Water Passage Design
MTH has combined sixty years of water passage design with
a multistage mechanical concept to achieve maximum capacity
and pressure while minimizing horsepower requirements. By optimizing
the number of pumping stages with each water passageway, MTH
improves both efficiency and pressure in the 150 • 250
• 160 • 260 • 170 • 270 Series, exceeding
the standards realized by previous techniques.
Impeller Profile
One of the most notable improvements in regenerative turbine
pump technology incorporated in 150 • 250 • 160
• 260 • 170 • 270 Series pumps involves the
ability to determine the optimum impeller width and blade length.
These factors have a significant effect on the required horsepower
versus pressure curve for regenerative turbine pumps. By optimizing
these for each 150 • 250 • 160 • 260 •
170 • 270 Series pump, peak efficiency is improved and
“off peak” horsepower requirements are reduced as
well.
Impeller Blades
After the most favorable impeller profile has been determined
for a particular water passageway cross-section, MTH calculates
the number of blades needed to maximize the performance of that
pump. Current blade design in 150 • 250 • 160 •
260 • 170 • 270 Series pumps increases both efficiency
and design pressure without the manufacturing difficulties associated
with producing contoured blade impellers.
State-of-the-art computer controlled machines simplify manufacturing
of the various MTH impellers utilized in the 150 • 250
• 160 • 260 • 170 • 270 Series. The
result is a high performance pump providing efficiency characteristics
exceeding those of more expensive units.
NPSH Requirements
150 • 250 • 160 • 260 • 170 •
270 Series regenerative turbine pumps meet low net positive
suction head (NPSH) requirements without efficiency loss. This
is achieved by keeping the inlet fluid velocity low and then
gently accelerating to passageway velocities.
Low NPSH Requirements
250 • 260 • 270 Series regenerative turbine pumps
provide exceptionally low NPSH requirements to suit boiler feed
water deaerator applications.
This reduced NPSH is obtained by using a first stage centrifugal
Francis vane impeller with inlet flow paths shaped to maintain
a constant fluid velocity. This reduces entry losses to the
impeller as well as maintaining pump efficiency. A multi-vane
diffuser is used in conjunction with the centrifugal impeller
for balancing radial loads and extracting the maximum pressure
from the flow produced by the first stage impeller. Pressure
and flow produced by the low NPSH inducer assures that the succeeding
stages are adequately fed.
200 Series
Inducer for Low NPSH |
 |
The 200 Series inducer style pumps are ideally suited
to applications where available NPSH at the pump inlet
is limited, such as boiler feed water deaerator service.
A centrifugal Francis vane impeller with low NPSH characteristics
is utilized as the pump’s first stage impeller,
accounting for the lower inlet head requirement.
This first stage impeller is used in conjunction with
a multi-vane diffuser to provide the NPSH required by
the second stage regenerative turbine.
Available NPSH as low as two feet can be effectively
handled with 250 • 260
• 270 Series pumps, depending on the pump model
and capacity. |
|
