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Unloaders Selecting the right system Vincent van der Wijk
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Page 1: Unloaders - Approved Industry Suppliers · system featuring a highly efficient vertical chain conveyer has the lowest OPEX value of the available CSUs. With lower overall efficiency

Title | Author | 2005

Unloaders

Selecting the right system

Vincent van der Wijk

Page 2: Unloaders - Approved Industry Suppliers · system featuring a highly efficient vertical chain conveyer has the lowest OPEX value of the available CSUs. With lower overall efficiency

2 | © Bühler |

Agenda

Unloaders | Vincent van der Wijk | 2014-01-22

1

2

3

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5

6

7

8

Practical implications

Functional principles and technical configuration

Energy consumption

Active working range

Rest unloading of product out of the hatch

Selecting the right ship unloading system

Operational handling & Maintenance costs

Product protection

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3 | © Bühler |

Selecting the right ship unloading system.

For efficient unloading of grain and other free flowing bulk goods, several continuous ship

unloading systems (CSU) such as a vertical chain, pneumatic, and belt conveyer are employed

worldwide. Each of these systems is founded on sophisticated, powerful technology and can be

the perfect instrument for a specific area of application. An often-used rule of thumb is that

pneumatic unloaders are an option with lower unloading capacities up to 600 t/h, while

mechanical unloaders show off their strengths at higher capacities.

Unloaders | Vincent van der Wijk | 2014-01-22

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4 | © Bühler |

All continuous ship unloaders serve the same basic

purpose: to unload grain or other bulk goods as efficiently

as possible. But each system possesses specific

advantages that make it the preferable choice for certain

areas of application. To make an informed and well-

founded decision on which unloader is the best solution

for your terminal, basic issues have to be considered and

evaluated, such as costs, energy consumption,

availability, safety, etc.

With unloading vessels of more than 10.000 DWT, the

average capacity for the total unloading process, in

combination with the reliability of the unloader during

operation, are the key functions. Because the unloader is

the backbone of a terminal and its overall operation,

fluctuations in capacity or breakdowns have a direct,

significant impact and create high overall costs.

Moreover, several regulatory specifications relating to

personnel and environmental safety are influencing the

choice and level of investment for new unloaders. The

Technical University of Munich has compared the three

unloading systems shown below. Safety and regulations

for the unloader applies not only to the operating

personnel, but also to the equipment itself. For the owner

of a port terminal, it is inadvisable to try to save on safety

factors, and inadequate performance with regard to these

criteria can have a serious impact on running the

business.

Chain Belt Pneumatic

Availability ++ - +

Material breakage ++ + --

Ease of operation ++ - +

Safety of unloader +++ - +

Dust emission ++ - ++

Noise emission ++ ++ -

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5 | © Bühler |

Selecting the right unloader

Page 6: Unloaders - Approved Industry Suppliers · system featuring a highly efficient vertical chain conveyer has the lowest OPEX value of the available CSUs. With lower overall efficiency

6 | © Bühler |

Practical implications.

Key investment criteria are the operational expenditures

(OPEX) in combination with the capital expenditure

(CAPEX). For an optimal customer solution, these criteria

should be in balance. As shown in the figure, the Buhler

system featuring a highly efficient vertical chain conveyer

has the lowest OPEX value of the available CSUs. With

lower overall efficiency and relatively high replacement

costs, the belt conveyer and pneumatic systems have a

higher OPEX and are therefore less favourable unloading

options in this case.

To show the bottom line implications of the study made by the TU Munich, Buhler has prepared a

comparison between the three continuous unloading systems based on a customer project

developed in Central Europe which projects to unload grain. The project details are in the

customer profile.

Customer profile

Yearly Unloading volume 600.000 t

Energy costs € 0.15 kWh

Daily operating hours 22

Daily tie-up costs € 25,000

Nominal capacity 600 t/h

Demanded availability 90 %

Daily personnel costs € 247.5*

* € 5 p/h= Ø 2.25 m.p

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7 | © Bühler |

System comparison

Chain Belt Pneumatic

Average efficiency 75 % 65 % 65 %

Annual unloading days 67 77 77

Annual personnel costs 16.600 19.230 19.230

Energy (kWh/t) 0,4 0,3 0,8 – 1,0

Annual energy costs 36.000 27.000 76.500

Annual tie-up costs 1.683.500 1.942.500 1.942.500

Annual wear & tear costs 48.000 96.000 96.000

Annual operating costs 1.785.000 2.084.000 2.134.200

Unloading costs per ton € 2,97 € 3,47 € 3,56

Profit lost € - 300.000 € - 350.000

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8 | © Bühler |

Functional principles and technical configuration.

