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Design
The NCR-pumps are centerline mounted single stage overhung pumps (designated pump type OH2). They have a heavy duty bearing bracket to accept all forces imposed upon the pump shaft and maintain rotor position during operation. The pumps are mounted on an API baseplate and direct coupled to the drivers.
The pump is of back-pull-out design. That means rotating pump unit (including bearing bracket, intermediate casing, shaft sealing and impeller) can be removed without disassembly of the volute casing. Suction and discharge pipe remain connected.
In connection with the standard spacer coupling, motor can remain bolted down to base plate.
Volute casing
The single or double volute casings of standard design are cast en bloc and centerline mounted.
The design pressure rating for the
standard materials is 4000 kPa (40 bar or 600
psi) at38°C(100°F).
Pump flanges are full or spot faced on the back
and designed for through bolting.
Drain connection is available at the bottom. No vent connection required because of the self- venting configuration.
The radially split casings have metal-to-metal fits, with confined compression controlled gaskets to avoid blow outs.
The pumps are designed for satisfactory performance if they are subject to the forces and moments in table 4 of the standard.
Fully jacketed volute casings are available as an option. Pumps can be heated or cooled with water, steam or oil. Maximum allowable heating temperature 330°C (620°F), maximum pressure 24 bar (350 psig). Flanged connections for heating fluid are standard.
Pumps with jacketed casings may be required if the melting or cristallization temperature of the pumped fluid is higher than the pump's ambient temperature.
Impeller
The standard pump impellers are closed, manufactured of single-piece castings with solid hubs. The impellers are keyed to the shaft and secured by a cap screw with Heli-Coil insert.
The impeller thrust loads are hydraulically balanced by wear rings and balancing holes to the suction side. Special care was taken when designing the impeller eye to achieve low NPSH-values.
The impellers are properly statically and dynamically balanced according to paragraph 5.9.4 of the API 610, respectively ISO 1940-1, grade G 2,5.
Wear rings
Renewable wear rings are provided at volute casing, intermediate casing and impeller. The wear rings are held in place by screws. Running clearances meet the requirements of paragraph 5.7.4. (clearances are used to limit internal leakage and to balance axial thrust).
Mating surfaces of the hardened materials have a difference in Brinell hardness of at least 50 HB.
Inducer
For certain applications with very low NPSHA- requirement, inducers can be provided.
Contrary to former inducer designs, this inducer offers NPSH-improvement from minimum flow to maximum flow.
Retrofit of inducers on site is possible without change of suction pipe.
Vibration monitoring
The bearing housings are dimpled to facilitate hand held vibration transducers.
Threaded connections for permanently mounted transducers or flat surfaces for magnetic based vibration measurement equipment are available on request.
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