The crew of the bulk carrier Desert Moon observed Beaufort Force 5 about an hour before her hydraulic windlass motor burst at Santos anchorage, Brazil, on 28 September 2023. She was in light ballast, in rough seas with a 1.8-knot current, and she was pitching and rolling moderately to heavily. Her bosun did not survive the injury.

Hydraulic windlass motor, band brake and anchor chain on the forecastle of a bulk carrier — Illustrative image of a hydraulic anchor windlass. It does not show a ship named in the reports.

The Marshall Islands investigation report came out in August 2024, and SAFETY4SEA carried its findings in February 2026. It is worth reading in full if you work on a forecastle, because the sequence is so ordinary.

The chain had paid out to 11 shackles in the water, so the master decided to leave the anchorage. Heaving started at 04:08. At 04:32, with eight shackles in the water, he ordered a stop. The bosun applied the brake by hand and put the control lever in neutral. Within the next minute the chain began to pay out. He ran to disengage the chain lifter, and then the motor failed. Debris hit his right leg and caused an open fracture with arterial bleeding.

What followed was worse. Pilotage was suspended. A service boat arrived at 08:15 but left because transfer was too risky, and weather ruled out a helicopter. At 09:45 the master cut the anchor chain and headed for the pilot station. Doctors boarded at 11:18, and the bosun was declared dead at 11:25.

How the hydraulic windlass motor failed with nobody heaving

The two brakes on this windlass had a designed capacity of about 300 t together: roughly 200 t on the windlass brake and 100 t on the parking brake. The investigators could not establish the actual figure on the day, but they assumed wear and tear had reduced it. They also could not determine whether the manually applied brake wheel was fully closed.

Their conclusion was that shock loads from the ship’s movement exceeded the combined brake capacity. The parking brake slipped and overheated, and it transferred torque to the motor. That force destroyed the hydraulic windlass motor.

One line in the report deserves attention. It says oil pressure did not cause this failure, and it found no sign that the pressure relief valve had failed. Any crew that thinks of a relief valve as full protection should take note of that.

The Stellar Voyager hydraulic windlass motor failed differently

Compare the tanker Stellar Voyager off Tees Bay in March 2009. Her crew was heaving in, with gusts up to 30 knots and a 2 m swell, when the chain rendered. According to the MAIB report, the motor then reversed and acted as a pump. MAIB concluded that over-pressurisation was the most likely cause, with pressure rising too fast for the relief valve. The cylinder block fractured, the operator suffered serious injuries, and a piece of casing landed 40 m away.

So one report points to overpressure, and the other says pressure was not the cause. MAIB itself said causes probably differ from case to case and asked manufacturers to investigate further. However, the two cases share a starting point: the chain load went beyond what the windlass could take.

Nor were they isolated. A 2009 MAIB bulletin also listed the tanker Young Lady in 2007 and an LPG vessel off Florida in 2009, among others. CHIRP, citing DNV GL, attributes 24% of anchor losses to winch or motor failures, 34% to weather and 21% to operational procedures.

What the investigators tell crews to do

Recover the anchor early. MAIB’s first advice is to watch the forecast and recover the anchor before conditions make it hard. CHIRP’s generic advice is to heave up and find sea room if Force 6 is expected. Desert Moon is a useful warning here, because the wind alone did not look severe. Sea state and ship motion matter too, and CHIRP notes that ballasted ships suffer more from windage.

Take the load off first. MAIB advises using the main engines to relieve chain tension before heaving in. It also says to stop heaving as soon as significant tension or difficulty appears. On Stellar Voyager it called the repeated attempt to recover the anchor poor practice.

Brakes, covers and servicing around a hydraulic windlass motor

Treat the brake as a component with limits. The RMI report points out that a brake wheel not fully closed reduces capacity, and that friction during rendering can affect the brake lining. If your chain has rendered, inspect the lining rather than assuming all is well.

Look at the motor cover. The hydraulic windlass motor on Desert Moon had none, and the report lists that as a factor that may have contributed. OCIMF added protection recommendations to its anchoring guidance in 2010. After this casualty the company ordered covers, and the flag issued a safety advisory on motor protection. Check your own windlass today, and think about where people stand during anchor work.

Read the manual, then question it. This windlass had regular shipboard maintenance, including six-monthly oil sampling, but no manufacturer service engineer had ever attended it. Its manual did not ask for that. Manuals for windlasses installed in 2023 do recommend a maker’s inspection every two years. When an engineer inspected the starboard windlass after the accident, the list included hoses, gear oil, bearings and bushings. RMI’s lesson is a periodic service by a recognised station.

Teach the limits. MAIB found that many seafarers do not know the limits of a hydraulic windlass motor and its system, and that most are unaware it can fail catastrophically under excess load. RMI’s first lesson says the same thing fifteen years later. If nobody on board can state your limits, find them before the next anchorage.

How Berth Marine can help

We overhaul and repair windlasses and mooring winches on board, including inspection of drums, brakes and gearboxes with the findings reported. We also overhaul hydraulic motors and valves, on board or at our workshop in Tuzla, Istanbul. Slow drum speed, brake slip and oil leaks are early warnings, and our guide to hydraulic warning signs covers more. To arrange a check, send us the vessel details, the equipment maker and model, and your next port.

This article summarises published investigation reports for general information. It does not replace the manufacturer’s instructions or your safety management system.