21 Mar 2013
As part of our continued expansion, Zenith has developed an offshore division. So far during 2013 we have several offshore projects involving flare tip replacements around the globe without the use of helicopters or barge cranes. Typically, we are asked to present an initial concept design and budget costings. Very often any in-situ lifting davits and access platforms cannot be relied on for integrity due to the effects of heat radiation and the marine environment. So the first stage often involves the actual design of the temporary lifting davit and temporary platform itself, incorporating the necessary details which would allow the tip to be lowered and hoisted into position.
The second being the structural appraisal of the existing flare stack/boom to ensure the additional loading of the platform and the eccentric load of the tip whilst it was being removed/installed does not adversely overload the system. The design of the lifting davit is developed to minimise the moment forces at the base of the davit, consequently minimising the ‘push/pull’ reactions on the stack itself. In order to achieve this, the length of the upper boom is kept to a minimum while the introduction of a back stay wire effectively balances out the overturning forces. The majority of the forces are transferred through the davit structure in compression.
The latest Building Information Modelling (BIM) software is typically used, enabling a smoother workflow and interoperability between the drafting and the analysis packages. A loading assessment and detailed structural analysis of the davit and existing stack is undertaken, with a number of loading permutations to establish the stress increases in the stack. The stress increases are interrogated within the model in order to establish if they are beyond the permissible limits.
“We carry out the entire project from front to back providing structural engineering and on-site execution of the works, inclusive of the temporary access and replacement of the davit. All temporary works are installed at the start of the shutdown and removed prior to the flare going back on-line. We have gained invaluable experience in carrying out projects in remote parts of the globe. Projects of this nature require detailed planning and logistical know-how whether we are operating in the Pacific Rim, the Gulf or elsewhere,” comments Darren Smith, Business Development Director.