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DW Rotary lobe pump
By Product Manager Jesper Holst Rasmussen
Product training
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Definition and classification of pumps
Vane Ecentric casing
Vane screw Screw spindle
Impeller Peristaltic (hose)Ecentric
Rotary LobeGear
Rotating pistonScrew spindle
PumpsPositveDispla-
cement
Reciprocal Piston
Diaphragm
RotarySingleRotor
Multi
Rotor
The most common APV pumps are in bold type in the two tables.
DW PD Pumps
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The DW range Rotary LobePumps for the 21st century
A development from the first RotaryLobe Pump launched back in 1932
DW PD Pumps
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Front cover
Shaft, main
Shaft, auxiliary
Gears
Brearing, font Bearing, rear
Rotorcase
Profiled front covergasket
DW - Construction
Rotor
Rotor screw
Clamp ring
Feet
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Rotors
Feet
Inlet Outlet
Front view
Chassis Machined in one fixing
Small tolerances
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DW - Construction
Exploded view
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DW - Construction
Exploded view
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Expanding cavities are formed at the inlet drawingthe liquid into the rotors.
Meshing of the rotors forces the fluid out of thepumping chamber.
DW - Construction
Principles of operation
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Internal leakage is fluid that travels from the high pressure side to the lowpressure side of the pump.
Internal leakage is present because of the slip paths between stationary androtary parts in the product area.
hVol = Volumetric efficiency = (theoretical displacement - slip)
theoretical displacement
LeakageLeakage
Leakage
FlowFlow
DW - Construction
Slip Internal leakage
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Efficiency of the pump Slip
Slip increasesproportionallywith pressure
Slip increaseswith the cubeof tolerance
Slip decreaseswith increasingproduct viscosity
DW - Construction
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Rotor types
Tri-lobeCommonly useddesign, used invarious applications
Bi-lobe (DW-pump)Used for fluids wherelarge particles mightoccur.The volumetric efficiencydepends on the angle of
the rotor tips
Multi-lobe (R-pump)Used where largeinlets are required orsmooth flow
Bow-tie rotorGood volumetric efficiencyDisadvantage, localcavitation at high speed
Rotary piston (DW-pump)High volumetric efficiencyDisadvantage, expensiveproduction costs due to smallmanufacturing tolerances
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Pulsation Characteristics
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Local cavitation
Trilobe rotors Rotary piston
rotors
Consequence of cavitation
noise
less output
damage to the fluid
vibrations
Cavitation can beminimised by
reducing the internalfluid velocity
optimising the rotor
shape
DW - Construction
Occur when the rotorsmove apart. This change inspeed and volume pulls themedia apart.
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Pulse-free performance
Patented design of rotor tips andgrooves. DW pump runs without pulsation'sand internal cavitation
The patented grove design insures a steady,pulsation free filling and discharge of theproduct.
The patented rotor design allows for higherrotation speed and still maintain a gentle
product treatment.
The pulsation free operation extend thelifetime of valves, instruments etc.significantly.
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Pulsation
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Comparison of measurements on bi-lobe and piston rotors
Measurements at the pump outlet
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Versions available: Multi-duty 110C
High efficiency 110C
High temperature 180C
Super tight (NGA only)
DW - Construction
Rotor Types
Rotary Piston
Pulsation free flow, dueto patented design
Low NPSH valuerequired
No rotor timing
Bi-Lobe
Low internal cavitation
High pressure operation
Lower cost
Rotor material
Stainless steel AISI 316L
NGA (Non-galling Alloy)
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See Operating manual - section 6.6
All rotor types are available in NGA
Rotor type Strength WeaknessMultiDuty 110oC Rapid product temperature
changes up to 80C Relatively high efficiency
High temperature180oC
Tolerances allowtemperature shock changesup to 180oC
Low efficiency due to largetolerances
High Efficiency110oC
High efficiency due to smalltolerances
Can not withstand large shocktemperature changes (ex.