Mechanical:

Buhler's Portalink mechanical ship unloading system transports

bulk material to the pier at low speed using two independent

high-performance chain conveyors, one in the vertical conveying

arm, the other in the boom. The Portalink has a standardized

design based on years of experience and is optimally configured.

The advantages of this design principle with few wearing parts

and low conveying velocity include high dependability, low

energy costs and reduced maintenance requirements. Low wear

also ensures a constant conveying capacity with no losses in

performance over the entire life cycle. Thanks to the minimal

maintenance requirements, the amount of downtime of the entire

installation decreases while system availability increases.

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9 | © Bühler |

Functional principles and technical configuration.

Pneumatic:

Pneumatic ship unloading systems include several additional

components such as telescopable spouts, airlocks, filter systems

and the suction nozzle. These parts require more maintenance

and thus also lead to higher maintenance costs. The high

conveying velocity of the bulk material also contributes

significantly to the high level of wear – unexpected failures of the

installation are more probable with this system.

Additionally, many of the parts must be designed to be

particularly resistant to wear in order to withstand great forces.

The frequency at which parts must be replaced is naturally

greater, which increases the amount of downtime of the

installation and reduces the availability of the system.

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10 | © Bühler |

Functional principles and technical configuration.

The higher amount of wear also automatically causes a loss in

capacity that reduces the overall efficiency of the unloader. The

berthing times of ships can also increase due to sudden

stoppages in operation, leading to higher berthing fees.

These disadvantages are less critical at lower conveying

capacities and low annual throughput, since wearing parts do not

need to be replaced as often and maintenance requirements are

lower as a result.

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11 | © Bühler |

Overall efficiency

While the Portalink unloading system continues to unload at

constant full capacity as the level of bulk material sinks, the

throughput of the pneumatic unloading system decreases

by at least 10 % with a decreasing bulk material level and

the suction pipes fully extended. The overall efficiency of

the mechanical Portalink system is 87 %, whereas with the

pneumatic system, efficiency is only 66 %. The result is

astonishing!

There are various reasons for the time savings offered by

the mechanical unloader, all influencing the efficiency, such

as the use of heavy bucket loaders to unload the material

residues and the difference in throughput.

For a customer with an unloading capacity of 600 t/h and

mainly having Panamax size vessels the unloading time for

the Panamax vessel comes to only 99 hours using the

mechanical unloader, where a pneumatic unloader

completes the process in a total of 131 hours. This

represents roughly a 25 % increase in time for unloading a

single ship!

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12 | © Bühler |

Active working range.

Together with ease of operation, the working range and flexibility of the unloader is important. With a larger

effective working range, the unloader can unload a broader area without moving, and thus increase the overall

efficiency of the operation. Two persistent myths exist regarding unloading systems. The first myth is that

pneumatic unloaders have a greater reach in the hatch than mechanical systems. The second myth is that with

pneumatic unloading, the material left in the hatch after the main unloading phase is removed more efficiently

and without the deployment of bulldozers.

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13 | © Bühler |

Mechanical:

Mechanical unloading systems like the Buhler Portalink use

the so-called "kick-in/kick-out system" to move the unloader

arm through the hatch to unload with optimal coverage. In

this process, the conveying arm moves through the bulk

material in a curve. In this manner, it reaches the bulk

material below the rim of the cargo hold without requiring

repositioning of the ship (with stationary systems) or the

Pneumatic:

Pneumatic solutions are often compared with the vacuum

cleaners used at home. In theory, this sounds logical, since

both systems have a flexible hose and can move around

easily – but nothing is farther from the truth. In practice,

bulldozers and bucket loaders are used to effectively

remove all the bulk material residues from the cargo hold.

Pneumatic unloaders can only adjust the position of the

unloader (with mobile systems).

This flexibility significantly

speeds up the unloading

process and minimizes the

need for bulldozers for removal

of bulk material residues.

conveying arm vertically or

horizontally. The bulk material

below the rim of the cargo hold

cannot be reached, requiring

bulldozers to be used earlier

and leading to longer unloading

times.

