Two Heavy Duty Dewatering Pumps for Cofferdam and Diaphragm Wall Construction
PUMPS CASE STUDY
NORTH RIDGE PUMPS
Two Heavy Duty Dewatering Pumps for Cofferdam and Diaphragm Wall Construction
Our latest case study discusses our design , development and construction of two 4 ” long coupled heavy duty Self-Priming Pumps we are despatching for dewatering on a current construction project . The pumps will be used for the removal of water during diaphragm wall and cofferdam construction .
A diaphragm wall is used for deep trench excavation which can be prone to the accumulation of nuisance water , and a cofferdam is a watertight enclosure allowing workers to locate equipment adjacent to waterlogged , flooded or bodies of water where construction may take place .
THE DEWATERING PROCESS
Once the diaphragm walls and cofferdam are constructed , the dewatering process can begin . This involves temporary lowering of the groundwater level by pumping from purpose-built bores fitted in the work area . Groundwater is removed from inside the walls of an underground structure and pumped back into the ground outside the structure , through a series of pipes and reinjection bores .
HOW DID OUR PUMPS MEET THE BRIEF ?
Here at North Ridge Pumps , we ’ re not tied to a single pump technology , so we can provide the best pump for a particular application and designed for the lowest lifetime cost . In fact , we can use our expertise to offer a bespoke solution , not something straight off the shelf .
For this particular project brief , we calculated that a robust design of a heavy duty self-priming pump was needed . This was because the project required pumps to be operating for long periods , prime quickly and handle fluids which might contain a variety of solids .
Our pumps are unlike other designs of self-priming pump as they are built with an armoured volute , which protects the main casing from abrasive wear , as well as high speed impacts from solids .
What ’ s the difference between pump casing and volute ?
A pump casing is often referred to as a volute . A volute is a spiral-like geometry with an increasing through-flow area , reducing the speed of the fluid and increasing the static pressure . The fluid exiting the impeller is then diffused towards the casing discharge nozzle .
We built our cofferdam pumps using ductile iron which ensures that each unit is durable , handles solids up to 50mm x 24mm in diameter without loss of flow , and will perform well for many years to come .
The pumps needed to meet a range of duty points from 50M ³ H to 150M ³ H at up to 60m head , so we fitted the pumps with motors suitable for operation via Variable Frequency Drive ( VFD ).
What ’ s more , as our cofferdam pumps needed to meet three duty points , we constructed them with two control panels in a metal enclosure with integrated Danfoss inverters . This not only achieves the three duty points , but also activates the pumps via float switches .
The enclosures were built in full metal enclosures with IP55 protection , for installation in rugged , hostile environments .
In addition , the panels were built with a variety of features for pump protection and automated dewatering . These include on / off pump control via 4ma to 20ma input , pressure switch and float control , motor overload and phase failure protection . There ’ s also a back-up battery with GSM connection , so that operators can monitor the operating status of the pumps 24 / 7 .
In total , both dewatering pumps have three separate float switches for fully automatic control at Low level for Stopping the pumps , High level for Starting the pumps , and for Alarm and increased flow rate . Probes were also supplied to enable the pumps to operate in areas where float switches may not be suitable , such as in some tanks or narrow pits .
If you have a site you ’ re looking to dewater or are simply want a high volume transfer pump in an easy to maintain , low maintenance , reliable surface-mounted unit , speak to North Ridge Pumps to see how we can help .
For further information , please visit www . northridgepumps . com
72 PECM Issue 63