Buchi DuMaster D-480 User Manual download pdf (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

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Buchi DuMaster D-480 User Manual Page 243

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