Impressive scaffolding project in the maritime industry: membrane replacement in LNG carrier
The challenges of assembling a scaffold in an LNG tank
Whether oil platforms, refineries, mining, bridges, or shipyards, scaffoldings’ possible fields of application are almost limitless. Each location has its own challenges and pitfalls. In shipbuilding and ship maintenance in particular, scaffolding must not only be versatile and adaptable to the individual shape of a ship, but also be particularly resistant and easy to handle. Small material supply possibilities, harsh weather conditions and cramped or angled working spaces are just some of the challenges faced by scaffolding in the maritime industry. But how do you implement a scaffolding project in shipbuilding and ship maintenance? The project of the Spanish company GABADI S.L. in cooperation with Scafom-rux España shows how the challenges of scaffolding in the maritime industry can be solved.
Coping with little space and sensitive material
The task: the complete tank membrane of a 215-metre-long LNG carrier was to be replaced. To prevent leaks in the renewed tank, the replacement of the membrane required the highest precision from the GABADI team. Even before the start of the project, the necessary work steps were therefore rehearsed for 3 months in order to minimise possible sources of error in advance.
The tank of an LNG carrier consists of a membrane made of the iron-nickel alloy Invar, which has to withstand large temperature fluctuations. This is because LNG must be cooled down to its boiling point at 162 °C during transport in order to maintain its density, which is 600 times lower than in its gaseous state. However, when the LNG carrier is in the shipyard without cargo, the temperatures inside the tank reach up to 40 °C and higher. In order to ensure the greatest safety at all times despite these extreme temperature fluctuations inside the tank, the primary and secondary membranes of the tank must be renewed regularly. This is not an easy task: Not only is space scarce when replacing the membrane, but also the utmost care must also be taken as the material can be contaminated easily.
The project required a safe and efficient working platform that allowed the team to get as close as possible to the tank walls without damaging the material. GABADI hired 800 tonnes of material from Scafom-rux's modular scaffolding system RINGSCAFF for this purpose. To avoid contamination by dirt during the membrane replacement, Scafom-rux rented out completely new scaffolding material for the project.
Minute planning and preparation were the key to success
A total of 50 team members erected the work platform encompassing the entire tank within two weeks, with 20 people alone responsible for the material supply. This had to be planned and prepared particularly carefully, as it could only be done through a round opening in the ceiling of the tank. Because of this difficult transport of the scaffolding material into the interior of the tank, it was provided by the manufacturer in several deliveries adapted to the order of the scaffold assembly. Using a crane, the scaffolding material was thus transported step by step into the interior of the tank and installed there.
After setting up the working platform made of RINGSCAFF material, the old membrane layers could be removed, shredded and transported out of the tank by crane. After that, first the outer membrane was replaced, then the insulation boxes made of plywood were screwed onto it and finally the Invar panels of the inner membrane were attached and precisely welded with automatic welding equipment.
Rented special parts were the cost-effective solution for coping with the shape of the tank
For these work steps, the working platform had to be particularly close to the tank’s walls. Since the membrane tank is typically octagonal in shape, conventional scaffolding would not reach close enough to the wall without losing its stability.
Being as close to the tank’s walls as possible could only be achieved by extending the work surface with brackets. To ensure that the work could be carried out with as few barriers as possible, GABADI used over 1,500 telescopic brackets without spigots for the standards. The plus: these special parts were also provided by Scafom-rux as rented material and could be returned at the end of the project.
Time-savings thanks to guided loading of the scaffolding material for the return transport
The membrane renewal was successfully completed within 6 months with a total of 120 people involved in this complex project. Within 10 days, the RINGSCAFF working platform was dismantled, whereby a lot of time was saved by the fact that a Scafom-rux yard employee guided the GABADI team in the efficient loading of the material for the return transport. After dismantling the working platform, the outer invar membrane layer could also be applied to the bottom and lower side wall of the tank, which had previously been left out to prevent the material from being damaged by the load.