HYDRAULIC RE-RATE INCREASES CAPACITY AT DESALINATION PLANT

CHALLENGE

Our customer operates a desalination plant situated on a large island in the Caribbean. They wanted to increase the plant’s overall capacity from 46,543 USgpm to 54,000USgpm – around 16 per cent – without

changing the existing 600hp motors. This required an increase in flow rate from each of their six clearwell single stage pumps from 7,757 USgpm to 9,000 USgpm.

SOLUTION

To achieve the desired increase in capacity, the ClydeUnion Pumps aftermarket team at Celeros Flow Technology changed the impeller from hydraulic type L to hydraulic type H. This change decreased the required NPSH and allows each pump to operate at the desired higher flow rate of 9,000 USgpm without changing the motor power.

Several design modifications on the suction casing and wear rings were necessary to accommodate the change in impeller and optimise future pump performance. The seawater service of the pump also required a change in material to high corrosion resistant stainless steel.

All the modifications were designed and implemented by Celeros FT engineers, and the modified pumps were then reassembled and tested at our inhouse facilities to ensure they would perform as anticipated.

OUTCOMES

The re-rated pumps are achieving flows of 9,588 USgpm at full power, exceeding the desired target of 9,000 USgpm, and delivering efficiencies of almost 75 per cent. Following the re-rate, our customer requested the supply of a seventh pump. This will bring the expected total capacity at the desalination plant to more than 65,000 USgpm.

FINANCIAL ILLUSTRATION

At motor full power (600 hp) the increase in capacity is more than 20% (from 7,757 to 9,588 USgpm) for a cost on one pump:

• Supply of H type wheel = 27,000 Euros
• Supply of suction casing set (suction casing + suction bell + wear ring) = 20,000 Euros