Water hammer valves, more accurately called water hammer arrestors, prevent or reduce the damaging effects of water hammer by absorbing the pressure surge created when a valve quickly closes. Instead of a literal "valve," a water hammer arrestor uses a combination of springs and/or air chambers to cushion the shock.
Here's a breakdown of how they function:
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The Problem: Water Hammer: When a valve in a water system closes suddenly, the water flowing upstream slams into it. This rapid deceleration creates a pressure wave that bounces back through the pipes, causing noise, vibration, and potentially damaging pipes and fixtures. This is water hammer.
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The Solution: Arresting the Surge: Water hammer arrestors are designed to provide a compressible cushion that absorbs the kinetic energy of the moving water. This prevents the pressure from spiking.
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Two Main Types:
- Air Chamber Arrestors: These are simple devices that contain a sealed air-filled chamber. When a pressure surge occurs, the air compresses, absorbing the shock. Over time, the air can dissolve into the water, reducing effectiveness. Some air chamber arrestors have a bladder to prevent air loss.
- Spring-Loaded Arrestors: These use a spring-loaded piston or diaphragm. When the pressure surge occurs, the spring compresses, absorbing the shock. These are typically more compact and reliable than air chamber arrestors, as there's no air to dissolve.
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Mechanism of Action (Generalized):
- Normal Flow: Under normal flow conditions, the arrestor is in a resting state.
- Pressure Surge: When a valve closes quickly, creating a pressure surge, the increased pressure forces the piston/diaphragm against the spring (in spring-loaded arrestors) or compresses the air (in air chamber arrestors).
- Energy Absorption: The compression of the spring or air absorbs the kinetic energy of the water, preventing a sharp pressure spike.
- Pressure Stabilization: The arrestor gradually releases the stored energy, damping the pressure wave and preventing it from bouncing back through the system.
- Return to Normal: Once the pressure returns to normal, the spring or air pressure returns the piston/diaphragm to its resting position.
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Why they are important: Preventing pipe damage, reducing noise, and prolonging the life of plumbing fixtures.
In summary, water hammer arrestors employ compressible elements (air or springs) to absorb and dissipate the energy of pressure surges, thus protecting plumbing systems from the damaging effects of water hammer.
