Check valves, also known as vents, are one of the most important safety and performance features on the fuel cell, allowing air in and out of the fuel cell while keeping fuel contained within the bladder in the event of a rollover. Similar to discriminator valves, check valves use a stainless steel or chrome steel ball to allow air in/out of the tank but blocks fuel when the vehicle turns upside down.
Check valves come in a variety of sizes and styles according to the intended filing application; the larger the vent the faster the bladder will fill. Standard check valves are made from aircraft grade aluminum (either 5052, 6061-T6, 6063-T6) and are either welded or bolted to the fill plate directly. "Inline" or external check valves are not suitable for use with fuel cells unless accompanied by another check valve located in the plate.
Bulkhead Style Check Valves
Machined from standard JIC aircraft fittings these vents come in sizes from AN-04 to AN-16. The bulkhead JIC platform allows any JIC style fitting to be attached for routing of the vent line around and out the vehicle.
Billet Check Valves
Machined from solid or thick-wall tube aluminum these check valves are generally larger than bulkhead style ones, ranging in size from .625" to 2.25" diameter. Usually used in conjunction with large fills and dry break systems these use chrome steel balls and are machined for maximum flow out of the tank.
Similar to a check valve or vent, discriminator valves prevent fuel from traveling up the vent line during filling when the tank is full. Utilizing an anti spill mechanism that shuts off air flow when fuel enters the chamber. The valve also operates independently and will close/shut off if overturned regardless if there is fuel in the chamber. Because of it's ability to prevent fuel from traveling up the vent line and out the vehicle they have become popular on vehicles utilizing dry break fill systems and pressurized fill systems.
NOTE: Because it is located outside the tank it does not replace the need of a traditional check valve.