CIP)Super Tight(NGA)
High efficiency also for lowviscosity fluids
Expensive Non Galling Alloysnecessary (75% Ni)
DW - Construction
Rotor Types
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Non Galling Alloy (NGA)
NGA rotors are used where a high efficiency or minimum of slip is required.
Typically where the pump is used for dosing or low viscosity applications.
NGA is a soft stainless steel which do not gall (damage) the surface likeconventional stainless steel.
NGA rotors can have smaller clearance than High efficiency rotors.
NGA rotors can touch the pump house or front without damaging (Galling)the house or the rotors.
NGA rotors have Higher efficiency due to reduced slip.
DW - Construction
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NPSHrequired
The NPSHreq. is significantly lowerfor DW pumps compared tocompetitor products.
Since the inlet is behind the rotors
The fluid easily flows into the pump
Inlet volume is increased
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NPSHrequired
Is describing the necessary inlet pressure to avoid cavitation.
Varies from pump to pump.
Depends on rotor width, inlet port diameter, rotational speed, and the fluid viscosity,temperature and vapour pressure.
NPSH required for positive displacement pumps is defined as a 5% reduction inflow at constant rotational speed, viscosity and differential pressure.
Flow rate
Inlet pressure
NPSHR
Norm. flowrate
Flowrate 5%reduction
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Cavitation
Is evaporation of the fluid inside the pump.
Occurs when the pressure in the pump falls below the vapour pressure of the fluid.
Results in: decreased volumetric efficiency
noise
vibrations
damage to the pump, the fluid, and the system.
Cavitation is avoided by keeping the inlet pressure at the pump above the necessarypressure to avoid cavitation, ie. NPSH available > NPSH required.
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EHEDG: European Hygienic Engineering & Design Group
Hygienic pump design = compliance with EHEDG
DW - Construction
EHEDG
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Pumps are classify based on the gear size DW1 - DW7 Dimensioned based on deflection of the shaft
31 models in the pump range
Flow
[l/min]
Pressure
[bar]
n
[rpm]
Weight
[kg]
Dimensions
[mm]
DW1/ 003/ 7.5 40 7.5 1400 18.5 260x218
DW7/420/30 2200 30 600 700 1016x627
DW7/1016/7 5800 7 600 800 1119x627
DW Product range
Classification
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DW Product range
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DW 7/1016/07 rotary lobe pump with 8 inlet
DW Product range
A broad range
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Standard pump
DW pump is equipped with:
Single mechanical shaft seals Sic/Carbon
EPDM O-rings Fittings? Rotor multi duty (lobe or piston) Motor?
DW - Standard
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Options
The following standard options are available in the DW range:
Bareshaft pump
Pump with constant speed geared motor, suitable for inverter drive use. Up to 37 kW these areavailable with stainless steel motor shroud.
Pump with geared motor with constant or manually variable speed. Pump base plate and coupling guard in stainless steel.
Lobe rotors suitable for max. 110C or max.180C product temperature, in stainless steel 316L orNon Galling Alloy (NGA).
Piston rotors suitable for max. 110C product temperature, in stainless steel 316L or NGA.
Elastomers in EPDM, FPM (Viton) or ISOLASTTM.
Single mechanical shaft seal in SiC/Carbon or SiC/SiC, flushed or non-flushed.
Double mechanical shaft seal in SiC/Carbon or SiC/SiC . Single EPDM lip seal for DW1-5.
Triple PTFE lip seal (confectionary) for DW1-5.
Packed gland with sealing thread in PTFE impregnation, for DW1-5.
Horizontal or vertical suction and discharge ports.
Rectangular inlet.
Cooling/heating jacket on rotor case and front cover.
Pressure relief valves on DW1-5.
