On most oil and gas jobs, industrial valves are specified in the same breath as the pipe, the flanges, and the fittings they connect to — and then sourced from a different supplier. That separation is where projects bleed time. The valve body, the pipe flanges it bolts to, and the gasket stud bolt nut set between them have to come from the same material family, the same heat-number traceability, and the same pressure class. When they do, the line passes hydrotest on the first try.

This guide is built around that reality. We work through the seven valve types that show up in the bulk of refinery, gas-transmission, and offshore service, then move to the standards, materials, and test plans that make them safe to ship. The aim is practical: when you finish reading, you should be able to look at a line class on a P&ID and know which valve to call for, which standard to stamp on the purchase order, and which questions to ask your supplier before the goods leave the mill.

What an Industrial Valve Actually Does on a Pipeline

A valve is a deliberate restriction. The job of the designer is to make it open when flow is wanted, close when it is not, and stay where it was put for the next fifteen to twenty years. Three functions cover almost every service on an oil, gas, or petrochemical line:

• Isolation — a full-bore shut-off that lets you cut a section of line or a piece of equipment for maintenance. Gate and ball valves dominate this duty.
• Regulation — a partial-bore adjustment that holds flow, pressure, or level at a set point. Globe valves are the traditional answer; control valves are the modern one.
• Protection — an automatic response to abnormal conditions. Check valves prevent backflow; relief and safety valves protect against overpressure.

The right valve is the one that does its job, and nothing else. A gate valve used for throttling will erode in a season; a globe valve used for isolation will give the operator a hernia. Type, size, and pressure class are decisions you want to make once, on paper, before the PO is cut.

The Seven Valve Types You Will Spec Most Often

Every refinery, terminal, and gas plant draws from the same short list. The job descriptions below cover what each one is good at — and where it should be left on the shelf.

Gate Valve

A sliding wedge or knife lifts out of the flow path. When fully open, the bore is essentially unrestricted, so pressure ｄｒｏｐ is minimal. This is the workhorse for on/off isolation on crude, product, and gas lines. It is not a throttling valve — partial opening erodes the seat faces and the valve will not shut off tightly afterwards. Specify a gate valve for full-bore isolation, in particular where ASME Class 600 and above is involved.

Ball Valve

A quarter-turn of a bored ball opens or closes the line. Floating-ball designs handle low to medium pressure; trunnion-mounted designs (API 6D) handle the high-pressure transmission service that dominates gas and offshore. Ball valves shut off fast, seal tight, and survive frequent cycling — which is why they have largely replaced gate valves on new pipeline construction and on pig-launcher / pig-receiver stations.

Globe Valve

A disc moves perpendicular to the flow, throttling it in a controlled way. The tortuous path costs pressure, but it gives the operator precise control — the reason globe valves are still specified for feedwater, fuel-gas regulation, and chemical-injection metering. On instrument and sampling lines, a small globe valve is often the difference between a steady reading and a wandering one.

Check Valve (Non-Return)

A passive device: it opens with forward flow and slams shut when flow reverses. The three common constructions are swing (low to medium pressure, larger lines), lift (better for high-pressure steam and process), and dual-plate (compact, fast-closing, the default for API 6D pipeline service). Every pump discharge and every compressor station needs at least one. Skip them and a trip event becomes a water-hammer event.

Butterfly Valve

A disc rotates in the flow. The body is short, the weight is low, and the price is the lowest of any full-bore valve — which is why butterfly valves dominate water, fire-protection, and low-pressure gas distribution. Wafer and lug styles clamp between standard steel flanges. For high-pressure hydrocarbon service, the industry still reaches for ball or gate.

Plug Valve

A cylindrical or tapered plug rotates to open, close, or divert flow. Multi-port versions ｒｅｐｌａｃｅ a manifold of single valves in slurry, chemical, or wellhead service. Lubricated plug valves were once the standard for oil-field manifolds; modern lined and sleeved plug valves have largely taken over in corrosive and low-emission service.

