Electric Windlass Troubleshooting And Repair

Alatas ServiceField Service
LocationAsia, Singapore
Equipment TypeElectric Windass
CranesNippon Pusnes, Electric Deck Machinery, NSI60EW

BACKGROUND

The crew reported a malfunction with the anchor windlass on the starboard side. While tying the mooring ropes, there was a hammering noise, and at greater speeds, the winch began hunting and then abruptly stopped. The crew removed the electric motor and brake system, but the magnetic brake on the motor was confirmed to be normal. The crew then examined the gearbox and discovered a damaged bearing, but they were unable to pinpoint the source of the hunting problem. Alatas Specialists were called in for additional troubleshooting and repairs.

ALATAS’ SOLUTION

ALATAS deck machinery service department dispatched a Sr. Service Engineer and a team of mechanics, specializing in electric deck machinery troubleshooting and repairs, along with the required spare parts for this Nippon Pusnes winch.

The windlass gearbox, type MRP1702V then was opened, and the bearings were replaced. Upon testing, the hammering noise was solved, but the hunting problem still existed.

This was traced to a defective Motor Pulse Generator (MPG). Our engineer found that the speed feedback from the motor encoder (Motor Pulse Generator) is fluctuating when the speed is more than 700rpm. A new MPG needs to be ordered.

Our engineer also determined that the motor brake pads are worn beyond the brake wear limit and need to be replaced. The brake air gap was 2.15mm whereas the max. allowed air gap for this brake is only 1.8mm.

Job scope

Detailed work report of repairs carried out on the STBD Windlass as follows:

• A-frame was erected over the windlass electric motor.
• Windlass spinning was smooth at low speeds but became hunting at high speeds when tested without a load.
• Stoped testing & proceeded with bearing replacement.
• E-motor was successfully removed.
• Removed motor brake covers & found brake springs are covered with grease & dried grease. Serviced and cleaned the brake
• Removed gearbox connecting shaft & found both bearings are damaged. Bearings were cut off and replaced.
• Shaft seal & O-ring found worn off. Replaced using high-temperature Viton shaft seals
• All mounting flanges were then polished up & gearbox was boxed up, using Loctite at the appropriate areas & screws
• E-motor was then installed & all foundation bolts secured.
• Brake unit was also serviced and reassembled. The brake airgap was only 2.15mm with nuts fully screwed in. Recommend new brake pads to be installed. (Max allowable airgap is 1.8mm)
• All wirings reconnected & tested.
• Tested windlass at 100rpm to 700rpm. Rotation was smooth & brake was operating as usual.
• Tested windlass above 700rpm. Rotation starts jerking.
• Checked on drive unit & found motor speed feedback was fluctuating and unstable. Speed & direction command from controller found stable and recommended to replace new motor PG unit & to check all connecting wires & terminal to have proper and secure contacts in the process.
• Test with actual anchor UP & DOWN for 3 meters with bosun at low speed only. Everything is working as usual.

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