Choosing a suitable valve for specific applications is essential in designing a process system. This article will dive into the properties and characteristics of gate valves, ball valves, and butterfly valves and the distinct differences between each type. Knowing how to set these valves apart and how they will interact with your setup will help you decide which type best suits your needs.
Because valves are an integral part of piping systems that convey liquids and gases, they are one of the most common components found across most industrial sectors. They regulate liquid or gas flow by allowing it to start and stop, and they must function adequately to prevent leaks and unwanted discharges. They are also effective means to route flows or isolate parts of the piping process for maintenance or monitoring.
Valves come in various sizes and configurations, but their sole purpose is to regulate and control the gas or liquid passing by the pipe. In this article, we will compare the three most common types of valves: gate valves, ball valves, and butterfly valves. We will start by defining each component, exploring what each type can do, and what makes them effective, and reliable tools.
As the name implies, gate valves act as gatekeepers. The term originated from the closing component of the valve sliding into the flowing fluid to induce shut-off, thereby functioning as a gate. Gate valves have a flat- or a wedge-shaped gate on a threaded stem, and the gate plates move in a straight line parallel to it.
When closed, the gate moves into the flow path and seats into a cavity opposite the stem, creating a solid seal. It is entirely out of the flow path when opened, resulting in zero-flow obstruction or pressure drop. Gate valves work best in high-pressure systems as used in low-pressure systems where a tight seal is critical and might need special accommodations. A low-pressure operation might lead to seeping at the valve while closed.
These linear motion isolation valves should be kept either completely open or closed as partial opening can cause damage - not used to control medium flow. Gate valves isolate specific areas of the supply network for repair, maintenance, new installation activities, and reroute flow across the pipeline.
Its simple design and versatility in low-pressure drop applications make gate valves one of today's most commonly used valves. It is designed to be full-port valves - meaning the valve port is the same size as the inner diameter of a connecting pipe. A full-bore gate valve allows fluid to pass through the pipeline without obstructing or producing a pressure drop. This also makes cleaning the line easier.
Gate valves are widely utilized with bigger pipe diameters, ranging from 2" to the largest pipelines, because they are less complex to design compared to other large-sized valves.
As the name suggests, ball valves are quarter-turn valves that use a rotatable ball with a bore to regulate gas and fluid flow from one opening to the next. The opening is in line with the pipe, allowing the medium to flow freely when turned on. When turned off, the gap is perpendicular to the flow of the medium, stopping it completely.
Also called shut-off valves, ball valves are the only way to shut off medium flow immediately. They are incapable of immediate redirection. Ball valves are best used with gases because they have a robust seal. They can withstand temperatures of up to 350°C and up to 700 bar pressures. Because of their simple structure and compact sizes, typically ranging from 0.5 cm to 30 cm, ball valves are easy to use and repair.
Ball valves are known to be durable and reliable, closing securely even after prolonged rest periods and functioning well even after many cycles. Ball valves have a higher resistance to contaminated media than other types of valves and provide a good seal despite the unclean medium. These features make ball valves an excellent choice for control and shut-off applications, where gate valves are frequently chosen. But gate valves lack the power of those alternatives in throttling applications compared with ball valves.
Butterfly valves are named after the rotating disc opening and closing the valve. They are quarter-turn rotational motion valves frequently used to shut off flow in pipelines. Also known as flap valves, butterfly valves are composed of a disc fixed on the valve's stem, and it rotates around the stem to control the flow of the medium in the pipeline. A butterfly valve is fast and easy to actuate, requiring only 90 degrees of movement to move from fully open to close.
Because the disc sits perpendicular to the flow when open, a minor pressure drop and slight flow turbulence are unavoidable. This means butterfly valves are not generally suited for use in processes containing solids, grit, and other abrasive material present in them, particularly in waterworks, as they might collect on the disc and prevent a tight seal when attempting to close the valve. Unlike gate valves, the lack of flow restriction elevates the risk of fluid hammering. Fluid hammering can cause a sudden increase in pressure and damage the instrumentation.
These valves are applied in various processes and industries, including water supply, distribution, collection, and pumping stations. They also have a wide range of uses, especially in flow isolation. Easy fabrication and compactness are two of their primary advantages over other types of valves, resulting in lightweight, cost-efficient products with smaller installation footprints and faster actuation rates.
The plate moves in a straight line parallel to the stem in gate valves. These are lightweight valves with a flat bottom seat gate, precision casting valve body, and integral glue coating. Gate valves are shut-off valves designed to open and close completely to allow unrestricted flow.
Ball valves contain a stem and ball which turns horizontally. The ball valve is best used in applications requiring on and off control without pressure drop. These valves are characterized by a long service life and provide reliable sealing during their lifespan even when they are not in use for a long time. As a result, ball valves are more popular shut-off valves than gate valves.
Butterfly valves are small and simple compared to the gate valves and ball valves. Their lightweight and compact design make them suitable for installation in tight spaces. In addition, the disc has a 90-degree reciprocating rotation capacity which makes regulating the flow and facilitating a complete, leak-proof shut-off more convenient.
The gate valve is a complete on and off valve. The gate plate, which regulates the media, can only open or close entirely. As a result, the pressure drop is minimal, and the flow is bi-directional. The design of the gate is primarily wedge-shaped and does not facilitate flow regulation. The ends of the gate valve are either threaded or flanged.
The ball valve drives the valve handle to rotate by a transmission, which in turn causes the ball to pivot perpendicular to the media flow. It opens when the ball's hole is in line with the flow and closes when it is spun 90 degrees by the valve handle. While mainly used for non-slurry applications, ball valves are also suitable for applications that need a tight shut-off. The immediate opening and closing of the ball make ball valves essential in some applications that require media isolation.
The disc moves around its axis in a butterfly valve, enabling complete or partial opening and closing. This makes the butterfly valve suitable for partial isolation and flows that need to be regulated. The primary characteristic of this valve is the change in the deflection of the butterfly disc, making it an appropriate choice for large diameter applications compared with other types of valves..
Thanks to its robust open and close mechanism, the gate valve has the most minimum pressure drop among other valves. Gate valves offer no resistance to the flow of fluid, making them unfit for controlled applications. The straight-through flow path provides minimum erosion and turbulence. Media accumulation is almost negligible in gate valves.
Ball valves have an uncomplicated structure and a good sealing performance. Ball valves are lightweight, easy to operate, have low material consumption, small driving torque, trim installation size, and offer minimal pressure drop. The ball valve is best used for general working fluids such as water, acids, solvents, and natural gas and media with extreme working conditions, such as oxygen, hydrogen peroxide, methane, and ethylene - making the ball valves a versatile option. Gate valves are commonly used in low-pressure applications.
The butterfly valve's speedy opening and closing speed make it suitable for throttling, flow regulation, and adjustment control. However, the pressure loss is more considerable than the ball and gate valve. Hence, the pressure loss and limitations in operating temperatures should be considered when choosing a butterfly valve.
Using gate valves, ball valves, and butterfly valves have their advantages and disadvantages, largely dependent on the requirements of the application where they are going to be installed. Generally, gate valves are ideal for strict sealing applications and do not require frequent operation. On the other hand, ball valves are best suited for systems with periodic shut-off requirements. Lastly, butterfly valves are most suitable for throttling purposes, occupying less space for massive systems.
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