A dip chart depends on the tank's inside diameter and length, not on its size in KL. A narrow, long tank and a wide, short tank can both hold 20 KL, but at the same dip they hold different litres. BPCL's two 20 KL models differ by over 1,000 litres at a dip of 142.5 cm.
The same 20 KL, two shapes
BPCL uses two 20 KL tanks:
| Model | Inside diameter | Length | Full | At a dip of 100 cm | At 142.5 cm |
|---|---|---|---|---|---|
| Older 20 KL | 210 cm | 600 cm | 20,782 L | 9,761 L | 15,013 L |
| RE-DRG-382 20 KL | 200 cm | 671.8 cm | 21,105 L | 10,553 L | 16,086 L |
At 100 cm the gap is 792 litres. At 142.5 cm it is 1,073 litres.
Why
A dip measures height, and litres depend on how wide the circle is at that height and how long the tank is. The narrower tank reaches the same height with less fuel per slice, but it is longer, so each slice counts for more. Two different circles never share a chart.
Other companies
- BPCL also has three 10 KL tanks, 184, 190.5 and 200 cm across, and two 15 KL tanks, 184 and 200 cm across.
- IOCL and HPCL tanks of the same nominal size are different shapes again.
So the right question is never “which size?” but “which diameter and length?” The Dip Density app asks you to choose the company, the size and then the model for this reason.
Figures here are for reference. Your oil company’s certified calibration chart, approved instruments and the Marketing Discipline Guidelines always prevail.
Questions
How do I find which model my tank is?
Look at the tank's calibration chart or drawing for its inside diameter, and compare the full dip on the chart with the diameter. The deepest dip on the chart is the tank's inside diameter.
The full litres look the same. Why does it matter?
Only the full tank is the same. Everywhere in between, the chart differs. A stock figure from the wrong chart is wrong every day, by up to a thousand litres.