Picking the right valve is important, as different types have different features and uses. Some of them only have two states: open or closed. Others allow fluid flow and pressure to be modulated. Distinct valves also cause different amounts of pressure loss. Depending on the situation, specific features are needed.
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One of the most common types of valves is the globe valve. In this article, we explain how globe valves work, including their advantages and disadvantages. Then, we look at the different shapes of globe valves and compare them to other types of devices, like gate valves and ball valves.
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To decide if a globe valve is right for your application, consider its three core features. First, they are lateral movement valves, which means they open or close based on the up-and-down movement of a stem. Second, they allow, stop, or throttle fluid flow. Some valves have only open and closed states, but globe valves can throttle flow without totally stopping it. Third, they cause significant head losses compared to other valves, a tradeoff for the throttling services.
From the outside, globe valves have three parts, a handwheel, a bonnet, and a body. The bonnet houses a stem, and when the handwheel is turned, the stem screws up and down in the bonnet. The end of the stem has a small component called a disk or plug, which can be metallic or non-metallic and may come in different shapes, depending on the need.
The globe-shaped body for which the valve is named houses a seat. The seat is a metal frame that divides the body into two chambers and has a hole to allow fluid to pass. When the valve is open, fluid flows up through the opening in the seat. To close it, the stem is screwed down until the disk blocks the seat’s opening.
One of the main advantages of globe valves is their ability to throttle or modulate flow. Besides being closed or open, they can also be partially open. This allows you to adjust flow without totally stopping it.
The main disadvantage of globe valves is the comparatively significant head loss they create. Head loss, also called pressure loss, refers to the amount of resistance a liquid encounters as it flows through pipes. The more resistance, the more pressure that is lost. Gravity, friction (of the fluid against the walls of the pipe), and turbulence all cause this loss. Valves and fittings cause pressure loss mainly through turbulence.
Globe valves force fluid to change directions as it passes through, creating loss and turbulence. The exact amount of loss depends on factors like fluid velocity and friction factor. However, it’s still possible to review the pressure losses from different valves using a metric called the L/D coefficient.
A valve’s L/D coefficient lets us compare it to a straight section of pipe with the same friction factor. L and D stand for length and diameter, respectively. A valve with L/D=5 creates the same friction loss (all else being equal) as a section of pipe with a length-to-diameter ratio of 5. The larger L/D is for a component, the higher the head loss it creates.
A standard globe valve has an L/D=340, compared to an L/D=30 for a 90-degree pipe elbow.
Globe valves come in three shapes—t-pattern/z-pattern, y-pattern, and angle pattern. Each form stops or throttles fluid flow in the same way, but the path of flow—and thus the head loss—differs.
Most globe valves are t-shaped globe or z-shaped. They are called “t-pattern” for the profile of the valve—the inlet and outlet of these valves are in a straight line. “Z-shaped” is arguably more descriptive, however, because it refers to the path of the water as it flows through the valve rather than the device’s external shape. In the standard z-shaped globe valve, the water changes direction twice in a pattern that resembles the letter Z. As mentioned, standard Z-shaped valves cause the most significant head loss, with an L/D=340.
Y-pattern globe valves are modifications of z-pattern valves. The inlet and outlet are still in a straight line, but the bonnet and stem are placed at an angle to the body (as opposed to perpendicular), forming a y-shaped profile. This provides a straighter path for the water than the z-shape, reducing head loss. For y-pattern globe valves, L/D=55.
The inlet and outlet of angle valves are oriented at 90 degrees from one another, and these devices serve both as elbows and valves. Because they only make fluid change direction once, they create less head loss than z-shaped valves, with L/D=150.
Globe valves are ideal whenever you need to modulate flow, but you don’t have to worry about the amount of pressure loss. Some applications include:
Globe valves aren’t the best choice for control valve applications in fire sprinkler systems, where pressure is at a premium. Instead, butterfly valves are commonly used.
There are several alternatives to the globe valve, and understanding the different options can help you pick the right valve for the job. Two major alternatives to the globe valve are the gate valve and the ball valve. First, let’s consider the differences between globe and gate valves.
Gate valves, like globe valves, are linear-motion valves. They are opened and closed by turning a handwheel that screws a stem in and out of the bonnet. When a gate valve is closed, an obstruction is pushed down by the stem perpendicular to the path of the fluid.
Unlike globe valves, gate valves don’t require fluid to change directions—the flow path is straight. As such, gate valves cause very little head loss (L/D=8). However, they do not throttle as well as globe valves—fluid flow rate in a gate valve is not proportional to how open the valve is at any moment.
Unlike globe valves and gate valves, ball valves are rotary-motion valves. This means that ball valves open and close when the obstacle rotates rather than opening and closing with the lateral movement of an obstruction. Specifically, a ball-shaped component with a hole through it spins in its housing, either stopping the fluid or letting it pass.
