Al Jaber critical column replacement

Despite restrictive site conditions heavy lift and specialized transport company Al Jaber still managed to save time on a refinery column replacement project in the United Arab Emirates.

ADGAS, part of the Abu Dhabi National Oil Company (ADNOC) group, is a leading player in the united Arab Emirate's energy sector. It owns and operates an LNG plant in Das Island, UAE. The plant consists of two identical trains with associated utilities commissioned in 1977 and a third train, with associated utilities commissioned in 1994, which produces LNG, LPG, pentane and molten sulphur.

The project was to replace the main cryogenic heat exchanger column (MCHE) in ADGAS Train 3 at Das Island. Improvements in the technical capability of MCHEs made ADGAS decide to replace the column.

In undressed condition it is 59 metres tall, 5.5 metres in diameter and weighs 300 tonnes. Completely dressed the column stands 59 metres tall, is 12.5 metres in diameter and weighs 455 tonnes. Another important point is that its centre of gravity is offset from the geometrical centre of the column.

ADGAS approached Al Jaber Heavy Lift (AJHL) to study and prepare the constructability report for all associated tasks and then hired the services of AJHL as a contractor to execute the job. AJHL had pre-assessed the critical aspects of the project during the initial feasibility study. In the final report to ADGAS, AJHL made proposals to overcome these difficulties to execute the job safely.

Time pressure

The biggest challenge was to minimise the time of replacement and tie-in of the exchanger. AJHL proposed to build two temporary foundations about 50 metres from the existing column and to bring in the new column in a pre shut down phase. It would then be erected on one of the temporary foundations so that it could be dressed up and ready for tie-in during shut down in a minimum possible time.

The pre shut down phase of the project started with the preparation of a barge for receiving the MCHE directly from the heavy lift vessel. The column was received directly onto the barge Al Jaber 37. The barge then sailed to Das Island and berthed at the construction jetty where the column was off loaded. Subsequently the column was reloaded onto self propelled modular trailers (SPMT) and shifted to the site. Placement of the new bare column onto the temporary foundation was carried out safely.

During the shutdown the old column was removed from its existing foundation on 24 October 2009 and placed on the second temporary foundation. After two days, on 26 October 2009, the dressed up new column was shifted from its temporary foundation to the existing foundation and tied in with the plant as per the planned dates on the shut down schedule.

This unconventional methodology resulted in considerable reduction in the time that the plant was shut down, Al Jaber says.

Factors

Other major factors which made the project more critical included the site conditions, limited space in the plant for manoeuvring of trailers, and height restrictions along the route from harbour to train 3. In addition Al Jaber had to contend with a jetty without any break water or roll on-roll off facility, an LNG loading jetty right beside them, the heavy traffic of LNG carriers and a limited draft available for barge berthing.

The available draft in Das island harbour and construction jetty restricts the heavy lift ships that can berth there. The 5,000 tonne capacity Al Jaber 37 was chosen because it only draws around 2.5 metres draft for berthing in Das Island waters.

In addition, along the route from the harbour to train 3, LNG loading jetty supply lines cross the road, which restricted the transportation of the column from Das Island harbour to train 3. To solve this Al Jaber proposed to receive the column at the construction jetty onto its 56 axles of self propelled modular trailers and then transport it to the lifting point.

Due to a requirement of long reach with high capacity to erect the column from a 45 metre radius a 1,600 tonne capacity Terex Demag CC 8800-1 lattice boom crawler crane and a 600 tonne capacity Terex Demag CC 2800 lattice boom crawler crane were used as main and tailing cranes, respectively.

The most important aspect of the execution of the whole project was the co-ordination between client, other subcontractors and AJHL.

Arranging documentation from the local and government authorities, for example, security passes for personnel and equipment, work permits, etc were the integral requirements of the project. All these requirements were arranged on a timely basis by staff at the Abu Dhabi head office.

Making plans

Many planning sessions were held internally and also with the client to plan for the equipment and labour requirements and their mobilisation schedule to ensure that personnel and equipment were available in the Island on time ready for the lift.

Al Jaber's health and safety procedures and documentation are developed to international standards and they are comprehensively applied, according to the company. "Our quality procedures are fully certified and comply with ISO 9001-2004 and our personnel are all trained and externally certified to appropriate levels, which comply with international standards. This ensures that our teams are capable of handling expensive and delicate equipment and are fully aware of the consequences and impact on project schedules if not handled correctly," explains a spokesperson.

Al Jaber reports that in 2009 it achieved 2.5 million man-hours without lost time accident. "We are delighted with this achievement which is the result of the combined efforts of AJHL management and staff together with the support and commitment of our customers," says Al Jaber.

To the satisfaction of the customer, Al Jaber completed both of the project shutdown phases ahead of the planned date without any lost time accidents (LTA). The MCHE was so delicate that, for warranty purposes, the manufacturer installed vibration detection equipment inside the MCHE so vibration could be analysed after completion of each element of the work. Results were well within acceptable limits, according to Al Jaber.

Al Jaber cites this project as an example of how early involvement, teamwork, a meticulous approach to safety and operations, and an in-depth understanding of the client's needs and operational requirements can make it possible to work successfully in a restrictive and dangerous location.