Pressure Relief Valve (PRV)
This is a safety device for the relief of excess pressure. Excess pressure can result from:
- Thermal expansion of trapped gas after the regulator. LPG vapour has a large expansion coefficient and is effected by changes in temperature. When associated with an OPSO system the PRV prevents nuisance tripping of the shut off.
- Creeping lock up pressure due to dirt between the regulator seat and the seat pad, this is the first line of safety for downstream appliances
The type of PRV used in Clesse regulators in this catalogue are Limited Relief valves. These will show in the tables with Y or N in a PRV column if applicable to the regulator family group. This type of relief valve discharges a low flow (less than 10% of nominal regulator flow rate) and deals with excess pressures resulting from a) and b) above.
- The relief valves, will be either vented through small concealed holes in the regulator, or in some cases will have an external vent hole that can be connected to a pipe to be vented away from the regulator position.
- In the case of an external Vent hole for pipe connection, this will be denoted in the Tables in clock format with 0h having the vent positioned over the outlet of the regulator and 6h when located over inlet.
- There is an additional PRV style on certain regulators that will be able to be positioned in Multiple locations dependent on the installation, These are called Giro Vents and will be denoted in the tables if this has the function.
OPSO (Over Pressure Shut Off) Device
The OPSO safety device cuts off the gas flow in the event of abnormal overpressure that can be caused, for example, by an operating fault in a regulator (impurities on the valve seat or deterioration of a part) or by a defect in installation or liquid LPG entering the regulator. OPSO safety devices can be fitted to high or low pressure regulators.
They are the last line of defense to ensure gas pipework and appliances are not subjected to high pressures above and beyond manufacturer’s limits.
If an OPSO device continues to trip shut DO NOT continue to use and get a qualified gas installer to examine the gas installation to ascertain if any fault is causing the OPSO to activate.
The triggering pressure of OPSO safety devices can be adjustable or fixed , however they always come factory preset at an appropriate pressure. Low pressure OPSO must operate below 150mb and are normally set at 100mb.
Regulators fitted with these will show in the tables with a Y in an OPSO column if applicable.
OPSO’s currently are not mandatory for cylinder installation having no more than two cylinders under UK legislation however – Clesse recommends that when supplying fixed pipework installation wherever then an OPSO device be fitted.
UPSO (Under Pressure Shut Off) Device
The UPSO device, cuts off the gas flow in the event of an abnormal fall in pressure that can be caused, for example, by flow rate exceeding the capacity of the gas installation, (Cylinder size, Pipework sizing, Wrong regulator etc…), or the run out of gas and are normally associated with bulk tank supply.
This safety device applies on low pressure regulators, and if fitted will show in the tables with a Y in an UPSO column.
The UPSO triggering pressure is not adjustable (except on large capacity BP2402FC). Regulators provided with an adjustable outlet pressure will see the triggering pressure automatically adapted to the outlet pressure setting.
Where applicable, all installations, adjustments and maintenance work must be carried out by persons who have the necessary skills to do so and are qualified according to the regulations in force for that particular installation.
