Instrumentation Monthly Test | Measurement | Control
A water purification plant in Malaysia was experiencing significant problems when handling lime chemical as part of their treatment process.
Previously, the plant had solenoid metering pumps installed for the dosing of the chemical. Solenoid metering pumps are known for their highly accurate delivery of chemicals, however in the case of handling lime this pump type often experiences difficulties due to the nature of the lime chemical. Lime chemical is a suspension of the milled lime in water, which has a distinct tendency to ‘coat’ all areas of the pump due to the lime particles falling out of suspension and culminating in a stubborn build-up. As the fluid passes through the metering pump, the ball valves, small tubes and chambers begin to block, similar to a human artery furring with fatty deposits.
This eventually causes a significant blockage and a rise in back pressure, which causes any sealing to fail and catastrophically leak, coating the surrounding environment with the chemical, which is very difficult to remove. For every failure, inspection and service, the plant was losing many hours in downtime, expense of the labour and spares charges and the inconvenience of clean-up costs.
A local contractor was called in to solve this problem. The contractor recommended the move from solenoid metering pumps to Verderflex peristaltic hose pumps. As part of this recommendation, both the contractor and the local Verder team worked together to deliver a presentation of data, reference sites and operational practices to demonstrate the quality and success of the pumps in other installations.
Presented were the key benefits of using a Verderflex peristaltic pump
- Excellent at handling abrasive, viscous fluids such as liquid lime
- The constant compression and relaxation of the flexible hose which prevents the lime coating the flow path
- Faster and easier to service than other pumps as there is just a simple hose and lubricant change to perform
- The constant revolution of the rotor assembly delivers a flow rate proportionate to the rpm. This results in an accurate delivery of chemical which can be easily controlled through an inverter and if necessary an analytical probe such as a pH meter.
The installation of 4 Dura 35 pumps (35mm hose ID) has seen a great improvement in the dosing process: The pumps are now operating for a consistent and unbroken period with only a planned inspection and maintenance procedure necessary. The expenditure on service contractors visiting the plants has been greatly reduced with no loss of quality to the dosing process.
The water purification facility were so impressed with the upgrade to their facility, the engineering team have specified the Verderhus screw-channel centrifugal
pump for circulating the lime chemical within the holding tanks, which maintains the homogeneity of the suspension. This has an exponentially beneficial effect of reducing the cleaning of the tank due to sedimentation and prevents the pump from having to work as hard drawing in extraviscous lime slurry.
By choosing the Verderhus screw-channel, the purification plant has the perfect pump for handling a high flow rate of a viscous, yet flowable slurry. Thanks to its open impeller and helical, corkscrew-like impeller, the Verderhus excels at the efficient passage of lime slurry with a BEP in excess of 70%. The
pump is insensitive to clogging and changes in viscosity. The customer gains the benefits of a positive displacement pump in terms of the viscosity handling and the benefits of a centrifugal pump for larger flows.
With the proven performance of the Verderflex pumps, the plant has specified 4 pumps each at further 3 dosing processes with additional Verderhus pumps to ensure the smooth circulation of the lime.
Verder Ltd.
Unit 3, California Drive
Castleford,
West Yorkshire, WF10 5QH
United Kingdom
TEL +44 (0) 1924 221 001
FAX +44 (0) 1132 465 649
MAIL sales@verder.co.uk
WEB www.verder.co.uk