Laboratory centralized gas supply/one-stop service for laboratory gas path engineering

The laboratory centralized gas supply system generally consists of high-pressure steel cylinders, gas switching devices, pressure reducing devices, valves, pipelines, filters, alarms, terminal boxes, regulating valves and other parts. In our laboratory construction, the centralized gas supply system has the characteristics of economy and safety.

Economy refers to the construction of a centralized gas cylinder room can save limited laboratory space, the replacement of gas cylinders do not need to cut off the gas, to ensure the continuous supply of gas. Because all the points that use the same gas come from the same gas source, the user only needs to manage fewer cylinders and pay less cylinder rent. This way of gas supply can reduce transportation costs, reduce the amount of gas returned to the gas company in the empty bottle, to achieve the purpose of economic application. Safety refers to the centralized storage and supply of gas sources to ensure that analysts and testers are protected from toxic and harmful gases in experiments.

Centralized gas supply has become the main trend of laboratory development and construction because of its safety, convenience, beauty and ease of management. Compared with traditional decentralized gas supply, centralized gas supply can realize safe gas cylinder management, accurate gas monitoring, long-lasting gas supply and intelligent system control.

Construction preparation

1, the construction personnel should carefully check the construction design drawings before construction, organize the construction according to the technical requirements of the drawings, strictly implement the relevant procedures, specifications and quality inspection and evaluation standards, there are changes and changes in the design personnel in a timely manner to negotiate with the design changes, do not change the design drawings at will, key construction parts should be detailed construction technical disclosure.

2. After entering the construction site, the construction team shall obey the unified arrangement of the employer, protect all kinds of finished products on the site, arrange temporary electricity consumption, and carefully check the electrical equipment, distribution box and wires.

3, materials, equipment should have the factory certificate and material certification documents, test reports, after entering the site with the employer for quality, specifications, quantity and other verification work and form a written inspection record.

Gas pipeline laying planning points:

(1) The outlet of the gas cylinder valve is GB standard external thread (G5/8 "). In order to facilitate the connection between the pipeline system and the gas cylinder, a conversion joint (gas cylinder joint) should be provided from the outlet of the gas cylinder valve to the pipeline system.

(2) In order to easily replace the gas cylinder during use, a high-pressure spiral pipe with high pressure resistance should be provided between the above-mentioned gas cylinder connector and the regulating valve.

(3) As the gas pressure inside the cylinder is about 20-25MP, the pressure at the use point is small, the gas pressure changes, and the difference between the mesh values is large, so a primary pressure reducing valve should be set at the outlet of the cylinder, and a secondary pressure reducing valve should be set before the gas use point.

(4) Each gas system should be equipped with a device that can quickly cut off the gas supply in an emergency. In order to ensure the convenience of the switch system, the switch valve of this project adopts a ball valve.

(5) In order to prevent the outside air from entering the pipeline system when replacing the bottle, a ball valve should be set up. The ball valve is connected to the emptying pipe. The emptying pipe should be reliably connected to the atmosphere. The emptying pipe of combustible gas and combustion-supporting gas should be set independently. The outlet of the emptying pipe should be equipped with explosion-proof check valve to prevent the occurrence of backfire.

(6) in the flammable gas hydrogen and B fast system, in order to prevent the occurrence of backfire phenomenon, should be in the system low pressure end (after a pressure reducing valve) installation of explosion-proof check valve.

(7) the gas pipeline system outlet, in order to facilitate the switch system, should be equipped with a use point ball valve.

(8) In order to ensure the purity of the gas and the air tightness of the pipeline system, all pipes are 316L stainless steel pipes, and the inner surface is treated with BA.

(9) In order to facilitate the maintenance and replacement of the valve, while ensuring the air tightness of the system, the connection between the pipeline and the valve should be connected by a high-pressure double ferrule joint.

(10) The pipe fixing parts (pipe clamps) shall be made of high temperature resistant materials, which shall be strong, light and durable.

(11) The control panel of the regulating valve, the control panel of the outlet point and all pipelines shall be pasted with the gas identification of the gas composition.

