Product category:
OEM Pumps
News Release from: Robbins and Myers | Subject: Sludge cake pumping
Edited by the Engineeringtalk Editorial
Team on 08 March 2001
Cost Effective and Efficient Sludge Cake
Pump
Moving increasingly dry dewatered, sewage sludge cake efficiently and cost-effectively is a problem for many sewage treatment works.
Moving increasingly dry dewatered, sewage sludge cake efficiently and cost-effectively is a problem for many sewage treatment works Many works use a belt or screw conveyor to move the cake from one point to another
This article was originally published on Engineeringtalk on 22 Aug 2000 at 8.00am (UK)
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These have several associated environmental and maintenance problems.
Odour nuisance is common on open conveyors and cake spillage leads to environmental and safety concerns.
Screw conveyors often break down and unscheduled maintenance costs rise accordingly.
The answer in many cases is to use a progressing cavity (PC) pump.
However, due to the non-Newtonian nature of sludge cake, a pump will generally only fill around 50% of each cavity within the pumping element [this is referred to as 'volumetric efficiency'].
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Materials handling specialists Robbins and Myers, based in Chandlers Ford in Hampshire has solved this problem by designing the 2000 HS progressing cavity pump that combines performance and low life costs.
This unit accepts dry sludge from a variety of sources - belt filter presses, silos, plate and frame presses, vacuum filters and centrifuges.
Capital and operating costs are reduced and the unit requires a much lower level of maintenance compared to other sludge cake transport methods.
The unit's capital costs are a fraction of the price of a piston pump.
The whole unit is enclosed, reducing odour problems - an important point when sewage treatment works are sited near to residential areas.
The pump unit has five flexible installation options, saving a significant amount of space.
Sludge cake can follow existing pipe routes, which saves interior building space.
In tests, this unit has out-performed piston ram pumps, screw conveyors, serpentine and belt conveyors.
The new design combines reduced power demand with increased mechanical efficiency.
This is an important point to consider as all UK water companies face increased electricity bills from April 2001, when the climate change levy is introduced.
In order to offset the impact of the levy, water companies will need to reduce energy demand significantly to reduce the impact of a 10-15% increase in electricity charges.
One way of doing this is by fitting energy efficient pumps wherever possible.
Dry sludge cake enters the 2000 HS pumping unit via the oversized open top hopper.
A load cell electronic weight control system guarantees that the pump is not overloaded.
Flow is automatically adjusted.
From here the cake drops onto the self-cleaning intermeshing twin feed screws that counter rotate.
This device removes the need for an extended auger, as used with other PC pumps.
The twin screws exert a positive pressure on the sludge cake, forcing it into the cavities within the pump, filling them to 100% capacity.
This is the most efficient feed system on the market.
This design, with its high volumetric efficiency, is a vast improvement on piston pumps that generally have a volumetric efficiency of around 60%.
The unit's smaller drive system is also more efficient and results in fewer energy losses than hydraulically driven pumping systems.
It is also quieter and eliminates other problems associated with hydraulic drives such as oil leaks and oil disposal costs.
The pump is able to handle up to 32% solids at flow rates of 45 m3/hr but operates at a much lower operating pressure.
Hence the piping, drive components and other equipment are under less stress.
Two variable speed drives are fitted to both the feeder and the pump to match input with output and this immediately reduces energy demand.
For transfers of extremely dry material over long distances, up to 150 m.
in some instances, an optional slip injection system can be fitted to this Robbins and Myers unit.
A dilute polymer lines the inside of the pipe reducing nominal line loss and further reducing power demand.
Pressures are reduced by up to a factor of 4 - typically a pressure of 20 bar can be reduced to just 5 bar using this system.
This reduction in power demand significantly cuts energy costs and the smaller pipe diameters required means much lower installation costs.
The revolutionary 2000 HS system has been extensively tested and proven to be extremely reliable, efficient and cost effective.
In addition, Robbins and Myers are able to offer warranties on rotor and stator life enabling water companies to accurately predict whole life costs.
Combined with improved energy efficiency and low maintenance costs, there is now an effective answer to the problem of sludge cake handling.
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