We hear more about repositioning large vessels as some sweet young things appear on the scene.

Please think about your trimming situation and the extensive crowding involved in keeping a vessel stable. You will spend much more time positioning the vessel than you will spend loading it. Vessels were never meant to be loaded or unloaded in such fashion. Barges maybe, large geared vessels no. I would refer you to a photograph on the Bedeschi website where such a fixed machine, or very similar, has actually been put into operation. Please note the coal strewn all over the comings. Furthermore you will be interfering with the ships gearing clearances as the vessel shunts to and fro and last but not least you will require a lot of hatch closures if the vessel works in the rain.

Handymax vessels are geared: according to the classification definition. so you have on-board cranes which can gradually transfer cargo into adjacent holds as the hold nearest the berth gets filled. If you stick the beast near the middle you can work both adjacent gearings and thereby match the output of your grab crane. ■

Dear Trav,

Shifting a 55000 dwt ship is not usual, due to the extra lost time in shifting the ship compared to shifting the (un)loader 9 times.

Sometimes, there are restrictions for shifting a vessel, s.a. tidal, wind, current, etc.

An ungeared 20000 dwt ship is approx. the upper limit, whereby shifting the ship is considered but never preferred.

Another disadvantage is the required jetty length, which will be approx. 50% longer than for a traveling loader.

Probably a much higher investment than a traveling loader

Whether the ship is geared does not change much in operation, the loading boom has to be luffed or slewed anyway, whether the ship is moving or the loader.

The same goes for opening and closing the hatches.

Use your background skills.

Take care ■

The last study we performed was using a Handymax with a single pedestal. We were advised by the shipping company that they would need to move approximately 5 to 7 times in order to load. If we installed twin towers it would only have to move once. The cost of the twin pedestal system is a factor. Depending on how far away you are from your supply you will also possibly need vfds on the supply chain to be able to fully stop and start when the boat repositions. The cranes on the Handymax always seem to be in the way of proper loading. What is your material? Sticky or Free flowing? Fluidized or stable? Because of the cranes on the Handy this effects the numbers of times you need to reposition.

Direction of mooring and mooring lines are more dependant on port conditions than anything else. What is your port? ■

Originally Posted by travis.bassan

Hi,

......

Shiploader: Luffing and cross travel (i.e no long travel hence hatch changes require re-positioning of vessel)

Vessel Type

Handymax – 55,000 DWT with 5 hatches

Loading methodology

5 x 1x,xxx t pours + trimming pour – please confirm

............

Draft Survey – please confirm

......

Trav

Without a slewing capability you are possibly going to have to load the holds well past the deck before you can shovel the crud back indoors for trimming. Or what??

What does the vessel loading manual say about the hull stresses in such a situation?

How will you close the hatch covers when it rains?

When would draught surveys be undertaken?

What is your proposed hydraulic depth?

What is the gearing capacity of the vessels?

I am wondering how you became involved in large scale projects before having to cut your teeth on lower risk jobs. I have seen offshore jetties proposed for berthing 6 large ore carriers 12km out to sea in a Western Australian hurricane region. This was for loading very low value iron ore. Is your project offshore? If it is then you must seriously examine the very frequent imposition of severe berthing energies against a relatively small structure. Etc, etc... ■

Dear Trav,

Assuming a 5 Holds Handy max of 55000 dwt:

5 repositions mean that each hold can be fully loaded in one operation.

In case the first holds have to be loaded for 50% and then filling the holds are filled for the full 100%. Probably an extra shifting is required for trimming.

In that scenario, 9 repositions are required.

The total reposition length is then 13 hold-lengths

A 55000 dwt ship has a total length of approx. 225 m and the required jetty length is the approx. 1.5 times the ship length (335 m) + the mooring lines.

Loading the hold with coal requires a full coverage of the hatch opening, especially when the coal is of a light density.

Luffing and an extendable loading boom cannot reach the closest corners.

If the loading is done with a belt conveyor, luffing gives only a very limited range.

A trimming device at the end of the loading boom can help.

Slewing and an extendable loading boom can reach the closest corners as long as the slewing is not hampered by deck gear.

A loading spout can mostly reach the hole hatch opening.

A trimming device or a loading spout can be very dusty operations.

The jetty time for a 55000 dwt ship loaded with approx. 750 tons/hr gives 74 hr loading time plus 7 * 4 hr reposition approx. 100 hrs operation.

Approx. 1 ship a week gives approx. 50 ships per annum = approx. 2750000 tons/annum

Probably 15% less in case downtime for maintenance has to be accounted for.

Whatever the loader construction is ( you have not supplied that information) this should be the way to calculate what you are looking for

Take care ■

Originally Posted by travis.bassan

..... The infrastructure is existing and has been in operation for some decades perhaps this was not clear in my first post.......

Trav

Originally Posted by travis.bassan

...

Unfortunately I do not have the technical details of the shiploader although these have been requested. .......

........In addition as it is such a simple route with only 3 mechanical items (wharf/pier conveyor, shiploader receival boom conveyor and shiploader discharge boom conveyor ) cumulative reliability factors should be relatively good compared to more complex material handling systems at bigger ports.

It certainly wasn't clear. Otherwise the astute respondents would have immediately asked "What is the present loading time?" But then we don't know the loader details. Neither do we know the extent of the question. Is it intended to screw more out of the client by providing slewing. Otherwise there is nothing you can do with this one except 'Just do it.'

Why do I say this? Because if you can load the new Handymax with the existing, newly revealed, boom conveyor there is little point in claiming to load much smaller vessels unless they were handling materials which could be downluffed and still clear the holds on exit and also upluffed to an extent which would at best roll the vessel to starboard or worse throw material into the drink. If the boom is long enough to serve a Handymax how did it tuck into a smaller ship?

Basically your colleagues' situation is dead in the water. They have an unsatisfactory infrastructure which their client wishes to uprate without CAPEX. There is nothing any landlubbing engineer should do in this situation It is a matter purely between the Port Authority and the Shipper. Do not get involved further!

PS Reference to 'cumulative reliability' being relatively very good falls away in the face of a previous reply that the facility has been working for decades. Nothing lasts for ever: not even in a marine situation. ■