FACTORY SETTINGS
Each transmitter is normally set at Heatec to display fuel level in feet (Figure 3). This setting cannot be changed in the field by plant personnel.
However, the specific gravity of fuel can be changed in the field by plant personnel.
Heatec normally sets the transmitter for a specific gravity of 0.880 before the tank is shipped. This is the specific gravity of waste oil. Other fuel oils have somewhat different specific gravities.
If the specific gravity of actual fuel in your tank is higher than 0.88 the transmitter will indicate a fuel level that is higher than it really is. But if the specific gravity of actual fuel in your tank is lower than 0.88 the transmitter will indicate a fuel level that is lower than it really is. Incorrect indications can either lead to overflowing the tank when it is being filled or unintentionally running out of fuel.
Specific gravity is the weight of fuel compared to an equal volume of water at the same temperature. Pure water weighs 8.333 pounds per gallon and has a specific gravity of 1.000. Thus, the specific gravity of fuel equals the weight of fuel divided by the weight of water.
DETERMINING SPECIFIC GRAVITY
If you don’t know the specific gravity of the fuel you use, ask your supplier. If the supplier doesn’t know, its easy to make your own determination. Here’s how:
Fill a container with fuel oil and weigh it. Then fill the same container with water and weigh it. (Both fuel and oil should be at approximately the same temperature.) Weigh the container empty and subtract its weight from each of the other two weights. Now, divide the weight of the fuel by the weight of the water. The result is the specific gravity of your fuel. For better accuracy, use a fairly large container, such as an empty 55-gallon drum.
Example: Suppose that 55 gallons of your fuel weighs 442.3 pounds, whereas 55 gallons of water weighs 458.3 pounds. 442.3 divided by 458.3 equals 0.965, which is the specific gravity of the fuel in this example. (This is the specific gravity of No. 6 fuel oil.)
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Figure 4. Specific Gravities Of Fuels
and Transmitter Settings
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Commercial fuels
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Specific Gravity
at
60 degrees F
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Transmitter
Full Scale Blind
Settings
(Mode 6)
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0.970
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450.1
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No. 6 oil
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0.965
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447.8
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0.960
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445.4
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0.955
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443.1
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0.950
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440.8
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No. 5 oil
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0.945
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438.5
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0.940
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436.2
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0.935
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433.8
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0.930
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431.5
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0.925
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429.2
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0.920
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426.9
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0.915
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424.6
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0.910
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422.2
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0.905
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419.9
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No. 4 oil
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0.900
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417.6
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0.895
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415.3
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0.890
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413.0
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0.885
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410.6
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Waste oil
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0.880
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408.3
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0.875
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406.0
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0.870
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403.7
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0.865
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401.4
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0.860
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399.0
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0.855
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396.7
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No. 2 oil
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0.850
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394.4
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0.845
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392.1
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0.840
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389.8
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0.835
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387.4
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0.830
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385.1
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