Can Globe Valves and Gate Valves Be Used Interchangeably? The Answer Is NO!
Globe valves, gate valves, butterfly valves, check valves, ball valves and other types are indispensable control components in various pipeline systems nowadays.
Every type of valve differs in appearance, structure, function and application. However, globe valves and gate valves share some similarities in shape, and both can cut off medium flow in pipelines. For this reason, many people with limited exposure to valves confuse the two.
Structural Differences
Attention should be paid to selection when installation space is limited:
A gate valve can tightly seal against the sealing surface relying on medium pressure to achieve zero leakage. During opening and closing, the sealing surfaces of the disc and seat remain in contact and rub against each other, so the sealing surfaces are prone to wear. When the gate valve is nearly closed, the pressure difference before and after the pipeline becomes large, which accelerates the wear of sealing surfaces.
The structure of a gate valve is more complicated than that of a globe valve. For the same nominal diameter, a gate valve is taller while a globe valve is longer. In addition, gate valves are divided into rising stem and non-rising stem types, while globe valves have no such classification.
Working Principle
When opening or closing a globe valve, it adopts the rising stem design. When turning the handwheel, the handwheel rotates and lifts together with the stem. For a gate valve, turning the handwheel lifts or lowers the stem, while the handwheel position remains unchanged.
They differ in flow control. Gate valves are designed for fully open or fully closed operation, whereas globe valves are not. Globe valves have specified inlet and outlet directions, while gate valves have no direction requirements.
Moreover, gate valves only have two states: fully open and fully closed. The gate disc travels a long stroke, resulting in a long opening/closing time. The travel of the disc of a globe valve is much shorter. The disc of a globe valve can stop at any position during movement for flow regulation. Gate valves can only be used for shutoff with no regulating function.
Performance Differences
A globe valve can be used both for shutoff and flow regulation. It features high fluid resistance and requires more effort to open and close. Nevertheless, the short distance between the disc and sealing surface results in a short stroke for opening and closing.
Since gate valves only operate fully open or fully closed, the medium flow resistance inside the valve body passage is nearly zero when fully open. Therefore, gate valves can be opened and closed with little force. However, the long distance between the gate disc and sealing surface leads to a long operation time.
Installation and Flow Direction
A gate valve performs equally well for flow in both directions. There is no requirement on inlet and outlet orientation during installation, and medium can flow bidirectionally. A globe valve must be installed strictly in accordance with the arrow marked on the valve body to indicate flow direction. There is a clear specification in China’s valve standardization document: the flow direction of globe valves shall be from top to bottom.
Globe valves adopt the flow-under-seat arrangement (low inlet, high outlet). Visually, the connected pipelines are not on the same horizontal line. The flow passage of a gate valve lies on a single horizontal line, and the stroke of a gate valve is longer than that of a globe valve.
In terms of flow resistance: when fully open, gate valves have low flow resistance while globe valves have high flow resistance. The flow resistance coefficient of ordinary gate valves is approximately 0.08~0.12, requiring low operating force and allowing bidirectional medium flow. The flow resistance of ordinary globe valves is 3–5 times that of gate valves. Tight shutoff must be enforced to achieve sealing. The disc of a globe valve contacts the sealing surface only when fully closed, so the sealing surface suffers minimal wear. For globe valves equipped with actuators due to high flow resistance, attention shall be paid to adjusting the torque control mechanism.
There are two installation modes for globe valves:
Medium enters from below the disc.
Advantage: The packing is free from pressure when the valve is closed, extending packing service life. Packing can be replaced even when the upstream pipeline is pressurized.
Disadvantage: The driving torque is roughly twice that of the top-inlet mode. The stem bears large axial force and is prone to bending.
This mode is generally only applicable to small-size globe valves (below DN50). Globe valves of DN200 and above adopt the mode where medium flows in from the top. (Electric globe valves usually adopt top inlet.) The disadvantages of the top-inlet mode are opposite to those of the bottom-inlet mode.
Sealing Performance
The sealing surface of a globe valve is a small trapezoidal side surface of the disc (depending on disc geometry). If the disc falls off, the valve is equivalent to being closed. (It cannot achieve tight shutoff under large pressure difference, yet it delivers decent non-return effect.) A gate valve relies on the side surface of the gate disc for sealing. Its sealing performance is inferior to that of a globe valve. If the gate disc falls off, the valve will not close automatically like a globe valve.
