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Valves are an integral part of any piping system, whether that be a compressed air system or for conveying liquids and other gases. They are typically used to control and regulate the media in question.
Butterfly valves and gate valves are two of the most common types of valves found across industries. They have significant differences in their design, mechanisms, applications, and more, and so, this article will provide you with all the relevant information on both!
Table of Contents
- What is a Butterfly Valve?
- What is a Gate Valve?
- The Differences Between Butterfly Valves & Gate Valves
- FAQs (Frequently Asked Questions)
What is a Butterfly Valve?
Butterfly valves, or also referred to as flap valves, are composed of a fixed disc on the stem of the valve which is used for opening and closing the valve. This disc rotates around the valve’s stem so that the flow of the medium can be regulated in the system. To open or fully close, the valve’s disc requires a 90° rotation.
These types of valves can be used for either regulating or isolating a media flow with ease of control. However, butterfly valves are associated with leaving residual materials inside of the pipelines.
Here’s an example of a butterfly valve readily available on Amazon!
Butterfly Valve Advantages
- Affordable in large sizes
- Can easily control the flow easily and suitable for throttling fluids
- Fast operation time – ideal for emergency shut-offs
- Lightweight and compact designs
- Suitable for use with moderate to high temperature and pressure conditions
Butterfly Valve Disadvantages
- Likelihood of water hammers
- Movement of the disc is unguided so can be affected by flow turbulence
- They leave resisdual materials in pipes
- Thick liquids can prevent disc movement
- Thickness of the valve’s body creates resistance which will obstruct flow and cause pressure drop even when fully open
What is a Gate Valve?
Gate valves, or also referred to as sluice valves, cut off the flow of the medium in a pipeline by lifting a rectangular or round gate from the medium’s flow path. The gate’s directional movement is perpendicular to the flow of the medium, and they’re sometimes known as cut-off valves.
These types of valves are used when there is a desire for minimum restrictions and uniform linear flows. They can either be completely open or completely closed, which will not allow for the adjustment of the medium’s flow. Due to this, the medium’s discharge is typically complete and there are no residues left in the system’s pipes.
Here’s an example of a gate valve readily available on Amazon!
Gate Valve Advantages
- Allow uniform linear flows and are bi-directional
- Can provide an unobstructed flow in the fully open position so pressure loss is at an absolute minimum
- Can withstand higher pressures compared to butterfly valves
- No residues left in pipes
- Prevent water hammer due to wedge slow operation
Gate Valve Disadvantages
- Can only be completely open or completely closed with no adjustments for the flow allowed
- More expensive in larger sizes than butterfly valves
- Operation speed is slow due to the gate valve’s high opening height
- They occupy a larger space for the installation and operation compared to butterfly valves
- Valve’s seat and gate will erode badly if kept in partially open state
The Differences Between Butterfly Valves & Gate Valves
Given the definitions of the butterfly valve and gate valve, along with their advantages and disadvantages, you should have a good idea already about the differences between them. But, I would like to dig into it a bit further and focus on the following differences:
When it comes to their design, gate valves utilize a gat or wedge whilst a butterfly valve uses a rotating disc which allows for or prevents the flow of the medium. I’ll explain further how they work in the next section, but here I would like to present the various designs of each type of valve because there are so many variations of each.
Butterfly Valve Designs
The body of the butterfly valve is most commonly one of the following:
- Butt-welded – directly welded in the pipeline for high pressure applications
- Flanged – has a flanged body and raised rims to allow for its installation between two flanged pipes with the same dimension as the valve
- Lug type – they have threaded “lugs” or inserts around its circumference that permit bolt passages
- Water type – used to maintain a unidirectional pressure or positive pressure
And, their disc offset designs are:
- Zero offset (concentric) – have their seals lined against the edge of the elastomer lining which ensures a tight shut-off. The stem is then mounted in a vertical axis at the center of the disk
- Double offset (double eccentric) – a high performance butterfly valve which is specifically designed with two offsets of the stem. This movement is calculated with a specific cone profile to address shut off of any high pressure applications
- Triple offset (triple eccentric) – three offsets to help provide a tighter seal. Involves a double offset with an additional offset of the disk seat axis
Gate Valve Designs
The body of the gate valve is most common one of the following:
- Bolted-bonnet – most popular design and commonly found in gate valves. Gasket is used to seal joint between body and bonnet
- Pressure-sealed bonnet – suitable for extensively high pressure and high temperature applications. The higher the body cavity pressure, the greater the force on the gasket in a pressure seal valve
- Screwed bonnet – simplest and most inexpensive
- Welded-bonnet – popular where disassembly is not required
And, their disc designs:
- Wedge gate – the most common & widely used gate valve disk type because of its strength and simplicity. A gate valve with a solid wedge may be installed in any position, and it is suitable for almost all fluids, and, it can be used with turbulent flow
- Flexible wedge gate – a one piece solid disk with a cut around the perimeter which helps improve seat alignment and offers better leak tightness
- Parrallel slide gate – two solid pieces held together with the help of a special mechanism. Offer spring-loaded bi-directional sealing
When it comes to their working mechanism, butterfly valves belong to the category of quarter-turn valves and they consist of a rotating disc that helps to regulate the medium flow. The disc is held at the center of the valve’s body by a stem and unlike gate valves, they have a short operation time because the operator is only able to rotate at 90° to either allow or block the medium’s flow.
