Ball, gate, globe, butterfly and check valves for wellsite and gathering duty, transmission pipelines, refinery process units and petrochemical plants — with the trim materials, API standards and documentation these projects require.
Request a Quote →The oil and gas chain is usually described in three stages, and the valve duty changes completely between them. Upstream covers the wellhead and the gathering system: Christmas tree valves, choke and flowline isolation, test and production manifolds, separator and heater treater isolation, and the tank battery. Pressures are high, the fluid is a mixture of oil, gas, water and sand, and the equipment is often unattended between visits. Reliability and simple maintenance matter more than fine control.
Midstream covers transport and storage: gathering and transmission pipelines, pump and compressor stations, metering and custody transfer skids, tank farms, and loading and unloading arms. Here the flow is single phase or dense phase, the sizes are large, and the priority shifts to full-bore unobstructed passage for pigging, tight isolation for product segregation, and double block and bleed where two different products meet. Refining and petrochemical covers the process units themselves, where valves work across a wide band of temperatures and pressures and where the medium may be hydrogen, amine, caustic, acid or a hot hydrocarbon.
The practical consequence is that the same nominal valve type appears in all three stages but with different construction. A ball valve on a wellsite test line, a ball valve on a transmission pipeline and a ball valve in a refinery unit are not interchangeable even when the size and pressure class match, because bore, sealing arrangement, trim material, fire-safe construction and documentation all differ. The enquiry has to state which stage, which fluid and which codes apply.
Read more about how valves behave in aggressive hydrocarbon service on our valve material selection guide.
| Valve Type | Typical Duty in Oil, Gas and Petrochemical Service |
|---|---|
| Ball valve | The general isolation valve for hydrocarbons. Quarter-turn operation, tight shut-off, and a full bore in the trunnion-mounted pattern for pipeline and pigging duty. Three-piece and welded-body patterns suit manifolds and skids. |
| Trunnion-mounted ball valve | Large-diameter, high-pressure pipeline and station isolation where the stem load is carried by trunnion bearings rather than by the seat, keeping operating torque manageable. |
| Gate valve | Refinery and utility isolation, pump discharge and general on/off duty where a full-bore passage and low pressure drop are wanted. Multi-turn operation, so not for rapid isolation. |
| Globe valve | Throttling and frequent-operation duty on small lines, drains, vents and sampling points where a more nearly linear characteristic is useful and some pressure drop is acceptable. |
| Control valve | Pressure, level and flow regulation on separators, columns, reboilers and compressor anti-surge circuits. Trim selection follows the flashing, cavitating or noisy nature of the service. |
| Check valve | Pump and compressor discharge protection, and where reverse flow must be prevented without operator action. Closure speed and the resulting surge pressure are the sizing considerations. |
| Butterfly valve | Large-diameter cooling water, utility, flare and vent lines, and process water where space and weight favour a compact valve over a gate or ball valve. |
| Triple-offset butterfly valve | Where a metal seat with a tighter leakage class is specified on large lines, including high-temperature process and steam service where an elastomer seat is unsuitable. |
| Knife gate valve | Produced sand, sludge, slop and catalyst handling, and any line carrying solids or a heavy slurry where a standard seat would be blocked. |
Carbon steel remains the working body material for hydrocarbon service, with WCB castings and forged equivalents covering the majority of refinery and pipeline valves. Stainless steel grades are selected where corrosion, not pressure, is the governing condition: CF8M for general corrosive hydrocarbon and utility duty, duplex and super duplex where chlorides and stress corrosion cracking are a concern, and higher alloys for specific acid or amine services. Low-temperature grades are required where the valve will see autorefrigeration or a cold box, because ordinary carbon steel becomes brittle at low temperature.
Trim is where the engineering judgement concentrates. Soft-seated ball valves with PTFE or reinforced PTFE seats give tight shut-off at moderate temperatures, while metal-seated designs are used for high temperature, abrasive or high-cycle service where a soft seat would extrude or wear. Stem and seat facing materials such as 13 percent chrome stainless, SS316, stellite and hard-facing alloys are chosen against the combination of pressure, temperature, cycling and particle content. Where the medium is dry gas or contains fine solids, the harder facing is what determines service life.
Sour service is the requirement that most often changes the material route entirely. Where the fluid contains hydrogen sulphide, NACE MR0175 / ISO 15156 governs the acceptable materials and the maximum hardness, because hard, high-strength steels are susceptible to sulphide stress cracking. In practice this means the valve body, trim, bolting and any welding must be assessed against the sulphide stress cracking and stress corrosion cracking limits, and the H2S partial pressure and fluid condition must be stated in the enquiry. Hardness testing and material certification are part of the evidence that a sour service valve conforms.
Fire-safe construction is the other recurring requirement. On hydrocarbon duty, projects commonly specify that a soft-seated valve be tested to demonstrate that it continues to limit leakage after a fire has destroyed the primary seat. A fire-safe test result to API 607 or API 6FA is a project specification for a qualified order, and where an enquiry calls for it we assess the requested design against that requirement rather than treating it as a standing approval.
