Flow lines are removed for scrap when an oil or gas field is depleted. It is an essential step from an environmental point of view, returning the seabed to the condition it was in before the field began production.
But when DOF Subsea was appointed to run a decommissioning operation in the Bass Strait to remove flow lines from the seabed there, project engineer Jun Ikeda faced some particular challenges.
With the offshore construction vessel that the flow lines are loaded onto costing by the day, time was of the essence. Plus DOF Subsea needed to fit any cutting shears to an existing crane arm.
"The shears had to have a low enough weight while still having sufficient crushing force to easily cut through the product," Ikeda explained.
"The weight issue was because we were mounting them on an existing crane/manipulator on a vessel that had limited load carrying capacity."
His problems were solved by Embrey Attachments, a Victoria-based manufacturer and distributor of attachments including scrap metal and demolition shears, grapples, universal processors and concrete pulverisers for the demolition, scrap, waste, recycling and construction industries.
Sales manager David Embrey quickly recommended the company’s EDS30 demolition shears to Ikeda to cut the flow lines into sections which can then be loaded onto an offshore construction vessel and later turned into scrap.
With the need to make sure the shears could cut the flow lines, Embrey suggested Ikeda try a test run with the EDS30 shear before sending them into Bass Straight.
"David was able to tell us the location and owners of some EDS30 Embrey shears in our area so we could conduct cutting trials using some sample flow line off cuts," Ikeda explained.
The trials were a resounding success.
"The shears were perfect for the job because they can cold cut. They are like scissors, they can slice through without creating a spark," Embrey said.
"Also they could be fitted to the overhead crane’s arm on a rotating hitch, which gives them ultimate manoeuvrability."
The flow lines Ikeda’s project were removing and cutting were already flushed and cleaned so there was not any oil remaining in them, but using shears that do not create sparks is still a safety issue whenever flow lines are being decommissioned.
"Hot cutting methods like oxy or saw cutting or grinding can’t be used," Embrey said.
"You can’t use anything that might create a spark. With the EDS30, there are no sparks."
Power is also crucial to slice flow lines with a diameter of 220mm made of several layers of different materials including high tensile steel wires, so it was important the custom-made EDS30 demolition shears had a high power to weight ratio.
"That means they are light enough, but also powerful enough," Embrey added.
And the overall result?
"DOF Subsea finished the work a week ahead of schedule."
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