Liquid cylinder repair and maintenance can add up to big bucks for gas distributors – but it doesn’t have to. We have one simple tip that can keep cylinders in good working order and result in significant cost savings.
Liquid Cylinders 101: The Vacuum
First, a quick review of the basic design element that makes a cryogenic cylinder work so well: an extremely strong vacuum between the inner vessel and the outer stainless-steel shell. As James Dewar discovered back in the late 1800s, that vacuum makes all the difference for the longevity of a cryogen.
Without a strong vacuum, the cylinder is essentially inoperable. Under normal conditions, a cylinder loses about 1-2 percent of its contents per day. But without that vacuum, cryogens boil off incredibly fast – almost like pouring liquid nitrogen into a bucket.
The Achilles Heel: A Tiny O-Ring
Nearly all cryogenic cylinders are manufactured with a vacuum port welded onto the crown, in varying diameters and sizes. Inside that port is a simple o-ring. Inevitably, dirt and exposure to UV rays compromises the o-ring’s integrity, causing them to dry out and slowly lose their vacuum quality.
Here’s the Tip: Always Check and Maintain That O-Ring.
Letting an o-ring deteriorate is what leads to very costly repairs and tank downtime. Whenever the tank goes in for a refill, make the following standard procedure:
- Check the dust cap. Make sure it’s not cracked or broken, and fits nice and snug. Replace a cap that’s not doing its job.
- Check the o-ring for dirt and debris, and remove any you find.
- Put a small bead of O2-safe grease around the seal and vacuum valve and replace the cap.
Following that quick, simple protocol will keep your tanks in service and out of the repair shop. Curious about what a bad vacuum might look like? Check out this post on How to Tell if You Have a Bad Vacuum on your Dewar.
See our interactive liquid cylinder diagram with complete replacement parts list.
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