(12) The bottle fixing frame shall be made of ABS engineering plastic.

Key points of construction technology:

(1) Both ends of all stainless steel pipes are sealed with plastic covers. After entering the construction site and before installation, the plastic covers can be removed.

(2) All pipe fittings shall be purged with high purity nitrogen for more than three times before being installed into the system.

(3) When laying the pipeline, attention should be paid to straightness. The pipe bender shall be used at the pipe bend, which shall not be bent with bare hands. When cutting the pipeline, the special pipe cutter shall be used for operation, and it is strictly forbidden to cut the pipeline with a saw. After the pipeline is cut off, special tools should be used to deal with the fracture, and ordinary iron knives are strictly prohibited.

(4) In the pipeline route, a set of pipe clamps should be set every 1.5 meters.

(5) The pipe shall be provided with casing at the crossing wall and floor, and the gap between the casing and the pipe shall be filled and sealed with other materials.

(6) All regulating valve fixing panels, all outlet point fixing racks and all pipelines shall be affixed with gas marks marked with the composition and concentration of the corresponding gas.

7) After all system components are installed, high-purity ammonia gas shall be used for more than three times of high-flow purging.

(8) After purging is completed, use high-purity nitrogen for leak detection and pressure retention test, and the test pressure should be 1.5 times of the working pressure.

(9) in the whole construction process should pay attention to the construction safety, especially high altitude operation (in the ladder or scaffolding construction), should have special care.

Construction acceptance

After the completion of construction, we shall carry out the system inspection of centralized gas supply together with the Employer. The inspection contents are as follows:

(1) Whether the material of the component meets the material requirements in the contract.

(2) Whether all connection points are safe and reliable.

(3) Whether the pipeline layout is reasonable and beautiful.

(4) Whether the gas mark is correctly pasted and beautiful.

(5) Whether the pipeline connection is correct.

(6) Pressure test: Fill high-purity nitrogen into the system pipeline, and the pressure is equal to the working pressure. Visually inspect whether all parts are broken and deformed, and whether the pipeline fixing frame and pipe clamp are loose and fall off for 21 hours.

(7) Pressure drop test: Fill the system pipeline with high-purity nitrogen at a pressure of 1.5 times the working pressure. After 24 hours of pressure retention, whether the pressure gauge reading changes by less than 0.25%.

(8) Leak test: Fill the system pipeline with high purity nitrogen, the pressure is 1.5 times of the working pressure, apply special leak detector at the connection of all parts of the system, and check whether there are bubbles every 5 minutes. This test process lasts for 30 minutes.

General laboratory centralized gas supply is to place gas cylinders in different gas cylinders according to the different properties of non-combustible and combustible, and then transport the gas to the laboratory (instrument end) through the pipeline system. At the same time, the pressure and flow rate of the gas can be adjusted directly according to the requirements of the experiment itself through the pressure reducer installed on the test bench, so as to better achieve the experimental effect. The characteristics of the laboratory centralized gas supply system are mainly reflected in three aspects: safety, economy and purity.

1. Safety: The cylinder (gas cylinder) is placed in a safe area outside the work area, and the staff can cut off the gas supply in an emergency through the equipped remote cut-off system. The reasonable arrangement of the cylinder storage area can maintain the safe distance between the combustion-supporting container and the combustible container. There is no longer high-pressure equipment in the workplace accessories, and there is a ventilation device in the cylinder room, so the potential danger of flammable or toxic gas leakage can be avoided. Cylinders must still be operated by trained and qualified personnel to reduce the chance of major accidents.

2. Economy: The limited laboratory space can be saved by building a gas cylinder room, and the gas does not need to be cut off when replacing the steel cylinder, which not only saves time but also ensures the continuous training supply of gas. The staff only has to manage fewer cylinders and pay less cylinder rent, because all the points of use of the same gas come from the same gas source. This mode of supply will eventually reduce transportation costs and reduce the amount of residual gas in empty bottles returned to gas companies, making cylinder management more uniform and standardized.

3, purity: the reduction of the frequency of cylinder replacement leads to the reduction of the probability of impurities entering the system, which improves the accuracy of the experiment.