Catch it in the lorry, before decanting: dip each compartment against its calibration certificate. A short dip is made up to the correct level from the lorry and written on every invoice copy, signed by you and the driver. Once decanted, a shortage can only be argued from tank dips, which are far less certain.
Before decanting: the lorry’s dips
Each compartment has a calibration certificate stating the product level for its full quantity. Release the master valves so lines are full, let the lorry settle, and dip each compartment with the certified rod.
If a dip is short, or water is found, MDG 2024 clause 1.2 (xi) says the shortage “should be made up by filling to the correct level through the dispensing pump and the quantity so filled should be recorded on the back of all the Invoice copies.” Record each compartment’s observed dip and the quantity filled. Both you and the driver sign.
This is the only shortage the system recognises on the spot, because it is measured against a certificate.
After decanting: the tank’s dips
Received = litres after − litres before + litres sold meanwhile. The tanker unloading calculator does the sum. Before you call it a shortage, check:
- The dips. One bar misread on a bar rod is 2 mm, about 25 litres in a 20 KL tank near half full. See reading a dip rod.
- Settling. A dip taken while the surface still moves is unreliable.
- Sales. Was anything sold from the tank during unloading?
- Temperature. Litres at a warm tank and litres at a cool depot differ. Comparing at 15 °C with the VCF calculator removes it.
A pattern, not one load
One load a few litres out proves little. The same tank short on load after load, by more than temperature explains, is worth raising with your sales officer, with your dips, times and densities written down.
Figures here are for reference. Your oil company’s certified calibration chart, approved instruments and the Marketing Discipline Guidelines always prevail.
Questions
My tank shows 15 litres less than the invoice. Is it short?
Not necessarily. The invoice states litres at the depot's temperature. Your tank dips measure at the tank's temperature, and a single dip reading is only good to a few litres. Small differences either way are normal.
What if my pump is dry and I cannot fill from the lorry through the pump?
Clause 1.2 (xi) says that if the outlet is dry, the shortage is measured by drawing product from another compartment with a calibrated measure.