Every type of valve differs in appearance, structure, function and application. However, globe valves and gate valves share some similarities in shape, and both can cut off medium flow in pipelines. For this reason, many people with limited exposure to valves confuse the two.
Structural Differences
Attention should be paid to selection when installation space is limited:
A gate valve can tightly seal against the sealing surface relying on medium pressure to achieve zero leakage. During opening and closing, the sealing surfaces of the disc and seat remain in contact and rub against each other, so the sealing surfaces are prone to wear. When the gate valve is nearly closed, the pressure difference before and after the pipeline becomes large, which accelerates the wear of sealing surfaces.
The structure of a gate valve is more complicated than that of a globe valve. For the same nominal diameter, a gate valve is taller while a globe valve is longer. In addition, gate valves are divided into rising stem and non-rising stem types, while globe valves have no such classification.
Working Principle
When opening or closing a globe valve, it adopts the rising stem design. When turning the handwheel, the handwheel rotates and lifts together with the stem. For a gate valve, turning the handwheel lifts or lowers the stem, while the handwheel position remains unchanged.
They differ in flow control. Gate valves are designed for fully open or fully closed operation, whereas globe valves are not. Globe valves have specified inlet and outlet directions, while gate valves have no direction requirements.
Moreover, gate valves only have two states: fully open and fully closed. The gate disc travels a long stroke, resulting in a long opening/closing time. The travel of the disc of a globe valve is much shorter. The disc of a globe valve can stop at any position during movement for flow regulation. Gate valves can only be used for shutoff with no regulating function.
Performance Differences
A globe valve can be used both for shutoff and flow regulation. It features high fluid resistance and requires more effort to open and close. Nevertheless, the short distance between the disc and sealing surface results in a short stroke for opening and closing.
Since gate valves only operate fully open or fully closed, the medium flow resistance inside the valve body passage is nearly zero when fully open. Therefore, gate valves can be opened and closed with little force. However, the long distance between the gate disc and sealing surface leads to a long operation time.
Installation and Flow Direction
A gate valve performs equally well for flow in both directions. There is no requirement on inlet and outlet orientation during installation, and medium can flow bidirectionally. A globe valve must be installed strictly in accordance with the arrow marked on the valve body to indicate flow direction. There is a clear specification in China’s valve standardization document: the flow direction of globe valves shall be from top to bottom.
Globe valves adopt the flow-under-seat arrangement (low inlet, high outlet). Visually, the connected pipelines are not on the same horizontal line. The flow passage of a gate valve lies on a single horizontal line, and the stroke of a gate valve is longer than that of a globe valve.
In terms of flow resistance: when fully open, gate valves have low flow resistance while globe valves have high flow resistance. The flow resistance coefficient of ordinary gate valves is approximately 0.08~0.12, requiring low operating force and allowing bidirectional medium flow. The flow resistance of ordinary globe valves is 3–5 times that of gate valves. Tight shutoff must be enforced to achieve sealing. The disc of a globe valve contacts the sealing surface only when fully closed, so the sealing surface suffers minimal wear. For globe valves equipped with actuators due to high flow resistance, attention shall be paid to adjusting the torque control mechanism.
There are two installation modes for globe valves:
Medium enters from below the disc.
Advantage: The packing is free from pressure when the valve is closed, extending packing service life. Packing can be replaced even when the upstream pipeline is pressurized.
Disadvantage: The driving torque is roughly twice that of the top-inlet mode. The stem bears large axial force and is prone to bending.
This mode is generally only applicable to small-size globe valves (below DN50). Globe valves of DN200 and above adopt the mode where medium flows in from the top. (Electric globe valves usually adopt top inlet.) The disadvantages of the top-inlet mode are opposite to those of the bottom-inlet mode.
Sealing Performance
The sealing surface of a globe valve is a small trapezoidal side surface of the disc (depending on disc geometry). If the disc falls off, the valve is equivalent to being closed. (It cannot achieve tight shutoff under large pressure difference, yet it delivers decent non-return effect.) A gate valve relies on the side surface of the gate disc for sealing. Its sealing performance is inferior to that of a globe valve. If the gate disc falls off, the valve will not close automatically like a globe valve.
