Siemens VALVEGYR LDU11.523A27 - Leakage Rate Calculation; Leakage Rate Formula and Example

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Building Technologies Division CC1N7696en
20.04.2016
Calculation of the leakage rate escaping from a length of pipe
Q
Leck
=
(P
G
- P
W
) x V x 3600
P
atm
x t
Test
Q
leck in dm³/h Permissible leakage rate in dm³ per hour or liters per hour
P
G in mbar Overpressure in pipe section between the valves to be tested, at
the beginning of the test phase
P
W in mbar Overpressure set on pressure switch «DW» (normally set to 50
% of the gas mains pressure)
P
atm in mbar Absolute pressure (1.013 mbar normal pressure)
V in dm³ Volume of test space confined by the valves to be tested, includ-
ing the space in the valves themselves
T
test in s Duration of proving time
P
G = 30 mbar
QLeck =
(30 - 15) x 10.36 x 3600
1013 x 27.5
= 20 l/h
P
W = 15 mbar
P
atm
V
= 1013 mbar
= 10.36 dm³
Any valve leakage rate exceeding 20 l/h causes the LDU11...
to initiate lockout
t
Test = 27.5 s

Note!
Select volume of pipe section (V) between the gas valves to be checked and over-
pressure (PW) set on pressure switch (DW) such that the maximum permissible gas
leakage rate (QLeck) will not exceed the rate specified in the local regulations.
Legend
Example