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Concentration of gas in the laboratory
2018-05-04
The concentration of gas in the laboratory is to store all the cylinders in the cylinder room. The gas cylinder is transported to various laboratories (i.e., the instrument end) through the pressure relief valve and gas transmission pipeline. The flow is as follows:
First, when the gas cylinder is stored in a centralized way, the flammable gas and the combustion gas must be stored separately and well ventilated. Inflammable gases, such as acetylene, methane, hydrogen and so on, such as oxygen and air, should be set up, and the special gas cylinder room should be set up for the poison gas.
Two. Operation principle
The laboratory gas supply has two levels of decompression and multilevel decompression. The two stage decompression is to use the first stage pressure reducing valve and the new pressure reducing valve at the end of the cylinder to achieve the purpose of two stage decompression. The laboratory generally recommends two stage decompression, which can ensure the purity and flow rate of the gas is stable, and can also maximize the accurate terminal gas pressure (recommended).
Three. Valve introduction
When selecting the pressure relief valve, the type of gas, the range of the allowable pressure change, the maximum amount of gas and the flow rate, the structure of the pipeline and the use place must be considered.
A) because of the different uses of various gases, the choice of material will be different, such as: ordinary inert gas valve body and valve core can be used for chromium plating (with the continuous demand of production and process, 316 material stainless steel), acetylene and corrosive gas valve body and valve core must be used 316L stainless steel material;
B) the gas purity of 5, 6 non corrosive, inert gas material still recommends stainless steel valve body, stainless steel valve core and stainless steel valve core, stainless steel valve body and stainless steel valve are recommended for corrosive and poisonous gas material with gas purity 6.
Gas cylinders, high pressure pipes, gas cylinders, pressure reducing valves, gas pipes, terminal pressure reducing valves and terminal instruments are stored centrally, and flammable and combustion supporting cylinders are stored separately.
C) cylinder pressure relief valve (first class pressure relief valve)
According to the frequency and gas consumption of the gas, the cylinder pressure relief valve is divided into single bottle type decompression and multi bottle decompression, and the multi bottle decompression can be divided into semi-automatic decompression and full automatic decompression, and the cost will be different as well.
The cylinder pressure relief valve is usually installed directly on the gas cylinder (Dan Ping), and it can also be installed on the wall (double bottles or multiple bottles).
Note: the inlet pressure of the cylinder pressure reducing valve is about 30~300bar, the outlet pressure is about 8~15bar, the working temperature is -20~+50 degrees, and the leakage rate is 3.10-7mbar.l/s
D) terminal pressure relief valve
According to the needs of the user and the actual conditions of the instrument and equipment, the terminal pressure relief valve can have many choices. For example, a device needs several kinds of gas and is equipped with several terminal pressure relief valves. At present, most laboratories have adopted this method (recommended), and the pressure is stable and the flow is stable.
Four, laboratory gas alarm
In a modern laboratory, safety must be given priority. Because the gas cylinder is all centralized storage, in order to facilitate the user to focus on inspection, save cost and operation time, but also there is a security risk, but if the early warning measures, safety measures in place, the danger is avoidable!
A) gas leakage alarm
If the cylinder is stored in a centralized way, the user only needs to install a gas leakage detector in the proper position of the laboratory (which is installed flammable, explosive, rotten or oxygen concentration detector in the specific case). The user can send out a sound and light warning through the central linkage signal to the alarm box, so that the user can find and repair it immediately.
B) gas undervoltage alarm
When the user works in the laboratory, it is necessary to know whether the gas is running out, the pressure of the cylinder is enough, and the automatic switching system with the undervoltage alarm is particularly important at this time. Through the electrical contact low pressure alarm, the pressure signal is fed back to the under voltage alarm box, thus realizing the continuous gas supply.
Five. Some accessories in the laboratory:
Purge valve: the gas valve and pipe is purged high pressure gas, when replacing the cylinder when the operation (installed in the cylinder pressure relief valve end), to ensure the purity of the pipe terminal gas.
Cut-off valve: turn off valve, installed between the cylinder pressure reducing valve and cylinder, better, can also be installed at the instrument terminal, when the on-off valve is used.
Flowmeter: used to regulate gas flow
Six. The advantages of centralized gas supply in the laboratory:
A) the purity of the positive gas;
B) continuous gas supply, the system can switch between cylinders in manual and automatic way to ensure continuous gas supply.
C) low pressure warning, when the air pressure is lower than the alarm limit, the alarm device can automatically alarm.
D) the gas pressure is stable, and the system adopts two stage decompression to supply gas, so that a very stable pressure can be obtained.
E) high efficiency, through the gas supply control system, it can make full use of the gas in the gas cylinder, reduce residual gas allowance and reduce the cost of gas consumption.
F) it is easy to operate, and all cylinders are stored in the same location to reduce handling and installation operations, save time and cost.
G) without cylinder in laboratory, it can improve safety, enhance safety and save laboratory operation space.
H) convenient inspection and maintenance;
I) reduce the renting of gas cylinders. Centralized gas supply can reduce the number of cylinders, thereby saving the cost of gas cylinders.
