Centrifugal pumps bearings

Process results, mixing, 316, 323, 324 Process safely, 399 Properties of gases/vapors, 439 Pumping of liquids, l60 Pumps centrifugal, 161-164 ANSI Standards, 161 Bearings, 168... 

The most common maintenance problem with centrifugal pumps is with the seals. Mechanical seal problems account for most of the pump repairs in a chemical plant, with bearing failures a distant second. The absence of an external motor (on canned pumps) and a seal is appeahng to those experienced with mechanical seal pumps. 

You can t begin to resolve problems in your centrifugal pumps, bearings and mechanical seals, until you learn the numbers 60°, and 240°, with respect to your pump cutwater. 

Actually, everything we said about bearings, mechanical seals, piping, TDH, system curves and mating the pump curve to the system curve, the affinity laws, cavitation, horsepower and efficiency arc as applicable to PD pumps as centrifugal pumps. 

The active magnetic bearing s versatility allows it to be used in almost any rotating machine. Examples include compressors, blowers, pumps, turbines, centrifuges, x-ray tubes, vacuum pumps, spindles for... 

Since centrifugal machines are too big to control by frequent stopping and restarting, some form of capacity reduction must be inbuilt. The general method is to throttle or deflect the flow of suction gas into the impeller. With most models it is possible to reduce the pumping capacity down to 10-15% of full flow. There are no components which require lubrication, with the exception of the main bearings. As a result, the machine can run almost oil-free. 

Fig. 4.1-27 shows a multistage canned-motor centrifugal pump with a separate water-cooling circuit for the motor, such as is used, for example, to circulate carbon dioxide at 300 bar system pressure. The pump rotor is mounted in the motor area the tandem pump stages operate over-mounted on both sides of the bearings. This arrangement is recommended if the required differ-... 

For mechanical heat equivalent, the following are recommended (a) For pumps, use 50 percent of the connected motor horsepower for centrifugal pumps that are deadheaded, unless better information is available, (b) For agitators, use 100 percent of the vendor rated shaft input horsepower for the input shaft (total power less drive and bearing inefficiencies) for the actual material in the vessel. 

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