CONTINENTAL EDISON BCT-0538A Guide D'utilisation page 10

(Important: Before replacing the sealants or piercing the cooler kit,
you must always follow the instructions marked on the keg to
eliminate the excess gas and ensure that the keg has rested long
enough to avoid foam coming out through the cooler piercing pin or
tap faucet. And it is no need to release the gas and replace the seal
rubber if you use Heineken keg, because Heineken keg has its own CO2
pressure inside, no need to provide the CO2 from outside CO2 pressure
system.
Figure 2
Figure 3
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