DW - Options
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Single mechanical shaft seals
Single mechanical
Carbon / silicon carbide seal: Clean fluids (not sticky or abrasive)
Silicon carbide / silicon carbide seal: Abrasive, tacky (sticky) products
Single flushed mechanical - low PressureFlush
Crystallising media in contact with the atmosphere Liquids close to their boiling pointWhere dry running of the seal faces may occur
DW - Options
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Product wetted end
Same as Single Flushed seal+
High temperature products
Vacuum extraction
Solidifying products
Aseptic processes
Hazardous or toxic products
DW - Options
Double mechanical shaft seals
High or low Pressure flush
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The packed gland:Max. 10 BarAbrasive slurries, viscous and aggressive productsNot hygienic, not suitable for CIP.
The confectionery seal (Triple lip seal):Max. 6 BarChocolate.Not suitable for CIP
DW - Options
Alternative shaft seals
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Elastomer
EPDMUsed in standard applications, not oil resistant
Flourocarbon (Viton)Good heat resistance feasibility's, used in applications containing oil
Perfluoroelastomers (Isolast)Used in chemical applications, resistant to most chemicals, low frictiongood heat resistance, excellent mechanical qualities.
DW - Options
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Enlarged rectangular port for high-viscosity products.Inlet area is increased by 100 - 200% dependent on pump size.
Rectangular inlet
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Rectangular inlet
DW - Options
New construction will belaunched in August
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Constant temperature of the liquid in a pump.
The thermal jacket facilitate the heating or cooling of the pump chamber prior
to product entry.
Thermal Jacket
DW - Options
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Thermal Jacket
DW - Options
New construction will belaunched in August
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Standard Relief Valve
DW - Options
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Tube version TYPE 1
Folded version TYPE 2
Baseplate
Hygienic Aspects
DW - Options
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DW pump mounted on the hygienic tubular support with shroud.
The shroud protects gear and motor during washing of the eqipment.
DW - Options
Motor shroud
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Pump drive (motor)
Constant speed drive = Nordgear
Manual variable speed drive = SEW (On request)
Speed control via Frequency converter = Nordgear
DW - Options
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Wide range - 31 models
Patented Rotor design
All external surfaces are in Stainless steel
No painted surfaces
Easy to service
Inlet / outlet port orientation easy to change on site
Self draining when vertically ported
Low NPSH required EHEDG certified / FDA approved materials / 3A certified
EHEDG certified integral pressure relief valve
DW Customer benefits
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Dairy
DW - Applications
To & From Pasturisers
Tank Transfer Duties
To & From Heat exchangers
Tanker Pumps
Finished Products
Products
Yoghurt Products
Concentrates Cream
Cheese Products
Butter
Dairy spreads
Dairy based drinks
Ice cream
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Food
DW - Applications
To & From Pasturisers
To & From Heat Exchangers
Bulk Transfer
Tanker loading/unloading
Transfer from cookers and
Mixers to filling lines
Evaporation
Finished Products
Products
Meat products
Egg Products
Bakeries
Jams &
Preservatives
Baby Food
Sauces & Soups
Permeat
Condensed Milk Confectionery
Sugars & Chocolate
Gelantine
Glucose & Syrups
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Brewery and soft drinks
DW - Applications
Bulk Storage
Separator Feed
Pasturiser Feed
Dosing
Tanker Loading/Unloading
Filling Lines
General transfer
Products
Beer
Yeast Trub
Spirits
Carbonated Drinks
Cider
Fruit Juice &
Concentrates
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Pharmaceutical and toiletries
DW - Applications
Bulk Transfer
Dosing
Process Tank Supply
Filling
Products
Shampoos
Liquid soap
Hand Cream &
Lotions
Make up
Moisturizer
Toothpaste
Insulin
Water for injection Antibiotics
Ointments
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Chemical
DW - Applications
General Transfer
Tanker Loading/ Unloading
Dosing
Bulk Storage
Products
Acids
Solvents
Detergents
Emulsions
Photographic film
coating
Paint, Ink & Resin
Oils Adhesives
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General industry
DW - Applications
Bulk Transfer
Dosing
Tanker Loading/Unloading
General Transfer
Products
Clay Coating
Starch
Latex
Pigments
Dyes
Resins & Pastes
Vegetable/Mineral
Oils Paints