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14 | © Bühler |

Rest unloading of product out of the hatch.

Mechanical:

Many modern unloading systems with mechanical technology are

equipped with a winch integrated in the boom for moving large

bulldozers into the cargo hold for highly efficient rest unloading.

Depending on the capacity of the unloading system, they can

offer a high load-bearing capacity up to 15 tons.

In this case, the use of a single heavy bucket loader is sufficient

to remove all cargo residues. The last remaining product in the

hatch can conveniently be placed in the bulldozer's bucket and

simultaneously lifted onto the pier.

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15 | © Bühler |

Rest unloading of product out of the hatch.

Pneumatic:

Pneumatic unloading systems have a lighter construction and are

equipped with winches with a limited maximum load-bearing

capacity of 3.5 tons. If winches capable of bearing heavier loads

are preferred, larger steel constructions are required, leading to

increased costs compared to standard systems.

Often, several smaller bulldozers or bucket loaders are moved

into the hold to remove the remaining bulk material. Increased

unloading time and berthing time of the ships results in an

increase in costs.

The basic advantage pneumatic systems offer, i.e. being able to

remove literally every grain from the hold, is countered by their

(physically determined) low residue unloading capacity.

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16 | © Bühler |

Operational handling.

Mechanical:

With the mechanical Buhler Portalink unloading system,

operating staff only occasionally has to intervene in operation.

The conveying arm automatically sinks into the bulk material and

discharges large amounts of cargo at a constant throughput level

before repositioning becomes necessary.

The static construction of mechanical unloading systems does

however have a disadvantage in that the water level can vary

significantly during unloading. In this case, additional

repositioning is required to adjust the unloader to the water level

difference.

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17 | © Bühler |

Operational handling.

Pneumatic:

Without the benefit of the automatic "sink-in" function, operators

of pneumatic unloading systems have to manually adjust the

position of the conveying arm depending on the height of the bulk

material and reposition the suction nozzle accordingly.

The disadvantage of this flexibility: As the length of the

telescopable spout increases, throughput decreases.

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18 | © Bühler |

Energy consumption.

Mechanical unloaders have a lower energy

consumption per ton compared to pneumatic

unloading systems. Thanks to a reduced design with

few components and a lower conveying speed, the

energy consumption of mechanical unloading systems

like the Buhler Portalink is significantly lower.

By comparison, the energy consumption of mechanical

unloaders is approximately 0.35 – 0.4 kWh per ton. where

pneumatic systems average roughly 0.85 – 0.9 kWh/t; older

systems even require more than 1 kWh/t.

Depending on conveying capacity and local energy prices,

mechanical unloading systems can save the user tens of

thousands of Euros each year.

In light of the continuing trend toward higher energy prices,

it stands to reason that in the future, mechanical unloading

systems may also become more attractive for lower

capacities – above all in countries where energy is

expensive.

High levels of specific energy consumption also have a

negative impact on the overall power supply of an

installation – and on costs for the provision of energy. The

necessary investment costs, as well as the annual

increases in electricity rates, are often overlooked in

calculating the overall costs of a system. In this regard,

mechanical unloading systems are clearly superior to

pneumatic solutions.

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19 | © Bühler |

Energy usage throughout the hatch

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20 | © Bühler |

Product protection.

Mechanical:

Mechanical solutions like the Buhler Portalink/Portalino

unload bulk material at a constant low velocity. This not only

Pneumatic:

The physical properties of pneumatic solutions require the

conveying speed to be higher than that of mechanical

The overall high product quality leads to higher margins than with pneumatic unloading

systems – a financial aspect that shouldn't be underestimated in light of increasing grain prices.

reduces wear and the

maintenance costs of the

system, but also ensures that

especially sensitive grain is

unloaded in an exceedingly

gentle manner. In this way,

damage to the product is

minimized and financial losses

caused by high reject rates are

avoided.

systems. The resulting higher

maintenance costs are not the

only disadvantage; critical

disadvantages also include

higher reject rates and lower

product quality, which in turn

leads to lower market prices.

Additionally, greater system

wear results in reduced

unloading throughput.

Page 21: Unloaders - Approved Industry Suppliers · system featuring a highly efficient vertical chain conveyer has the lowest OPEX value of the available CSUs. With lower overall efficiency

21 | © Bühler |

www.buhlergroup.com


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