
B-70254EN/01 4.MAINTENANCE
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4.6 LASER GAS
4.6.1 Laser Gas Specification
Supply the laser oscillator with a mixture of gases that satisfy the
conditions listed below.
(1) Composition ratio and accuracy
CO
2
:5±0.25%
He : 40±2.00%
N
2
:55±2.75% (N
2
balance)
(2) Water (H
2
O): 5 ppm or less
(3) Hydrocarbon (CnHm): 1 ppm or less
(4) Gas purity: 99.99% or higher
4.6.2 Gas Pipe
Observe the following cautions for piping between the laser gas
cylinder and laser oscillator.
(1) Use nylon tube having an inside diameter of 8 mm or larger
(Junlon AS1 manufactured by Junkousha, or equivalent). Do not
use a rubber or urethane tube.
(2) Use a swage-lock vacuum joint. Do not use a one-touch coupler,
quick coupler, or hose-band joint.
(3) Minimize the length of tubing. It should be kept within 5 m.
Never exceed 15 m. For a length of 15 m or greater, use stainless
pipe.
(4) If it is necessary to use metal pipe for lack of an alternative, use
stainless bright annealed pipe. Minimize the number of joints
used. Connect pipes, if necessary, using a swage-lock vacuum
joint or by TIG welding. Do not use silver soldering or copper
piping. Piping should be installed by a vacuum piping specialist.
Do not extend metal piping over 30 m.
(5) Always keep the piping materials clean. Do not allow foreign
matter to get in the pipe.
(6) Use a pressure reducer that is free from gas leakage.
(7) After installing the pipe, check it for gas leakage, using a liquid
leak checker (Gyupoflex : A98L-0001-0856, detecting bubbles
caused by leaking gas) or a clamp test1).
Clamp test
Open the valve of the gas cylinder to pressurize the inside of the
pipe, then close the valve. Check to see if the pressure in the
pipe becomes low with time. Monitor the primary pressure of the
gas reducer for over 8 hours. If the gas pressure becomes lower
by 10% within 8 hours, gas is likely to be leaking. Take an
appropriate measure.