim Material to the Service Fluid

Once the standard is fixed, the next decision is metallurgy. The wrong material here is the single biggest reason for in-service valve failure. Use this as a starting decision map:

For marine and offshore buyers, the copper nickel alloy family deserves specific attention: 90/10 Cu-Ni is the workhorse for ship seawater cooling and is typically paired with EEMUA 144 / 234 copper nickel flanges for full system compatibility.

4. The Tests a Valve Must Pass Before It Leaves the Mill

Every reputable mill-direct supplier will perform at least the following five tests as a minimum, with the test report attached to the MTC (Mill Test Certificate). Ask for them in the QA plan before issuing the PO:

• Shell test (hydrostatic body test) — pressurize the body cavity at 1.5× the rated pressure; no visible leakage, no pressure ｄｒｏｐ.
• Seat test (low-pressure air or hydrostatic) — confirms tight shut-off; for Class 900+ the test pressure rises to 1.1× rated.
• Backseat test (stem seal) — performed with the valve fully open, verifies packing integrity.
• Operation torque test — confirms the valve can be opened/closed with a standard actuator or hand-wheel without exceeding the maker's torque curve.
• NDT (PT, MT, UT or RT) — surface and sub-surface inspection per ASME V, depending on the casting/forging route.

For LNG, cryogenic and sour-service valves, additionally require cryogenic impact test at –196 °C (per BS 6364), fire test per API 607 / API 6FA and fugitive emissions test per ISO 15848 / API 624. A NACE MR0175 certificate is mandatory for any valve in contact with wet H₂S.

5. Why Bundled Sourcing Beats Buying Valve-by-Valve

A refinery, terminal, desalination plant or boiler house is not a collection of standalone parts. It is a piping system. When the stainless steel pipe arrives in one container, the flanges in a second, the fittings in a third, and the valves in a fourth, mismatches show up only on site — wrong facing, wrong bolt circle, wrong MTC traceability.

Bundled sourcing from a single mill-direct supplier solves this in three ways:

• One BOM, one MTC set. Every item carries a heat number traceable back to the same raw-material batch.
• One shipping window. The whole piping package — carbon steel pipe line pipe, BW / SW / threaded fittings, RF / FF flanges, gaskets & stud bolts, and the industrial valves — is consolidated into the same vessel or container, reducing demurrage.
• One technical contact. Pressure-class, facing-type, weld-prep and material-certification questions are answered by a single engineering team, not four sales desks.

6. Where a 30-Year Mill-Direct Partner Fits In

EZ STEEL INDUSTRIAL has been producing industrial steel pipe, fittings, flanges, gaskets, stud bolts and industrial valves since 1994, with 500+ employees and an annual output of 480,000+ tonnes out of Changsha, China. The factory is qualified to API, EN and ASME requirements, with an ISO 9001-accredited lab and ASME / AWS-certified welding procedures.

The company's eight product lines — carbon & carbon-alloy steel, stainless steel, copper-nickel alloy, heat-efficiency tubes, pipe fittings, pipe flanges, gaskets & stud bolts, and industrial valves — let a buyer build a complete bolted-joint assembly from one supplier, from the line pipe to the last stud bolt. References include the South-to-North Water Diversion Project, the West-East Gas Pipeline Project, petrochemical plant piping, marine vessel metal pipeline systems and steam power plant pipelines.