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[3] Airtightness Test
Items to be strictly observed :
1. Pressurize the equipment with nitrogen up to the design pressure and then judge the equipment's airtightness, taking
temperature variations into account.
Reasons :
1. Use of oxygen as the pressurized gas may cause an explosion.
[4]
Vacuuming
1. Standard degree of vacuum for the vacuum pump
Use a pump which reaches 65 Pa (0.0094 psi) or below after 5 minutes of operation.
In addition, be sure to use a vacuum pump that has been properly maintained and oiled using the specified oil. If the
vacuum pump is not properly maintained, the degree of vacuum may be too low.
2. Required accuracy of the vacuum gauge
Use a vacuum gauge that can measure up to 650 Pa (0.094 psi). Do not use a general gauge manifold since it cannot
measure a vacuum of 650 Pa (0.094 psi).
3. Evacuating time
•
Evacuate the equipment for 1 hour after 650 Pa (0.094 psi) has been reached.
•
After envacuating, leave the equipment for 1 hour and make sure that the vacuum is not lost.
4. Operating procedure when the vacuum pump is stopped
In order to prevent a backflow of the vacuum pump oil, open the relief valve on the vacuum pump side or loosen the
charge hose to drawn in air before stopping operation.
The same operating procedure should be used when using a vacuum pump with a check valve.
–5–
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