DIAJET - abrasive waterjet cutting

Cold Cutting in Hazardous Environments

NEWS from DIAJET issue 3

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Diajet Launches Specialist On-Site Cutting Service

In order to make the Diajet's unique hazardous area cutting capabilities available to companies and contractors with a one-off need, Diajet Ltd now provides operators and equipment for difficult dismantling and repair/modification projects.

The service specialises in developing tailored cutting plans and creating bespoke manipulation and shielding systems where required, in order to execute precision cutting projects. The fact the power unit can be located many metres away from the target, and only a single hose is required to supply the compact cutting head which can cut any material, means that accurate machining can be carried out in confined spaces. The service is available for both on and offshore projects and with its ability to cut in flammable atmospheres plant downtime can be minimised.

Complex Offshore Cutting Completed

In a highly focussed effort over 3 days Diajet personnel completed an offshore cutting project on the internals of a glass lined slug catcher. Using specialised manipulators developed on mock up rigs, Diajet's expert engineers removed a 20" pipe stub and an internal baffle system to a precision of <1mm.

Cutting on the mock-up rig

Access to the vessel was restricted to an 18" manway through which all equipment and shielding had to pass. Entry to the vessel, with minimal ventilation, required both breathing equipment and protective clothing and the engineers were working virtually blind during cutting operations.

However the cold machining characteristics of the Diajet and the precise pre-adjusted manipulators ensured a perfect cut without damage to the surrounding coatings. This allowed the prefabricated modifications to be installed without adjustments and the work to be completed within the time window.

Mine's Older than Yours - so there!

In response to our last article Andrew Stocks of Precision Water Cutting Services in South Africa has contacted us with the news they have two Diajet 345 Bar Jetknife systems some 18 to 20 years old, which they proudly say are still in regular use.

We have also recently paid a service visit to an example of an X2C twin vessel system (around 17 years old) as it is still being used on North sea cutting projects.

We think we have now found our oldest working unit - unless you know better! If you know of an even older Diajet that is still working - let us know!

Did you know....

DIAJET will cut in hydrogen-oxygen atmospheres?

Test work done for the HSE's Safety Engineering laboratory demonstrated cutting in hazardous atmospheres. The gas mixtures were then detonated with a spark to prove that they were indeed explosive!

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Bridge Cutting Project

Diajet has successfully completed a cutting project on a Victorian cast iron bridge, as part of a new urban transport tramway. The bridge, which was coated in high lead paint, required strengthening to accommodate new HGVs and disruption had to be kept to a minimum. Services that had been laid over the years included gas mains and 30 KVA electricity cables. Their location was uncertain and shops had also been built on part of the bridge to within 0.3m of the outer girders.

Cutting close to cables

The cut had to be a controlled depth in order to relieve the girders but not sever them, allowing them to sink onto the new reinforced concrete supports. As headroom below the girders was highly restricted a specialised manipulator and clamp was designed to secure the cutting head and small holes were excavated in the roadway to allow access to the top of the beams. Cuts were executed in all beams sometimes within centimetres of the cables and gas pipes.

A more extensive account can be seen in the Institute of Civil Engineering magazine later in 2006.

Going with the Flow

Abrasive jet cutting utilises a very simple, powerful mechanism - similar to firing millions of tiny bullets at the target. The problem normally is delivering the "bullets", without breaking the pipeline!

In DIAJET systems, by clever use of fluid dynamics the flow patterns within the pipe is controlled so that the solid is kept in suspension. As a result, the hose life can be measured in 1000s of hours!

The approach flow to the nozzle and its design accelerate the suspension in a very short distance to speeds in excess of Mach 1. The cooling and flushing of the cut prevents the formation of a heat affected zone and cleans the cut.