SEALLESS
PROCESS PUMPS TYPE AM/KM/KMV
AM - ANSI dimensional
KM - ISO dimensional
KMV - Vertical Inline
General
Magnetic coupled DICKOW-Pumps of series AM / KM / KMV is of sealless design. The containment shell forms a closed system with hermetically sealed liquid end. Materials of construction are cast iron, ductile iron or 316SS. Containment shell is constructed of 316SS or low energy loss Hastelloy C.
Applications
Magnetic driven KM / KMV pumps are designed to improve plant reliability and
personnel safety in the Oil & Gas, Petro-Chemical and Chemical industries,
especially when handling toxic, explosive or other dangerous liquids, which
react on contact with the atmosphere. For all these services the containment
shell replaces expensive and complex double acting mechanical seals with
external fluid reservoirs and the necessary control equipment. KM / KMV pumps
offer exceptional benefits to the end user and fulfill all environment
protection regulations.
Maximum operating temperature 390F (200 C) The maximum allowable
working pressure is 232 PSI (16 bar). The maximum drive power is 30HP at 3500
RPM.
Construction
KM pumps are single stage, volute casing pumps with closed impellers, back-pull-out design, with end suction and top centerline discharge flange. Pump casing is foot mounting is supplied as standard. Unit is frame mounted or closed coupled to the motor. Capacity and flange to flange dimensions for KM Pumps comply with ISO 2858. Type "AM" is available to ANSI B.73.
Containment shell
The containment shell is designed as a pressure vessel to separate the pumpage from the atmosphere. The containment shell is bolted to the bearing housing in a manner that allows removal of the bearing bracket including outer magnets and ball bearings without exposing the pumped liquid to the atmosphere.
Magnetic coupling
The single elements of the multipolar magnetic coupling are manufactured of a permanent magnet material, Cobalt Samarium-Rare Earth" with unlimited lifetime. The magnets in the internal rotor are completely encapsulated and no contact with liquid occurs.
Energy is transmitted to the hermetically sealed liquid end by a bank of external magnets passing motive force through the containment shell to a bank of internal magnets. Inner and outer magnet rings are locked together by magnetic force and work as a synchronous coupling. The inner magnet ring transmits the required torque direct to the impeller. The magnetic drives are designed for electric motors, direct on line starting. Should a subsequent increase of motor power be required, i.e. when installing a larger impeller, the nominal power of the coupling can be increased by an additional series of magnets.
Internal clearances
The internal clearance between inner rotating magnets and containment shell
depends on the wall thickness of the shell. However, a minimum clearance of 1 to
2 mm (0.04" - 0. 0 8") will be provided in any case. This, together
with wear resistant sleeve bearings, allows handling of fluid with solid
particles.
Containment shell protection
The different clearances between the rotating outer magnets and stationary containment shell and the rotating magnet holder and bearing bracket adapter, prevent rubbing of magnets on the containment shell in the case of ball bearing failure.
Internal circulation, pressurized magnet end
When the pump is in operation it generates eddy currents which heat up the
containment shell and the pumpage in the magnet area. This heat is dissipated by
internal circulation. The internal circulation flows from the discharge directly
behind the impeller, through the pump shaft to the rear rotor impeller vanes.
Pressure increase by the rear impeller leads circulation back to the discharge.
The capacity of the circulation flow, together with pressurization of the magnet
end with the sleeve bearings, prevents vaporizing or flashing of the pumpage in
this area when handling boiling liquids.
Sleeve bearings
The internal bearings are of the sleeve type, positioned in the pumpage. The stationary bearings are located centrally in a common bearing housing which maintains correct alignment. Standard material is diamond coated pure Silicon Carbide, highly resistant against corrosion and wear and providing limited dry running capability.
NPSH-Conditions
Due to the internal circulation from discharge to discharge, no liquid at
elevated temperature will re-enter the impeller eye. Handling of boiling liquids
is possible without an increase of NPSH-required.
Balanced thrust loads
The thrust loads of the closed impellers are partially balanced by wear rings and balance holes in the impeller hub. Residual forces on the impeller act towards the suction flange. These forces are balanced by the rotor design. The difference between the constant pressure P4 at the rear rotor area and the variable pressure P5 at the front side creates a counter force in the direction to the containment shell. The value of this reaction force depends on the pressure P5, which is dependent on the variable gap S. that means, the internal rotor floats until the forces at impeller and rotor are balanced. The thrust bearings work as start-up rings only. Measurement of thrust load as part of the performance test is possible.
Options
Outer ball bearings for frame mounted units
The drive shaft of the AM / KM type is carried in generously dimensioned anti-friction bearings, protected by radial seal rings against the environment. Grease or API 610 oil lubrication is available. Pumps can also be close-coupled for cost, alignment and space savings.
Monitoring
Connection for temperature detection elements for containment shell surface temperature is available as standard. Dry running protection and monitoring of ball bearings and containment shell temperature with the patented MAG-SAFE System is highly recommended.
Inducer
To improve NPSH-required conditions, suction inducers are available. The inducers are designed such that NPSH-improvement is provided from minimum flow up to BEP. Retrofit of inducers on site is possible by re-machining the volute casing and without change to the suction pipe.
