BUCHI DuMaster D-480 - Manual (Page 243)

Operation Manual D-480 ©BÜCH Labortechnik AG
9 - Repairing the instrument 243
Leak test procedure
Process
The execution of the leak test takes place in several steps. The leak test always starts with testing of
the whole system (Whole leak test). If the program detects a leak during the whole leak test, it will
provide additional test stages. The purpose of these test stages is to test only a certain section of the
system in sequence. As long as no leak can be detected the next section will be added to the test.
However, after a leak has been detected, the location of the leak must be inside the section added
last. In the "Leak test" dialog the tubing diagram of the analyzer is displayed. The gas ways are
colored differently depending on the test stage carried out currently:
 No coloring: Whole leak test and/or gas ways not tested yet,
 Blue coloring: Gas way currently under test,
 Green coloring: Gas ways already tested.
By means of this coloring a detected leak can be localized easily: It must be in the blue colored
section.
A test stage is started by clicking the Start button. The "Leak test" dialog will open. Here, the test run
can be observed.
Each leak test stage takes place in the following phases::
 Pressure build-up
 Stabilization
 Test
Pressure build-up
During this stage, the valves are switched to positions allowing pressure build-up in a certain section
of the system.
Stabilization
During this stage, first the gas inlet valve is closed. The system waits for a set time to allow stable
pressure conditions in the subsequent test stage. If system pressure does not reach a defined
minimum pressure after this stage has ended, the leak test is regarded as having failed. If minimum
pressure is reached, the system moves on to the next stage.
Test
During this stage, first the system maintains the initial pressure of the instrument. During this stage of
the test, the system constantly compares current pressure with the initial pressure previously
measured and calculates the current drop in pressure. If the drop in pressure exceeds a certain
threshold during this stage of the test, the leak test is regarded as having failed. If the drop in
pressure stays below the threshold, the system moves on to the next stage.
Replacing fuses
The fuses
The following table lists the different fuses.
Fuse holder label Responsible for... Fuse specifications
F1 Furnace 1 25 A
F2 Furnace 2 10 A
F3 Furnace 3 10 A
F5 + F6 Power supply 10 A