Sutro Group has recently completed the maintenance of unloading arms at Liquified Natural Gas sites in the UK. Our rope access specialists were tasked with maintaining the arms with the support of our NDT and Drone inspection services. The project was completed within budget and ahead of schedule with zero lost time incidents.
An unloading arm is a mechanical arm consisting of articulated steel pipes that connect a tankship such as a gas tanker to a cargo terminal. Natural gas is a cornerstone in the UK energy supply and is the fastest-growing main source of fuel. To be transported, it must be liquefied to reduce its volume six hundred times by lowering the temperature down to -162°C. This means that special attention has to be paid to maintaining the loading arms as they are required to withstand extremely low temperatures.
The project team consisted of four specially trained rope access engineers to carry out the work. The project team was supported by a Sutro project manager who was responsible for the communication between the rope access technicians and the onsite planning and maintenance department.
This team structure can be deployed at sites throughout the UK and Europe to maintain up to 10 unloading arms at any given site.
The benefits of maintaining unloading arms with specialist rope access teams compared to using scaffolding and cranes include:
- A safer method of work
- More cost-effective
- Fast deployment and de-mobilisation mean less downtime for the unloading arm
- Self-contained Sutro teams minimise Permit To Work issues
A typical unloading arm maintenance regime is as follows:
- Rig the product line with chain blocks and slings at the bottom of the base riser, ready for it to be disconnected from the birth connection and the arm at style 50.
- Fit product lines with brackets at the top of base riser to hold it in place while disconnected from the arm.
- Unbolt product lines at style 50 and lower inside of the base riser.
- Strap secondary counterbalance weights with 5 ton chain blocks to the inboard arm ready to disconnect and release inboard pantograph table from its sheath in preparation for stowing of the arm.
- Remove instrumentation, rotameters & potentiometers for service or replacement.
- Rig turfor cables from the top of the inboard arm to the back of the birth ready for stowing of the arm.
- Remove cables from base riser coil and stow at style 50 ready for disconnect.
- Drain down and remove hydraulic lines from base riser and style 50, thus disconnecting all electrical and hydraulic lines from base riser to the arm ready for lifting.
- Remove grease lines from slewing collar/pantograph wheel.
- Rig / remove and lower off inboard cylinders ready for stowing on the arm.
- Remove and lower off working platforms from style 50.
- Rig primary weights with straps and pulleys for control while stowing arm.
- Disconnect slewing collar and rotate to avoid jamming at lift.
- Pull arm horizontally using turfor cables chain blocks and pulleys to stow the arms horizontally.
- Assist barge team / crane team / lifting supervisor in connecting the bow shackles to the lifting eye of the inboard arm.
- Unbolt arm at style 50 to allow for lift.
- Arm serviced at dry dock in Pembroke.
- Rebolt arm upon lift from barge to style 50, cradle upon return.
- Reverse turfor pulley and chain block operation to stand the arm back up on the birth.
- Reconnect inboard cables.
- Reposition and re-bolt slewing collar.
- Refit style 50 working platforms.
- Lift and fit new inboard drive cylinders.
- Refit grease lines.
- Reconnect hydraulic and electric lines.
- Remove turfor and chain blocks from inboard arm.
- Fit new ladder system to riser.
- Reconnect and assist with check and test of perc collar and emergency release system for style 80.
- Refit new potentiometers and calibrate with jetty control.
- Grease and service new pantograph cables.
- Assist in oil check and test operations ready for the recommissioning of birth
With 25 years of experience working for blue-chip clients in a range of sectors including industrial, construction, power, utilities, oil & gas sectors we have the expertise to deliver industry-leading results. Call us today on 0800 069 9395.