Windlass: Construction, Working, and Classification Society Rules for Windlass and Chain Stopper
The windlass is a device used for handling the anchor, both for paying out (dropping) and heaving in (pulling up) the anchor. It is also utilized for handling lines and warping the ship alongside in a dock, canal locks, or harbor.
Construction:
– The windlass consists of three main components: the primary shaft, intermediate shaft, and two main half shafts.
– These shafts are equipped with corresponding pinions and gear wheels.
– The primary shaft is driven by a worm and worm wheel, coupled to a hydraulic or electric motor.
– Cable lifters, mounted freely on the main half shafts, rotate independently of the shaft.
– Cable lifters have sprockets on their circumference that engage with the links of the anchor chain or cable.
– A brake band, operated by a screw, is fitted around the brake drum, located on the outer edge of the cable lifter rim.
– The brake band is used to control the speed of the anchor chain when paying out and to lock the cable in a stationary position.
– The main gear wheel is keyed to the main half shafts and can be moved laterally for clutching and declutching with the cable lifter.
– Each end of the intermediate shaft is connected to a warping drum through a dog clutch.
Working:
To Pay Out (Drop) the Anchor:
1. Engage the main gear wheel with the cable lifter.
2. Slightly heave in (pull up) the anchor chain using the hydraulic or electric motor.
3. Remove the chain stopper pawl (guillotine bar/bow stopper pawl).
4. Apply/tighten the brake on the cable lifter.
5. Disengage the main gear wheel.
6. Release the brake and control the speed of the cable paying out by using the brake.
7. Apply/tighten the brake on the cable lifter when the anchor has reached the desired depth.
8. Place the chain stopper pawl in the chain-holding position to take the load of the anchor and anchor chain, preventing stress on the windlass.
To Heave In (Pull Up) the Anchor:
1. Engage the main gear wheel.
2. Start the electric/hydraulic motor.
3. Heave in (pull up) the anchor and anchor chain by controlling the motor and rotating the cable lifter.
4. Apply/tighten the brake on the cable lifter when the anchor is raised.
5. Place the chain stopper pawl in the chain-holding position.
Classification Society Rules for Windlass and Chain Stopper:
– The windlass should be suitable for the size of the anchor chain cable used.
– It should have sufficient power.
– Each anchor should be provided with one cable lifter connected to the main gear wheel through a release coupling (clutch).
– The cable lifter should have a brake.
– Each chain cable should be equipped with a chain stopper pawl between the windlass and the hawse pipe.
– Windlass should have a torque-limiting device (slipping clutch).
– It should be able to exert a continuous pull for 30 minutes.
– Windlass should also be able to exert 1.5 times the continuous pull for at least 2 minutes.
– Mean hosting speed should not be less than 9 m/min.
– The windlass brake should be sufficient for safe stopping of the anchor chain cable when paying out.
– Windlass should be able to withstand a pull of 45% of the breaking strength of the chain cable without permanent deformation or break slip.
– Chain stoppers and their attachments should withstand a static pull of 80% of the breaking strength of the chain cable without permanent deformation.
Electrical or electro-hydraulic drives are commonly used in windlasses.
Slipping Clutch / Torque Limiting Device:
To avoid excessive stress and shock loads on the motor when the anchor cable comes to a sudden stop, a slipping clutch is fitted between the motor and the gearing. When the windlass gearing side shaft comes to a sudden stop, the motor side of the shaft slips and continues to rotate, preventing excessive stress on the motor.