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Roll-Over Valves and Misc


FTA fuel tank atmospheric vents are designed for class 7 & 8 diesel trucks. Some of our vents are also used on fuel tanks for Marine, Agricultural, Off-Road, Generator and some gasoline engine applications.  All of the our atmospheric vents move air and vapor from inside the tank to the outside and also move air from outside the tank to inside.  When the fuel inside the tank heats up it expands; tanks heat up from the sun and from hot aerated fuel returning to the tank from the engine.  Our vent releases, to atmosphere, the air that is displaced when the fuel expands and prevents pressure build up inside the tank. When fuel cools inside the tank it shrinks in volume and our vent prevents a vacuum occurring inside the tank. Our vent also helps remove the air when the tank is filled with fuel.
 
The Code of Federal Regulations CFR 393.67 states that vehicles traveling on United States highways must be equipped with a non-spill air vent.  All FTA vents contain a float to seat and seal in the vent body when the vent is inverted from the vertical position.  In the inverted position, the steel ball presses the float against the seat in the body. This prevents fuel from leaking in the event of a truck rollover.  The float also seals and stops fuel sloshes from exiting the tank.
 
FTA “Full Function” vents perform a safety function in accordance with the Code of Federal Regulations CFR 393.67. Our “Full Function” vents provide a safety venting system to prevent the rupturing of the fuel tank in the event the fuel tank is subjected to a fire. The lead which retains the cap in our “Full Function” vent melts when it is heated to its melting temperature. When the lead melts, the pressure inside the tank and the spring inside the vent remove the cap from the vent and relieves the internal pressure.
 
FTA “Full Function” vents also provide a pressure relief function. 1) Diesel truck engines pump hot aerated fuel back into the fuel tank. Excess fuel is used inside the engine to cool injectors and is then pumped back into the fuel tank to cool. Some engines return enough hot aerated fuel to pressurize tank and keep the float corked. 2) When the fuel tank is near full, the sloshing of fuel pushes the vent float up against the seat and corks off the vent. These two actions cause internal build up of pressure. Our pressure relief function prevents buildup of internal tank pressure after the vent is corked. Excessive internal tank pressure could cause engine malfunction and tank rupture. Our “Full Function” vents prevent this. (Full Function vents are not applicable for gasoline fuel tank applications)


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