Overview of gate valves&#;
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Gate valves are one of the most common types of valves in the isolation category. They can be found in every refinery, chemical plant, power station, and industrial production facility, and can be manufactured in sizes ranging from DN6 to . gate valves are chosen for the primary purpose of fluid shutoff. It is for this reason that gate valves are often referred to as "cut-off" or "blocking" valves.
Gate valves are generally used in the fully open or fully closed operation. When fully open, the pressure drop through the gate valve is very small; when fully closed, the pressure sealing performance is very good. Due to the fit of the gate and seat ring, there is almost no leakage when the gate valve is closed. However, in the case of very low back pressure (generally not less than 0.34 bar, 1 bar = 105 Pa), some leakage may occur.
Another advantage of gate valves is that they usually open and close very slowly, a feature that prevents fluid water hammer effects from damaging the piping system.
The main limitation of gate valves is that they cannot be used in throttling conditions. When gate valves are used in dry throttling service, the fluid often has a high flow rate near the seat, which can cause erosion. Also in the partially open state, the gate will swing under the impact of the medium, which will cause damage to the seal. Usually, gate valves are more prone to seat and gate seal surface wear than globe valves, and the repair of such wear is difficult to be accomplished by means of grinding and polishing.
Because the structural characteristics of the gate valve are very suitable for large-scale devices, its application range is expanding, and to high temperature and high-pressure development. The maximum diameter of the gate valve has reached DN, in the ammonia plant has been a large number of high-pressure gate valve PN320, for oil and gas drilling wellhead gate valve working pressure up to 138MPa. manufacturing a high-temperature and high-pressure gate valve is the key to solving the problem of wedging the gate plate due to temperature changes, as well as ensuring its reliable sealing performance. To this end, the gate and seat sealing structure should be studied and improved. Resilient seats and resilient floating seats have begun to be applied to enable the gate valve to achieve inlet sealing, outlet sealing, or double sealing of import and export.
Composition of gate valve&#;
Gate valve, also called the gate valve, mainly consists of the valve body, bonnet, gate, stem, seat and seal packing, and other parts.
The gate valve is the opening and closing member (gate), driven by the valve stem, along the seat (sealing surface) to do a linear movement of the valve. Generally, the gate valve can not be used to regulate the flow, only a cut-off device can be used, either completely open or completely closed. Among the various types of valves, the gate valve is the most widely used one. It is suitable for both normal temperature and pressure conditions, as well as high and low temperature and high and low-pressure conditions, and can be applied to a variety of different media through the selection of different materials.
The advantages of the gate valve:
&#;Small fluid resistance. Gate valve body's internal media channel is straight, the media flow through the gate valve does not change its flow direction, so the fluid resistance is small.
&#; structure length (the distance between the two ends connected to the pipe) is small. As the gate is disc-shaped, is placed vertically in the body of the valve, and the globe valve flap (also disc-shaped) is placed parallel to the body of the valve, so compared with the globe valve, its structure length is smaller. Such as the PN16, and DN150 globe valve, the structure length of 480mm, while the same parameters of the gate valve structure length are only 350mm.
&#; opening and closing less effort. When opening and closing the gate movement direction is perpendicular to the direction of media flow, while the shut-off valve flap is usually closed in the direction of movement and seated in the opposite direction of media flow, and therefore must overcome the force of the medium. Therefore, compared with the shut-off valve, the opening, and closing of the exposition valve is more labor-saving.
&#; Media flow direction is not restricted. The medium can flow from both sides of the gate valve in any direction through the gate valve and can achieve the purpose of connection or cut off. Easy to install, suitable for the flow direction of the medium may change in the pipeline.
&#; When fully open, the sealing surface is subject to minimal erosion of the working medium.
&#;The structure of the body is relatively simple, and the manufacturing process is good.
