【Haichuan Equipment Guessing Game】One cylinder with three bars – what are these small tubes used for?

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It should be a safety valve; what’s the purpose of wrapping yellow transparent tape around the flange in the poster’s image?

Don’t normal pilot-operated safety valves have two pressure guide tubes? Why does this valve have three?

Generally, pilot-operated safety valves have a filter; why is this considered a valve?

A pilot-operated safety valve (also known as a pulse safety valve) is a type of safety valve that relies on the discharge of fluid from a pilot valve to drive or control the main valve; the pilot valve itself is a standard spring-loaded safety valve. Safety valves belong to the category of automatic valves and are primarily used in boilers, pressure vessels, and pipelines to ensure that pressure does not exceed specified levels, thereby playing a vital role in protecting both human safety and the proper operation of equipment. Based on the opening height of the safety valve disc, they can be divided into slightly open safety valves and fully open safety valves. Classification and editing: Pilot-operated safety valves can be classified according to their structural design into pendular type, lever type, spring type, and pilot-operated (pulsating) type ； Based on the valve body structure, they can be divided into closed and open types. A closed-type safety valve prevents the discharged medium from leaking outside; it directs all of the fluid to a designated location through its outlet, and is generally used with toxic and corrosive media. For safety valves used for air and steam, non-enclosed safety valves are commonly employed. The selection of safety valve products should be determined based on the actual sealing pressure. For spring-loaded safety valves, there are several operating pressure levels for springs within a certain nominal pressure (PN) range. When placing an order, in addition to specifying the valve model, name, medium, and temperature, it is also necessary to indicate the sealing pressure of the valve body; otherwise, the valve will be supplied at its maximum sealing pressure.

This post was last edited by xlxuiin on 2019-6-20 at 14:10, with the addition of a pressure outlet duct for the safety valve to ensure sealed discharge of the gas in the main valve’s gas chamber. This is generally used in situations where the medium does not allow direct discharge to the atmosphere.

1. Normal closed state (operational state): When the system is working properly and the pilot valve is in the closed position, the system pressure is transmitted through the inlet pressure pipe, the pilot valve, and the air chamber pressure pipe to the dome-shaped air chamber at the top of the main valve’s disc. This creates a downward net force on the main valve disc, keeping it in the closed state. 2. Release state: When the system pressure reaches the set value, it overcomes the spring force of the pilot valve, causing the pilot valve to open. The shuttle then closes the air inlet channel of the pilot valve, allowing the pressure in the main valve’s air chamber to be released through the pilot valve. Since the system pressure is higher than the return pressure, the shuttle closes the air inlet channel, thereby preventing fluid flow within the pilot valve. At this point, the pressure in the main valve’s air chamber drops sharply, the valve disc of the main valve opens completely, and the fluid is released through the main valve to reduce the pressure. When the system pressure drops to the return pressure, the spring force of the pilot valve overcomes the force exerted on the shuttle by the pressure at the valve inlet; the pilot valve returns to its original position, the push rod pushes the shuttle aside, and this allows fluid to flow back into the dome chamber of the main valve, thereby closing it.