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Details of the test:
The standard UNI 11137: 2012 can be adopted for testing already existing internal piping systems. This test
requires to charge the piping up to the test pressure, then wait for an unspecified stabilization time until the
thermal effects caused by the test gas compression are nulled, and then calculate the amount of the possible
leakage from the measure of the pressure decays in 1 minute time for Methane and LPG in air and 2.5 minutes
for the LPG fuel.
The test pressure should be as close as possible as the reference conditions following explained.
REFERENCE CONDITIONS: According to the combustible gas to be used in the piping, the tightness test must
be performed in one of the following reference conditions:
Methane: Reference pressure for test with supply gas 2200 Pa
Test pressure with air 5000 Pa
L.P.G.: Reference pressure for test with supply gas 3000 Pa.
Test pressure with air 5000 Pa.
Note: CHEMIST 600 allows the user to perform the tightness test even with a combustible gas different
from the supply gas. Anyway the reference standard does not provide a reference pressure in this
situation, so the reference pressure is taken like test gas is the same. Test result should be considered
only indicative.
CHEMIST 600 allows the user to customise the stabilization phase:
STABILIZATION: the stabilization phase duration can be set in the 1 .. 99 minutes range. As the UNI 11137:
2012 standard does not prescribe any stabilization duration, the factory setting for this value is borrowed from the
UNI 7129-1: 2015 standard, which requires a minimum stabilization time of 15 minutes.
The waiting time can however be interrupted by activating the context key ' ' even if the interval is not
over.
The tightness test performed according to the UNI 11137: 2012 standard requires the input of some data
regarding the piping system and the test conditions, as described in the following.
COMBUSTIBLE GAS: consider that the amount of the leakage is strictly related to the nature of the gas under
pressure. When the tightness of a piping has to be evaluated it is mandatory to specify the family to which the
gas belongs: Methane or L.P.G.
TEST GAS: again the amount of the leakage is related to the nature of the gas under pressure, therefore it is
mandatory to specify the type of the gas used: Natural Gas, L.P.G. or air. Please note that the gas used for the test
could also be different from the gas to be used in the plant and could even be a not flammable gas.
TYPE OF TEST: An accurate tightness test performed according to the UNI 11137: 2012 standard requires to
know the piping volume.
Because this data if often unavailable, CHEMIST 600 splits the test from the beginning into two different paths:
Preliminary: valid for systems with a volume under 18 dm
3
(litres), the most frequent, where it is not required to
enter the value of the volume since it is assumed that the system has a volume of 18 dm
3
.
Complete: in this case it is necessary to set the volume of the system by entering the numeric value if known, or
by calculating the amount as the sum of the contributions of the different sections of piping or, even, by
assessing the measurement with a simple procedure that requires the injection into the system of a known
amount of gas using a syringe.
If you use volume calculation, for each section of piping it is necessary to set the material, the nominal diameter
and the length of the same. CHEMIST 600 calculates the volume of the section ("partial volume") and it adds it
up, activating the context key ' ' (sum piping), to the calculation of the volume of the system. To correct any
errors of to modify the current calculation, the subtraction operation is also allowed by activating the context key
' ' (subtract piping).
When the 'Volume measurement' option is selected instead, the procedure, described also in the flow charts of
the tightness test according to UNI 11137: 2012, is described in the following steps:
Close both valves of the piping kit supplied for the test.
Connect the syringe to the kit opposite to the pump.
Press the key relative to the context key ' '.
Open the valve on the side where the syringe is connected, take exactly 100 ml (100 cc) of the gas present in
the system.
Wait for the stabilization of the pressure of the system. After a few seconds, the device displays the measured
OK
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