Thread Content
Introduction to Safety Accessories: Safety accessories are safety devices installed on equipment to ensure the safe operation of pressure vessels. These include safety valves, burst disc devices, emergency shut-off devices, pressure gauges, level gauges, temperature measuring instruments, fusible plugs, and so on. I. The safety accessories of pressure vessels, classified by their performance or purpose, can include the following four types: 1. Pressure relief devices: Devices that automatically release pressure when a pressure vessel is under excessive pressure. Such as: safety valves, rupture discs, and fusible plugs, etc. 2. Metering device: refers to a device that can automatically display the process parameters related to safety during the operation of a container. Such as: pressure gauges, thermometers, level gauges, etc. 3. Alarm device: Refers to an instrument that can automatically emit audible signals or other distinct alarm indications when unsafe conditions arise during the operation of a container, putting it in a dangerous state. Such as: pressure alarms, temperature detectors. 4. Interlock device: A control mechanism designed to prevent operational errors. Such as: interlocked switches, linked valves, etc. II. Among the safety accessories for pressure vessels, the most commonly used and critical ones are safety pressure relief devices, pressure gauges, etc. 1. Safety valve: Its feature is that it remains airtight under the normal operating pressure of the pressure vessel; once the pressure inside the vessel exceeds the specified level, it automatically and quickly releases the medium from within the vessel, ensuring that the pressure stays within the maximum allowable range at all times. Safety valves can be divided into spring-loaded safety valves, lever-type safety valves, and pulse-type safety valves. Under normal circumstances, safety valves should be installed on the container body as much as possible; liquefied gas should be placed in the gas phase section, while also taking safety in terms of discharge into account. 2. Shrapnel: Also known as an explosion-proof membrane, it is a type of rupture-type safety device characterized by good sealing performance and a rapid pressure-release response. It is generally used on high-pressure, non-toxic gas cylinders, such as air and nitrogen. The burst disc pressure on a gas cylinder is generally set to be higher than the filling pressure of the cylinder, but lower than the maximum allowable pressure rise specified for the cylinder. 3. Fuse plug: It utilizes a low-melting-point alloy contained within the device, which melts at high temperatures to open a passage and allow gas to escape through the holes in the fuse alloy, thereby releasing pressure. Its advantages include a simple structure and easy replacement; moreover, the operating pressure, determined by the melting temperature, is relatively easy to control. It is generally used for containers where the gas pressure is not high and is determined entirely by the temperature level. For example, the melting temperature of the fusible plug on low-pressure liquefied gas chlorine cylinders is 65°C〖HT6〗〖SX（B-1mm〗+3〖〗-1〖SX）〗. When comparing these three safety devices, a safety valve can close itself after releasing excessive pressure, allowing the container and device to continue to be used, whereas a burst disc or fusible plug cannot be used any longer after releasing excessive pressure, forcing the container and device to stop operating. When selecting safety valves and fuse plugs, the safe discharge volume must be taken into account; for rupture discs, factors such as the calculation of the discharge area and thickness are important to consider. 4. Pressure gauge: It is a device installed on pressure vessels to measure the pressure of the medium. The types can be divided into: spring-type pressure gauges, suitable for pressure vessels with general media. Diaphragm pressure gauge, suitable for pressure vessels with corrosive media.