By Capt. Neeraj Bharti, Founder, Master Mariner · Published · 2 min read
Reading HM 50: turning the previous/next cargo matrix into a cleaning plan
Ask a tanker officer how they decide how to clean for a grade change and many will say "HM 50". The Energy Institute's guidance on preparing tanks and lines for marine tank vessels carrying petroleum and refined products is the reference most of the industry uses. But a guideline is a starting point, not a plan. Here is how to turn it into one.
What HM 50 is
HM 50, published by the Energy Institute (EI) and now in its sixth edition (2024), gives guidance on preparing tanks and lines on petroleum tank vessels, mainly when changing between refined products. Its aim is to maintain product quality using minimum effective washing procedures. It is written for sea-going tank vessels, and it does not cover chemicals or gases.
Its best-known feature is a previous cargo / next cargo matrix: find the last cargo on one axis and the next on the other, and the guide points to a recommended level of preparation.
What the matrix gives you
- A recommended level of cleaning for the cargo pair
- An indication of whether hot or cold washing, extra rinsing or draining and drying are needed
- A consistent, recognised reference that charterers and inspectors also know
That consistency is valuable. If a cargo goes off-spec later, showing that tanks were prepared in line with recognised guidance is part of the evidence.
What it does not give you
HM 50 does not know your ship. A practical plan must add:
- The real cargo history, including the last three cargoes, not just the last
- Coating type and condition: old coating may need more than the matrix suggests
- Sludge and sediment: a tank needing demucking will not respond to washing alone
- The cargo system: lines, pumps, coils and slop tanks
- The charterer's own requirements, which may be stricter than the guidance
- Practical limits: heat available, fresh water, slop capacity, time and people
From matrix to plan
- Find the cargo pair in HM 50 and note the recommended preparation.
- Check the charterer's voyage instructions for any stricter requirement.
- Adjust for coating condition and known sediment.
- Write a tank-by-tank plan: wash medium, temperature, cycles, chemicals if any, manual finishing, drying.
- Add the cargo system: every line, pump, coil and branch, with method and sign-off.
- Add slop handling and safety requirements.
- Agree the inspection standard.
- Keep the plan and the logs in the record pack.
See the DPP to CPP changeover guide and lines, pumps and heating coils.
How Cleanship helps
We build cleaning plans from the cargo pair, coating, sediment and ship's systems, using recognised guidance as the base, and carry out the work from our bases at Fujairah and in India. See our DPP and CPP tank cleaning service or contact us.
Sources & further reading
Frequently asked questions
What is HM 50?
The Energy Institute's guidance on preparing tanks and lines on tankers carrying petroleum and refined products, best known for its previous-cargo and next-cargo matrix. The current edition is the sixth, published in 2024.
Does HM 50 cover chemicals?
No. HM 50 covers petroleum and refined products, not chemicals or gases.
Is following HM 50 enough to pass inspection?
Not on its own. The plan must also account for cargo history, coating condition, sediment, the cargo system, the charterer's own requirements and practical limits on board.
Why does following recognised guidance matter in a dispute?
If a cargo goes off-spec, showing that tanks were prepared in line with recognised guidance and properly recorded is part of the evidence that the ship did its job.
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