Instead of turning a handwheel, a ball valve is typically opened or closed with a wrench handle. Only a quarter-turn (90 degrees) is needed to open or close it—much faster than turning a handwheel multiple times. Quick closing can actually be a problem because of water hammer. When fluid flowing through a pipe is suddenly stopped, its momentum has nowhere to go because water is non-compressible. Water hammer occurs when a pressure wave propagates back through the pipe, potentially causing damage.
Since ball valves don’t force water to change direction, they create very little head loss (L/D=3). As with gate valves, this low pressure loss comes with the tradeoff of little throttling capability. Ball valves are either open or closed, with little in-between.
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When building a piping system, it’s important to choose the right components for the job, which is especially true with valves. Because globe valves force water to change directions even when fully open, they create comparatively large pressure losses. One of the core advantages of globe valves, however, is their ability to modulate water flow. They can be open, partially open, or closed.
Gate valves and ball valves, two alternatives to globe valves, cause minimal pressure losses. However, they don’t provide throttling services like globe valves. For applications where pressure is at a premium, gate or ball valves are better choices than globe valves.
Shop our inventory of standard (z-pattern) globe valves and angle valves. For other options, shop our full selection of valves, including ball valves. If you don’t see the item you need, contact us, and our customer service team will help you out.
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Valves, in their varying shapes and sizes, hold massive industrial importance. From regulating the flow of liquids and gases to shutting off the supply completely, industrial valves play crucial roles in myriad contexts. But how does one precisely tell whether a water valve – be it a gate valve, ball valve, globe valve or butterfly valve – is open or closed? This is a question that may seem daunting.
how to tell if a valve is open or closed 1 Valve TypeOpen StatusClose StatusGate ValveHandle turns counter-clockwise; the stem is raisedHandle turns clockwise; stem is not raisedBall ValveHandle aligns with the pipeline directionHandle is perpendicular to the pipeline directionButterfly ValveButterfly/disc and handle are parallel to the flow of liquidButterfly/disc and handle are perpendicular to the flow of liquidGlobe ValveHandwheel is turned counter-clockwise; stem is raisedHandwheel is turned clockwise; stem is not raisedCheck ValveFluid is flowing in the permissible directionFluid is not flowing or flowing in the opposite directionA gate valve, the most common type of industrial valve, plays an essential role in various water supply systems, controlling the flow of water and other fluids. However, how to tell if a valve is open or closed can often pose challenges.
Determining the open or closed status of a gate valve involves two main methods: checking the flow direction and inspecting the valve’s control handle. If water or another fluid flows through the valve in the direction of flow, this implies that the gate valve is in its open position. Conversely, if there is no discernable flow, then the faucet or gate valve is in a closed position.
The observation of the control handle or lever also provides reliable evidence of whether the gate valve is open or closed. Gate valves usually come with a lever or handwheel to regulate their positions. When the handle aligns with the direction of the piping, the valve is open. Conversely, when the handle is perpendicular, the valve is closed position.
Modern technology also offers automated solutions to monitor and control gate valve statuses. For instance, pressure sensors can determine whether a valve is open or closed based on the pressure level. Position sensors can track the physical position of the valve, determining its operational state. This automation offers precise control and helps to efficiently manage water supply systems.
To open a gate valve, you typically need to turn the handwheel in an anti-clockwise direction. Keep rotating the handwheel until it cannot be turned any further, indicating the valve is now fully open. However, it’s important to add that over-spacing can potentially damage the valve. Therefore, after fully opening the valve, you should make a small (about quarter) clockwise turn.
how to tell if a valve is open or closed 3Closing the valve, as you may have guessed, involves rotating the handwheel in a clockwise direction. When the handwheel cannot be turned further, the valve is considered fully closed. Examine your gate valve visually and physically to ensure you’re operating it correctly.
A ball valve, characterized by its spherical disc that controls the flow path, can be analyzed by looking at the handle. As with the gate valve, the lever on the ball valve will be in line with the pipe if the valve is open, and perpendicular if it is in the closed position.
how to tell if a valve is open or closed 4Visual checks alone can often determine the status of a ball valve. Unlike most types of valves, the handle on a ball valve is flat, making the “on” and “off” positions easier to distinguish. However, do note that some advanced ball valve types also come with automation for remote control, similar to gate valves.
To open a ball valve, ensure the handle position on the ball valve aligns with the valve’s body. To do this, twist the valve’s handle anti-clockwise. Continue until the handle stops; this signals the ball valve is fully open.To close the ball valve, turn the handle clockwise until the handle stops moving. The handle should now be perpendicular to the body of the valve, signifying a closed position.Bear in mind that, like gate valves, the spherical disc inside the ball valve controls the flow of water or other fluids. The predetermined alignment of the handle and the valve’s body serves as an indicator of its open or closed condition.
