Gate valves are used in a wide range of applications, most commonly in water pipelines handling process water as a utility, and in wastewater treatment. There are, however, some considerable drawbacks to this valve&#;s usage, mainly due to the slow closing and opening action.
The goal of most continuous processes is quickly achieving its steady state; the excessive times of the dynamic state are equivalent to process inefficiency and financial losses. Any delays in doing so can cause losses and problems, so gate valves are usually not the most optimal choice.
The reason behind the time-demanding gate movement is that the gate valve needs more than 360 degrees of hand wheel rotation from a fully open to a fully closed position. Consequently, the most common purpose of using gate valves is a restriction of medium flow. However, we frequently see them employed for controlling pressure and temperature, as well.
Gate valves can also achieve the required flow rate &#; the parameter we want to control &#; even when partially opened. In this case, it is important to keep in mind the required calculated Cv to pass the required flow. Restricting the opening of the valve beneath the required calculated Cv means the desired flow cannot be passed and thus the openness of the valve can impact the flow rate. Changing the size of the valve in question, and if kept sufficiently open, will only impact the velocity of the media but keep an equal flow rate.
During the gate's movement &#; which is performed either manually by the operator, or by using an actuator &#; water flowing through the pipeline does not have any purpose. It may be considered a complete loss because its mass flow is not the target one.
Compared to the gate valve, the butterfly valve &#; due to its specific construction &#; provides a much faster opening/closing action. The butterfly valve uses a fixed disc on a metal rod, which requires 90 degrees of rotation between the fully open and fully closed position. Let&#;s explore some of the other benefits for choosing butterfly valves that are as important when designing your systems.
Gate valves are usually cheaper than butterfly valves for nominal diameters below DN80. However, due to their robust structure and the need for additional support, their price abruptly increases with the diameter. On the other hand, the butterfly valve has a compact design in all sizes: it requires less space for mounting even in larger pipelines, making it a more affordable option once the diameter goes over DN80. Because pipeline diameters in wastewater treatment or in water-as-a-utility applications can be quite large, the butterfly valves come are a perfect solution.
Besides acting as an off/on flow control, butterfly valves are a great solution for regulating the fluid flow rate. Due to its specific design, a butterfly valve can easily control fluids with both small and excessive flow range requirements. Butterfly valve manufacturers usually provide information on the relation between the valve&#;s opening and flow rate, under constant pressure conditions.
Valves are integral parts of piping systems for conveying liquids and gases and are available in various sizes and designs. Their sole purpose is the control and regulation of these media in a secure manner.
Gate valves and butterfly valves are two of the most popular types of industrial valves. These two have huge differences in both of their structural designs, usage, and working conditions.
In this article, we are going to discuss the differences between gate and butterfly valves. Let us start by defining these two in the next section to find their differences before we elaborate further on the details.
Gate valves, also known as sluice valves, cut off a medium in a pipeline by lifting a rectangular or round &#;gate&#; from the medium&#;s path. The direction of the gate&#;s movement is perpendicular to that of the medium&#;s flow.
Gate valves are cut-off valves which are only used when minimum restrictions and uniform linear flows are desired. They can either be completely open or completely closed which does not allow the adjustment of the medium flow. The medium discharge is normally complete and no residues are left in the pipes.
Butterfly valves are also known as flap valves. They are composed of a fixed disc on the valve&#;s stem for closing and opening the valve. This disc rotates around the valve&#;s stem to regulate the flow of the medium in the pipeline. The direction of the disc&#;s movement is in place rotation only and requires a 90° rotation to fully open or fully close the valve.
Butterfly valves can either be used for regulating or isolating fluid flows and can control the flow easily. However, they leave residual materials in the pipeline.
After the general definitions of gate and butterfly valves, you may have already noticed the differences between the two. Most especially their design, how they work, and their recommended applications. Let us discuss these further by tackling their differences one by one.
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Gate valves use a &#;gate&#; or a wedge whilst butterfly valves use a rotating disc to allow or prevent fluid flow. Moreover, gate valves and butterfly valves have different body and disc designs as stated below.
For detailed descriptions of the gate valve types and butterfly valve types discussed above, you can read these two articles.
Gate valves use a movable door or gate to open and close the valve. This gate is lowered or raised using a mechanically assisted operator which is normally a threaded screw. Since gate valves can either be in the fully open or fully closed state, the resistance of the fluid flow when the valve is fully opened is smaller. This is because when the gate valve is fully open, the gate is entirely out of the medium&#;s path, providing an unobstructed flow.
In general, gate valves act as restrictions to the medium flow and they change the medium&#;s speed rather than its rate of flow. Moreover, the closing and opening speed of the gate valve is slow due to its high opening height.
Butterfly valves belong to the category of quarter-turn valves and they consist of a rotating disc to regulate the medium flow. The disc is held at the center of the valve&#;s body by a stem. Unlike gate valves, butterfly valves have a short operation time since the operator is only rotated at 90° to allow or prevent fluid flow in the passageway.
A butterfly valve is usually operated using an actuator which turns the valve&#;s disc either parallel or perpendicular to the flow. The disc is parallel to the flow when the valve is in the fully open state and is perpendicular to it otherwise. In addition, the butterfly valve&#;s thickness creates resistance which obstructs the medium flow and causes the pressure to drop even if the valve is fully open.
Gate valves have good sealing performances so they are often used for pipelines requiring strict sealing but do not need frequent switching. They can only be used in the fully open or fully closed state and not for regulating or throttling the medium flow rate because accurate control cannot be achieved.
If the valve is kept in the partially or intermediate open state, the valve&#;s seat and the gate will erode badly in just a short time. The chattering wedge will also tend to cause noises and vibrations in the pipeline.
Moreover, because the speed of the gate valve&#;s opening and closing operation is slow, they are not ideal for pipelines that require emergency shutoffs. But when pressure along the pipe is considered, gate valves can withstand higher pressures compared to butterfly valves.
Lastly, gate valves are widely used in large piping systems requiring uninterrupted bi-directional liquid and gas flows or in time-based uni-directional media discharges.
Industrial butterfly valves are lighter compared to gate valves and thus are more convenient to operate and install for applications dealing with large pipe diameters. They are ideal for installations with limited space in which wafer butterfly valve types are recommended. In fact, butterfly valves are comparatively more extensively used in large sizes compared to gate valves.
Because butterfly valves open and close quickly and can be frequently operated, they are ideal for applications that require quick opening and closing, especially for emergency shutoffs. And aside from truncation purposes, they are also used to adjust or throttle flow rates. For pipelines containing small impurity particles, it is recommended to use butterfly valves.
Moreover, butterfly valves are termed high-performance valves because of their suitability in applications under moderate to high temperature and pressure conditions.
Under normal conditions in the same specifications, diameter, and material, butterfly valves are more affordable compared to gate valves. Gate valves may have lower prices than butterfly valves in smaller sizes but their price also rapidly increases with the increase in caliber diameter. So in larger sizes, butterfly valves are still cheaper which makes them more extensively used in various industries.
After discussing the differences between gate valves and butterfly valves, below are the compiled advantages and disadvantages of each valve type.
Gate valves and butterfly valves have their own strengths and weaknesses depending on the application requirements where they are going to be installed. In general, gate valves are ideal for applications that need strict sealing only and do not need frequent operation especially when an unobstructed flow is desired. But if you need a valve for throttling purposes that occupy less space for huge systems, large butterfly valves would be ideal.
For the majority of applications, butterfly valves are more extensively used. Huamei offers high-performance butterfly valves in different end-type connection, material body, seat, and disc designs. Feel free to contact us for further questions about our products.
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