Page 100 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

Insfalhtion, Maintenance, and Repair of Yerrical Pumps 85

to restore the flatness and squareness of flange faces and the con-
centricities of rabbet fits. Only skim cuts should be used and con-
centricities and tolerances must be maintained.

3. Coupling bores may be restored by chrome plating followed by an
internal grinding operation. However, this is generally an expen-
sive procedure.

4. Both the driver half coupling and the pump half coupling should be
installed with snug sliding fits.
5. Large couplings or couplings operating at 3,600 RPM and above
should be placed on a mandrel and dynamically balanced, using
procedures similar to those used for the dynamic balancing of im-
pellers.

Maintenance and Repair of Pump Shaft Couplings
Both threaded and keyed shaft couplings are found in circulating, deep-
well, and submersible pumps. Shaft couplings are relatively inexpensive.
They should be stocked, and replaced if corrosion or damage makes them
unserviceable.

Auxillary Piping Requlrements
Special attention to auxiliary piping requirements can reduce mainte-
nance and repair costs, especially those related to barrels, seals, and
packing. This is particularly true if the pumped liquid is very hot, very
cold, volatile, or when the pump suction is under a vacuum or very high
pressure. Reference 3 covers auxiliary piping requirements for these
cases.
Maintenance and Repair of Packed Stufflng Boxes

Almost all process pumps are equipped with mechanical seals. Packed
stuffing boxes are generally found only in deepwell pumps and circulat-
ing pumps handling cold clean water or with a cold clean water injection
below the packing.

1. Soft braided fabric packing impregnated with lubricant is satisfac-
tory for low pressure applications. Lubricated synthetic packing is
advisable for higher pressures.

2. Preformed packing rings promote a quicker and better packing job.
However, if the replacement packing is in a continuous coil it must