High speed gouging with a robotic system

2 min read

When a Norwegian oil refinery set its sights on becoming the safest in Europe, it challenged Jet Set Hydro Technics to develop a method for removing worn storage tank bottoms using ultra-high pressure waterjets. Using a robotic system, the refinery was able to work towards their goal with safety, speed and efficiency.

Ragworm is powered by a 55,000 psi (3,800 bar) diesal waterjet intensifier pump
Ragworm is powered by a 55,000 psi (3,800 bar) diesal waterjet intensifier pump

Jet Set met the refinery’s challenge by developing Ragworm, a unique robotic system which uses dual 46,400 psi (3,200 bar) waterjets to strip the tank walls from their old floors and roofs without the risk of explosion or the creation of toxic fumes associated with traditional cutting methods such as oxyacetylene torches.

Martin Grijpstra, president of Jet Set said: “Ragworm is at least five times faster than cutting with torches and 30 times faster than the standard gouging method and you have no follow-up damage to the tank terp (foundation). We can set up three or more Ragworm robots at once in the tank to do the job and you can be doing other work in the tank at the same time as we are cutting. This way you can save time and time is money!”

Named for a bait worm that lives on the ocean floor, Ragworm crawls along the bottom of a tank and cuts away sheet after sheet of steel plate. It can also ride along the side of the tank and separate the walls from the floor and roof.

The Ragworm is powered by a 55,000 psi (3,800 bar) diesel waterjet intensifier pump manufactured by Jet Edge Inc of St. Michael, Minnesota, USA. Using only 4 litres (1 gallon) of water per minute, Ragworm has minimal impact (5 cm or 2 psi) on the underlying terp. It requires only two operators, one controlling the diesel-generated power-pack and Jet Edge waterjet intensifier pump located outside the tank, the other controlling the cutter unit within the tank. Ragworm can easily cut through 6 mm-thick (.24”) carbon steel at an average speed of 100 metres (328’) per hour.

Since its first project, Jet Set’s mission has been to constantly improve safety, speed and efficiency, Grijpstra noted. Refinements over the last year have almost doubled Ragworm’s cutting speed.

Last February, Jet Set simultaneously deployed two Ragworm machines at the BP-operated INEOS Finnart Ocean Terminal in Scotland. When cutting started, the tank renovation project was eight days behind schedule. To the surprise of the main contractor and site management, the project was four days ahead of schedule when the cutting was done. Jet Set’s operators cut the complete bottom of the 70 metre (230 feet) diameter tank into plates of 6X2 metres or 19.7X6.6’ in no more than 100 cutting hours, despite the fact that 20% of the tank was double plated.

After trying different waterjet pumps, Grijpstra decided to power Ragworm with Jet Edge intensifier pumps because of the Jet Edge pump’s ability to produce a flow rate of 15.52 litres (4.1 gallons) per minute and power two machines at the same time.

Jet Set has grown since introducing Ragworm, Grijpstra said. The company, which was started in 1988 and is co-owned by Gripstra and his wife, Sonia Grijpstra-Muir, now provides contract mobile waterjet cutting services to the petro-chemical industry throughout Europe, Canada and the United States. It manufactures 80% of its Ragworm systems for its own use, and sells 20% of them to other contractors. Ragworm’s US customers include Exxonmobil, Total Refinery, BP INEOS Refinery, VOPAK Tank Terminal and Conoco Phillips.