8/3/2019 Bulk Carrier 0905

http://slidepdf.com/reader/full/bulk-carrier-0905 1/128 SHIPREPAIR AND CONVERSION TECHNOLOGY 3RD QUARTER  2005

STEEL repairs, carried out earlier this year on

two Torvald Klaveness-owned bulk carriers,

 Ballangen and  Bauta, at Malta Shipyards,

demonstrated how Intelligent Engineering's (IE)

SPS Overlay technology can be used to speedup repairs to this type of vessel.

Until recently, re-instating tanktops was an

expensive and time-consuming process

involving the cropping out of steel and replacing

it with new plating and longitudinals. However,

in this situation, using SPS Overlay, the existing

thinned tank tops of the Klaveness vessels were

used as one side of the new composite. The class

society, DNV, carried out extensive analysis

 prior to execution of the work.

Since they were built at the end of the 1980s,

the Klaveness self-discharging Handymax

designs Bauta and Ballangen have served their 

owners well. Frequent maintenance of thedouble-bottom tanks had ensured that the

coating systems were in good condition;

however, the constant wear and erosion from

cargo and handling equipment led to the steel

tanktops coming close to the minimum allowed

thickness. Rather than re-assess alternate

loading possibilities, Klaveness decided to

re-instate the tanktops.

'There were three key reasons for using SPS

overlay', says Sverre Grønn, technical manager 

at Klaveness. 'First, the need for a predictable

schedule for the work was essential. Second,

we avoided the need to clean and then

re-coat the double-bottom ballast tanks, saving

considerable inconvenience and work. Last, but

not least, the final tanktops would be more

durable and resistant to damage than their 

  predecessors, minimising future deformation,

allowing for easier discharge and cleaning'.

Klaveness approached DNV for approval of 

the use of SPS Overlay, and the class society's

major concern was not the sandwich design

itself, but its termination at the base of the

hopper tanks and stools. As the double bottom is

a major contributor to longitudinal strength, the

transfer of stresses between the conventional

structure and the sandwich was seen as a

 possible hotspot for future through-life fatigue.

Considerable time savingsDNV conducted a detailed finite-element

method (FEM) analysis, and working together 

with IE, a satisfactory solution was found. Stuart

Rolland, from Intelligent Engineering, observes,

'Torvald Klaveness avoided lengthy deviation

and time out of service by conducting the repair 

at Malta Shipyards rather than travelling to the

Far East. The repair took 23 days rather than an

estimated 56 to crop and replace the tops, and

deviation was only eight days each way. With

charter rates as they currently stand, the

opportunity costs savings could not be ignored'.

The work was conducted in Malta in

conjunction with IE's field engineers. In total,

3025m2 of SPS Overlay on  Bauta was

completed in just 23 days in a number of steps.

The process involved cleaning and grit-blasting

the tanktops; attaching the perimeter bars and

top plates, and injection of polyurethane

elastomer, which cures to form a solid core

within three hours. A similar programme of 

work was also carried out on  Ballangen.

IE points out that the steel repairs on the

Klaveness bulkers demonstrated how SPS

Overlay can also be used to repair bulk 

carrier bulkheads. On  Ballangen, excessive

diminution of the bulkhead between hold No 5

and the engineroom was repaired using

the technology. The extra work involved

integrating 225m2 of SPS Overlay bulkhead

repair, extending to a height of 8m, with over-

steelwork to the hatch coamings and the side

shell.

The non-intrusive nature of the SPS process

meant that the repair could be carried out at

the same time as other work and avoided a

requirement for extensive and time-consuming

fuel tank cleaning in the engineroom and

double bottom. Moreover complex cable and

  pipework on the engineroom side of the

  bulkhead remained intact throughout the

repair. At the same time, a slight design

modification made possible by the use of SPS

Overlay enabled water ingress alarm sensors

to be installed with additional protection.

IE points out that SPS Overlay can provide

fire protection equivalent to A60 and so can

satisfy fire regulations for insulation between

flammable cargoes such as fertilisers, and the

ship's fuel tanks. Furthermore, it can be used

to strengthen existing tanktops to enable

higher point loads, so increasing cargocarrying capacity for cargoes such as steel

coil.

IE is now working on another notable bulk 

carrier repair project, this time involving

Gayle Eustace, for an American owner. This

work is being carried out in Mexico at a yard

in Vera Cruz, and is the second occasion

where the bulker has been upgraded using

SPS.

Speeding up bulk carrier repairs

An overhead view of re-instatement work, using Intelligent Engineering's SPS Overlay, in progress

at Malta Shipyards on the bulk carrier Bauta .

SPS Overlay was additionally used to make repairs to the bulkhead between No 5 hold and the

engineroom on Ballangen .