Localize leakage on fuel cell system

AR06.00-P-0005RFW

Localize leakage on fuel cell system

30.11.2018

Engine

780 in model 253.992/993

1

Fuel cell cover

2

Filler neck

3

Plug

Pfeil A

High-pressure test point

Pfeil A

High-pressure test point

Pfeil A

High-pressure test point

Pfeil B

Medium-pressure test point

Pfeil B

Medium-pressure test point

 Danger

Risk of suffocation due to inhalation of inert gases. Risk of injury when working on pressurized parts.

Wear safety glasses and protective gloves. Work in well-ventilated rooms only.

AS00.00-Z-0034-01RFW

 Danger

Risk of explosion caused by escaping hydrogen or overheating of the fuel tanks when working on the hydrogen system. Risk of frostbite to body parts caused by escaping gas and by touching component parts carrying gas when emptying fuel tanks. Risk of asphyxiation caused by inhalation of air diluted by hydrogen. Risk of burn injuries by coming into contact with an invisible pale blue hydrogen flame.

AS00.00-Z-0030-01B

Topical note

Notes on fuel cell system

AH00.00-P-0022-01RFW

Notes on safety-relevant components

AH00.00-Z-0019-01A

Identify the location of the leak on the fuel cell system with diagnostic support

1

Release pressure in fuel cell system with vehicle diagnosis system.

AR06.00-P-1001RFW

2

Ensure that the requirements for driving into the workshop are fulfilled.

Topical note

Requirements for driving into the workshop

AH00.00-P-0021-01RFW

3

Print out "tank system, fuel cell, form event log," fill out, and attach to the vehicle somewhere clearly visible.



OF00.00-P-3000-21RFW

4

Remove fuel cell cover (1).

5

Remove transmission tunnel underfloor paneling and underfloor paneling upstream of the rear axle.

AR61.30-P-1001RFW

6

Check the fuel tank for external damage.

7

Fill the high-pressure line system with 20 to 50 bar forming gas via the filler neck (2).



000 588 21 21 00 Leak tester

WS47.00-P-0045B

Pressurize fuel system

AR47.60-P-0017-01RFW



Connect STAR DIAGNOSIS and read out fault memory

AD00.00-P-2000-04B

 The manual valves of both fuel tank must have been sealed.

 Use commercially available forming gas bottle bundles.

8

Check specified value 20 to 50 bar with diagnostic system.



Connect STAR DIAGNOSIS and read out fault memory

AD00.00-P-2000-04B

9

Relieve pressure in filling nozzle and remove filling nozzle.

AR47.60-P-0017-01RFW

10

Perform a leak test at 20 to 50 bar on the high-pressure test points (arrows A).



000 588 03 21 00 Gas detector

WS47.00-P-0019B

 Use safety glasses and protective gloves.

 Specified value at all high-pressure test points (arrows A):  under 20 ppm with a measurement duration of 10 to 30 s.

If a leakage has been clearly localized,



release the pressure of the forming gas in the fuel cell system with a diagnostic device, and then perform repair work.


Depressurization of the forming gas does not have to take place in the open air.
The fuel line system does not contain any hydrogen.

 To do this, select the following menu item:
Fuel cell control unit (N116/2) 
Actuations 
depressurization of fuel high-pressure, system pressure, operating pressure

11

Fill the high-pressure line system with 700 bar forming gas via the filler neck (2).



000 588 21 21 00 Leak tester

WS47.00-P-0045B



Connect STAR DIAGNOSIS and read out fault memory

AD00.00-P-2000-04B

Pressurize fuel system

AR47.60-P-0017-01RFW

12

Relieve pressure in filling nozzle and remove filling nozzle.

Pressurize fuel system

AR47.60-P-0017-01RFW

13

Perform a leak test on the high-pressure test points (arrows A) at 700 bar.



000 588 03 21 00 Gas detector

WS47.00-P-0019B

 Use safety glasses and protective gloves.

 Specified value at all high-pressure test points (arrows A):  under 20 ppm with a measurement duration of 10 to 30 s.

If a leakage has been clearly localized,



release the pressure of the forming gas in the fuel cell system with a diagnostic device, and then perform repair work.


Depressurization of the forming gas does not have to take place in the open air.
The fuel line system does not contain any hydrogen.

 To do this, select the following menu item:
Fuel cell control unit (N116/2) 
Actuations 
depressurization of fuel high-pressure, system pressure, operating pressure

14

Fill the medium pressure line system with 9 to 14 bar forming gas via the diagnostic system.



AD00.00-P-2000-04B

 The forming gas in the high-pressure line system is sufficient for filling.

 To do this, select the following menu item:
Fuel cell control unit (N116/2) 
Actuations 
Leak test of the system pressure

15

Perform a leak test at the medium pressure test points (arrows B, C) as well as all components in the medium pressure line system.



000 588 03 21 00 Gas detector

WS47.00-P-0019B

 Use safety glasses and protective gloves.

 Specified value at all medium pressure test points (arrows B, C):  under 20 ppm with a measurement duration of 10 to 30 s.

If a leakage has been clearly localized,



release the pressure of the forming gas in the fuel cell system with a diagnostic device, and then perform repair work.


