9
MEDIUM PRESSURE GAS SUPPLY SYSTEM
(see BT 8058 - BT 8530/1 - BT 8531/1)
When a high delivery is required, the Gas Supply Company requires a unit with a pressure reducer and meter to
be installed, and provides a connection to the medium pressure gas supply (several bars).
This unit can either be supplied by the Gas Supply Company or the User according to Gas Supply Company
specifications.
The pressure reducer in this unit must be sized in order to be able to supply the maximum gas delivery required
by the burner, at the normal gas pressure.
Experience shows that it is best to use reducers of a good size to contain the considerable increase in pressure
when the burner stops at a high feed rate (the Standards require the gas valves to close within one second).
We recommend using a reducer that can provide almost double the maximum feed (m 3/h) required for the
burner.
Where a number of burners are used, each one must be fitted with its own pressure reducer. This will allow the
gas feed pressure to be maintained at a constant level, independently of whether one or more burners are working
at the same time, thus enabling accurate regulation of the gas feed, and therefore combustion, resulting in better
performance.
Gas piping must be adequately sized according to the quantity of gas to be supplied, therefore it is advisable to
keep the load loss within modest values (not more than 10% of the gas pressure at the burner). Remember that
the load loss is added to the existing pressure when the burner stops, hence the greater the load loss in the piping
the higher the pressure at the next ignition.
If the gas pressure reaches unacceptable levels when the burner stops (rapid closing of the gas valves), an
automatic relief valve must be installed between the reducer and the first burner valve, and also the relative
adequate pipe for discharge into the open air.
The pipe must end in a suitable place, protected from rain, and be fitted with a flame trap.
The pressure relief valve must be adjusted in order to completely discharge all excess pressure. For gas pipe
sizes, see drawing no. BT 8058.
A ball cock, gas filter, anti-vibration union, and flanged fitting must also be installed near the burner (see BT 8530/
1 and BT 8531/1).
