A client was buying an AHTS to tow an 8,200-tonne barge across three oceans. The seller's bollard pull figure and the vessel's actual certified performance were not the same number — and the gap mattered.
A client planned to purchase an AHTS (Anchor Handling Tug Supply) vessel in China and use it to tow a large accommodation/crane barge from Dubai to West Africa — a route running through the South China Sea, the Indian Ocean, and around the Cape of Good Hope, entirely outside the Red Sea corridor. The barge being towed displaced roughly 8,200 tonnes. Everything about the plan depended on one number: how much bollard pull the vessel could actually deliver.
The seller's documentation listed 400 tonnes.
Seavantek reviewed the vessel's actual machinery and certification rather than taking the spec sheet figure forward. The vessel's four main engines — a matched set of Wartsila 8-cylinder and 6-cylinder units — gave a combined output of just over 11,000 kW. Run against the towing winch's certified rating and the vessel's real sea trial performance, the verified bollard pull came to 95 tonnes average, 120 tonnes maximum. The 400-tonne figure on the spec sheet was the winch's rated pull — a completely different number from what the vessel could actually exert through the water.
A 400-tonne bollard pull would have made the vessel comfortably capable of the tow. A 120-tonne bollard pull against an 8,200-tonne barge is a materially different risk profile — adequate in calm conditions, but insufficient margin for heavy weather across three ocean legs, particularly rounding the Cape. Had the deal proceeded on the seller's figure, the client would have committed to a delivery voyage with the wrong vessel for the job — discovered only once underway, with a barge under tow and no easy way to change plans mid-ocean.
Seavantek's finding didn't stop the purchase — it corrected the plan around it. With the real bollard pull established, the recommendation was to route via the Cape only (avoiding the Red Sea corridor entirely, independently justified by regional security conditions at the time) and to engage an escort tug for the Cape leg at minimum, where sea state risk is highest relative to the vessel's real towing capacity.
The client proceeded with the acquisition with accurate technical expectations instead of the seller's marketing figure — and with a voyage and risk-mitigation plan built around what the vessel could actually do, not what its winch was rated for.
A spec sheet number is only as good as its source. “Bollard pull: 400 tonnes” and “winch rated pull: 400 tonnes” can appear identically on a summary sheet, and only checking the vessel's actual machinery output and certified sea trial data reveals which one you're really being sold. This is the gap between reading a seller's summary and reading the primary source — and it's the difference between a voyage plan built on fact and one built on hope.
