Boil-off test

The 'boil-off test' service function must be used to check the boil-off system at regular intervals.

Running the test

Precondition

The following requirements must be met for the boil-off test to be run by the CE module:

• Tank fill level at least 6000 g of hydrogen
  
• Engine runs without faults in the H2 mode
  

Running the test

After the test start, the following sequence is run:

• Check of test requirements.
  
• Start of the boil-off test in the CE module.
  
• Let the engine run at idle speed until a tank pressure of at least 5.5 bar has been reached. A check is run here as to whether the boil-off valve remains closed.
  Notes:
  The pressure build-up can take up to 15 minutes.
  The engine idling speed must not be increased beyond 2000 rpm.
  Once the required tank pressure has been reached, the engine can be switched off.
  
• Check as to whether the boil-off valve opens after 5 minutes at the latest.
  Note:
  Only this test can determine whether the boil-off valve opens too late.
  
• After opening the boil-off valve, a check is run as to whether the temperature of the boil-off oxidant reaches a temperature of at least 240 ^oC after 8 minutes at the latest.
  

Test result

If a fault occurs, fault information is displayed.

If the fault ”boil-off valve does not open” occurs, the crack-off pressure of the boil-off valve must be checked. If necessary, replace the boil-off valve.

Any other faults that occur lead to storage of a fault code memory entry in the fault code memory of the CE module. Troubleshooting continues with the following test modules:

• Test module 'Pressure sensor BOIL-OFF' (for faults in the area of the pressure control)
  
• Test module 'Temperature sensor BOIL-OFF' (for faults in the area of the temperature recording system)
  

The test modules are adopted automatically into the test plan if a corresponding fault is determined.

Test abort

If the test sequence is aborted due to a fault, the boil-off test activated in the CE module must be completed as follows:

• Switch off ignition and terminal R
  
• Place the CE module in the sleep mode
  

For this reason, the service function must be run to the end in all cases!

Shortened test sequence

If it is determined at the start of the service function that the boil-off system is already active, the oxidant temperature is monitored immediately.