Cryogenic tanks are used for the storage of cryogenic liquids.
Cryogenic liquids are typically liquefied gases at -150 °C or lower. Common gases include oxygen, argon, nitrogen, hydrogen, and helium. Cryogenic tanks are also used for storing liquefied gases at slightly higher temperatures, examples of which include liquefied natural gas (LNG), carbon dioxide and nitrous oxide.
The tanks often provide a bulk gas source for a gas supply and distribution system. The applications include metal processing, medical technology, electronics, water treatment, energy generation and the food industry. Cryogenic liquids are also used for low temperature cooling applications, such as engineering shrink fitting, food freezing and the storage of bio-samples.
Cryogenic tanks are designed and manufactured to a high specification following international design codes. They have very efficient insulation to maintain the liquid at its cold temperature. They are available for static, mobile or transportable applications.
Static cryogenic tanks are designed for use in a fixed location. Smaller mobile tanks, mounted on wheels, are also common within workshops and laboratories. Static cryogenic tanks are generally classified as pressure vessels, as such new tanks and their associated systems must be manufactured and put into service in accordance with the Pressure Equipment (Safety) Regulations.
Transportable cryogenic tanks that are, or are intended, to be used for the carriage of cryogenic liquids must comply with the Carriage of Dangerous Goods and Use of Transportable Pressure Equipment Regulations.
There are also a range of non-pressurised open neck vessels (Dewar flasks) available for those applications requiring direct access to the liquid.
The tanks are available in a range of sizes, pressures and flow rates.
Static cryogenic tanks must comply with the Pressure Systems Safety Regulations. They are required to undergo a formal examination by a competent person following a written scheme of examination, as well as routine inspection and maintenance. Advice is available in BCGA CP 39.
Transportable cryogenic tanks must comply with the Carriage of Dangerous Goods and Use of Transportable Pressure Equipment Regulations. They require periodic inspection and testing. In Great Britain this must be carried out under the supervision of an Appointed Body, who is an Inspection Body authorised by the National Competent Authority, the Department for Transport (DfT). Information on Inspection Bodies who have been appointed to undertake various functions in connection with the inspection of tanks and / or pressure equipment can be found on the Vehicle Certification Agency (VCA) website. BCGA GN 48 provides advice on the role of Inspection Bodies.
All examinations, inspections, maintenance and tests must be documented and records have to be kept for the life of the tank.
In service, owners and the users of cryogenic tanks have legal responsibilities and a duty of care to ensure their equipment is maintained and operated safely. BCGA Leaflet 12 provides advice and guidance on appropriate practice. The user must carry out routine safety inspections, including daily checks, refer to BCGA Leaflet 11. When in use a small amount of frosting and ice may be seen. Small quantities should not be a cause for concern, but the quantity of ice should be routinely monitored. If ice continues to build-up, de-icing should take place to prevent the ice build-up becoming excessive, advice is available in BCGA Leaflet 21.
A gas supplier will only fill a tank once they have established that it is safe and legal to do so, refer to BCGA CP 48.
Cryogenic tank repair and modification
Any repair or modification to a cryogenic tank shall only be carried out by a competent repairer in accordance with the design codes to which it was manufactured, taking into account current requirements in legislation. Such repairs or modifications shall not affect its integrity or the operation of any protective devices, refer to BCGA CP 39.
All repairs and modifications have to be documented and records have to be kept for the life of the tank.
Cryogenic tank revalidation
Overtime cryogenic tanks may deteriorate due to aging, fatigue, etc. Cryogenic tanks require a formal periodic assessment to ensure they remain safe for continued use, this is called revalidation. This revalidation period shall be decided by a Competent Person but shall not exceed 20 years. Due to the nature of their service a shorter period for mobile tanks is recommended (refer to BCGA CP 39). When revalidation takes place a report is produced which is to be kept with the tank records for the life of the tank.
A tank shall only be disposed of with the owner’s permission.
Where a cryogenic tank is provided under a contract agreement with an equipment or gas supplier, they shall be contacted to make arrangements for the return of the tank.
Before disposal all cryogenic liquid shall be removed and the cryogenic tank shall be rendered non-reusable as pressure equipment.
Some cryogenic tanks contain hazardous products in their vacuum space, e.g. insulation material called perlite, and therefore these tanks should only be disposed of by an approved competent and specialist disposal contractor.
Links to a number of tank providers or disposal providers are available below. To view the full list, please click here.
Within BCGA cryogenic tanks are the responsibility of Technical Sub-Committee (TSC) 1. Members can access information on TSC1 via the Committee Meetings page.
The design, installation, operation and maintenance of bulk liquid carbon dioxide storage systems at users’ premises. All tanks up to 250,000 litres capacity are included.Go To Download Page
This code of practice applies to transportable, vacuum insulated, tanks of not more than 1,000 litres water capacity, for the following gases: Nitrogen, argon, oxygen, carbon dioxide, helium or nitrous oxide.This code provides guidance for the minimum requirements for: General safety precautions, design and construction, operation, tank management and filling, transportation, in-service examination, modifications/repairs and records.Go To Download Page
This document covers the installation of cryogenic liquid storage tanks and associated equipment at customer sites. For liquid oxygen, nitrogen and argon. Tank sizes range from 0 to 125000 litre water capacity.Go To Download Page
Pressure systems require regular examination, inspection and maintenance to ensure the continuing integrity of the equipment and the safety of personnel. This code covers the principles and a risk based methodology to meet these requirements. It includes guidance on Written Schemes of Examination, Ageing Pressure Equipment Assessments and Revalidation of pressure vessels.Go To Download Page
The design, installation and operation of systems used for the storage of biomedical materials at cryogenic temperatures, using liquid nitrogen as a sacrificial refrigerant.Go To Download Page
This document covers cryogenic flammable liquid storage tanks and associated equipment at customer sites. Tank sizes range from 0 to 125000 litre water capacity. It provides guidance on their design, installation, commissioning and the operation of cryogenic flammable liquid storage installations.Go To Download Page
Details the responsibilities of the User, the Tank Owner and the Gas Supplier when filling third party owned tanks used for the storage of refrigerated liquefied gases at a User’s premises. It includes a procedure to inform BCGA members of tanks which are deemed unsafe to fill.Go To Download Page
Clarification of the legislation in the UK for transportable pressure equipment, including the various type approval and conformity assessment requirements.Go To Download Page
BCGA Leaflet 11 outlines some daily safety checks that users responsible for cryogenic tanks are to carry out. These are independent of safety checks which gas supply companies’ drivers will conduct at delivery times.Go To Download Page
An information leaflet which reminds users and owners of liquid gas storage tanks of their legal duties and responsibilities to ensure the equipment is installed, maintained and operated safely.Go To Download Page
Outlines the problems associated with an increasing quantity of ice formation within a cryogenic installation and provides a methodology for safely removing the ice.Go To Download Page
BCGA publish several publications providing advice and guidance on the on how to use, store, transport and handle cryogenic gases safely. All BCGA publications are accessible via the Publications page.