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CTI Cryogenics Compressor Preventive Maintenance


Properly maintained cryopumps and compressors are critical to the optimal performance of a cryogenic vacuum system, which reduces unscheduled downtime. While the cryopumps themselves receive a great deal of attention, most customers are not aware of the requirements for compressor maintenance or the consequences for not properly maintaining their compressors. Typically, in a large installed base, the fleet of compressors will not have had their adsorbers changed at the required intervals as identified in Table 1.

Table 1

Compressor Absorber Replacement Interval
Compressor Model 1 Year 3 Years
P300 Tower  

Compressor Adsorber

The cooled helium may contain some residual oil vapor from the compressor. This oil vapor would condense in the cryopump regenerator and severely hamper its ability to produce the cold temperatures required for cryopumping. To remove oil vapor, an oil separator and an oil adsorber are used. The oil adsorber contains activated charcoal to filter out the remaining oil in the helium by adsorption and has a finite service life therefore, it must be replaced with a new adsorber per Table 1. If the adsorber is not replaced at the recommended service intervals this will significantly increase the risk of oil vapor contamination in the helium circuit.

Removing the Compressor Adsorber

1. When working with high voltage equipment safety is a major concern, always lock out and tag out the equipment.
2. When the compressor’s power is properly locked out disconnect the input power cable from the compressor.
3. Disconnect the helium supply and return lines on the compressor.
4. Remove the rear panel from the compressor to expose the adsorber. Consult the manual for your model of compressor for proper instructions to remove the rear panel.
5. Using two wrenches (1 1/8th and 1 3/16th) remove the helium line coupling on the bottom of the adsorber. It is important to perform this task quickly to minimize helium leakage. Reference Figure 1

Figure 1 - Disconnect Helium Line Coupling

a. Remove the two bolts, nuts and washers that are used to secure the adsorber to the base on the compressor base. Save the nuts, bolts and washers for reinstalling the new adsorber.
b. Carefully remove the adsorber from the base of the compressor.

Installing the Compressor Adsorber

1. Remove the caps from the adsorber couplings.
2. Write the date of installation on the adsorber’s decal.
3. Install the adsorber into the compressor’s base.
4. Install the removed nuts, bolts and washers and tighten with a wrench.
5. Connect the helium line coupling to the adsorber by hand then using two wrenches (1 1/8th and 1 3/16th) as identified in Figure 2 to tighten the coupling.

Figure 2 - Connecting Helium Line Coupling

6. Replace the rear cover to the compressor.
7. Verify that the Static Charge pressure is within the range identified in Table 2 for your specific model compressor.
8. If the Compressor’s Static Charge pressure is not within Table 2 limits refer to the compressor’s manual for adding or removing helium.
9. Reconnect the helium supply and return lines on the compressor.
10. Reconnect the input power cable to the compressor.
11. Remove the lock out and tag out from the compressor.
12. Apply power to the compressor.

Table 2

Static Helium Pressure
Model Static psig
8200 245-255
8500 195-205
8510 195-205
9600 240-250
9700 220-330
IS 1000 340-350
1020R 180-190

In addition to contacting PTB Sales for technical support, we also provide adsorber sales, compressor repair and for large installed base customers we offer an installed base audit. The audit uses proprietary PTB Sales iCAR-C™ software in conjunction with trained personnel. We will review all of the parameters of your cryogenic vacuum system and identify installation and/or configuration concerns. In addition, we provide recommendations for repair and/or service based on performance data, operational hours, observations and technical knowledge of your cryogenic vacuum systems.

If technical assistance is required, please contact our Customer Service Representative.

  • 1-855-PTB-SALES (1-855-782-7253) Inside the United States of America
  • 1-626-385-3585 Outside the United States of America

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Document # PTB-T35-0005 Rev 01       © 2014 PTB Sales, Inc.