What’s a crown valve?

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A crown valve regulates and dissipates pressurized steam in industrial steam boiler systems. It can also allow steam to enter the piping system. Crown valves are used as safety measures and have indicators to show if they are open or closed. Early valves were made of cast iron, but steel and bronze became standard for higher pressure systems. Operators must exercise caution when opening or closing the valve to avoid water hammer and damage to the boiler system.

A crown valve, also known as a shut-off valve, is an essential part of an industrial steam boiler system that is used to regulate and slowly dissipate pressurized steam in a boiler. It can also be used to allow steam to leave the boiler and enter the piping system, providing heat, power or other steam functions. These boiler systems are usually too large to be used anywhere but an industrial plant. The crown valve gets its name from the location where the valve is indicated on the boiler – directly on the top, or crown, of the boiler unit.

Crown valves are also used as a safety measure for boiler systems because they have regulators that allow the release of overpressures that can build up if too long elapses between opening and closing the valve. The crown valve is equipped with indicators that allow the boiler operator to immediately identify whether the valve is open or not. The controllers also ensure that the operating status of the boiler is visible from any point of view. These types of valves are not considered continuous release valves or controlled release valves, as crown valves must be fully opened or tightly closed.

Early crown valves were typically made from cast iron, making them very heavy and often unreliable. Cast iron would bind under great pressure, making it very difficult for the valve to open when pressure has built up behind it. After steel and bronze crown valves became the standard for settings where boiler units produced higher steam pressures, the introduction of steel and alloy crown valves quickly became the standard among many methods of production of industrial crown valves.

When a boiler operator is performing the task of opening or closing the crown valve of a boiler unit, the operator must exercise caution and open or close the valve slowly and deliberately. Not doing so can cause something called water hammer, which occurs when a large amount of steam pressure is released from the boiler too quickly and “hit” the joints in the piping system. If the boiler group is closed too quickly by the crown valve, a sudden increase in boiler pressure can occur, which can damage the connections in the boiler system. Quite often, a secondary valve is fitted in many high pressure systems to avoid any of these circumstances.

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