Pump shaft

Typical apphcations for the nickel—copper alloys are in iadustrial plumbing and valves, marine equipment, petrochemical equipment, and feedwater heat exchangers (see Piping systems). The age-hardened alloys are used as pump shafts and impellers, valves, drill parts, and fasteners (see Pumps). 

Shafts. Shafts shall he suitable for hook-type sleeve. Shaft material shall he (SAE 1045 steel on Duron and 316 stainless steel pumps) or (AISI 316 stainless steel on CD-4MCu pumps and 20 stainless steel pumps). Shaft deflection shall not exceed. 005 at the vertical centerline of the impeller. 

These pumps incorporate an electric motor whose rotary assembly is hermetically sealed inside a stainless steel or exotic alloy can. The motor, pump shaft and bearings all operate wet inside the pumped liquid as show ii in Figure 6-12. 

If the condition should be oecasional, the solution could be to install a variable speed motor. If the condition is permanent, the solution could be to reduce the impeller diameter, replace the pump, or increase the diameter of the pipe. If normal operations require living with the condition, then increase the diameter of the pump shaft to improve the L/D factor. 

Pump shaft and driver shaft alignment is very important for long useful equipment life, and to extend the running time between repairs. Besides, good alignment reduees the progressive degradation of the pump. 

This is the most popular method used in industry tttday because the investment in equipment is moderate and its effectiveness is proven. This method uses two dial indicators, one on the pump shaft and the other on the motor shaft. 

At Pump Installation Be sure the motor shaft centerline is below the pump shaft centerline so that it can be shimmed upward. Make sure the motor mount boltholes have sufficient play to allow for some lateral adjustment. Many pumps and motor assemblies are shipped from the factory on a common channel iron base plate. The manufacturer alleges that they arc already aligned at the factory. You need to verify and correct this alignment in all cases. 

Sleeve bearings on some older, slower, larger pump shafts can withstand dirt contamination better than ball and roller bearings. This is because the tolerances are not so strict with sleeve bearings, the surface area of contact is greater, and the lubricant flushing action is better. The sleeve bearing material of construction is... 

Labyrinth seals work best when the pump is running. Centrifugal force favors the labyrinth seal s action. Earlier models were only specified for horizontal pump shafts. Later models are designed for both horizontal and vertical pump shafts and effectively perform their function whether the pump is running or off... 

The outside diameter of the lip. seal fits and seats into the housing bore (transmission or pump). The inside diameter, with the elastomeric lip, rides onto the spinning shaft (whether vehicular drive shaft or pump shaft). 

After a few revolutions, the rubber lip of the oil seal beeomes an abrasive lip, w hieh eats a groove into the stainless steel pump shaft. The rubbing aetion abrades the pump shaft, removing metal, and depleting the ehromium eontent of the stainless steel, wdiieh further aeeelerates its erosion. 

Figure 13-17 shows a balanced, single, rotary dement seal mounted onto the pump shaft, pressed against the stationary face and gland, mounted in the seal chamber. Note the individual component parts of the rotary element. 

The torque eapaeity of the pump shaft must be greater than the torque eapaeity of the shear pin in all eases. We assume that failure of the pump shaft oeeurs at the interferenee of these two torque distributions. From equation 4.89, the torque eapaeity of the shear pin ean be determined by substituting the ultimate shear strength of the weak link material, for L, giving ... 

Therefore, the Normal distribution parameters for the pump shaft torque capacity are ... 

Solving equation 4.94 using Monte Carlo simulation for the variables involved, the shear yield strength required for the pump shaft material is found to have a Normal distribution with parameters ... 

From equation 4.94 and using Monte Carlo simulation again, the actual torque capacity of the pump shaft using the 070M20 steel grade is found to be ... 

Finally, the interference between the applied torque and the pump shaft torque capacity can be analysed to determine if separation between them is too great leading... 

Figure 4.61 Weak link torque capacity shown relative to the applied torque and the torque capacity of the pump shaft...

Exposure in a solution that is passivating and yet not far removed from the passive-activity boundary may lead to coiTosion if the exposure involves a strong abrasive condition as well. Pitting of pump shafts under packing handling sea water is an example of this abrasive effect. 

The motion of the piston rod is reciprocating through this packing as contrasted to the rotating motion of the centrifugal compressor or pump shaft. In many applications, it is important to prevent any part of the shaft that has heen inside the cylinder and exposed to the gas from being... 

In chilled-water systems, pump shaft power adds to the heat of the circulating water. Similarly, if the chiller has a water-cooled condenser pump heat is added to that handled by the final cooler. Power is proportional to the flow and pressure ... 

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