Are gate valves good for flow control?

Globe valves are a type of control valve used to stop, start and regulate the flow of media through a pipe. From the outside, they have a spherical body design; inside, a plug-like disc sits on the end of a threaded rotating stem, which raises and lowers to control media flow. Globe valves are part of the linear motion valve family, which means that the valve mechanism moves along a straight line.

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Globe valves provide a tight seal with low chances of leakage, which is why they are a common choice in high-pressure, industrial piping systems.

How Do Globe Valves Work?

Globe valves are designed so that the media flowing through them does not travel in a straight line. Rather than encountering a perpendicular blockage at the valve, the media must take a slight vertical detour up through the valve cavity, where it meets the plug disc. As the valve stem is turned via wheel and raises to allow media through, the disc moves parallel to the flow. The position of the stem tells operators whether the valve is open or closed.

This vertical movement is what enables the globe valve to regulate media flow, rather than simply stopping or starting it. The distance between the disc and the seat determines the flow rate: the farther apart the disc and seat are, the higher the volume of media passing through. Globe valves are ideal for throttling, or regulating the flow of media while in a partially open position, and make starting and stopping flow less abrupt which can help prevent water hammer.

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Because their design forces media to change direction (horizontal to vertical), globe valves create a high-pressure drop. They are best used in applications that require only unidirectional flow, where massive changes in pressure are not an issue and where safety and leakage are primary concerns. Globe valves are often found in piping systems that transport corrosive, viscous, highly pressurized or extremely hot or cold media.

Most of the working parts of a globe valve lie inside the cavity, and access to the internal components is through the top; this is known as top-entry design.

No, gates are not used for throttling flows in other than aquarium situations. Faucets in your house are more like globe valves in older faucets and cartridge type valves similar to ball valves in newer faucets. You may have a gate valve on the incoming water line from your water meter but it is intended to be fully open or fully closed only for maintenance.
When you are under house or boosted pressure and throttle with a gate you are causing cavitation across the gate and seat areas due to the velocity and pressure drop. Say you have 60 psi on one side and an open pipe or hose on the other, the velocity across the small cross surface area that is open is sonic velocity and causes tremendous wear plus vibration between the gate and the threaded shaft which leads to more wear. In an aquarium we may have 4 feet of head (1.7 psi) to dissipate across one side to the other so wear is negligible. Its rare to find an aquarium pump that pumps more than say 15-16 feet of head or less than 7 psi and most are in the 11-12 feet of head range or about 5 psi, you can put your finger over the end of the pipe and stop the flow.

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