LEAK TESTING OF COMPONENTS

Fuel Cell Bipolar Plates
DESCRIPTION OF TECHNICAL CHALLENGE
Fuel cell stacks consist of two endplates and several bipolar plates separated
by membrane electrode assemblies (MEAs). Essentially the bipolar plates are
the electrically-conducting plates which join together the anode of one cell tothe cathode of another. Bipolar plates contain two cavities and one internalloop:

Two cavities for the fuel cell process gases – hydrogen and air /oxygenone internal loop for cooling liquid to maintain an optimum processtemperature of the stackBoth cavities and the internal loop need to be tested for leakage. Thehydrogen path must not leak hydrogen to the outside as hydrogen gas isflammable. The cooling path must not leak cooling liquid to the outside not tocause any electric shortage but also not to lose cooling capacity. Last but notleast hydrogen must not leak into the cooling channel as this would cause
corrosion of material and also can create problems with the pump in thecooling channel due to gas bubbles in the liquid.
Different leak rate requirements apply for the different scenarios:

Fuel stack are assembled from MEAs, bipolar

plates and two end plates. The hydrogen path
The leakage of hydrogen to the outside as well as into the cooling channel
is only created after two bipolar plates and an-4-6
should typically be limited to leak rates in the range of 10 ... 10 mbar l/s toMEA have been joined.
limit the amount of hydrogen being released. The leakage of cooling liquidfrom the cooling channel should be limited to leak rates in the range of 10-4 ..
10-5 mbar l/s as leaks of this size will block with the cooling liquid and not allow
any further cooling liquid to leak out.

THE INFICON SOLUTION
Testing for leakage of cooling liquid
To test the coolant loop of a bipolar plate, the coolant loop is evacuated from
air and backfilled with helium before the coolant loop is sealed off. The bipolar
plate is then placed in a vacuum chamber. After the vacuum chamber has
been evacuated, an LDS3000 leak detector is connected to the vacuum
chamber and any helium leaking from the coolant loop is detected. After thechamber has been vented, helium may be reclaimed from the cooling loop.
Fuel cell bipolar plates are typically tested
in a vacuum chamber leak test due to low
leak rate requirements and need for highthroughput.

LEAK TESTING OF COMPONENTS
FUEL CELL BIPOLAR PLATESTesting for hydrogen leakage to the outside
Before testing for hydrogen leakage to the outside, the hydrogen cavity needs tobe closed and sealed off. The resulting volume is then evacuated and backfilledwith helium before the inlet port is closed and the bipolar plate is placed in avacuum chamber. The vacuum chamber is evacuated and an LDS3000 leakdetector is connected to the chamber. Any Helium leaking from the hydrogencavity is detected by the leak detector. If a leak was detected, in a second test it
can be determined if the leak is to the outside or into the cooling channel.
If no helium is detected, no relevant leaks from the hydrogen cavity to the outside
nor into the cooling channel exist. The chamber is then vented and the helium
may be reclaimed from the hydrogen cavity.

Testing for hydrogen leakage into the cooling channel
With the hydrogen cavity still charged with helium and sealed off, now the coolingchannel is connected to a vacuum pump and evacuated to vacuum pressure. TheLDS3000 leak detector is now connected to the cooling channel and any heliumleaking from the hydrogen cavity into the cooling loop is detected by the leakdetector. The cooling loop is vented after the test and helium may be reclaimed
from the hydrogen cavity.
If no leak is detected, the leak found in the previous test is a hydrogen leak to theoutside.

BENEFITS OF LEAK TESTING WITH TRACER GAS

High reliability of leak detection
Repeatable and reproducible processResults traceable to national standards
No influence of temperature or humidity
Identification of leak source

For more information, please visit us atwww.inficonautomotive.com
or call your nearest sales representative.

www.inficon.com

reachus@inficon.com

Due to our continuing program of product improvements, specifications are subject to change without notice.
mias00en-01 (2006)©2020 INFICON