Thunder Cranes successfully completed the challenging first phase of a crane replacement project in offshore Angola. The goal of the first phase of the project was the safe removal of a platform crane boom. Our scope included comprehensive site surveys for detailed planning, followed by rigging and lifting operations with portable-modular cranes.

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Case Summary

The PALP2 crane boom at Sonangol’s PALP2 offshore platform  in Angola had to be removed after it had suffered a  technical failure. Following the failure, the crane boom was hanging from the luffing cylinder, and was temporarily immobilized in a suspended position.

Our client – NPE – brought in Thunder Cranes lifting experts to execute the boom removal project using our modular crane.   The modular crane was chosen as a safer and more cost-effective alternative to a crane barge. The modular crane rigged up on deck would provide stability and precision, while a barge crane, due to sea conditions, would be in a dynamic situation.

Our TC20 stiff leg crane was used for the project due to its capacity, hook height, and portability.  The TC20 was supported by a TC05 assist crane.

The project involved rigging, skidding, welding deck reinforcements, and a rope access team.

Challenges & Solutions

Key Challenges:

  • PALP2 crane is broken and only PALP1 crane is functioning but it is located 150m from PALP2, making it challenging to bring modular cranes to the worksite.
  • PALP2 crane boom is hanging in a hard to access position, and it cannot be cut into smaller sections due to hydraulic oil leak hazard.
  • There are space constraints on the PALP2 17 deck, which makes it challenging to rig up modular cranes.
  • Structural reinforcements will be needed at the PALP2 rig up location due to strengthen 17 deck beams.

Solutions:

  • Multiple site surveys and studies were required before the methodology could be confirmed. Many aspects of the job – from rig up procedure, to equipment and materials – needed to be customised, or fabricated, specifically for this project. TC worked with NPE to provide expertise, engineering support, and step-by-step procedures for the job.
  • To carry out the critical lift, Thunder Cranes proposed the TC20 portable-modular stiffleg crane. We determined that the TC20 could be rigged up and positioned next to the broken PALP2 Crane, and from there it would be in a position to carry out a complex lifting plan (described below).

Modular Cranes

  • TC20 to carry out the critical lift. TC05 served as the assist crane for rigging up TC20.

Tie Down System

  • Deck reinforcements and spacer pads were required at the PALP2 17 deck in order to support the installation of the TC20/TC05 modular crane.
  • Engineering calculations and drawings were carried out by Thunder Cranes and I-beams and Spacer Pads were ordered, custom fabricated and flown in from UAE.
  • The 17 deck was cut open and i-beams & spacer pads were welded in by specialized welding contractors.
  • The base beams for TC20 and TC05 were then welded to the spacer pads with dog plates.

Scaffolding

  • Due to space constraints, the handrails at 17 deck were removed, and scaffolding was used to extend the platform by 1 metre.
  • Scaffolding was installed below 17 deck to provide a workfloor for welders, and also to protect production and piping equipment on 11 deck.

Transfer from PALP1 to PALP2

  • PALP1 and PALP2 are connected via a bridge walkway.
  • PALP1 has a functioning crane which was used to offload TC05 & TC20  from the supply vessel to a lay down area on PALP1.
  • Manual skidding with trolleys was used to transfer the TC05 & TC20 crane components & powerpacks from PALP1 to PALP2.
  • The work site was on 17 deck, however due to width restrictions, some TC20 components had to be moved on the 11 deck, and then lifted with TC05 from 11 deck to 17 deck on PALP2.

Rope Access & Specialized Rigging

  • PALP2 boom was hanging in a hazardous and hard to access position. Rope access teams were needed in order to first secure the boom, and then to install slings and hook the slings up to the chain blocks which were hooked onto the TC20 main block.
  • By positioning TC20 boom over the PALP2 boom, the rope access team would be able to rig up to, ascend and hang off the TC20 boom to safely access the PALP2 boom.
crane-replacement-offshore-platform

Steps/Sequence of Work

  1. Mobilization offshore for site preparation works – removal of obstructions, erection of scaffolding, welding deck reinforcements. 16 Sept 2022
  2. TC05 & TC20 mobilization offshore to PALP1. 17 Oct 2022.
  3. TC05 & TC20 crane components lifted by PALP1 platform crane from supply vessel to the first staging area on PALP1.
  4. TC05 & TC20 crane components skidded from PALP1 to PALP2.
  5. Welding of Spacer Pads for TC05 and TC20.
  6. TC05 base beams installed and welded to spacer pads with dog plates.
  7. TC05 rig up without any assist crane, followed by 3rd party inspection and load testing.
  8. TC05 lifting components of TC20 from 11 deck to 17 deck.
  9. TC20 base beams installed and welded to spacer pads with dog plates. rig up
  10. TC20 rig up supported by TC05, followed by 3rd party inspection and load testing.
  11. Following the TC20 rig up and load test, the crane boom removal operation could begin.
  12. Rope access technicians secure the broken boom with a system of brackets, clamped from the PALP2 pedestal to the PALP2 boom and then proceed to remove the boom’s aluminium walkway and also proceed to prevent hydraulic lines from leaking.
  13. Rope access technicians weld stoppers for more secure sling placements and proceed to sling the boom and hook up the slings to chain blocks on TC20 crane hook.
  14. TC20 now takes the PALP2 boom weight under tension, allowing the rope access technicians to safely disconnect the luffing cylinder and brackets so that the boom is now completely detached and hanging freely from the TC20 hook.
  15. Engage chain blocks for lowering the hanging boom from a vertical into a horizontal position.  Laydown PALP2 boom on 11 deck. Completed on 22 November, 2022.
  16. Supply boat come alongside platform and TC20 lowers PALP2 crane boom from 11 deck to supply boat deck.

Outcome

The boom take down was successfully carried out on 22 November 2022.  The project timeline from site preparation and deck reinforcements works, to modular crane installation and boom removal works, was just 67 days despite the many challenges.

The project was completed safely, successfully and on time, thanks to excellent preparation and teamwork with clients and partners. This project was many months in the planning and complex in the execution, including the requirement to execute creative, complex rigging and skidding procedures.

Our clients experience can be summarized by the following feedback from Sonangol’s lead engineer for the project:

“Very good planning and execution. Safety first in every part of the project from beginning to end. The service met all objectives and surpassed our expectations”.

– Marinela Chipepe, Mechanical Engineer

Application
  • Lifting Solution for Crane Replacement Offshore
Challenges
  • PALP2 crane in difficult to reach location
  • Space constraints
Our Service
  • Offshore Rental Crane TC20 & TC05
  • Complex Rigging & Skidding
  • Crane Operators
  • Detailed Planning & Preparation
Benefits
  • Cost effective, safe, precision lifting solutions
Location
  • Angola