Refrigerated and Cryogenic Liquid Safety

Refrigerated and cryogenic liquids, cold gas vapors, or the cold exterior of a vessel or piping holding a refrigerated or cryogenic liquid can freeze human tissue on contact. Delicate tissue, such as the eyes, can be damaged by the exposure to cold gases even when the contact is too brief to damage the skin. Touching an uninsulated surface can cause your skin to stick to the material, resulting in skin tears when you try to pull away. Breathing cold vapors can damage your lungs. Direct contact with refrigerated or cryogenic liquids, cold gas vapors, or uninsulated pipes or vessels containing refrigerated or cryogenic liquids should be avoided. Use of appropriate personal protective equipment, also referred to as PPE, is an important way to protect yourself from the cold associated with refrigerated and cryogenic liquids.

Refrigerated and cryogenic liquids and their cold gas vapors can cause common materials like steel, rubber, and plastics to become brittle and break. This can be particularly dangerous in the case of a spill or unexpected exposure, where materials not designed for refrigerated or cryogenic service can rupture or crack.

Small quantities of refrigerated or cryogenic liquid will convert to very large quantities of gas as they vaporize. For example, liquid nitrogen expands at a ratio of 700 to 1, meaning one unit of liquid nitrogen will produce 700 units of gaseous nitrogen. If the vaporized gas is trapped in a sealed container, it will produce very high pressures. Any vaporization that occurs when product is trapped in piping between valves or within equipment without appropriate pressure relief can lead to a violent rupture potentially causing an uncontrolled product release, injury to personnel, or damage to property and equipment. For this reason, pressurized refrigerated and cryogenic containers are protected by pressure relief devices that relieve pressure from the container or piping by venting excess vapor. Non-pressurized liquid containers are equipped with loose-fitting caps that can come off to allow excess pressure to escape. Never block or tamper with any pressure relief devices.

A refrigerated or cryogenic liquid container that has cold spots or frost on the outside, is venting continually, or shows a rapid pressure rise on the tank pressure gauge is showing signs of loss of vacuum. Also, plugs of ice or foreign material can form in the vents and openings of these containers or their piping, preventing proper pressure relief. The vessel can rupture if the proper action is not taken quickly. Prevent plugs by following the supplier’s operating procedures.

If you have a container that is showing signs of loss of vacuum or has formed an ice plug, follow your company’s procedures for handling these containers or contact your gas supplier for immediate assistance. Do not attempt to remove the plug without consulting the supplier. If possible, remove the vessel to a remote location in accordance with the supplier’s recommendations.