Vacuum Furnace Maintenance Tips

Leak Testing in Vacuum Furnaces

When your vacuum furnace system does not reach the correct vacuum level or if evacuation time is too long, it is essential to perform a leak test.  First, check the vacuum transmitters and if they operate correctly, check the furnace leak rate.  An acceptable leak rate is measured from 1 x 10^-4 mbar and should not exceed  3 x 10^-4 mbar x l/s.  A higher leak rate means leaks in the system.

Leaks are most probable in the following places:

• furnace door lip seal
• main vacuum valve
• butterfly vacuum valves
• power feedthroughs of heating elements and gas blower motor
• thermoelement feedthroughs
• pneumatic cylinder feedthroughs
• heat exchanger feedthroughs
• vacuum pumping system flanges
• flange connections and screw joints in gas system
• furnace chamber welds and gas buffer tank

If leaks cannot be identified with the general inspection of the system, it should then be tested with a helium leak detector at the most sensitive range <5 x 10^-11 mbar x l/s (example:  ULTRATEST UL. 200, Leybold Vacuum). 

Specially trained and experienced staff should perform this test. 

The latest design, materials and equipment specifications should be obtained from the company before any reliance is placed on the enclosed since changes may occur due to product improvement.