LPG Fuel Tank Components (1) Fuel Gauge (2) 80% Stop Bleeder (3) Pressure Relief Valve (4) Service Valve (Tank end male coupling) (5) Filler Valve (6) Alignment Pin (7) Vapor Withdrawal Tube (Only used with Vapor Withdrawal) (8) 80% Limiter Tube (9) Liquid Withdrawal Tube (10) Foot Ring (11) Fuel Level Float (12) Collar Fuel Gauge In figure 5 a visual fuel gauge is used to show the fuel level in the tank. A mechanical float mechanism detects the liquid propane level. A magnet on the end of the float shaft moves a magnetic pointer in the fuel gauge. Some units have an electronic sending unit using a variable resistor, installed in place of a gauge for remote monitoring of the fuel level.
The gauge may be changed with fuel in the tank. DO NOT REMOVE THE FOUR LARGE FLANGE BOLTS THAT RETAIN THE FLOAT ASSEMBLY, WITH FUEL IN THE TANK! WARNING It is not a legal practice to fill the tank through the liquid contents gauge. In some applications a fixed tube fuel indicator is used in place of a float mechanism. A fixed tube indicator does not use a gauge and only indicates when the LPG tank is 80% full. The fixed tube indicator is simply a normally closed valve that is opened during refueling by the fueling attendant. When opened during refueling and the tanks LPG level is below 80%, a small amount of vapor will exit the valve.
When the LPG tank level reaches 80% liquid propane will begin exiting the valve in the form of a white mist (Always wear the appropriate protective apparel when refueling LPG cylinders). In order for this type of gauge to be accurate, the tank must be positioned properly. When full (80% LPG) the valve is closed by turning the knurled knob clockwise. Typically a warning label surrounds the fixed tube gauge which reads STOP FILLING WHEN LIQUID APPEARS. Service Valve The service valve is a manually operated valve using a small hand wheel to open and close the fuel supply to the service line (fuel supply line).
The service valve installs directly into the tank and has two main categories, liquid and vapor service valves. Liquid service valves used on portable LPG tanks use a 3/8” (3/8” NPT) male pipe thread on the service valve outlet for attachment of a quick disconnect coupler. An excess flow valve is built into the inlet side of the service valve as a safety device in case of an accidental opening of the service line or damage to the service valve itself. The excess flow valve shuts off the flow of liquid propane if the flow rate of the liquid propane exceeds the maximum flow rate specified by the manufacturer. CAUTION When the tank is in use the service valve should be completely open.
If the valve is partly open, the vehicle may not be getting enough fuel to operate efficiently. In addition to possibly starving the engine for fuel, a partly open valve may restrict the flow enough to prevent the excess flow valve from closing in the event of a ruptured fuel line. Most liquid service valves have an internal hydrostatic relief valve and are usually labeled “LIQUID WITH INTERNAL RELIEF”. The hydrostatic relief valve protects the fuel service line between the tank and the lock off from over pressurization. The internal hydrostatic relief valve has a minimum opening pressure of 375 PSIG and a maximum pressure of 500 PSIG.
These type of relief valves have an advantage over external relief valves because the propane is returned to the tank in the event of an over pressurization instead of venting the propane to atmosphere. 2 3 7 8 9 1 5 6 12 11 10 4 Figure 5 Outlet Excess Flow Valve Figure 6 G420E/G424E Tier LP Engine LPG and LPG Fuel Tanks 10