How does an over-pressure safety device S2SR work?
In Germany, it is usual for July and August to be the warmest months with an average temperature of approx. 18 degrees Celsius. If we take this value as a basis, the gas flows out of an LPG cylinder with a pressure of almost seven bar. The cylinder pressure is therefore 140 times higher than the pressure which should finally be applied to the consumer equipment (50 millibar).
The cylinder pressure cannot be stated exactly, because, among other reasons, LPG is a mixture of propane and butane. Pure propane has a vapour pressure of 7.3 bar at 20 degrees Celsius.
Worst case
If a gas cylinder pressure regulator does not have an S2SR over-pressure safety device, in the worst case, this value may end up directly on the connected gas equipment. This will inevitably lead to malfunctions and leaks.
Pressure regulators with an integrated S2SR over-pressure safety device operate in two stages. If one of the two stages fails, for example due to contamination, foreign bodies in the valve or a defect, the other stage reduces the outlet pressure to a maximum of 150 millibar.
Minimum risk: Damage to the device
If no S2SR is integrated, in the worst case, the cylinder pressure could hit the consumer equipment such as gas stoves, gas barbecues or heaters without anything to prevent this.
The consequences are difficult to forecast. It’s clear, however: Damage to the consumer equipment is the minimum risk.
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Help visual indicator
Pressure regulators with an S2SR usually have a visual indicator. In regular operation, the user sees a green field on the visual indicator. The display only changes to red once the outlet pressure is above the threshold of 80 millibar. In contrast to the over-pressure safety shut-off device OPSO, the S2SR cannot be reset. The operator of the system must replace the pressure regulator with a new one as soon as possible and dispose of the old one.
No retrofitting
The S2SR over-pressure safety device cannot be retrofitted by the operator. It is mainly integrated in pressure regulators for small cylinder systems (5 and 11 kilogram gas cylinders) or not, as the case may be. The following presents a short selection of models with an integrated S2SR:
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- Includes excess flow device: Low pressure regulator for household and industry – for use outdoors
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- Low pressure regulator for boats and ships
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- Pressure regulators for household and industry – for use outdoors
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- Pressure regulators for household and industry – for use in buildings
