Wedge, parallel slide and slab gate valves to API 600, API 602 and API 6D for refinery, pipeline, utility and marine lines. Made in Britain by Young & Cunningham, selected, supplied and supported in the GCC by Petromarsh.
Tap a part to see what it does. The blue line is the line fluid. With the wedge lifted clear, the bore is straight and unobstructed.
Handwheel. Turns the threaded yoke nut. Many turns move the wedge a short distance, so the valve opens and closes slowly, which protects the line from surges. Large or high-class valves get a bevel gearbox or an actuator.
Yoke. The frame on top of the bonnet that carries the yoke nut. On an outside screw and yoke (OS&Y) valve the stem thread sits here, away from the line fluid, where it can be greased.
Stem. Connects the handwheel to the wedge. On a rising stem valve it climbs as the valve opens, so you can see the position from a distance.
Gland packing. Rings of graphite or PTFE squeezed around the stem by the gland follower. It stops the line fluid escaping to air and is the main source of fugitive emissions, which ISO 15848 tests.
Bonnet. The pressure-retaining cover over the body cavity. It is bolted on with a gasket, or uses a pressure seal ring on high-class steam valves.
Body. The cast or forged pressure shell. It holds the seats and gives a straight flow path when the wedge is lifted. Wall thickness follows ASME B16.34 for the pressure class.
Wedge (gate). The closing member. It slides down between the two seats across the flow. It must be fully open or fully closed: part-open, the flow wears the wedge and seats.
Seats. Rings in the body that the wedge seals against, usually hard-faced with Stellite or 13% chrome. Seat tightness is tested to API 598.
Flanged ends. Raised face or ring joint flanges to ASME B16.5, with face-to-face length to ASME B16.10 so a new valve fits the old gap. Butt-weld and socket-weld ends are also common.
A gate valve opens by lifting a gate clear of the flow path and closes by pushing it down between two seats. Open, it leaves a straight bore with almost no pressure drop. It is made for isolation: fully open or fully closed.
When the gate is lifted into the bonnet, the fluid passes straight through. Pressure drop is close to that of the same length of pipe, and a pig can pass through a full-bore pipeline gate.
The gate is pushed between two seats. Line pressure presses it onto the downstream seat, so tightness improves as pressure rises. Low-pressure gas duty needs more care.
Part open, the flow hits the bottom edge of the gate at high speed. It vibrates, wears the seats and stops sealing. Use a globe valve to regulate flow.
Gate valves differ in the shape of the gate, how the stem moves and how the bonnet is sealed. Tap a type to see where it fits.
The simplest and strongest gate: a single tapered piece of metal. It suits most clean liquid and gas services, but at high temperature the body can distort and grip the wedge.
Common on utility water, firewater and hydrocarbon lines in GCC plants.
A groove around the wedge lets the two faces flex slightly. The wedge follows small distortions in the seats, so it seals better and is less likely to stick when the valve heats and cools.
The usual choice for refinery and petrochemical gate valves under API 600.
Two separate discs seal on parallel seats. In a parallel slide valve a spring and line pressure hold the discs on the seats, and the sliding action wipes the faces clean. The discs cannot jam from heat.
Used on steam and feed water lines in power and desalination plants.
A one-piece slab with a port the same size as the pipe. Open, the hole lines up with the bore, so the valve is fully piggable. Floating seats give a seal on both sides, and cavity relief is built in.
Common on export and trunk pipelines where pigs must pass.
On a rising stem, outside screw and yoke valve the stem climbs as the valve opens, the thread stays out of the fluid and position is easy to see. On a non-rising stem the thread is inside the body, so the valve is shorter but the position is hidden.
Rising stem OS&Y is the norm in GCC process plants; non-rising stem is common on buried water mains.
A bolted bonnet uses a gasket and studs, and suits most classes. A pressure seal bonnet uses line pressure to push a seal ring tighter, so it suits high-class, high-temperature steam valves where large bolted joints would be heavy.
Pressure seal valves are typical on high-pressure steam in power and process plants.
A gate valve is chosen by three material decisions: the pressure shell, the trim (stem, wedge faces and seats) and the packing. In the Gulf the usual concerns are seawater, sour gas, high temperatures and fugitive emissions.
| Part | Carbon and low-temp steel | Stainless and duplex | Bronze and special alloys |
|---|---|---|---|
| Body and bonnet | Cast or forged carbon steel, low-temp steel below −29 °CA216 WCB · A105 · A352 LCC · A350 LF2 | 316 stainless, duplex and super duplexA351 CF8M · A182 F316 · A995 4A / 5A | Bronze and aluminium bronze for seawater and marine dutyB62 · B148 C95800 |
| Trim | 13% chrome stem and wedge, hard-faced seatsAPI 600 trim 1, 5, 8 | 316 trim, with or without hard-facingAPI 600 trim 10, 12, 16 | Monel or alloy 625 trim for seawater and chloridesAPI 600 trim 9 · alloy 625 |
| Packing and gaskets | Graphite packing with low-emission rings, spiral wound or ring joint bonnet gaskets, chosen for temperature and fluidISO 15848-1 · ASME B16.20 | ||
Your piping class and datasheet name the code. The valve is built to it, plus your company specification where one applies.
Bolted bonnet steel gate valves for petroleum and gas service, flanged and butt-weld ends.
Compact forged steel gate valves, usually 4 inch and below, for socket-weld, threaded and flanged lines.
Slab and expanding gate valves for pipelines, with double block and bleed and piggable bores.
Pressure and temperature ratings, wall thickness and materials for flanged and welded-end valves.
Face-to-face and end-to-end lengths, so a replacement fits the existing gap.
Flange dimensions and butt-weld end preparation.
Shell, back seat and seat leak tests, with allowed leakage by valve type and size.
Type testing of stem seals for leakage to air, with tightness and endurance classes.
Material and hardness limits for equipment exposed to hydrogen sulphide.
Your engineers red-line our drawings, you approve the design twice before production starts, and you can witness the tests. Tap a step to see what happens and which documents you receive.
Young & Cunningham has made valves in Britain since the 1920s and has a long history of supplying the UK Ministry of Defence. Their gate valves come in outside screw, inside screw, rising stem, non-rising stem and parallel slide designs, in materials from bronze and cast iron to carbon, stainless and forged steel. Some of their valves supplied over 30 years ago are still in service. Petromarsh is their exclusive representative in the GCC.
If you have valve datasheets or a line list, send them. If you do not, the items on the right are enough for us to select the valve and reply with a proposal.
