Cryogenic Vacuum Pumps – Oxford Instruments Austin

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Cryogenic Vacuum Pumps – Regeneration Procedure

Oxford Instruments Austin

Cryogenic Vacuum Pumps –
Regeneration Procedure

August 2013 / Original Instructions

©2013 Oxford Instruments Austin. All rights reserved.
OIA_CryoPump_Regen_813 Original Instructions

Cryopump Regeneration Procedure August 2013 / Original Instructions

Cryogenic Vacuum Pumps – Regeneration Procedure

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1. When to regenerate
a. When there is an increase in base pressure
b. When there is an increase in pump down time
i. Loss of pumping speed
c. When there is an increase in pump temp
d. Extended power loss to the system
e. Partial venting of the system or pump to atmosphere
2. Warm up phase
a. Close high vacuum valve
i. Prevents gas and water to travel onto chamber
b. Shut down cryopump and compressor**
**For multiple pumps running on a single compressor, shutting down of the
compressor is not required.
c. Immediately start purge of N2 @150 deg. @1-2scfm with regulator pressure
at 25-30 psig
i. Make sure that purge valve opened
ii. Turn on blanket heater if equipped
iii. A very wet pump should be purged longer and brought over room
temp, not to exceed 150 deg. F
d. If explosive, hazardous or acid forming gases are present inside pump, the
relief port should be plumbed to a scrubber.
3. Roughing phase
a. Most important phase
i. All liberated gases are being removed from the internal surfaces. The
most important and most difficult gas to remove is water vapor.
b. If the cryopump is not at room temp or is holding excessive water vapor
when roughing starts:
i. The charcoal array can become saturated with water
ii. When pressure drops via roughing cycle

©2013 Oxford Instruments Austin. All rights reserved.
OIA_CryoPump_Regen_813 Original Instructions

Cryopump Regeneration Procedure August 2013 / Original Instructions

Cryogenic Vacuum Pumps – Regeneration Procedure

1. Water in the charcoal will evaporate then freeze. This will
lengthen the roughing time.

2. The temp can drop 50K.
a. The vapor pressure of water @250K = 600 microns
b. If you notice that you’re hanging up at 600 microns you
have ice on the 2nd stage charcoal array.

4. Rate of Rise Test
a. This determines if the pump has been thoroughly regenerated and is clean.
i. If this is not done, the pump will not have the designed capacity for
non-condensable gases.
b. Poor warm up / roughing pump procedures are the most common reason
for poor performance and the need for frequent regeneration.

5. If the Rate of Rise procedure is OK
a. Close off toughing valve when the pressure with in the pump = 50 microns
b. Measure the increase of pressure with in the pump for 5 minutes.
c. The Rate of Rise should not increase at a rate higher than 10 microns per
minute.
d. At the end of the 5-minute period, re-rough the pump to 50 micron if
needed.

6. If the Rate of Rise procedure has a problem
a. If the pressure is over 100 micron after 5 minutes
i. The pump is still dirty
ii. There is a vacuum leak
b. If the pump is dirty
i. The Rate of Rise will lesson with time
ii. Re-purge the pump and rough again
c. If there is a vacuum leak
i. The Rate of Rise will be consistent with time

©2013 Oxford Instruments Austin. All rights reserved.
OIA_CryoPump_Regen_813 Original Instructions