*Article published in CRANE BRASIL Ed. 69
The solution proposed by TechCon Engenharia for replacing the pump avoided the costs of mobilizing a crane or construction ship, and allowed the operation to be carried out with the offshore platform’s own crane.
To optimize costs and reduce environmental impacts, the offshore industry has sought to replace old equipment with new ones, with greater efficiency and lower emissions. One of the largest energy companies in the world, owner of offshore platforms in Bacia de Campos, RJ, began replacing water injection pumps in oil wells in order to increase the pressure and flow of injected water. For this, it was necessary to install a large pump, consisting of a metallic structure, motor, piping, transformer, electrical panels, damping system and other parts. In addition to several fragile control, process and instrumentation parts, the impact of which could cause severe damage to the equipment.
The platform crane did not have the capacity to lift the entire load and there was also no access for the crane to the final assembly position of the load, as it was located under the second deck of the platform, with 2 other decks and the drilling tower above. A possible solution would be to mobilize a crane ship or a construction ship to carry out the lifting. However, the cost of an offshore construction vessel for spot work, that is, occasional work, is approximately US$ 50,000.00 per day, with the need to mobilize it, for about US$ 500,000.00, in addition to the long time of mobilization.
Another need generated by replacing the equipment was reinforcing the deck floor to receive the new pump, which is much larger and heavier than the existing original pumps.
The solution to the problem of high pump weight and high cost with a crane ship was to divide the cargo into parts with weights compatible with the capacity of the offshore crane on the pedestal of the platform with lattice boom. This facilitated handling and reduced the risk of collisions, since the use of a crane ship would require a special procedure to avoid rocking the cargo to place it under the deck.
To solve the problem of crane access, 02 temporary platforms were manufactured and assembled, which functioned as “balconies”, extending the lower deck beyond the upper decks. The lifting project (rigging plan) included the structural design of these platforms as well as their lifting for assembly. Fixation was performed using screws, eyebolts, steel cable slings and turnbuckles. One of these temporary platforms was so practical that it was permanently incorporated into the platform.
This solution allowed the direct placement of the cargo on trolleys on wheels, equipped with lashing points to stabilize the cargo during movement. The wheels are guided by rails and for the larger loads, horizontal movement was handled by winches, ensuring smooth and safe movement from the temporary platform to the area below deck next to an overhead crane. This bridge, together with its bearing beams, was manufactured and assembled to lift the load under the deck and move it to its final position, which is also included in the rigging plan.
The place where the new pump was installed had to be cleared, removing the existing pump, the existing monorails and also the mezzanine structure of existing valves. For this, solutions were developed using the structure of the platform itself as a support for hoists, tie rods, slings, eyes and other lifting accessories, with a solution being detailed for each part. The structural integrity of the platform at each point was verified, guaranteeing safety of the hoist.
For the installation of the pump transformer, it was necessary to build a mezzanine with a metallic structure, as well as a temporary structure to support it during assembly. Due to the size of the mezzanine and the available space, the structure was divided into 3 modules, lifting with translation using hoists supported by the platform structure with welded eyes. The modules were
moved horizontally using hydraulic jacks and Teflon beams.
To reduce the uncertainty due to the dismemberment of the cargo, during the preparation of the rigging plan, TechCon Engenharia carried out field weighing to measure the weight of each part of the cargo, as well as precisely determine the center of gravity. Field inspections were also carried out to analyze interference and check dimensions so that the rigging plan portrayed the exact condition of the site. In operations where an existing rocker arm was used, structural verification was carried out using the finite element method.
In addition to the offshore lifting projects, onshore lifting projects were developed to place the various parts of the pump in containers and baskets for transporting and moving the containers and baskets to the platform support vessels (PSV). The rigging plan also covered lashing projects for all parts of the cargo for maritime transport.
When necessary, the structural design of lifting accessories such as skids, eyes and spreader frames was prepared. All operations contained in the rigging plan were successfully executed, and TechCon Engenharia supervised all lifting operations in the field.
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