Over the last couple of years, the number of desalination plants using PD pumps has grown. These plants have often been seen to return energy savings of 20% or more compared to traditional centrifugal pumps; and with proven efficiency rates up to 90%, the PD pumps offer the lowest life-cycle costs in the industry.
Today, the desalination industry acknowledges the advantages of parallel-coupled PD pumps when it comes to reliability, uptime and energy efficiency of the system.
This is also the case at a new 3,500 m3/day SWRO plant at a ship building and maintenance yard in Bahrain. Here, six Danfoss APP 30 pumps are mounted in parallel to achieve the required flow capacity. The multiple pump train ensures that the capacity can be increased incrementally according to the need for water at any given time. During operation, the production of water can be adjusted to consumption by changing only the speed of the pump to harvest additional energy savings. The same excellent solution could today have been achieved by using two APP 78 pumps.
Even when one of the pumps is down for maintenance, the system runs uninterruptedly giving great flexibility and reliability of supplies 24/7/365. The simple construction of the axial piston pump with few moving parts enables easy service and maintenance. Furthermore, the robust and simple design of the APP pumps allows them to run for minimum a year between service intervals.
The conclusion of the Bahrainian shipyard is clear: even though the upfront cost of six APP pumps compared to one CF pump might be seen as is a higher investment, the low cost of ownership throughout the lifetime of the plant and the predictable payback time bring significantly improved profit margins over the lifetime of the desalination plant.
