Tanks
Tanks are found at many facilities in Sweden. Tanks are most often used for storing some kind of liquid. They can be cylindrical or square.
Tanks are pressurised devices
In a tank, the pressure above the liquid surface must not be more than 0.5 bar, and it must not be exposed to a vacuum greater than 0.0065 bar. Despite this, it is considered a pressurised device.
This is because the large amount of liquid exerts pressure against the bottom and wall (jacket) of the tank. If the liquid level in the tank is 10 metres, the pressure at the bottom of the tank will be approximately 1 bar.
What are the risks with tanks and pipelines?
If a tank breaks, large amounts of liquid will come out. If the liquid has hazardous properties, those near the tank could be seriously injured or die.
The risks increase if the tank has been exposed to corrosion or other external influences such as collisions or other damage. Therefore, tanks in class A or B must be inspected regularly by an accredited inspection body.
As an employer, you are responsible for ensuring that all tanks in your business undergo the required checks and are safe to use.
How can the risks by remedied?
Create a good foundation for safe work by performing a well-conducted risk assessment. Your risk assessment is the basis for clarifying what supervision, maintenance and control the tanks in your operation require.
Continuous supervision is designed to detect small deviations such as leaks or other things that could lead to major damage at an early stage.
Working in a tank requires special precautions
Working in a tank is work with special risks that needs to be further risk assessed because it can be dangerous from several perspectives. It is also important to plan how to evacuate a person who finds themselves in distress in a confined space.
Get a better work environment through systematic work
As an employer, you must manage the work environment in a systematic way in order to improve it. Our provisions on systematic work environment management apply to all employers – regardless of the type of activities conducted or the risks that you and your employees may be exposed to.
Tanks with control class A or B
Certain tanks must undergo inspections by an accredited inspection body. These are tanks that have control class A or B. To find out if your tank is class A or B, you must first obtain the following information:
- the tank's volume
- whether the contents belong to fluid group 1a or 2a (To determine this, you may need the safety data sheets for the contents.)
- the maximum permissible temperature of the contents.
Tanks containing flammable products (i.e. products with a flash point below 100 °C) are exempt from the Swedish Work Environment Authority's regulations and must instead follow the Swedish Civil Contingencies Agency's (MSB) rules for joining together and control (MSBFS 2018:3).
However, the rules for monitoring and supervision still apply according to the Swedish Work Environment Authority's regulations.
Example of classification of tanks
Fluid group 1a
Tanks that have a volume greater than 5,000 litres but not more than 10,000 litres and contain a liquid classified as 1a, for example hydrofluoric acid (hydrogen fluoride, HF), have control class B. If the volume is greater than 10,000 litres, it belongs to control class A.
Fluid group 2a
Tanks that have a volume greater than 50,000 litres and contain a liquid classified as 2a have control class B if the temperature to which the liquid can be heated exceeds 65 °C.
Examples of such fluids are water or bitumen. These liquids are often stored at a temperature above 65 °C. A tank for liquids in fluid group 2a can never have control class A.
Find out more about tanks
Last updated 2025-12-01