By Capt. Neeraj Bharti, Founder, Master Mariner · Published · 2 min read
DPP to gasoline and naphtha: colour, odour and sulphur risk on the first clean cargo
Gasoline and naphtha are light, clear products, and that is exactly why they show contamination. A trace of dark oil changes their colour. A little sulphur-rich residue affects a sulphur specification. And naphtha bought as petrochemical feedstock is often judged strictly by buyers who care about what else is in it. As a first clean cargo after dirty products, both are demanding.
What goes wrong
- Colour. Dark residue from tanks, lines, pumps or coils discolours the cargo.
- Sulphur. Residue from high-sulphur fuel oil raises sulphur content.
- Odour. Some buyers reject cargo with an odour from the previous product.
- Heavy components. Traces of heavy oil can affect distillation and other specification tests.
- Water and particulates from inadequate drying or coating breakdown.
Should it be the first clean cargo?
Often not. After fuel oil or crude, many operators prefer to load a more tolerant grade such as gasoil first and move to gasoline or naphtha after another cleaning. Check whether the charterer accepts the ship's cargo history for the nominated grade, and consider an intermediate cargo if the history or coating is doubtful. See crude oil to clean products and cleanliness expectations by grade.
Preparing for gasoline or naphtha after DPP
- Thorough hot washing to remove dark residue, followed by cold and fresh water rinses.
- Whole-system flushing: lines, pumps, coils, stripping lines, vapour lines. See lines, pumps and heating coils.
- Manual finishing of shadow areas and coils, then stripping, mopping and drying.
- Coating check. Old coating that holds dark cargo is a colour risk.
- Ventilation to clear odour.
- Pre-inspection to a high standard, and first-foot samples if agreed.
Safety
Gasoline and naphtha are low-flash, volatile cargoes. Before loading, tanks must be properly inerted according to the ship's procedures, and all cleaning work and entries must be complete and closed out.
See the DPP to CPP changeover guide.
How Cleanship helps
We plan and carry out changeovers to demanding grades from our bases at Fujairah and in India, and can advise before fixing whether an intermediate cargo is the safer route. See our DPP and CPP tank cleaning service or contact us.
Sources & further reading
Frequently asked questions
Can a tanker load naphtha straight after fuel oil?
Sometimes, but it is demanding. Many operators load a more tolerant grade first, and the charterer's acceptance of the cargo history should be checked before fixing.
What contamination risks do gasoline and naphtha face after DPP?
Colour change from dark residue, sulphur pickup, odour, heavy components, water and particulates.
Why is naphtha cargo judged so strictly?
It is often used as petrochemical feedstock, and buyers can be strict about colour, sulphur and other contaminants.
How should tanks be prepared for gasoline after dirty cargo?
Thorough hot washing and rinsing, whole-system flushing, manual finishing, mopping and drying, a coating check, ventilation for odour and a careful pre-inspection.
- DPP to naphtha changeover
- DPP to gasoline tank cleaning
- naphtha tank preparation
- gasoline contamination tanker
- naphtha colour contamination
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