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@IST01530EEJ 01 917 5A0 19 041 1
P
:
Actual pressure measured by the instrument, in the selected measurement unit.
∆P
1
'
:
Pressure variation in the last minute, updated every 10 seconds. This value gives a rough indication
about the stabilization level reached in the piping system.
Wait time
: Remaining time before the stabilization phase ends.
Once the stabilization phase is terminated the tightness test is started. This test is performed by observing how
the pressure decays in time during a fixed 15 minutes interval, as stated in the applied standard.
During the tightness test phase the following values are displayed:
P
1
:
Pressure measured at the beginning of the test.
P
2
:
Pressure actually measured by the instrument.
∆P
:
Pressure variation with respect to the initial value. In case the actual pressure is lower than the
initial value (pressure is decreasing) this value has a negative sign.
Result
:
Reports the test result:
tight
when the pressure drop is greater than -10 Pa,
leak
when the pressure
drop is smaller than -10 Pa. Positive pressure changes are symptom of a temperature change
meanwhile the test is performed. Should this happen it is advisable to repeat the entire test.
Existing piping:
The standard UNI 11137-1 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. 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:
City gas:
Reference pressure for test with supply gas
1000 Pa
Test pressure with air
5000 Pa
Natural gas: 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
Standard to be defined
Somebody proposes 5000 Pa
Test pressure with air
Standard to be defined
Somebody proposes 5000 Pa
Note:
4400 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.
4400 allows the operator to customize the stabilization phase through the following parameter in the
stabilization menu:
WAI T TIME:
the stabilization phase duration can be set in the 1 .. 99 minutes range. As the UNI 11137-1
standard does not prescribe any stabilization duration, the factory setting for this value is borrowed from the UNI
7129 standard, which requires a minimum stabilization time of 15 minutes. The waiting can be interrupted any
time by pressing the ' ' key, even in case the interval has not fully elapsed.
The tightness test performed according to the UNI 11137-1 standard requires the input of some data regarding
the piping system and the test conditions, as described in the following.
PIPING VOLUME:
An accurate tighness test performed according to the UNI 11137-1 standard requires to
know the piping volume. Because this data if often unavailable, 4400 splits the test from the beginning into two
different paths: the first is adequate for pipings having volume smaller than 25 dm
3
(liters); this is the most usual
situation: in this case the volume value is not required because, through an 'overestimation' the piping is
assumed as having a volume of 25 dm
3
. The second path requires to input the piping value either directly
through the keyboard when known, or by a calculation which takes into account the sum of the contributions
due to each single pipe section or, finally, by measuring it through a simple procedure which requires the
injection into the piping of a known gas quantity through a graduated syringe.
In case the volume calculation is used, for each single piping section the ‘Add tube’ option must be selected and
then input the relevant material, nominal diameter and length. 4400 calculates the single section volume and
adds it, when confirmed, to the total piping value. For error correction or for modifying the ongoing calculation
the subtraction operation is also available.
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Summary of Contents for 4400
Page 1: ...4400 4400 Portable Combustion Gas Analyzers ...
Page 2: ......