Pressure Relief and Safety Valve

The last line of defence. Spring-loaded relief valves protect tanks, vessels, and low-capacity lines; pilot-operated relief valves handle the high-capacity compressor and separator duties. Every pressure vessel in the plant has at least one. Sizing a relief valve is a calculation, not a guess, and the API 520 / 521 series is the reference.

Matching Valve to Service: A Quick Decision Table

The table below compresses the most common service conditions into a one-line recommendation. Use it as a starting point, then confirm with the line class on the P&ID and the project piping specification.

Standards That Will Appear on the Body Stamp

The marking on a valve body is not decoration — it is the manufacturer's declaration that the casting, the design, and the testing all meet a published specification. The buyer who can read the stamp can spot a wrong part before it lands in the warehouse.

• API 6D — pipeline valves (gate, ball, check) for the bulk of oil and gas transmission service. The default for any line class above ANSI 600.
• API 600 / API 602 — bolted-bonnet and small-forged gate valves for refinery and process plants.
• API 6A — wellhead and Christmas-tree equipment, rated to the high pressures of upstream service.
• API 598 / ISO 5208 — the inspection and leakage test procedures that the body was tested to before shipment.
• ASME B16.34 — pressure-temperature ratings for steel valves. The reference when the line class on the P&ID is given as a Class number.
• ASME B16.10 — face-to-face dimensions, so the valve drops into the spool without re-work on site.
• API 607 / API 6FA — fire-safe testing for soft-seated ball and butterfly valves.
• ISO 15848 / API 624 — fugitive-emission testing for stem seals. Increasingly required in Europe and on LNG projects.
• NACE MR0175 / MR0103 — material requirements for sour service (H₂S-bearing fluids).

Material Selection: Body, Trim, and Seat

Material choice is driven by three things: the fluid, the temperature, and the corrosion allowance. The body, the trim, and the seat are usually specified separately, which is why two valves with the same body casting can have very different prices.

• Carbon steel (WCB, LCB, LCC) — the default for water, air, oil, and gas in the -29 °C to 425 °C range. Most refinery and pipeline industrial valves ship in WCB body with 13Cr or SS316 trim.
• Low-temperature carbon steel (LCB / LCC) — required for service below -29 °C (LNG, LPG, light hydrocarbons). Impact-tested to ASME B16.34.
• Stainless steel (CF8, CF8M / F316) — specified wherever corrosion, hygiene, or outdoor exposure is the design driver. Pairs naturally with stainless pipe flanges and stainless lines.
• Duplex and super-duplex (UNS S31803, S32750) — the workhorse for offshore, seawater, and sour service. Higher strength and chloride resistance than standard austenitic grades.
• Nickel alloys (Alloy 625, Alloy 825, Monel 400) — for acid, alkali, and seawater systems, often in copper nickel alloy lines.
• Alloy steel (WC6, WC9, C5, C12) — for high-temperature service in power and refinery hydroprocessing.

On a sour-service project, the body and trim must both meet NACE MR0175. On an oxygen or hydrogen service, the requirements tighten further — only specific alloys, hardness limits, and seal materials are acceptable. The wrong seat in an oxygen line is a fire risk; the wrong body in hydrogen service is an embrittlement risk.

How a Quality Industrial Valve Is Tested Before Shipment

Every valve leaves the manufacturer with a test certificate. The tests below are the ones that actually catch defects — the rest is paperwork.

