The Proper Way to Fill an OPD Propane Tank

OPD stands for "overfill protection device," a type of valve required on 4- to 40-pound propane cylinders approved by the Department of Transportation to prevent accidental overfilling of the cylinder. As liquid propane fills the cylinder, an internal float attached to the cylinder valve slowly rises. If the propane exceeds the maximum capacity level in the cylinder, the float moves the valve, closing off the flow of propane into the tank. Think of the float valve mechanism in your toilet tank and you'll get the idea. The purpose of the OPD is to prevent accidental overfilling -- not to let the filling attendant know when to stop pumping propane. By law, all propane tanks should be filled according to their rated weight volume and are considered full before the OPD valve automatically closes. The design of OPD valves also prohibits filling or emptying the cylinder unless the proper connector and hose are attached to the valve.

Open end wrench

Instructions

- 1
  Inspect the cylinder for dents, bulges or cracks. Look for excessive rust or a missing cylinder foot ring, collar or valve cover. Verify that the stamping on the cylinder is readable and indicates when the cylinder was manufactured and its last recertification date.
- 2
  Make sure the cylinder is fitted with the required OPD valve.
- 3
  Check the water capacity and the tare weight figures stamped into the cylinder. Water capacity (indicated by "WC") is a figure that expresses how much water the cylinder holds in pounds. The tare weight ("TW") indicates the empty weight of the cylinder.
- 4
  Consult the chart at the propane filling station to convert the water capacity of the cylinder to the amount of propane the cylinder will hold. The cylinder will be filled on a scale. When the scale reading equals the capacity weight of the propane plus the tare weight of the tank, the tank is full.
- 5
  Place the cylinder on the filling scale. Screw the fitting on the end of the fill hose into the threaded inlet on the OPD valve and tighten.
- 6
  Open the valve on the OPD valve by rotating it counter-clockwise as far as it will go. Open the bleeder valve on the tank.
- 7
  Reset the scale to zero. Start the pump and begin pumping propane into the tank.
- 8
  Stop the pump when the total weight displayed on the scale equals the tank's specified propane capacity weight plus the tare weight of the tank or when propane begins to spew out of the bleeder valve, whichever comes first.
- 9
  Close the bleeder valve on the tank. Close the valve on the OPD valve by rotating it clockwise.
- 10
  Unscrew the fill hose from the OPD valve.

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