The Care and Keeping of O-Rings


  • Always wear gloves when handling components of the system
  • Do NOT use acetone on the o-rings
  • Do NOT place the Cryostation s50 housing down on a surface flat – this will get debris on the o-ring. There is a notch in the side of the housing to set the housing down on. The s100 (Fusion) and s200 (Nanoscale Workstation) housings have bosses to keep the o-ring off the surface of the table.

Figure 1: Set Cryostation s50 housing on side notch when not in house


In most cases you should not need to replace your o-rings. General maintenance includes wiping the two o-rings on the housing down every 5-10 uses with a kimwipe or lens tissue.

Figure 2: Proper o-ring cleaning technique using a dry kimwipe

Note: You do not need to remove the o-rings to clean them, you just need to wipe the exposed surface. Next, add a small amount of (Apiezon) L-grease or other vacuum grease to the o-rings. You do not need a lot of grease, just enough that the surface of the o-ring has a shine to it. Before every cool down inspect the o-rings to make sure ensure they:

  1. Are free from debris
  2. Have a thin layer of L-grease


If there is a leak and it has appeared suddenly, it is best to check the o-rings first. Generally the culprit is around the housing o-rings or any o-ring seal that has been exposed, for instance a side panel o-ring or a window o-ring. Leaks in cryogenic systems are quite common. Generally, a quick inspection or cleaning of the housing o-rings will fix the issue, but occasionally a more thorough inspection is required (for this it is recommended to use a leak detector). The leak detector can be attached to the VCO port either on the vacuum line or on the cryostat. There is a ¼” VCO adaptor to KF25 adaptor in most accessory kits. This adaptor can be used for attaching a turbo pump to the system or the leak detector. Look for leaks at all o-rings seals, which include the housing, side panels, windows, bellows between the vacuum jacket and the sample chamber, and the top of the vacuum jacket near the cold head. Also, check the VCO port; in rare instances this can be loose and leak.


If an o-ring becomes nicked or damaged then you should replace it. Luckily, they are quite easy to replace. The window o-rings simply come out once the retaining ring and the window have been removed. The side panels are similar; the o-rings pop out once the side panel has been detached. The housing o-rings have more of a snug fit. It is important to not pry out the o-rings with metal tipped tweezers or anything else sharp, as this could damage the aluminum of the housing or the o-ring.

Figure 3: Do NOT remove o-rings with metal tipped tweezers

It is best to use either Teflon tipped tweezers or just your fingers to remove the o-ring.

Figure 4: O-Ring groove without o-ring installed


Montana Instruments uses Viton o-ring; we have deduced that these o-rings outgas the least in our systems.

  • The Cryostation s50 housing o-rings are McMaster Carr part number: 5267T133
  • The Cryostation s100 (Fusion) housing o-rings are McMaster Carr part number: 5267T353
  • The Cryostation s200 (Nanoscale Workstation) housing o-rings are McMaster Carr part number: 5267T242
  • The 50mm window o-rings are McMaster Carr part number: 5267T44
  • The side panel o-rings are McMaster Carr part number:  5267T41

If you require other part numbers, please contact Montana Instruments for information.