Huge Pumps will Cool Power Plants in the Bahamas

Pumping the cooling water up from pockets of saltwater 20 metres below the Caribbean coral reef places great demands on the design, production, and logistics.

he Danish company IRON Pump will have an important role to play when a completely new power plant is ready to supply electricity in the island nation of the Bahamas this autumn. The Danish pump specialist will supply four CLVS vertical turbine pumps with a capacity of 2,000 m3/h – 41 mlc to supply cooling water to the seven power plant motors, which will produce 132 megawatts combined.

The cooling water for the newly constructed power plant will be drawn from deep pockets of saltwater under the Caribbean island. As a consequence, IRON Pump’s mission was to supply specially designed two-stage pumps, 20 metres in length, capable of withstanding the harsh environment. This was accomplished despite a tight schedule for the delivery almost 8,000 kilometres across the Atlantic.

Harsh environment at a depth of 20 metres
Although IRON Pump is an expert in specially produced pumps, the scale of the Bahamas project presented a particular challenge. A project group of experienced engineers was put to the task, which required thorough preparation because of the length of the pumps and the fact that they weigh 11.1 tonnes each, according to Robert Jensen, Sales Engineer at IRON Pump.

– We have to take a lot of things into account when dealing with a pump with bowls positioned at a depth of 20 metres. This means we have a 20-metre long shaft that is subjected to heavy torque and the pipes themselves are very heavy. That is why we made calculations for the diameter of the shaft in the base and up through the shaft bearings, so we could be sure that the pump won’t buckle when it is started up.

In addition to strength calculations for the pump design, the project group at IRON Pump was tasked with ensuring that the application can withstand the warm, subterranean saltwater environment of the Caribbean.

– Warm salt water is aggressive so we manufactured the pump from stainless steel and applied an epoxy coating to protect against corrosion, among other things. We also put sacrificial anodes on the bowls, both inside and out, in order to protect the pump from corrosion, says Robert Jensen.

Quick delivery 8,000 km away
The delivery time was a decisive factor for IRON Pump’s customer in the Bahamas, who needed to use the first pump within a few months in order to test the power plant’s motors. The combination of large dimensions and short delivery time put extra pressure on both IRON Pump’s production facility and the company’s suppliers.

– Needing to assemble and test the parts for four large pumps within such a short period of time takes a toll on production. And when working with such large dimensions, it can be difficult to obtain the necessary materials from our suppliers from a purely practical point of view. Not least because of time considerations. But thanks to positive collaboration internally at IRON Pump and externally with our global network of suppliers, we succeeded, says Robert Jensen and continues:

– A project like this really gives a boost to production engineers and installers, who worked at full throttle. They find great satisfaction in helping to build a pump like this and they are proud of their work.

IRON Pump needed to use four 366 kW motors for the project, each of which operates one of the large turbine pumps. The size 400 motors, supplied by Hoyer Motors, weigh 3.1 tonnes and modifications include current-insulated bearings and rain protection.

– When the project landed on my desk, I called our contact at Hoyer straight away because I knew it was a special project. Not only because of the large motor size but also because the delivery time was a decisive factor for us. But I know from experience that Hoyer always makes a dedicated effort when we contact them directly with an important matter, he says.

At the end of August 2019, IRON Pump delivered the first of a total of four pumps that will supply cooling water when the power plant’s motors are tested. The project will also be followed through to the end by IRON Pump’s own installers, who will assist in installing the heavy-duty pumps in the Bahamas.