• Shell (hydrostatic body) test — pressurise the body to 1.5× the cold working pressure, hold for at least 30 s, look for leakage or visible deformation. Per API 598 / ISO 5208.
• Seat test — pressurise the closed valve from each side at the lower of 1.1× cold working pressure or 110 % of the rated seat pressure. Soft seats: zero bubbles. Metal seats: a defined leakage rate, never zero.
• Backseat test — checks the stem packing in the fully-open position. Important for gate and globe valves that may sit open for years.
• Double-block-and-bleed test — verifies both seats seal simultaneously, allowing the cavity to be drained. Standard on API 6D ball and gate valves for pipeline service.
• Operation torque test — measures the breakaway and running torque of the valve. Out-of-spec torque is the leading predictor of a valve that operators will not be able to close in an emergency.
• Cryogenic test (LNG service) — cool to -196 °C in liquid nitrogen, then perform seat and shell tests. Reference: BS 6364, ISO 28921.
• Fire test (API 607 / API 6FA) — 30 minutes in a 760 °C flame, followed by a seat test. Required for valves in flammable service.
• Fugitive-emission test (ISO 15848 / API 624) — sniffs the stem and body joints for VOC leakage. Increasingly mandatory on European and LNG projects.
• Non-destructive testing (PT, MT, UT, RT) — surface and sub-surface inspection of castings and welds. Hardness testing (Brinell / Rockwell) on bodies and bonnets confirms the heat treatment.

Integrating Valves with the Rest of the Pipe Package

A valve does not stand alone. It bolts to a flange, sits between two lengths of pipe, and is sealed by a gasket and a set of studs. If the parts are not from the same material family, or were not torque-checked to the same gasket design, the joint will leak — and the leak will be blamed on the valve.

This is the strongest argument for sourcing the package as a single bundle. A full pipe-and-fittings shipment usually contains:

• Pipe fittings — elbows, tees, reducers in BW, SW, and threaded constructions to match the line class.
• Pipe flanges — WN, SO, blind, threaded, lap-joint — in the same pressure class as the valve body.
• Gasket stud bolt nut sets — sized to the flange class, with the correct bolt grade (B7 / B7M / B8 / B8M) and the gasket type (spiral-wound, RTJ, soft cut, graphite) for the service.
• Industrial valves — gate, globe, ball, check, butterfly, plug, relief — selected to the line class.

When all four arrive together, the MTRs line up, the heat numbers match, the dimensions are consistent, and the warehouse inspector spends one day on the goods instead of four. For a contractor, that is the difference between a hydrotest that passes on the first pump-up and one that delays the schedule by a week.

Five Field Habits That Prevent Valve Problems After Start-Up

Most valve failures on a running plant trace back to one of five causes, and all five are addressable at the design or procurement stage.

• Wrong valve for the service. A gate valve on a control loop, a butterfly valve on a high-pressure hydrocarbon line, a non-NACE valve in sour service. Lock the type into the line class on the P&ID before the PO is cut.
• Mixed standards on the joint. A Class 300 valve between two Class 150 flanges, or an RTJ gasket on a flat-face flange. Verify face-to-face and end-connection on every spool drawing.
• Bolts that do not match the service. Carbon-steel B7 studs in chloride service will fail by SCC; B8 stainless in high-temperature service will creep. Match the bolt grade to the temperature and the medium.
• No PMI check at receipt. A 30-second gun check on a stainless body catches mix-ups between F304 and F316, and between carbon and stainless castings. Cheaper than a 30-day shutdown.
• No documented torque procedure. A hand-tightened flange on a spiral-wound gasket will not seal at design pressure. Use the gasket supplier's torque table and a calibrated wrench.

Sourcing Industrial Valves for an Industrial Project

For a buyer, the difference between a smooth valve procurement and a painful one is rarely price. It is traceability, stock depth, and the willingness of the supplier to hold MTRs, PMI reports, and test certificates in one place. A supplier who can ship forged and cast valves in carbon, stainless, duplex, and alloy — together with the matching pipe fittings, pipe flanges, and gasket stud bolt nut sets — removes a category of project risk that single-line vendors cannot.

That is the model that EZ STEEL INDUSTRIAL has built since 1994: a 500-person mill in Hunan, an annual capacity above 480,000 tonnes, and an export desk that ships pipe, fittings, flanges, and industrial valves as a single package to refineries, gas plants, offshore yards, and power stations across more than sixty countries. API, EN, and ASME certification, an ISO 9001 laboratory, and ASME / AWS-accredited welders are the supporting paperwork. The working principle is simpler: one supplier, one heat-number trail, one set of test certificates, one delivery to the site.