Bulk carriers deliver the majority of raw materials needed for construction, production processes and power generation. A vessel equipped with a MacGregor self-unloading or deck conveyor system offers efficient, reliable and dust-free bulk transfer.
MacGregor systems can handle many dry bulk commodities from powdery cargoes, such as cement and sulfur, to highly abrasive ones such as coal and iron ore. One of the most recent vessels to benefit from such a system is the first of four 20 000 dwt cement carriers; Apinya Naree was delivered in March 2014 and the second vessel of the series Boonya Naree was delivered on the 12 June 2014 from China Shipbuilding Industry Corporation’s enterprise, Shanhaiguan Shipyard. The vessels will each feature an autonomous MacGregor loading and unloading system and are all destined for Thailand-based Precious Shipping Public Company Limited (PSL), a pure dry cargo shipowner operating in the small Handysize and Supramax sectors of the tramp freight market.
The remaining two ships, Chanya Naree and Danaya Naree, are scheduled for delivery before the end of this year.
“The totally enclosed cement handling arrangements will ensure flexible, efficient and clean cargo operations up to a rated capacity of 1000 tph,” says Anders Berencsy, Sales Manager, Selfunloaders at MacGregor. “An additional benefit is that the computer-controlled systems are programmed for automatic operation by just one person, which reduces crew demands.”
The 149 m vessel will have four cargo holds, each divided into two compartments. The cement handling system is designed to accommodate two grades of cement. The ship can be loaded mechanically or pneumatically. It can be discharged mechanically to shore receiving conveyors or directly to tank trucks, or pneumatically in pipelines direct to silos.
All surplus air from the cargo holds both during loading and unloading is evacuated by means of dust collectors installed on deck. This ensures a clean environment for the crew and port.
Apinya Naree features a MacGregor cement loading and unloading system with a rated capacity of 1000 tph
During mechanical loading, material is distributed from the shore to the ship’s receiving system via a flexible bellows system. The receiving aeroslide divides the cement flow forward or aft into a horizontal screw conveyor positioned along the ship’s centre line.
The horizontal screw conveyor’s transport screw is divided into a forward and an aft section. The forward conveyor screw transfers cement to holds 1 and 2, whereas the aft conveyor screw loads holds 3 and 4. The screw conveyor has two outlets for each hold. Beneath each of these, except for the end outlets, is a sliding gate.
Each hold also has four inlets, two on the port side and two on the starboard, for pneumatic loading directly from self-discharging trucks on shore.
During pneumatic loading, material is distributed from the shore to the ship’s receiving hopper via two pipelines. On deck a distribution pipeline system is fitted with directional valves to direct the incoming cement to the chosen hold. Level indicators inside the hold notify the operator when the hold is full.
To reclaim cement from the holds, sloped aeration panels are installed on the tanktop in each hold. By blowing air through the fabric of the aeration panels, the cement becomes fluidised and flows towards the centre of each hold.
A vertical screw conveyor is installed inside a trunk at the centre of each hold. The fluidised cement is fed into the vertical screw conveyor via a transfer box equipped with two remotely-controlled flow-control gates. The vertical screw conveyors elevate the cement above deck and discharge it into the horizontal screw conveyor, running along the ship’s centre line.
By reversing the rotational direction of the horizontal screw conveyor, cement is conveyed to midship. Pneumatic discharge of the cement from the horizontal screw conveyor is via a buffer hopper placed inside the pump room. Cement from the buffer hopper is then fed to the blow pump system, which conveys it to silos on shore through two pipelines.
Mechanical discharge of the cement from the horizontal screw conveyor is via two further transfer screw conveyors installed on deck. The transfer screw conveyors move the cement to two bulk discharge boom conveyors located on the ship’s side. Bulk discharge booms are slewed out over the ship’s side and connected to the tank trucks on shore by means of flexible bellows.
Written by MacGregor
Read the article online at: https://www.worldcement.com/asia-pacific-rim/02072014/precious_shipping_receives_first_two_of_four_cement_carriers_15/