Checking Air-Tightness - Bosch ETT 008.31 Repair Instructions

8.2.2 Checking the pressure switches
- Switch off the device.
- Connect the calibration-gas inlet and the outlet for gas and
condensation and connect to a siphon as illustrated.
Keep hoses short.
- Connect a multimeter (continuity test) to pressure switch
pins 3 and 1 (pin 2 is not internally connected!)
- Carefully introduce pressure P (blow into the hose).
Check:
That both pressure switches audibly switch at 100 + 15 mm water gauge. The multimeter indicates continuity.
- Carefully let out pressure P.
Check:
That both pressure switches drop out audibly at 70 + 15 mm w.g. The multimeter indicates open contact.
Pressure switch off
If a pressure switch is faulty, replace it.

8.2.3 Checking air-tightness

Hoses are arranged as for the previous test. Build up system pressure to 1000 mm water gauge and seal off with a hose clamp. Allow
a stabilizing time of 1 minute, then observe for pressure loss for 1 minute. The system is sufficiently air-tight if the pressure loss is maximum
20 mm water gauge per minute.
In the event of a negative result, isolate different components from the test one after the other by sealing off the hoses leading to them,
until you have found the leaky component.
First of all, seal off the hose leading to the inlet for calibration gas EKG. This seal remains in place throughout the remainder of the test.
As regards the additional hoses listed below, seal them off one by one and open them again once the rest of the system has been tested!
Disconnecting
1)
Hose no. 18
Hose no. 17
Hose no. 16 1)
Hoses no. 24 + 19
Hoses no. 24 + 21
Hoses no. 20 +21
Hoses no. 20 +19
1) The pumps are tight in the reverse direction. Any minor leakage losses which occur nevertheless would not, on their own, constitute
a criterion for replacement. Leakage has an adverse influence on the delivery rate, however. See Section 8.2.4.
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Selects
Pressure switches, pump, etc.
Pressure switches, non-return valve, etc.
Pump
Connection for O measuring sensor
2
Analyzer part, if leakage is present here, this part may be further subdivided.
Upper safety tank, etc.
Lower safety tank, etc.
Pressure switch on
P (mm w.g.)