Page 82: of Offshore Engineer Magazine (Oct/Nov 2013)

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inability to deliver abrasive to greater depths,

Testing in Lake Superior cut a as well as pressure loss inside the hose or high 14in. diameter pipe underwater.

pressure tubing.

In 2010, Chukar Waterjet developed a waterjet system used at 1430m (5000ft) on the Macondo well in the US Gulf of Mexico. It needed to remove accumulating hydrates that were making it diffcult to cap the well. Other methods of removing the hydrates, including using metha- nol dispersant, had been unsuccessful.

Chukar used seawater pressurized by a hydraulic waterjet intensifer pump, in con- junction with a methanol dispersing system, to remove the hydrates from the bottom and the inside diameter of the spool as it was being lowered into place. The sealing surface was then able to go over the fange and mate with saw became stuck in the full fow pipe,” he says. the lower marine riser (with the spool acting as “After the saw was dislodged, a shear was then the connector), which the valve system could be used to cut off the riser, leaving a jagged cut.” mounted onto. Underwater welding and fame-cutting tech-

The system operated for extended peri- niques are well established, but safety risks have ods while at 1430m deep and 3° Celsius (37° placed increased pressure on dive operators to

Fahrenheit), with ambient pressures of 150 minimize reliance on both, he says.

bar (2100 psi) and exposure to salt water and The system developed by Chukar is able to methanol. carry enough abrasive on the waterjet skid in

Chukar has now extended the depth at which order to provide cutting of 50m (160ft) of 12mm- its UHP waterjet intensifer technology can thick steel, independent of depth, in a single work to more than 3000m, for both cutting and deployment. hydrate removal. The process of abrasive waterjet cutting typi-

In April, the latest system performed a cally involves a UHP (3900 bar) stream of water successful test cut in in Thunder Bay, Lake with an abrasive, such as garnet, added. Without

Superior, Ontario. An UHP waterjet pipe cutter abrasive, water-only waterjets are typically used was used to cut a 14in.- (356 mm) diameter, ½in. for cleaning or for cutting soft materials.

(12 mm) thick steel pipe, in under 20 minutes.

Using waterjet tooling, either hand-held or

Warren Christopherson, operations manager using an ROV, the UHP stream is directed to a at Chukar Waterjet, says that saws designed for surface or cutting area, for cutting holes or linear pipe cutting, including diamond-wire saws, can cuts, and cutting pipes from the inside or outside. cut off pipes or other offshore structures, but The system, controlled from the surface, they can bind, because they must enter into the is deployed with an umbilical cable, provid- saw cut gap (kerf) to complete the cut. ing power and communication, using either a “Attempts to cut off the riser pipe at the diver or ROV to aid skid and tooling placement,

Macondo oil well in 2010, with the use of a dia- depending on water depth. mond-wire saw, were unsuccessful because the For coating removal or hydrate remediation, seawater or methanol is pressurized to 3900 bar

During testing, the skid was deployed at Lake Superior.

by an intensifer-style pump, to create a uniform application to remove coatings like epoxy or concrete without damaging the substrate.

For cutting applications, seawater is pressur- ized to ultra-high pressure by the intensifer- style pump, and abrasive is added to create a cold-cutting tool, effective at cutting most mate- rial, including up to 250mm steel.

Chukar’s system is powered by a 150hp electric motor, running at 3000 volts and is aimed at cutting and cleaning, decommis- sioning, maintenance, and salvage, as well as emergency response use. Sea water, plain water or methanol can be used, along with abrasives added for cutting applications.

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