2 impeller selection and design
TRANSCRIPT
Impeller Selection & Design
The Municipal Task
Pumping municipal sewage means to pump
Water + X
And sewage pumps, large and small must be designed to cope with these „X“ up to a reasonable limit.
Design Criteria for Sewage Pumps
•X stands for everything, which can enter the sewer
•X can be things, which can pass a toilet or a gully and which we expect in sewage:
•Faecal, toilet paper•Grease from Restaurants•Sand from roads
•X can also be things which can pass a toilet or gully, but which we should not expect in a municipal sewer:
•Textiles•Paper•Plastic articles•…
Limits of Sewage Pumps
There may also be things in sewage, which we cannot expect, also if all the water has to pass a toilet or a gully:
•Big amounts of sand from construction areas•Trash from farms, markets, small industry, etc
In these cases the responsibles have to investigate and probably to educate!
If the sewer is broken or e.g. gully grills are removed, we have to face probably:
•Briggs and stones•Lockwood•Dogs, cats, …•Cars, bicycles, furniture, tyres, …
Here the system has to be improved and pumping stations and equipment have to be protected, e.g. by screens
The large pumps Motors with high kilowatt rating Long running hours Large hydraulics
Importance of Design Criteria:1. Motors with good efficiency (costs of motor)
2. Hydraulics with good efficiency (classical optimization)
3. Resistance against blockage (easy to achieve, as large flow means large passage, multi-vane, high power)
Design of Pumps for Municipal Sewage
The small pumps Motors with low kilowatt rating (90% of all
sewage pumps in Europe have 1.5 to 7.5kW)
A few running hours (typically in Europe 1000 hours per year)
Small hydraulics (80 to 150 mm)
Importance of Design Criteria:
1. Resistance against blockage (not easy to
achieve, as pumps are small and power is low) 2. Hydraulics with reasonable efficiency
(not easy, as blockage resistance needs low number of impeller vanes and special design)
3. Motors efficiency (not so important, as low running hours and low kilowatts)
Design of Pumps for Municipal Sewage
Q [l/s]
Impellers For Sewage Pumping
For small and medium sized pumps Vortex Impellers
Very good resistance against blockageLow wear by abrasivesVery low efficiencySmall to reasonable solids passage
Impellers For Sewage Pumping
Closed channel impellersInsufficient resistance against blockageHigh wear by abrasivesGood efficiencySmall solids passage
Open channel impellersContraBlock® Very good resistance against blockageMedium wear by abrasivesReasonably good efficiencyLarge solids passageThe compromise
The old way of design and optimization First trial
DesignPattern makingCastingMachiningHydraulic testBlockage test
First optimizationPattern modificationCastingMachiningHydraulic testBlockage test
….
Impellers For Sewage Pumping
Pump head vs. impeller position
CFD Simulation of Sewage pumps
Hybride Meshing
Impeller prototyped directly from 3D-CAD Systems
Impeller prototyped directly from 3D-CAD Systems
Contrablock Patent
United States Patent No. 3,447,475Titel: Centrifugal PumpRegistration: Jan 9, 1967Patent filed: June 3, 1969Inventor: Albert Blum
The oldest Leaflet including Contrablock: 1966
R&D tests– according to ABS Works Standard– documentation by Video
Field tests– in selected places around the world
• municipalities• hotels• jails, ...
ContraBlock®
Tested - tested - tested - ...
ContraBlock® Clogging Test
ContraBlock® Clogging Test
ContraBlock® Clogging Test