For project engineers and procurement teams sourcing industrial valves for oil & gas, petrochemical, power or marine service, the questions are always the same: which valve type, which standard, which material, and which test package will actually hold up in service. EZ Steel Industrial has been manufacturing and supplying valve-and-piping packages from Changsha, China since 1994, and the patterns we see on real projects are remarkably consistent. This guide collects the most useful ones into a single specification walkthrough you can apply to your next RFQ.

1. Start with Function, Not with a Part Number

Before browsing any catalog, write down the four operating parameters that drive every downstream decision: fluid type, pressure class, temperature range, and the duty cycle (full-open/closed isolation vs. throttling vs. check). Once those are locked, the valve family almost picks itself.

1.1 Isolation: gate and ball valves

For on/off duty in high-pressure pipelines, gate and ball valves dominate. Gate valves give a very low pressure ｄｒｏｐ when fully open and bidirectional sealing, which is why they are the default for crude oil and natural gas transmission at ASME Class 600 and above. Ball valves win where you need quarter-turn shut-off, tight sealing and low maintenance — for example, LNG lines, sour service, and pigging stations where API 6D trunnion-mounted designs are the norm.

1.2 Throttling: globe and control valves

When the job is flow regulation rather than isolation, globe valves are still the workhorse. The disc moves perpendicular to the flow, which gives precise control — at the cost of a higher pressure ｄｒｏｐ and a heavier body. Pressure control stations, metering skids and fuel gas systems are typical applications.

1.3 Check, butterfly, plug and relief

Swing, lift and dual-plate check valves protect pumps and compressors from reverse flow — pay attention to water-hammer risk in long, slow-closing lines. Wafer and lug butterfly valves are the cost-effective choice for large-bore, low-pressure water and air service. Plug valves handle slurry and corrosive fluids, often at wellheads. And pressure relief or safety valves (spring-loaded or pilot-operated) are mandatory on storage tanks, boilers and compressor stations; they are specified to protect the line, not to control it.

2. Match the Standard, Not Just the Size

A valve that is “the same size” as another is rarely the same valve. Standards dictate the body wall thickness, the face-to-face dimension, the testing regime and even the marking on the body. Mixing the wrong pair is one of the most common reasons packages are rejected at the receiving dock.

For LNG and other cryogenic services, also add BS 6364 and ISO 28921 to the spec. For fire-exposed service, API 607 / API 6FA is non-negotiable. And if fugitive emissions matter — and on most modern plants they do — reference ISO 15848 or API 624 on the datasheet.

3. Pick the Material to Match the Fluid

Body and trim materials are where projects go wrong quietly: a valve can pass every pressure test on the bench and still fail in twelve months because the wrong alloy was chosen for the service. The table below maps the most common material choices to the service they actually fit.

If the line is part of a copper-nickel seawater circuit — common in marine and offshore projects — pair the valve with copper nickel flanges to keep the galvanic series consistent. For higher-temperature process lines built around stainless steel pipe, the valve trim and the pipe should be specified together so that welding, NDT and corrosion allowance all line up.

4. Read the Test Section Like a Contract

Quality control testing is where a generic valve becomes a project-ready valve. The four tests that matter on every order are shell, seat, backseat and operational torque. Anything beyond that depends on the service.

4.1 The mandatory baseline

• Shell test (hydrostatic): body pressurized at typically 1.5× rated pressure for at least 30 seconds; no visible leakage or pressure ｄｒｏｐ allowed.
• Seat test: low-pressure air for soft seats, hydrostatic at 1.1× rated for high-pressure valves; acceptance per API 598 or ISO 5208 leakage class.
• Backseat / stem test: verifies the stem seal when the valve is fully open at 1.1× rated pressure.
• Operation torque test: confirms the valve can be opened and closed smoothly within the manufacturer’s specified torque.

4.2 Tests you add for severe service

• Cryogenic test (BS 6364 / ISO 28921): for LNG, down to –196 °C.
• Fire test (API 607 / API 6FA): 760 °C flame for 30 minutes, then seat test; metal seats must still seal.
• Fugitive emissions (ISO 15848 / API 624 / TA-Luft): VOC leak check at stem and body joints — Class AH/BH is the typical target.
• High-pressure gas test: helium or nitrogen at 1.1× working pressure, leak rate below 100 ppm per API 6D.

4.3 NDT on the body itself

Dye penetrant (PT) and magnetic particle (MT) catch surface and near-surface cracks in castings and welds. Ultrasonic (UT) and radiographic (RT) look for internal flaws such as porosity or inclusions. Hardness testing (Brinell or Rockwell) confirms the body, stem and seats meet the specified strength. All of this should be referenced on the mill test report that ships with every valve — if your supplier can’t produce one, that is the answer to your question.

5. Don’t Specify Valves in Isolation

Almost every real-world valve failure can be traced back to a mismatch with the surrounding piping package, not to the valve itself. A few items to keep on the same specification sheet:

• Pipe flanges — face type, finish and pressure class must match the valve’s ASME B16.5 / B16.47 rating. Mixing raised-face with flat-face is a common cause of joint leakage.
• Gasket, stud bolt and nut — material, bolt grade and tightening sequence are part of the joint design, not an afterthought.
• Pipe fittings — butt weld fittings for high-pressure process lines, socket weld fittings for small-bore high-pressure, and threaded fittings for low-pressure, non-critical service.
• Pipe body — carbon steel pipe for general service; line pipe to API 5L for oil & gas transmission; austenitic grades for corrosive chemistry.

Bundling the valve with its flanges, gaskets, studs and matching fittings avoids a recurring problem: the “right” valve arriving on site with mismatched flanges, or with stud bolts that don’t match the gasket reaction force. Sourcing them as one package, from one supplier, removes the coordination risk from your schedule.

6. A Short Checklist Before You Issue the RFQ

• Fluid, full operating pressure and temperature, and the design margin above that.
• Duty: isolation, throttling, check, relief — and how often the valve will be operated.
• Standard: API 6D, API 600, ASME B16.34 — whichever governs your piping class.
• Material: body, bonnet, trim, seat, stem and seal — all specified, not just the body.
• End connections: flanged (RF, RTJ, FF), butt-weld, socket-weld or threaded — and the matching flange standard.
• Testing scope: shell, seat, backseat, plus any cryogenic, fire or fugitive-emission tests the service demands.
• Documentation: MTR, NACE compliance (if sour), full traceability of heat numbers, and any project-specific inspection release.

If you can fill in every line on this list, you are issuing a specification, not a wish list — and the bids you receive will be comparable, which is the only way to make a fair award.