High-pressure, direct-injection fuel rails have a maximum allowable leak rate spec of 10-4 atmospheric cubic centimeters per second (atm-cc/sec). Leak testing fuel rails with helium, often with the fuel injectors installed, in a vacuum chamber is a common process.
A fuel rail is essentially a tube that delivers gasoline to individual fuel injectors in an internal combustion engine. Formerly, vehicle manufacturers designed fuel rails to withstand pressures of only 30 to 60 psig, a minimum requirement for port injection. Nowadays, to meet more stringent standards for fuel economy, emissions, and efficiency, fuel rails have been redesigned to withstand much higher pressures—up to 5,000 psig and beyond.
Greater test pressures mean greater helium usage, warranting the need for a helium recovery system. In order to avert additional helium costs associated with the higher test pressures, many companies have installed a VIC helium recovery system that would reclaim up to 98% of the helium used. Even with the cost of the recovery system and the installation to retrofit a customer’s machines, the cost of the new system can be recouped in a little over a six-month period.