36" Flare Lines
Overview
Working with their South East Asian partner Advantage Marine Services (AMS), they fulfilled the lifting scope to enable repairs at 14 locations along two adjacent 36”/24” flare lines with WT readings less than 2mm at the touchpoints while in-service.
Challenges included rigid connections between adjacent flare lines, significant lifting loads and pipe stresses to name a few which all had to be calculated and managed to ensure a safe lift while providing the access required to perform the repairs.
The Need & Challenge
Two flare lines along the top level of a pipe rack required inspection and remediation of corrosion/erosion damage at select touchpoints identified to have less than 2mm remaining wall thickness. Flare lines are critical to the safe operation of a plant and it’s an immense cost and challenge to take one out of service without shutting down production. The lines had to be safely lifted while in-service using an engineered methodology that included Lift Plans, Stress Analysis calculations, Methodologies and Risk Assessments.
Complicating these lifts were (1) a 36” connection to one of the flare lines which added extra weight and rigidity to the line being lifted, (2) a smaller 6” bridging connection between the two adjacent flare lines which was calculated could withstand no more than 5mm of relative vertical displacement before the connections became over stressed, (3) the weight and rigidity of the lines whereby lifting at a single location would risk overloading the supporting beam.
Solution & Outcome
After modeling the piping system using actual design & operating conditions and piping geometry, multiple iterations of varying displacements were applied to the piping. The restrictions were a maximum reaction load of 10 tonnes at each lift point and not to exceed 90% of the B31.3 Design Code Allowable stress on the piping system while providing a minimum of 45mm of lift to provide access for remediation.
The solution was a simultaneous lift at 4 locations to 2 different elevations summarized in the diagram below. A comprehensive Methodology was provided to direct crews during execution and to ensure the line was lifted and lowered as per the engineering calculations.
Some locations were along simply supported, straight runs of piping without interference from connections or fixed points. A stress analysis confirmed a simultaneous lift from 2nd adjacent supports would minimize pipe stresses and reaction loads against the supporting beam while providing free access to the target support for remediation.
Lifting was performed using the Ovolifts Multi-Jack (with a Working Load Limit of 10 tonnes each) from 2nd adjacent beams installed on either side of the target support. The two jacks were lifted simultaneously to reduce pipe stresses and the reaction loads against the lifting equipment. The ability to do this is one of the unique features of Ovolifts’ jacking system.
