Safety Technology Exchange Edition: Daily Question (2016.4.17)
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This post was last edited by 68589544 on 2016-4-19 at 11:21. Type: Short answer question (reward up to floor 30). Question: What are the safety accessories for pressure vessels? Safety accessories are safety devices installed on equipment to ensure the safe operation of pressure vessels; they include safety valves, rupture disc devices, emergency shut-off devices, pressure gauges, level gauges, temperature measuring instruments, fusible plugs, and more. Summary: 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. Measurement device: refers to an instrument 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: chain switches, interlocked 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 considerations for 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 within the device, which melts at high temperatures to open a passage and allow gas to escape through the holes in the fuse alloy that was originally used to fill the space, 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 a low-pressure liquefied gas chlorine cylinder is 65°C. 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 as well. 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.
Pressure gauges, thermometers, level gauges, safety valves, explosion-proof plates, pressure relief valves
Safety valves, rupture discs, level gauges, pressure gauges, etc.
Pressure gauge, thermometer, safety valve, rupture disc
Safety valves, rupture discs, pressure gauges, level gauges and temperature measuring instruments, isolation valves, etc
1) Safety valve: It automatically releases a certain amount of fluid when the pressure inside the container is high, thereby reducing the pressure； When the pressure inside the container returns to normal, the valve closes automatically. 2) Burst disc: It is pressed and ruptured by imported static pressure to release the medium and reduce pressure; it can no longer be used after rupture and must be replaced, meaning it does not have self-sealing properties. 3) Combination of safety valve and rupture disc device: There are three combination methods – a parallel combination of the safety valve and the rupture disc device, a rupture disc device installed in series between the inlet of the safety valve and the container, and a rupture disc device installed in series on the outlet side of the safety valve. 4) Blasting cap: When overpressure occurs, its weak layer breaks, allowing the medium to be released in order to reduce pressure. It cannot be reused after blasting and must be replaced. 5) Fusible plug: It belongs to the “melting-type” (“temperature-type”) safety relief device; it activates when the temperature of the container wall exceeds the limit. It is mainly used in small pressure vessels at medium and low pressures (such as liquefied gas cylinders). 6) Emergency shut-off valves, pressure relief valves: Emergency shut-off valves are usually installed in series with globe valves on the pipeline leading out of the container, so as to enable immediate shutdown of the leak in case of a significant leakage in the pipeline ； They generally also have the capabilities of overcurrent shutdown and overtemperature shutdown. The pressure relief valve has a small clearance; as the fluid passes through it, throttling occurs and the pressure drops, allowing high-pressure fluids to be delivered to low-pressure pipelines. 7) Pressure gauges, thermometers, level gauges (1) Pressure gauge: It indicates the pressure of the medium inside a container and is an important safety device for pressure vessels. (2) Level gauge: Also known as a fluid level meter, it is used to observe and measure changes in the liquid level inside a container. Especially for containers holding liquefied gases, a level gauge is an essential safety device. (3) Thermometer: Used to measure the temperature of the medium inside the pressure vessel; for vessels where it is necessary to control the wall temperature, a thermometer for measuring the wall temperature must also be installed.
Safety valves, pressure gauges, level gauges
Safety valves, rupture discs, burst disks, fusible plugs, emergency shut-off valves, pressure regulators, pressure gauges, thermometers, level gauges
Safety valve, level gauge, pressure gauge