Page 67 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

52 Practical Machinery Management for Process Plants
Table 1-6
Recommended Radial Gaps for Pumps

I
Recommended Radial Gaps for Pumps

10% 12%

The importance of not allowing pump piping to exert undue stresses on
nozzles and baseplates is simply not appreciated by many maintenance work-
ers, reliability professionals, and operators. When it is not possible for a
worker to manually push pump suction or discharge piping into position to
mate with the pump flanges, pipe stress is excessive and should be corrected
before inserting and torquing up the flange bolting. Regardless of flange and
nozzle size, it is never good practice to pull piping into place by means of
chainfalls or other mechanical stressing devices. Figures 1-19A and B clearly
show how piping induced stresses are prone to create pump-internal misalign-
ment sufficient to cause the destruction of even the best mechanical seals.6
Along the same lines, the customary practice of installing an entire pump-
and-driver set on a common baseplate and then attempting to level and grout
the entire assembly on the concrete foundation is not “best practice.” A reliabili-
ty-minded engineer will insist on installing equipment baseplates by them-
selves. This will greatly improve the probability of achieving truly level instal-
lations. A desirable side benefit will be improved grouting access and full grout
support under the entire baseplate. Figure 1-20 depicts grouting in progress.’

Figure 1-19. Piping-induced stresses are prone to create internal misalignment sufficient
to cause the destruction of even the best mechanical seals. (A) Seal rotating ring. (B) Seal
seat.