Standard sets in this sector come from the operating company or the engineering contractor, and they are applied strictly. The following are the requirements that appear most often in enquiries. They are standards that projects specify to suppliers, not approvals held by us.
| Standard | What It Covers in This Sector |
|---|---|
| API 6D | Pipeline valves: ball, check and through-conduit gate valves for transmission and gathering duty, with requirements around bore, cavity relief, piggability and pressure testing. |
| API 600 | Steel gate valves, bolted bonnet and rising stem, the standard refinery isolation valve in every piping material class. |
| API 608 | Metal ball valves for general refinery and process service, covering flanged, threaded and welded ends. |
| API 609 | Butterfly valves, referenced for large-diameter utility, cooling water and flare line isolation. |
| API 607 / API 6FA | Fire-safe testing of quarter-turn and pipeline valves. Where a project specifies fire-safe performance, the test requirement and acceptable leakage are stated in the purchase order. |
| ASME B16.34 | Pressure-temperature ratings, wall thickness and material requirements for steel valves, the baseline for most metallic bodies. |
| API 598 | Shell and seat pressure testing with defined test pressures, durations and permissible leakage, usually witnessed by third-party inspection. |
| NACE MR0175 / ISO 15156 | Materials for use in H2S-containing environments, setting the acceptable materials and hardness limits for sour service. |
| ISO 5211 | Actuator mounting flange dimensions, so actuated valves can be assembled and maintained without custom adapters. |
| IEC 60534 | Control valve sizing and the noise and cavitation considerations that drive trim selection. |
| EN 10204 3.1 | Inspection certificate format for the mill test certificate, traceable to the heat number. |
| ATEX / IECEx and PED | Area classification requirements for electric actuation in hazardous zones, and European pressure equipment documentation. Both are project-specific requirements that should be stated in the enquiry. |
In oil and gas, documentation is part of the deliverable and not an administrative extra. A purchase order normally defines a documentation requirement schedule at the enquiry stage, and the valve is not released for shipment until the records have been reviewed and, where required, witnessed. Preparing those records has to be planned into the manufacturing sequence rather than assembled afterwards.
The core package comprises a mill test certificate to EN 10204 3.1 covering body, bonnet, trim and bolting, each traceable to its heat number; shell and seat hydrostatic test reports to API 598 recording test pressure, duration and result; and dimensional inspection records confirming face-to-face length, flange drilling and actuator mounting dimensions against the specified standards. Where a hardness limit applies under NACE MR0175 / ISO 15156, hardness test records and the material certification supporting them are added. Where the project specifies fire-safe performance, the fire-safe test requirement is defined in the order and the result is documented with it.
Beyond the valve itself, orders usually require non-destructive examination records where the specification calls for weld examination, a positive material identification report where alloy verification is requested, and painting or coating records against the project specification. For actuated valves, the actuator and instrument datasheets, the mounting interface confirmation and a function test record are part of the same package. Third-party inspection at the works, with a release note issued before packing, is standard practice on project orders.
Our quality management system is certified to ISO 9001, and factory audit reports from SGS-CSTC are available. Product approvals such as API 6D, API 600, API 607, ATEX or PED are requirements that individual projects specify; where an enquiry calls for them we will confirm what can be provided for that qualified order rather than representing them as standing certifications. See our certifications page for the detail of what we hold.
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Sour service means the fluid contains hydrogen sulphide, which can cause sulphide stress cracking in hard, high-strength steels. The project documents the partial pressure of H2S and the fluid condition, and the material and hardness requirements follow from NACE MR0175 / ISO 15156. For a valve this affects body and trim material selection, maximum hardness limits, bolting and the welding procedure if the valve is welded. The requirement must be stated at enquiry stage, because it changes the material route rather than being a documentation detail.
A ball valve gives quarter-turn operation, a compact face-to-face and a cavity-free bore in the seated position, which makes it the usual choice for lines that must be opened or closed quickly, for piggable pipelines where a full unobstructed bore is wanted, and for double block and bleed arrangements. A gate valve is generally cheaper in larger sizes and gives a lower pressure drop when fully open, but it is a multi-turn valve and its seat pockets can trap solids. On hydrocarbons the ball valve is more often the specified isolation valve.
It is an arrangement of two isolating valves in series with a bleed valve between them, so that the cavity can be vented to confirm that neither valve is passing before work starts. It is common on metering, sampling and custody transfer skids. The bleed connection, cavity relief and drainage details need to be defined in the purchase specification because they determine the valve construction and the number of body connections.
API 6D covers pipeline valves, principally ball and through-conduit gate valves, and is written around pipeline isolation duty with requirements for full bore, piggability, cavity relief and pressure testing. API 600 covers steel gate valves of the bolted bonnet, rising stem type, which are typical for refinery and utility isolation. The two standards lead to different body constructions, so the choice follows the duty and the piping specification rather than a preference.
A mill test certificate to EN 10204 3.1 traceable to the heat number for body, trim and bolting, shell and seat pressure test reports to API 598, a witness or review of the fire-safe test where the project specifies it, dimensional inspection records against the face-to-face and flange standards, hardness test records where a hardness limit applies, and where relevant NACE MR0175 / ISO 15156 material documentation. Third-party inspection at the works and a release note before dispatch are normally part of the order.
Where a valve is actuated by an electric actuator, the area classification determines whether the actuator must be certified for use in a hazardous zone. That is an actuator and instrumentation matter as much as a valve matter, and the area classification and the required certification for the actuator package should be stated in the enquiry so that the correct assembly is proposed. Manual valves do not raise the same question, but the stem sealing arrangement still has to be suitable for the service.
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