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Parker Hannifin has worked together with EMS-Tech to help develop an integrated unloading system for a fleet of forebody vessels.

‘Our client, CSL International, was looking to complete a huge fleet renewal programme of its self unloaders,’ said John Elder, vice president, marine systems at EMS-Tech.

‘As well as requiring a reliable unloading system that would enable them to optimise productivity levels, CSL needed to carry out the project in the shortest time and at the minimum cost.

‘To do this, it was decided that the aft end of existing single skin tankers would be combined with new forebodies comprising integrated self-unloading systems.’ When it came to the design and supply of the boom slew system, EMS-Tech turned to Parker.

When designing the actuator for this application, Parker had to consider a wide range of system parameters, including the operating environment, slewing speed, and duty cycle, in addition to factors such as the ship list angle and wind load on the boom.

In addition to providing the torque required to slew the discharge boom, the actuator serves to support this very large boom structure and all imposed loads, which can be well in excess of 500 tonnes.

The Parker solution took the form of a 25 tonne rack-and-pinion hydraulic rotary actuator, coated with a rubberised epoxy paint at 175 micron dry film thickness to protect the system from corrosion in the hostile working environment.

The purpose-built system is able to control the boom accurately, providing 4.3 million Nm of holding torque and 3.5 million Nm of slewing torque at 275 bar.

The finished system is capable of discharging a variety of materials, including coal, stone, grain, ore, alumina, and limestone rocks at a rate of 5,000 tonnes per hour.

The actuator features a pinion gear bore that fits over a king pin tied into the structure of the ship.

The gear is fixed so that the housing rotates as pressure is applied to the cylinders, causing the actuator to turn at 12 per minute.

To give an idea of the scale of the cylinders, approximately 450 litres of oil are displaced for every 190 of rotation.

The boom is attached to the actuator by two trunnion pins that project from the sides of the actuator housing.

These trunnion pins carry the weight of the boom, in addition to transferring the torque from the actuator into the boom to rotate it off the centreline of the ship and into the required position.

The actuator is then able to hold the boom steadily against the torque generated by the list of the ship, as well as the wind loads trying to rotate the boom further.

A separate luffing cylinder and a rigid luffing linkage assembly are used to control the boom vertically.

This arrangement allows the boom to be positioned along the centreline of the vessel in a storage saddle when it is not in use, and, likewise, to be lifted out of the storage position when it is required.

With the bespoke rotary actuator assembled and connected to a purpose built hydraulic power unit, complete with directional valves, holding valves, and filtration equipment, Parker was able to help EMS-Tech meet its client’s requirements quickly and cost effectively.

Parker Hannifin — Parker Sales UK

With annual sales exceeding $10bn, Parker Hannifin is the world's leading manufacturer of motion and control technologies and systems, providing precision-engineered solutions for a wide variety of commercial, mobile, industrial and aerospace markets.

To meet its customers' needs in motion and control, Parker provides the broadest range of products available from any single supplier. This is supported by expertise in nine major technologies:

  • Hydraulics
  • Pneumatics
  • Electromechanical
  • Filtration
  • Process control
  • Fluid and gas handling
  • Sealing and shielding
  • Climate control
  • Aerospace

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