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Disadvantages of the gate valve:
&#;Sealing surface is easy to produce abrasions. When opening and closing the gate and the valve seat in contact with the relative sliding between the two sealing surfaces, under the action of the medium thrust easy to produce abrasion, thus destroying the sealing performance, and affecting the service life.
&#; more parts, the structure is more complex, manufacturing and maintenance are more difficult, compared with the cost of the globe valve are higher.
&#; shape size and opening height are larger, and the space required for installation is larger.
&#;Generally gate valves have two sealing pairs, which adds some difficulties to processing, grinding, and maintenance.
&#; The operating stroke is large, and the opening and closing time is long. Since the gate needs to be completely lifted to the top of the seat channel when opening, and all the gate needs to fall down to block the seat channel when closing, so the opening and closing stroke of the gate is large, and the opening and closing time is long.
Globe valves are linear motion valves that are widely employed to stop, start and throttle flow. In this blog, BM Engineering Supplies explains the function, advantages and disadvantages, and common applications of globe valves.
Globe valves are designed with a stem that moves up and down to regulate flow inside the valve, a disc (ball, composition, or plug) and seat, which is generally screwed into the valve body. Seats are designed in plane parallel or inclined to the line of the flow. These types of modulating valves are most commonly used to valve throttle, open or close flow in a system. The three basic globe valve body designs are Wye, Tee and Angle.
Advantages:
Good shutoff capability.
Moderate to good
valve throttlingcapability.
Shorter stroke (compared to a gate valve).
Easy to machine or resurface the seats.
Can be used as a stop-check valve.
Disadvantages:
Higher pressure drop (compared to a gate valve).
Requires greater force or a larger actuator to seat the valve.
The following are some of the typical applications of globe valves:
Cooling water systems.
Fuel oil systems.
Feedwater or chemical feed systems.
Boiler and main steam vents and drains.
Turbine lube oil system and others.
Bürkert&#;s Type pneumatically operated 2/2-way globe valve fulfils tough criteria for process environments. Unrivalled cycle life and sealing integrity is guaranteed by the proven self adjusting spindle packing with V-seals. The design enables easy integration of automation modules whether they are electrical/optical position feedback, pneumatic control units, an integrated fieldbus interface. The fully integrated system has a compact and smooth design, integrated pneumatic lines, IP65/67 protection class, stainless steel housing (with threaded, clamp or weld connection) and superior chemical resistance. Suitable for 10 bar(g) steam, an explosion-proof version is also available.
Valsteam ADCA&#;s PV25 On-Off valves are single seated, two-way body constructed with in-line straight connections. The PA pneumatic actuator features a rubber diaphragm and multi-springs, and its action can be DA-direct action (air to close) or RA-reverse action (air to open). Their wide application range allows these valves to be used with the most common process fluids, including water, superheated water, steam, air, gas and other non-corrosive fluids. Choose from either a single seated, two-way, direct or reverse action valve. The valve&#;s top flange is permanently attached to the body, meaning removal is unnecessary for replacing the actuator. Soft sealing comes as standard.
Bürkert&#;s Type 2/2&#;way Globe Valve consists of a pneumatically operated piston actuator and a 2/2&#;way valve body. The actuator is made of PA or, for special operating conditions, PPS. The reliable self&#;adjusting packing gland provides high sealing integrity. These maintenance&#;free and robust valves can be fitted with a comprehensive range of accessories for position indication, stroke limitation or manual override. The Type features bubble&#;tight shut off, ISA S75.03 Face&#;to&#;Face dimensions and a stainless steel 316L valve body. Available with flow direction below and above the seat, three and four-inch tube weld ends are available, as is a compact globe valve version.
If you&#;re in any doubt about which type of globe valve to opt for, or would simply like more information and guidance, BM Engineering would be only too happy to chat through your options with you. We stock globe valves up to 6&#; in size and can supply many variants on size and material from our partners on a next-day basis. Speak to a BM Engineering Supplies adviser today about our complete range of Globe Valves by calling 762 or .
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