Wear ring

Wear-ring clearances are excessive (closed impeller design). 

Overhaul pump. Renew wear rings if clearance is about twice design value for energy and performance reasons. 

Excessive wear ring (closed impeller) or cover-case clearance (open impeller). 

Replace wear rings or adjust axial clearance of open impeller. In severe cases, cover or case must be replaced. 

FIG. 10-94 Piston equipped with carbon piston and wearing rings for a non-hibricated cylinder. 

As we ve di,seussed, system design is responsible for much of cavitation. Yet, the maintenanee mechanic is responsible for stopping and preventing eavitation. And certainly, it s the maintenance mechanic who has to deal with the results of cavitation, the constant changing of bearings, meehanical seals, damaged impellers, wear rings and other pump parts. 

Wear ring tolerance - Close tolerances on the wear rings have a tremendous effect on the pump s efficiency, particularly for pumps with a low specific speed (Ns < 1500). 

The scratch marks on the circumference of these close tolerance rotary parts will correspond to. scratch marks on close tolerance stationary parts at approximately 60 around the volute from the cutwater. These marks will be vi.sible on the back plate with open impellers, or on the wear rings of pumps with enclosed impellers, or the ID bore of the restriction bushing at the bottom of the seal chamber where the shaft pa.sses through, or the ID of the seal chamber bore at the back end of the mechanical seal (Figure 9-6 and Figure 9-7, next page). 

Erosion is the wear of the pump internal parts by suspended solid particles contained in the fluid being pumped. The most affected parts are wear rings, shaft sleeves, packing, mechanical seal faces, lip seals, the pump casing and the impeller. 

Wear rings provide for a close running, renewable clearance, which reduces the amount of liquid leaking from the high pressure zones to the low pressure zones in the pump. They are commonly fitted in the pump easing and on the impeller (Figure 16-1, next page). 

You can expect the pump to loose 1.5 to 2% efficiency points for each one thousandths (0.001 inch) wear in a wear ring beyond the original... 

Effective and well planned maintenance can reduce the operating cost of your pumps and other ec]uipment as this example demonstrates. With differential pressure gauges on the pump, an amp meter and flow meter you can determine if strict tolerance parts arc worn. This indicates the need to take the pump into the shop for corrective procedures. If you don t do it, you are wasting your annual operating budget. As we mentioned in Chapter 6, the Wear Rings should be called Efficiency Rings. Now you know why. 

Liquid Wear Rings Wear Rings Shaft Sleeves Seal Seal Cage Gland Remarks... 

IMPELLER WEAR RING COOLING WATER-SEAL ... 

Avoid wearing rings. Wear gloves. Wash the hands and gloves after handling mercury Use catchpots under apparatus containing mercury... 

Wearing plates With open type impellers or end clearance wearing fits, these perform the same purpose as wearing rings do with radial clearances. 

SHAFT is heat treated, extra heavy to take maximum radial thrust. Shaft supports impeller between bearings for longer bearing, wearing ring and packing life. 

High efficiency, long life labyrinth wearing rings... 

Positive wearing ring seats eliminate leokage between case and rings... 

Liquid Casing Wear Rings Impeller Wear Rings Shaft Shaft Sleeves Type of Seal... 

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