DPP to CPP changeover: a practical planning guide for product tanker operators

What is a DPP to CPP changeover?

It is the full preparation of a tanker's cargo system, meaning tanks, lines, pumps, heating coils and slop tanks, so that a clean product can be loaded after a dirty one without contamination. It usually involves hot and cold machine washing, sometimes chemicals, manual cleaning of the areas machines miss, flushing of the whole pipeline system, draining, mopping, gas-freeing and inspection.

The job is defined by the cargo pair: what was carried last (and before that) and what is going in next. Fuel oil to naphtha is a different job from crude to gasoil, which is different again from fuel oil to jet.

Step 1: Understand the cargo pair and the standard

Before planning a single wash, pin down:

• The last three cargoes, not just the last one. Many charterers, especially for jet fuel, look at the cargo history.
• The next cargo and its specification. What does the charterer or receiver measure: colour, sulphur, flash point, haze?
• The inspection standard. Visually clean, "water white", or a wall wash test? Agree this before you start, not at the inspection.
• The coating. Coated or uncoated tanks, and the coating's condition. Old coating holds black oil.

The Energy Institute's HM 50 guideline, which covers preparing tanks and lines on tankers carrying petroleum and refined products, gives a previous-cargo / next-cargo matrix that is the usual starting point for the cleaning plan.

Step 2: Build the cleaning plan

A sound plan states, for each tank:

• Wash medium and temperature: hot seawater for heavy residue, cold for lighter work, fresh water for the final rinse
• Machine programme: number of cycles and how long each runs
• Chemicals, if any: which product, at what dosage and how it is rinsed off
• Manual work: which areas need hand hosing, mopping or demucking
• Sequence: which tanks first, and how slops are managed

Washing heavy residue cold is the most common false economy. Heat is what moves fuel oil.

Step 3: Do not forget lines, pumps and heating coils

More changeovers fail in the pipework than in the tanks. Residue hides in:

• Cargo and stripping lines and their low points
• Pump casings, especially on deepwell pumps, and their discharge lines
• Heating coils, which hold black oil on and between the coils
• Vapour lines, sampling points and drop lines
• Manifold and crossover pipework

Every part of the system that will touch the clean cargo has to be flushed and drained, and that needs to be in the plan with a check against it.

Step 4: Manual finishing, draining and drying

Machines wash what they can see. Shadow areas behind structure, bellmouths and suction wells usually need hand hosing and mopping. After washing, tanks must be stripped dry and mopped, because standing water and trapped residue are what turn up at the inspection, or worse, in the first-foot sample. Where heavy sludge has built up, it may need demucking before washing can succeed.

Step 5: Slops and waste

A changeover produces a lot of slops. Plan from the start:

• How slops are consolidated and decanted on board
• Where they will be discharged (port reception facility or barge) and the paperwork involved
• How to keep volumes down, for example by decanting and reusing settled wash water where appropriate

All discharges and transfers belong in the Oil Record Book.

Step 6: Gas-freeing and safe entry

Manual work means people in tanks that recently held black oil. Gas-freeing, atmosphere testing for oxygen, hydrocarbons, hydrogen sulphide and benzene where relevant, entry permits and a rescue plan are not optional. Follow the ship's safety management system and industry guidance such as ISGOTT.

How long does a changeover take?

It depends on tank count, residue, coating, heating available, team size and whether the work runs alongside a voyage. A ballast passage of several days is often the best window. Hot washing, manual work and drying can run in parallel across tanks if there are enough people. We cover the timeline in more detail in a dedicated article.

Ship's crew, riding squad or shore gang?

• Ship's crew can manage simpler changeovers if the time and people are there.
• A riding squad joins the ship and works during the passage, so the cleaning costs no port time.
• A shore gang works at anchorage or alongside, useful when time in port is available.

Many difficult changeovers use a combination of the three. See our DPP and CPP tank cleaning service.

Inspection and records

Before the inspector boards, carry out your own check: tanks dry, no residue in suction wells, coils clean, lines drained. Keep a complete record pack: the cleaning plan, wash logs, chemicals used, slop records, gas-free certificates and photographs. If a cargo goes off-spec, that pack is what shows the tanks were prepared properly.

Planning a changeover with Cleanship

We work from bases at Fujairah and in India, including Kandla. Send us the vessel, the last three cargoes, the next cargo and its specification, the coating type and condition, and the time and place available. We will come back with a realistic plan and duration. Contact us here, or see tank cleaning in the UAE and tank cleaning in India.