In a 100-km gas transmission line, the valves you choose will be opened, closed, and inspected thousands of times over a 30-year service life. Spec them wrong and you inherit a maintenance burden that compounds with every shutdown. Spec them right and the system simply runs. At EZ Steel Industrial, we have been manufacturing industrial valves alongside the pipes, pipe fittings, and pipe flanges that connect to them since 1994, so we have seen the same five questions come up on nearly every project.

This guide distills those five questions into a practical specification workflow. It is written for procurement engineers, EPC contractors, and plant operators who need a defensible selection before a purchase order is signed.

1. Start With the Service, Not the Valve Type

The single most common mistake we see is starting the search with a part number. A Class 600 gate valve that is perfect for crude-oil trunk lines is wrong for a 16-inch cooling water loop. Begin instead with four service parameters:

• Fluid phase and composition: Is it single-phase liquid, multi-phase, gas, or steam? Sour service (H₂S) demands NACE MR0175 compliance.
• Pressure and temperature envelope: Maximum operating pressure plus the design margin your code requires (typically 10 percent).
• Function: Isolation only, throttling, non-return, or overpressure protection. Each function has a narrow set of correct valve families.
• Cycle frequency: A valve cycled 50 times a day has very different seat-life requirements from one cycled twice a year.

2. Match the Valve Family to the Function

Once the service envelope is fixed, the choice of valve family follows almost mechanically. The table below is the same one we use internally when a customer asks for "the best valve" without further context.

3. Pair the Valve With the Right End Connections

A valve is only as good as the joint at each end. For high-integrity service, the pairing almost always ends up as a flanged connection with pipe flanges and a matching gasket kit, because it allows the joint to be opened for maintenance. For compact skid packages where weight matters, butt-weld ends remove the flange mass and the leak path entirely.

EZ Steel supplies the full join chain under one quality system: pipe fittings in BW, SW, and threaded variants; pipe flanges in carbon, stainless, alloy, and copper-nickel; plus gaskets, stud bolts, and nuts that share the same heat number trace as the flange. When the entire chain ships from one mill with one mill test report, the documentation burden at site drops dramatically.

4. Don't Forget the Heat-Transfer Line

Valves rarely sit alone. In power-plant and refinery service they sit upstream and downstream of heat efficiency tubes such as U-bend tubes and finned tubes inside a heat exchanger. If you only specify the valve and the exchanger separately, you can end up with a Class mismatch at the exchanger nozzle. Our recommendation: include the exchanger tube material and the nozzle standard in the same valve RFQ, even if the tubes are ordered later.

5. Insist on Test Documentation Before Shipment

Every valve we ship out of the EZ Steel facility passes the four tests that auditors ask about first:

• Shell test at 1.5x rated pressure with water, no visible leakage for at least 30 seconds.
• Seat test per API 598 / ISO 5208, including double-block-and-bleed where the design requires it.
• Backseat (stem seal) test with the valve fully open and the bonnet pressurised.
• Material and NDT traceability through dye penetrant, magnetic particle, ultrasonic, or radiographic test, plus a full mill test report (MTR).

For critical service we add cryogenic testing (-196 °C for LNG), fire testing to API 607 / API 6FA, and fugitive-emission testing to ISO 15848. None of these are optional in our shop, but they are worth confirming in writing on every purchase order you issue.

Where EZ Steel Fits in Your Supply Chain

Founded in 1994 and headquartered in Changsha, China, EZ Steel Industrial runs on a 480,000-ton annual capacity supported by more than 500 specialists. Our pipe, fitting, flange, gasket, bolt, and industrial valve lines are certified to API, EN, and ASME standards, with an ISO 9001-accredited in-house laboratory. The same scope has supplied the South-to-North Water Diversion Project, the West-East Gas Pipeline, petrochemical plant piping, marine vessel systems, and thermal power plant loops.

For buyers, that means a single point of accountability: one PO, one quality plan, one set of shipping documents, and one contact who can trace any heat number back to its casting record.