Gate Valves
A gate valve, also known as a sluice valve, is a common type of valve that operates by lifting a barrier, or "gate," out of the path of a fluid. They are primarily used for on/off service, meaning they are designed to be either completely open or completely closed.
How They Work
The core mechanism of a gate valve consists of a gate, a stem, and a handwheel (or other actuator). When the handwheel is turned, the stem is threaded to raise or lower the gate.
- Fully Open: When the gate is fully raised, it creates a straight, unobstructed flow path. This is a key advantage, as it results in a very low pressure drop and allows for "pigging," a method of cleaning pipes with a device that passes through the line.
- Fully Closed: When the gate is fully lowered, it seats against the valve body to block the flow of fluid completely.
Because the gate's movement is not linear with the handwheel's rotation, these valves are generally not suited for regulating or "throttling" flow. Using a gate valve in a partially open position can cause the gate to vibrate and lead to accelerated wear and tear on both the gate and the valve seat.
Key Features and Applications
Gate valves are distinguished by several characteristics:
- On/Off Service: Their main purpose is to isolate sections of a pipeline.
- Low Pressure Drop: When fully open, they offer minimal resistance to fluid flow.
- Slow Operation: They require multiple turns of the handwheel to fully open or close, which helps prevent hydraulic shock (water hammer).
- Common Materials: They are typically made from materials like cast iron, steel, brass, and stainless steel to handle a variety of fluids and pressures.
Common applications include:
- Water distribution systems.
- Large pipelines for crude oil and natural gas.
- Industrial processes where full flow is needed and flow regulation is not.