Depressurization of the forming gas does not have to take place in the open air.
The fuel line system does not contain any hydrogen.

 To do this, select the following menu item:
Fuel cell control unit (N116/2) 
Actuations 
depressurization of fuel high-pressure, system pressure, operating pressure

16

Perform a fuel cell leak test.

If no leaks were detected in the previous test steps.

AR06.00-P-0004RFW

Identify the location of the leak on the fuel cell system without diagnostic support

17

Only perform the following operation steps if diagnosis-based localization of the leak cannot be performed.

18

Print out the "Manual depressurization event log" form and fill it out during the procedure.



Manual depressurization event log, form

OF00.00-P-3000-22RFW

19

Manually release the pressure in the fuel cell system.

AR06.00-P-1000RFW

20

Ensure that the requirements for driving into the workshop are fulfilled.

Topical note

Requirements for driving into the workshop

AH00.00-P-0021-01RFW

21

Print out the "Protokoll Tanksystem, Formular" (tank system event log form), fill it out, and attach to the vehicle in a place where it is easily visible.



OF00.00-P-3000-21RFW

22

Remove fuel cell cover (1).

23

Remove transmission tunnel underfloor paneling and underfloor paneling upstream of the rear axle.

AR61.30-P-1001RFW

24

Check the fuel tank for external damage.

25

Fill the high-pressure line system with 20 to 50 bar forming gas via the filler neck (2).



000 588 21 21 00 Leak tester

WS47.00-P-0045B

Pressurize fuel system

AR47.60-P-0017-01RFW

 The manual valves of both fuel tank must have been sealed.

 Use commercially available forming gas bottle bundles.

26

Relieve pressure in filling nozzle and remove filling nozzle.

AR47.60-P-0017-01RFW

27

Perform a leak test at 20 to 50 bar on the high-pressure test points (arrows A).



000 588 03 21 00 Gas detector

WS47.00-P-0019B

 Use safety glasses and protective gloves.

 Specified value at all high-pressure test points (arrows A):  under 20 ppm with a measurement duration of 10 to 30 s.

If a leakage has been clearly localized,



Manually release the pressure in the fuel cell system, then perform repair work.

Manually release pressure in fuel cell system

AR06.00-P-1000RFW


Depressurization of the forming gas does not have to take place in the open air.
The fuel line system does not contain any hydrogen.

28

Fill the high-pressure line system with 700 bar forming gas via the filler neck (2).



000 588 21 21 00 Leak tester

WS47.00-P-0045B

Pressurize fuel system

AR47.60-P-0017-01RFW

29

Relieve pressure in filling nozzle and remove filling nozzle.

AR47.60-P-0017-01RFW

30

Perform a leak test on the high-pressure test points (arrows A) at 700 bar.



000 588 03 21 00 Gas detector

WS47.00-P-0019B

 Use safety glasses and protective gloves.

 Specified value at all high-pressure test points (arrows A):  under 20 ppm with a measurement duration of 10 to 30 s.

If a leakage has been clearly localized,



Manually release the pressure in the fuel cell system, then perform repair work.

Manually release pressure in fuel cell system

AR06.00-P-1000RFW


Depressurization of the forming gas does not have to take place in the open air.
The fuel line system does not contain any hydrogen.

31

Unscrew the stop plug (3).

 Ensure scrupulous cleanliness. No chippings, friction or dirt must enter the fuel cell aggregate.
Store the stop plug (3) in a clean, safe location.

32

Screw in the connection piece on the freed thread.

 Connector

*253589009100

33

Screw the adapter onto the connection piece.



253 588 01 21 00 Adapter

WS47.00-P-0043B

34

Connect the filling hose of the leak test device to the adapter and fill the medium pressure line system with 9 to 14 bar forming gas.



253 588 01 21 00 Adapter

WS47.00-P-0043B



000 588 19 21 00 Leak tester

WS83.00-P-0035B

 The high-pressure line system must not be depressurized, a counterpressure of  20 bar is required.

 Te filling hose of the leak test device remains connected during the following leak test.
Do not subject the filling hose to tension.

35

Perform a leak test at the medium pressure test points (arrows B) as well as all components in the medium pressure line system.



000 588 03 21 00 Gas detector

WS47.00-P-0019B

 Use safety glasses and protective gloves.

 Specified value at all medium pressure test points (arrows B):  under 20 ppm with a measurement duration of 10 to 30 s.

36

Release the pressure in the medium pressure line system via the leak test device.



000 588 19 21 00 Leak tester

WS83.00-P-0035B

37

Remove the filling hose of the leak test device from the adapter.



253 588 01 21 00 Adapter

WS47.00-P-0043B



000 588 19 21 00 Leak tester

WS83.00-P-0035B

38

Unscrew the adapter from the connection piece.



253 588 01 21 00 Adapter

WS47.00-P-0043B

 Connector

*253589009100

39

Unscrew the connection piece.

 Connector

*253589009100

40

Manually release the pressure in the fuel cell system.

AR06.00-P-1000RFW


Depressurization of the forming gas does not have to take place in the open air.
The fuel line system does not contain any hydrogen.

41

If no leaks were detected in the previous test steps, inform the relevant market support people.