Butterfly valves are typically operated by an actuator that turns the valve’s disc either parallel or perpendicular to the flow. When the valve is fully open, the disc is parallel to the flow, and when the valve is fully closed, the disc is perpendicular to the flow. The thickness of the butterfly valve, unfortunately, obstructs flow even when it is fully opened, and this causes a pressure drop.
A gate valve on the other hand uses a movable gate, or door, to open and close the valve. A mechanically assisted operator lowers or raises the gate, which is normally a threaded screw. The resistance of flow when the valve is fully opened is a lot smaller than butterfly valves because the gate is entirely out of the way, therefore flow is unobstructed.
In general, gate valves change the speed of the flow rather than its rate of flow. The opening and closing of the gate can be quite slow due to the height of the opening.
Typically, butterfly valves are the more affordable option of the two given that they have the same conditions, specifications, and materials. Gate valves can have lower prices than butterfly valves when they’re small but their price increases significantly with size.
Therefore, butterfly valves are more commonly found to be used across industries when the sizes are larger.
Butterfly valves are found to be installed in larger pipe diameter systems as they’re more convenient to operate and are lighter compared to gate valves. They are ideal for installations that have limited space and applications that require quick opening and closing, especially emergency shutoffs. Butterfly valves can also be used to adjust or throttle flow rates.
They are generally referred to as high-performance valves because they suit applications that are under high temperature and pressure conditions, as well as suiting use with pipelines that contain small impurity particles.
Gate valves are better suited to applications that require strict sealing but do not need as frequent switching between open and closed. They cannot be used for regulating or throttling because it is impossible to achieve accurate control with them.
Gate valves should not be used for pipelines that require emergency shutoffs, because their opening and closing speed is quite slow, and if they’re left in a partially open position they will erode rapidly. If pressure is the main concern, gate valves can withstand higher pressures than butterfly valves and so, they would be the better choice.
They are commonly found in systems that require uninterrupted bi-directional flow or in time-based uni-directional media discharge applications.
FAQs (Frequently Asked Questions)
Gate valves generally perform a lot better than butterfly valves under pressure and tend to outperform their counterparts in durability too. Butterfly valves are exposed to greater degrees of pressure differential, while gate valves are designed to allow flow without any undue pressure fluctuations.
Butterfly valves are not suitable for high differential pressures. The disc movement is significantly affected by flow turbulence, and with the valve disc being under high pressures, it will interrupt the flow of air, even in an open position.
Butterfly valves are used to allow and restrict the flow of a medium through a pipeline. Not only can these valves be fully open or fully closed but they can also be used to throttle or regulate the flow of the medium.
Yes, butterfly valves are designed for accurate flow and pressure control. They not only offer excellent control capabilities, allowing you to throttle or regulate the flow, but they also offer true isolation. This makes them ideal for applications where positive isolation is a requirement!
Butterfly valves have a preferred flow direction and they should be installed to satisfy this in order to extend the valve’s life span. They can however be bi-directional, but if they were to be installed backward the actuator thrust requirement to close them will be greater and so, they will take longer to operate.
Additional valve reading:
- Types of Compressed Air Valves – Guide To Pneumatic Valves
- Pneumatic Flow Control Valves – What Are They, How Do They Work?
- Air Compressor Air Line Non-Return valves/Inline (In The Air Line) Air Check Valves Explained
- Check Valve Sizes
- What is Check Valve Cracking Pressure
- Air Compressor Troubleshooting Check Valve
- Air Compressor Unloader Valve Explained
- Unloader Valves On Twin V Piston Compressor Guide
- 5 3 Valves Explained
- 5-2 Air Valves
- 4-2 Compressed Air Valves
- 3-2 Air Valves
- Drawing a 5/3 compressed air valve
- Draw A 5/2 Air Valve
- Pneumatic Soft Start Valves
- Solenoid Pilot Air Valves
- Compressed Air Solenoid Valve Guide
- Air Compressor Auto Drain Valves Guide
- Needle Valve vs Ball Valve
- Globe Valve vs Ball Valve
- Globe Valve vs Gate Valve
If you have any questions regarding butterfly valves vs gate valves, please leave a comment below, with a photo if applicable, so that someone can help you!