baltur COMIST 72 DSPGM, Instruction

Page: 14 / 70

14
GAS FEED SYSTEM AT AVERAGE PRESSURE a few bars (see BT 8058-BT 8530/1-8531/1)
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 utilising
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 at 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 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 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).
DIAGRAM FOR CALCULATING THE DIAMETER OF THE
PIPES IN RELATION TO THEIR LENGTH AND GAS FLOW
N° BT 8058
DIAMETER OF PIPES IN INCHES
LENGTH OF PIPES IN METERS
PRESSURE DROP IN mm OF H
2
O
FLOW IN m
c
/h OF METHANE p.a. 0,60