This Can Rules

There is a special five-gallon can known as a hand-held test-measure that plays an important role in the dispensing of gasoline at service stations. It is the policeman of the pumps. As any motorist in the U.S. knows, the pump computes the gasoline being served in a whirling display of U.S. gallons and tenths and likewise the cost in dollars and cents. But what if the measure is incorrect beyond a slight tolerance? To guarantee the proper measure official checks of the pumps are conducted from time to time by inspectors of Weights and Measures to determine the meters' accuracy.

The inspectors draw off exactly five gallons of gasoline (by the pump's meter) into the official can (test measure) which has a display gauge assembly mounted on the neck (see drawing and photographs). The level of the gasoline served (5 gals.) should correspond exactly to the zero mark on the gauge if the pump's meter is reading correctly.

The gasoline quantity and meter accuracy is checked by inspectors at every discharge point from the refinery to the station's pump. In this process a large device capable of measuring 1500 gallons is towed to the load rack of the refinery and the test carried out. Tests are also made of the accuracy of the metering by the tank trucks which deliver grades of gasoline to the stations.

In Pennsylvania, the office of Weights and Measures is under the PA Department of Agriculture. Nationally, the handbooks and other directives and codes are put out by the National Conference of Weights and Measures which is sponsored by the National Institute of Standards and Technology (NIST), all of which belong to the United States Department of Commerce.

Bradley Lundberg (left), Weights and Measures Inspector and the author, Samuel Pees, discuss gasoline test measuring details at a Kwik Fill station near Meadville, PA. Test measures at lower left.

Two 5-gallon hand-held test-measures used to check accuracy of gasoline pumps' meters at a servcie station.

Detail of gauge assembly on a 5-gallon hand-held test-measure. This stainless steel can (test measure) was made by Seraphin Test Measures Co., Rancocas, N.J.

Diagram of a 5-gallon hand-held test-measure showing components. From Handbook 105-3, National Institute of Standards and Technology, 1997.