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000608006_2007/06
DIAGRAM FOR CALCULATING THE DIAMETER OF THE
PIPES IN RELATION TO THEIR LENGTH AND GAS FLOW
N° BT
8058
DIAMETER OF PIPES IN INCHES
PRESSURE DROP
IN mm OF H
2
O
LENGTH OF PIPES IN METERS
FLOW
IN
m
c
/h OF METHANE p.a. 0,60
ENGLISH
GAS FEED SYSTEM AT AVERAGE PRESSURE
(see BT 8058 - BT 8530/ - BT 853/)
When high delivery is required, the Gas Distributing Company requests the installation of a unit comprising a
pressure reducer and a meter, and then connects it to the gas pipe network at average pressure (a few bars).
This unit can be supplied by the Gas Distributing Company or by the user, but should be according to the Gas
Company’s precise instructions. The unit’s pressure reducer should be large enough to supply the maximum gas
delivery required by the burner at the rate of pressure normally estimated for it.
From experience, we would recommend utilizing a large-scale reducer in order to attenuate the notable increase
in pressure which occurs when the burner comes to a standstill, with a high delivery. (Regulations require that
the gas valves close in less than one second).
As an indication, we would advise using a reducer capable of producing a delivery (m
3
/h) about double that of
the maximum amount estimated for the burner. If
several burners are to be used, each one should
have its own pressure reducer; this will enable the
gas feed pressure to the burner to be maintained at
a constant level even if only one burner is operating
at the time.
Consequently, it is possible to accurately regulate
the delivery and therefore the combustion, and thus
improve yield. The dimension of the gas pipeline
should be in function with the quantity of gas it has
to deliver. We advise maintaining the load loss at a
low level (not more than 10 % of the gas pressure
value at the burner); it should be kept in mind that
the load loss is added to the pressure existing when
the burner stops and therefore a subsequent start up
will occur at a pressure that rises in accordance with
an increase in the pipe’s load loss. Should the gas
pressure reach unacceptable values when the burner
stops (rapid closure of the gas valves), it is necessary
to install between the reducer and the first valve of
the burner an automatic overflow valve and relative
conveying pipe, of suitable section, in the open air.
The end of the conveying pipe in the open air should
terminate in a suitable place, be protected from rain
and have a flame trap.
The overflow valve should be regulated in such a way
as to completely unload excessive pressure.
See diagram n° BT 8058 for gas pipeline dimensions.
Near to the burner should also be fitted a cut-off ball
cock, a gas filter, an anti-vibration joint and a flanged
fitting (see BT 8530/1 and BT 8531/1).
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