| Dynaflow Regenerative Turbine Pumps |
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Similarities:
Both regenerative turbine and centrifugal pumps are "velocity" type pumps. Each
generates pressure and flow from the tangential and angular velocities imparted to the liquid by the speed
and shape of the impeller. In both pumps, pressure and flow can be modulated by throttling a discharge
valve.
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Head capacity characteristics:
The head-capacity curve displayed is indicative of a centrifugal pump (See Graph Below).
Relatively large flows can be generated at low to moderate heads. At higher heads approaching "shut off" (no flow
condition), the curve is nearly horizontal in direction. A slight change in head, as results from throttling
a valve, can alter the flowrate substantially. A flow change of 5 GPM, as when moving from point A to point B
on the curve (20 to 15 GPM), resulted by throttling a valve to increase the head by 3' or slightly more than
1 PSI of water pressure. Metering in this region of the pump curve is very
imprecise.
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Alternatively, the head capacity curve of a regenerative turbine pump has a different
shape (See Graph Below). It is nearly linear and slopes downward. At low to moderate heads, the flow is typically much
smaller than for a centrifugal pump. However, the slope never approaches a horizontal plane. Therefore,
throttling a valve for a regenerative turbine will permit more precise changes in flow, without major
overshooting or undershooting of the duty point. To throttle the flow of the regenerative pump from 20-15 GPM
as shown on the curve, a head change of 34' or 14 PSI of water pressure is required.
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Cavitation:
In a centrifugal pump, liquid enters and exits the pump in one revolution of the
impeller. During that short time frame the liquid velocity increases while the pressure initially decreases and
then increases reaching a maximum at the cutwater (discharge point). If the liquid entering the pump is
near its vapor pressure, it is likely that the initial drop in pressure will create vaporization of the
liquid and cavitation in the pump, with possible damaging effects.
In a regenerative turbine pump, liquid enters and exits the pump during several
revolutions of the impeller. The velocity and pressure increases of the liquid are more gradual than
for the centrifugal pump. A liquid entering the pump near its vapor pressure is less likely to experience
the pressure drop that can cause cavitation due to the smaller pressure gradient of the regenerative
turbine pump. Therefore, regenerative turbine pumps, typically, require lower net positive suction heads
than centrifugal pumps.
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Downward sloping, nearly linear head-capacity curve permits accurate throttling
with a control valve; overshooting or undershooting of the duty point, which frequently occurs with
centrifugal pumps, is minimized.
Modular balanced impeller elimintates axial thrust, removing a wear factor
associated with centrifugal pumps
Handles 20% entrained gases; ideal for tank stripping where vortexing or
cavitation can occur.
Upon tank evacuation, pump cavity remains filled with liquid, unlike centrifugal
pumps; this resists dry run damage.
Capable of reversible impeller rotation, with an accompanying reveral of the suction
and discharge porting.
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The standard materials of construction of the MTA Series is 316 SS. Optional materials include
Alloy 20, Incoloy 825, and Hastelloy C276.
Materials of construction for the standard pump are as follows:
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| Component |
Material |
| Housings |
316 SS |
| Impeller |
316 SS |
| Rear Casing |
316 SS |
| Shaft |
99.9% Silica Free Aluminum Oxide |
| Bearings |
Carbon Filled Teflon® |
| O-Rings |
Viton® |
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Materials of construction for the MT Series in polypropylene is as follows:
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| Component |
Material |
| Housings |
Polypropylene |
| Impeller |
PVDF |
| Rear Casing |
Polypropylene |
| Shaft |
99.4% Aluminum Oxide |
| Bearings |
Carbon Filled Teflon® |
| O-Rings |
EPDM |
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Materials of construction for the MT Series in PVDF is as follows:
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| Component |
Material |
| Housings |
PVDF |
| Impeller |
PVDF |
| Rear Casing |
PVDF |
| Shaft |
99.4% Aluminum Oxide |
| Bearings |
Carbon Filled Teflon® |
| O-Rings |
VITON® |
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