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Noise-free and safe storage of cryogenic gases

A new overflow valve type 2580 from valve manufacturer Goetze Armaturen prevents loud flow noises in storage tanks that can occur when the safety valves open.

The overflow valve is characterised by the fact that it ensures a continuous and quiet pressure reduction when used on tanks for the storage of cryogenic liquefied technical gases such as argon, oxygen, nitrogen or carbon dioxide. 

The overflow valve is adjusted to a pressure below the set pressure of the safety valves and thus prevents the safety valves of the tank from reacting. When the safety valves are fully opened, loud outflow noises are generated, which in most cases also significantly exceed the Immission guide value of TA Lärm (technical instructions for protection against noise) and deprive the neighbourhood from sleep. Thus, the response of the safety valves is often interpreted as a malfunction of the storage system and leads to the activation of the emergency plan including fire brigade, police and rescue services.

Using the overflow valve type 2580 can prevent this scenario.

But why do the safety valves respond, which are normally only supposed to respond if previous pressure regulators have failed? 

Technical gases are reduced to many times their volume that is current under ambient conditions by liquefaction at cryogenic temperatures. Thus, for example, 1 litre of liquid nitrogen at -196°C becomes a gas cloud of 691m³ gas at 15° and 1 bar ambient pressure. Hence, by liquefaction, a large amount of gas can be stored. In order to maintain the necessary low temperature, they are stored in vacuum-insulated tanks, similar to a thermos flask.

In cases where no gas is withdrawn from the tank, e.g. on weekends or holidays, etc., the pressure rises steadily due to heating from the environment until the maximum permissible design pressure of the tank is reached and the safety valves designed for this pressure respond.

The operating mode without the overflow valve means that the storage tank is constantly operated at the max. permissible design pressure and also beyond this when the safety valves respond. This is comparable to continuously driving a car on the motorway at full speed at the engine speed limiter - that this mode of operation has a negative effect on the service life becomes clear.

By using the overflow valve type 2580, only the quantity of gas that results from heat input into the vessel is maximally discharged. When gas is with-drawn, the valve closes so that no gas is unnecessarily lost.

The overflow valve type 2580 is available in the same application temperature range as Goetze's other cryogenic valves from -200 to +120°C and in nominal diameter DN8 with body material gunmetal. Usually, threaded screw connec-tions can be used at ½ inches. The overflow valve is easily mounted to the lower connections of the ball diverter valve. The therefor-necessary connecting pipe bend can be supplied directly. Other sizes and materials can be supplied on request.

> Data sheet series 2580