Operating Under Extreme Conditions

Operating Under Extreme Conditions

Extreme Operating Conditions at the Antarctic

We are proud to have been selected to supply high pressure pumps for an ambitious scientific mission to collect water and sediment samples from Lake Ellsworth, some 3 km beneath Antarctica. Cat Pumps positive displacement pumps will feed high pressure hot water as part of an innovative borehole drilling system operating under arduous conditions.

The British Antarctic Survey’s Lake Ellsworth Programme, which has been in planning for almost 15 years and which you may have read about recently in the media, will start drilling in December 2012 and over a period of three days will sink a 360mm diameter borehole through 3 kilometres of solid ice at -20ºC. This will be the first of Antarctica’s 400 known sub-glacial lakes to be measured and sampled and the most effective way to obtain rapid, clean access to the lake is by hot water drilling. A specially developed nozzle will be lowered slowly down to the lake, fed by a constant supply of water at +90ºC pumped at a pressure of 140 bar using four of our stainless steel triplex pumps.

This will be the largest hot water drilling system ever to have been constructed. Comprising several bespoke components, the system begins with a large reservoir of melted ice contained in three holding tanks, each with a capacity of 30,000 litres. This water is drawn through a four-stage filter system and a UV steriliser to avoid any contamination of the ice in the borehole and lake, then heated by a 1.5 megawatt boiler to the drilling temperature of 90ºC.

From there, four Cat Pumps’ model 3521C pumps in a ‘three duty plus one standby’ configuration produce a combined flow rate of 210 litres/min and need to overcome a backpressure of 140 bar created by the friction loss through 3.4 km of 32 mm bore hose.

Although hot-water drilling technology has been used extensively by Antarctic scientists on previous experiments, at 3 km this will be the deepest borehole ever made this way. The hot water drill must cope with the extraordinary environmental conditions yet operate continuously for 3 days to create a 360mm diameter borehole through the ice.

Once drilled, the team will lower a titanium probe through the hole to measure and sample the water, followed by a corer to extract sediment from the lake. But, as the borehole will quickly refreeze, reducing in diameter by 0.6 cm every hour, the team will have just 24 hours to access the lake before the borehole becomes too small to deploy the scientific equipment.

“Earlier small scale hot water drilling systems operated over a number years by the British Antarctic Survey have used Cat Pumps. Because they were exposed to the elements on the surface the main challenge was keeping the pumps from freezing, and heating the pumps was of great importance,” reports Andy Tait, Hot Water Drilling Project Manager, BAS. “Because this time our pumps are containerised, and the containers are heated to around 10ºC, freezing is not an issue. However, by the time we reassemble on site later this year the containers will have over-wintered in temperatures as low as -50ºC. This was a major consideration, so we did need to specify a pump that could stand up these harsh conditions and operate when drilling time arrived.”

“Cat Pumps have served well in the past and it seemed sensible to continue with that legacy,” explains Andy Tait. “We did consider alternatives, but having looked at the plunger pump, it made perfect sense for the pressure required and their robust nature. We knew that these pumps had in the past been run in Antarctica at temperatures below -10ºC and had performed well. To increase everyone’s confidence, Cat Pumps also commissioned an independent laboratory to carry out a soak-test, subjecting a complete model 3521 pump to temperatures down to -50ºC for 24 hours. Once returned to ambient temperature, the pump was thoroughly inspected and run-tested; it had suffered no ill-effects.”

A further enhancement to the system suggested, designed and developed by Cat Pumps, is the seal barrier system installed on each pump. This enables a biocide to be flushed between the plunger seals to reduce the possibility of any airborne organic material being drawn through the pump and contaminating the water supply.

“The whole of Cat Pumps UK have been brilliant in their support and service, which means a great deal,” continues Andy Tait. “It is easy to buy a pump, but what you cannot get is the knowledge and bespoke build that is needed for a project like this.”


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