Another mainstay in the roster of industrial and homeowners’ valve types is the butterfly valve. It gets its name from the disc inside the valve which resembles a butterfly’s wings. Knowing how to tell if a butterfly valve is open or closed is fairly simple. If the “butterfly” or disc inside the valve is parallel with the flow of water, the valve is open. If the disc is positioned perpendicularly, the valve is in a closed position.
These types of shut-off valves usually use a control lever for operation. Not only does the disc’s position indicate the state of the valve, but the handle does as well. If the lever handle is parallel to the piping, the butterfly valve is open; when the handle is perpendicular, the valve is closed.
To operate a butterfly valve, turn the handle or lever. To open the valve, rotate the handle so that it aligns with the direction of the pipeline. The butterfly or disc rotates within the valve body to allow flow (open position).To close the butterfly valve, turn the handle 90 degrees, so it’s perpendicular to the pipeline. Here, the disc is also moved to the perpendicular position, effectively blocking flow (closed position).
how to tell if a valve is open or closed 5Butterfly valves are a popular choice in large diameter pipelines for their lightweight, quick operation, and cost-effectiveness. However, accurate control of the flow rate can be trickier with a butterfly valve, given that even a small rotation of the handle results in a considerable change in flow rate.
Globe valves, specifically designed for precise flow control, vaguely indicate their state. As with most valves, an open globe valve has its handwheel turned counter-clockwise, allowing water supply to pass through. And by rotating the handwheel clockwise leads to a completely locked, or closed valve. However, the position of the wheel doesn’t always reflect an accurate picture of the valve’s status. To confirm, check the flow rate: an open valve leads to a steady water flow and a closed valve interrupts the flow.
how to tell if a valve is open or closed 6Operating a globe valve may require a bit more effort than a gate or ball valve since the disc inside a globe valve has to be screwed inward/outward to close or open the valve, respectively.To open a globe valve, turn the handwheel anticlockwise, which unscrews the disc and allows the flow of water or liquid through it. Conversely, to close the globe valve, turn the handwheel clockwise, screwing the disc into the seat and restricting the flow of water.The globe valve design makes them excellent for regulating flow, unlike ball valves or gate valves which mainly act as shut-off valves. This unique aspect earns them a special place in various applications like cooling water systems, fuel oil systems, etc., where the controlling flow is necessary.
Check valves are designed to allow flow in one direction, preventing backflow. When fluid flows in the permissible direction, it pushes the valve disc (or ball) open. When the flow ceases or reverses, the disc or ball is pushed back into the seat, closing the valve. Therefore, the check valve’s status actually responds to the conditions inside the pipeline, differing from manually operated valves like gate or ball valves.
Technically, you don’t manually open or close a check valve. The opening and closing of this type of valve are fluid-operated. The valve opens when the pressure from the flow of water or other media pushes the valve’s disc off the sealing device. If the flow reduces or reverses, the pressure decreases, and the valve closes due to the disc returning to the sealing device.
how to tell if a valve is open or closed 7Check valves are quite essential for systems that require one-way flow, such as pump and compressor discharge lines, cooling towers, etc. By understanding how they operate, you can better analyze the status of these automatically controlled valves.
Safety becomes paramount when dealing with valves, especially in industrial settings. Consequentially, understanding safety measures when inspecting a valve plays a crucial.
Before any inspection, ensure the system is depressurized and cooled down to the ambient or a safe temperature. Also, ensure that you wear personal protective equipment (PPE), including safety glasses, appropriate gloves, and protective footwear.
When dealing with valves under pressure, exercise caution. An open valve can abruptly release high-pressure gas or liquid that poses a hazard. Moreover, avoid over-tightening the valve, as it can damage the valve’s internal parts, leading to other complications.
Furthermore, isolation is important in keeping safe. When performing maintenance or repairs, the valve in work should be isolated to prevent sudden flow of fluid.
Lastly, understanding the mechanical operation of valves, their specifications, and system conditions is vital in maintaining a safe environment when handling valves.
In conclusion, understanding how to tell if a valve is open or closed and knowing how to operate various types of valves are essential skills. From gate valves, ball valves, butterfly valves to globe and check valves, each has unique functionalities and ways of operation. As an individual responsible for the operation of these valves, your priority should be to understand each valve’s operative principle and maintain them regularly for optimal functionality. Above all, the safety measures and precautions highlighted should never be overlooked when inspecting and operating valves. Doing so will ensure not only the lifespan of your valves but also the safety of individuals operating them.To discuss the use of valves with an expert, and to learn more about valves, please contact Dombor.
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