Safety valve: sometimes called pressure relief valve. For reciprocating water pumps such as metering pumps, when the outlet of the water pump is blocked or the outlet valve is closed due to human error, overpressure will occur in the pipeline. In order to avoid the pipe Roads, valve accessories, water pumps and their accessories are damaged due to overpressure, and a safety relief valve needs to be installed to release this part of the pressure. Especially for conveying flammable and explosive liquids, once overpressure and no safety valve are present, explosion accidents may occur. Therefore, the safety valve setting is very important.
I checked the relevant product catalogs and found that the safety valve setting and the back pressure valve have the same basic structure. The diaphragm and valve core are pressed against the valve seat by an internal spring. When the pressure in the system pipeline exceeds the preset pressure, the diaphragm, The spool is lifted and the medium is discharged to the container. The pressure can be set in the range of 0-1.0Mpa by adjusting the screw on site. The discharge pressure is generally set to be higher than the system pressure by 0.1-0.2Mpa, and the installation is generally as close as possible to the outlet of the pump. , There should not be any valve between the pump and the safety valve.
When the system component fails or the pipeline is blocked, the safety valve can automatically open and relieve pressure to protect the system host and various components from damage due to pressure rise. This is related to the characteristics of safety valve. Precautions for safety valve installation:
1) The safety valve on the equipment or pipeline should generally be installed horizontally.
2) The safety valve of the metering pump should be installed as close as possible to the protected equipment or pipeline.
3) The characteristics of safety valve should not be installed at the end of a long horizontal pipeline to prevent the accumulation of solid or liquid materials at the end, so as not to affect the normal operation of the safety valve.
4) The safety valve should be installed in a place that is easy to repair and adjust, and there should be enough working space around it.
5) The design of the outlet pipeline of the safety valve should consider that the back pressure does not exceed the pressure set by the safety valve. For example, for an ordinary spring safety valve, the back pressure does not exceed 10% of the fixed pressure value of the safety valve.
By the way, let’s talk about the back pressure valve: “The back pressure valve is directional. If the inlet and outlet of the back pressure valve are connected reversely, the back pressure will increase exponentially, causing harm to the system and possible danger.” This sentence I didn’t understand it very well at the beginning, but later I learned that the water inlet and outlet positions inside the valve are different from the contact area of the diaphragm. If the valve is installed backwards, more force is required to open the back pressure valve, otherwise it will “explode”. Phenomenon brings danger to the system, and some people think that the safety valve is the reverse pressure valve.
The construction principle of the safety valve is the same as the back pressure valve. Both control the opening pressure of the valve by adjusting the spring behind the diaphragm. However, the back pressure valve is generally installed at the end of the pipeline and is used for frequent or continuous opening. It is used to prevent the system pressure from suddenly rising above a certain value, which will affect the system safety. It will reset after the pressure is relieved. It is used occasionally to deal with sudden situations. It is generally installed near the beginning of the pipeline and is not allowed on the pipeline between the pump and the pump. Set up any valves. The set pressure of the back pressure valve must be lower than the working pressure of the metering pump, and it can only be opened in this way; the construction principle of the safety valve must not be less than the working pressure of the metering pump, otherwise, wouldn’t it be a safety valve? The pressure capacity of the valve should be greater.
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Tags: safety valve setting, characteristics of safety valve, the construction principle of the safety valve
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