Gas plants. Equipment and installation technique
The compatible gas supply system is needed for using high-purity gases! The following factors are the most important for gas supply system:
- pipeline system material
- pipeline system connector type
- reducer type and carrying capacity
Reducers for laser gas supply, cutting oxygen supply and welding gases supply
Reducers for high-purity gases are equipped with a metallic membrane and have a brass casing. In comparison with standard welding reducers, these ones have some advantages. Membranes are made of steel (Hastalloy) but not of rubber which is not diffusion-resistant. Reducers for high-purity gases are manufactured under strict quality control. As a result, the quality is higher. The rate of repeatability and reliability for high-purity gases reducers is higher than for standard ones.
Laser manufacturers often require double-step reducers for gas supply to the laser. Such reducers may be designed as a single unit or as individual units where the first unit may be used for pressure reduction, and the second unit may be installed directly at the workplace. For laser cutting of thick low-carbon steel plates, oxygen pressure must be decreased to values less than 1 bar (15 psi). This process is very sensitive to pressure fluctuations; thus the double-unit reducers shall be used to supply oxygen under pressure less than 1 bar (15 psi) for laser cutting.
Reducers for nitrogen supply for laser cutting
High capacity and permanent backpressure reducers are used. Nitrogen purity requirements for laser cutting process are not so strict as laser gas requirements. Because of high gas flow the hazard of cutting nitrogen contamination is rather low.
Backpressure of high pressure reducers shall be more than 30 bar (450 psi). Carrying capacity shall be more 50 m3/h (1750 cubic feet per hour); the most advanced systems require carrying capacity up to 150 m3/h (5250 cubic feet per hour) and more.
Each high pressure reducer must be equipped with a purging system. When a cylinder is replaced, the high pressure hose is connected to ambient air and the gas supply system may be contaminated with dust, moisture and gases. Before connecting of a new cylinder to the gas supply system, it is necessary to remove such contamination by purging the system several times.
Solid particle filter
Solid particle filters should be installed at the place of use. Solid particle filters prevent entry of such particles into the laser system. Particles may be present in the gas supply system. If no filters are installed, solid particles should be completely removed by purging the system with nitrogen before connecting the supply system to the laser.
Pipeline system material
Stainless steel and copper pipes free from oil and grease are used. Metal pipes ensure maximum protection against penetration of impurities and contamination of clear gases.
Minimum diameter for the following applications:
Laser gases: Zh8 mm x 1 mm
Cutting gases: Zh12 mm x 1 mm
Welding gases: Zh8 mm x 1 mm
(0.32/0.48 in. x 0.04 in.)
Pipe diameter is mostly determined by required gas flow as well as by system length, number of connectors and bends, and by other factors that cause pressure losses.
Pipe system connectors
The tungsten inert-gas cycle welding must be used to connect stainless steel pipes. During this process, the pipe must be internally purged with neutral gas. Copper pipes must be connected by brazing. During this process, the pipe must be internally purged with neutral gas to prevent formation of copper oxide. Copper oxides will cause damage of optics and electrodes in the resonator. Swagelok pipe fittings are also recommended for connecting stainless steel and copper pipes.
Do not use standard screwed fittings with Teflon seals!
The use of hose is not the best practice! Hoses are not diffusion-resistant in contrast to metal pipes. If the use of hoses can not be avoided, polyethylene hoses are preferable.
Standard policies, terms and conditions: