| *Current X41 models are based
on the T41 Series mechanically sealed pump
hydraulics, while the future X51 models based on the T51
Series are available upon special request for higher capacities
and pressures.
 Design Features
The hermetically sealed pump/motor combination uses
the process fluid itself for cooling, while a stainless steel
barrier keeps the fluid isolated from the stator wire and rotor.
A ceramic potting material is used to back up this .015 inch thick
barrier to provide mechanical strength under high operating pressures.
This special potting material is electrically insulating and also
has the property of being highly heat conductive to help dissipate
excess heat. Each and every pump is tested for barrier and containment
integrity before shipment.
Optional inlet/outlet threading is available to match your system
design needs. NPT threads are standard for North American usage
for compatibility with low cost, commonly available pipe fittings.
BSP is available for use with commonly available pipe fittings
in England and associated countries, while ISO is used for applications
where compatibility with international standards is important.
SAE threads are also available for use where the most highly reliable
leak-free connections are required.
The pump/motor units use three carbon bearings, with the motor
rotor positioned between two thrust bearings, and the impeller
supported on both sides to provide long running life. As with
all plain bearing pumps, keeping pumping systems free of solids
to prevent premature bearing failure is important. The X Series
is, however, designed with easily replaceable bearings that can
be changed out in a matter of minutes, providing a low cost means
of maintaining "like new" performance over long periods.
Specialized bearing materials are continuously being tested as
new applications arise to allow further extension of useable life
in harsh pumping applications. The rotor shaft bearings, as well
as the turbine impeller, are easily replaced during scheduled
maintenance events when used under severe operating conditions.
Like its T41 Series mechanically sealed counterpart, the X Series
hydraulic passageways are designed to minimize thrust on the self-adjusting
impeller to avoid upsetting its hydraulic balance, and to handle
low NPSH conditions which can occur in some applications. New
to the X Series is the location of the inlet and outlet on the
centerline of the impeller to further eliminate the potential
of axial imbalance that sometimes occurs during periods of marginal
NPSH availability. With these design features, MTH has eliminated
almost all of the bearing thrust loads in these units, and the
motor thrust bearings exist only to provide axial rotor positioning.
Vent/drain taps are provided on both ends of the pump/motor unit
to facilitate draining or air purging of the unit in either the
horizontal or vertical position. Proper air purging at startup
will help assure that the bearings are properly lubricated and
minimize startup wear and priming problems. SAE fittings are used
for both of these openings to assure a reliable leak-free fit,
and to minimize the potential of galling that can be troublesome
if over-tightening should occur.
All models feature top centerline suction and side discharge for
best inlet conditions. The entire unit can be rotated every 90°
to allow different inlet/outlet positions while maintaining best
fluid entry, particularly when suction pressures are approaching
the vapor pressure of the pumped fluid. There are no orientation
restrictions when installing these pumps. Vertical mounting (pump
up or down) has no effect on the unit's operation. This ability
to mount the pump in any position gives the customer added flexibility
in the design of their system.
Compactness also favors these canned motor pumps over magnetic
drive pumps. In fact, most models are no larger than their equivalent
close-coupled mechanically sealed pump/ODP motor cousins.
Advantages
The X Series should be considered for applications
where leakage cannot be tolerated. The seal-less design ends down
time and maintenance problems associated with mechanical seal
pumps.
The compact size fits most OEM situations where close-coupled
ODP motor/pumps will fit. These pumps can be easily mounted vertically,
with the pump end up using the motor end cap as the base, or horizontally,
using a standard or special mounting bracket, as necessary, to
fit each application.
The X Series has fewer parts than most pump/motor combinations,
which translates into easy assembly/disassembly for maintenance,
and for lower manufacturing costs which ultimately means a lower
price to the customer.
All rotating parts are enclosed, reducing ambient noise. No fans
or ball bearings, which are typically sources of noise, are used.
These pumps are exceptionally quiet due not only to their "plain
bearing" design, but also because of refinements in the water
passage hydraulics. This essentially eliminates the "high
pitched whine" that has previously been associated with regenerative
turbine pumps.
The seal-less canned motor design offers significant advantages
over magnetic drive solutions. The X Series pumps are actually
integrated into the motor housing to provide a very compact package
that eliminates the excess space requirement for a coupling, which
is often critical in tight OEM enclosures. This design is also
more reliable in that it has fewer parts and does not suffer from
the magnetic de-coupling problems or degradation that often occur
without warning in mag-drive units.
Materials
All standard X Series pump models have a 316 stainless
steel housing and a non-galling Waukesha 88 impeller. The Waukesha
88 alloy contains 70% nickel which is typically more corrosion resistant
than 316 stainless steel in most chemical applications.
A wide variety of "O" ring materials are available so
the pump can be compatible with almost any fluid. Viton, EPR, Buna,
Teflon, Kalrez, and other specialized materials can be made available
to suit the application.
Bearings made of various carbon combinations are compatible with
most fluids, while other bearing materials are available for testing
in special applications upon request. The three bearings provide
a large area for ample support of loads and long bearing life.
The selected motor insulation allows operation in high temperature
applications. Windings are suitable for operation at temperatures
of 200°C (392°F) and utilize NEMA Class N inverter grade
insulation for use with variable frequency drives and to provide
the longest life under all operating conditions.
Testing
 Like other
MTH products, 100% of X Series pumps are tested for proper operating
characteristics before shipment. For specially requested longer
term testing, a facility is available to simulate actual customer
applications. MTH can operate a pump under the customer specified
conditions for periods of time necessary to extrapolate minimum
service life, recommended service intervals, MTBF, or other information.
Testing quotations and proposals are based on the complexity of
the required test, and with any special fluids being supplied by
the customer.
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