Laboratory centralized gas supply system is also called central gas supply system. There is only one cylinder room in the layout of the building. One gas source of the same kind of gas is distributed through a 316L seamless stainless steel pipeline. Centralized gas supply is a more and more popular way of gas supply. It mainly consists of gas source, conveying pipeline, switching device, pressure regulating device, terminal gas point, monitoring and alarm. Composition of device, etc.
The materials of pipes and valves for centralized gas supply should be determined according to the types of gases, purity requirements, allowable pressure range, maximum gas consumption and flow rate, and use place, etc. Laboratory centralized gas supply is to supply carrier gas or fuel gas for various high-precision analytical instruments such as mass spectrometer, chromatograph, spectrometer, etc. The purity is between 99.99% and 99.999%, which belongs to high-purity gas. Therefore, 316BA stainless steel material should be selected according to GB 50751. A set of primary pressure relief valves (also known as high pressure relief valves) is equipped in the cylinder chamber of a gas supply system (the maximum range is generally 1.5-2 times the maximum working pressure of the pipeline). The pressure of the cylinder is adjusted to 0.4 MP and then input into the gas supply pipeline. Each gas point is equipped with an end pressure relief valve, which accurately adjusts to the required pressure and then inputs the gas equipment. Pipeline diameters larger than 1/2 inch should be welded by argon arc welding and polished by full welding; 3/8 inch and below pipelines can be connected by finished stainless steel four-way, three-way, elbow, direct and variable diameter connection conversion; gas supply pipelines can be laid in ceiling, wall panels and repair channels. If the maximum distance between gas cylinder chamber and gas point is more than 40 meters, gas supply pipelines should not use 1/4 inch or less pipelines. Transmission, because the pressure attenuation is large, it is easy to appear insufficient gas cylinder supply pressure, resulting in waste of gas.
After installation of gas supply pipeline, pressure detection and purging should be carried out. High purity nitrogen can be used for pressure detection and purging, and 1.5 times of working pressure can be used for pressure detection (working pressure is generally 0.4 MP, test pressure is 0.6 MP). The pressure drop of 24 hours is less than one reading, which is qualified for inspection. After the pressure test is qualified, the pipeline can be purged. The purging time is 30 minutes. After the purging, the pipeline valves can be closed and the qualified label can be affixed for the owner to put into use.
The advantages of centralized gas supply system are mainly embodied in three aspects: economy, safety management and purity.
1. Economy. Distributed gas supply needs to be equipped with a cylinder at one gas point. Each cylinder can not be completely exhausted and replaced because of low pressure. It has large investment and high daily operating costs. The centralized gas supply adopts one-drag and multi-mode, and the utilization rate of high purity gas is high.
2. Safety management. Distributed gas supply arranges high pressure cylinders in the instrument room. Some gases such as H2, C2H2, CO, CH4 are flammable gases. Flammable high pressure gas cylinders and operators are in the same room. Leakage detection and explosion release are difficult to achieve, which obviously increases the difficulty of safety management. Because of the workflow, convenient management, exhaust air and other reasons, the instrument room is usually located on the upstairs of the experimental building, together with the pretreatment room, which increases the workload of loading and unloading cylinders.
3. purity. Centralized gas supply adopts semi-automatic or full-automatic pressure relief valve joint, cylinder automatic switching gas supply, uninterrupted, pipeline 316L seamless stainless steel pipe, can always ensure the purity of gas in the pipeline.
In summary, centralized gas supply is being adopted by more and more laboratory customers due to its advantages in economy, safety management and purity.