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Liquiflo Installation, Operation & Maintenance Manual
1.5
General Operation
The successful and safe operation of a pump is not only dependent on the pump but also on each of the system
components. It is therefore important to monitor the entire pumping system during operation and to perform the
necessary maintenance to keep the system running smoothly.
A normally operating centrifugal pump will deliver a steady and pulse-less flow, be relatively quiet and have a
predictable flow rate and power requirement based on the impeller size, operating speed, differential head and
fluid specific gravity. Performance curves for centrifugal pumps are normally based on pumping water at room
temperature.
Centry Model 620 performance curves can be obtained from the Liquiflo website:
www.liquiflo.com. For viscous liquid applications, a performance correction is required (see Section 3.9).
Pumps operating with mechanical seals should have no leakage of the process fluid. Pumps operating with
packing should have a normal leak rate of 8 to 10 drops per minute with low viscosity liquids. Pumps operating
with a double mechanical seal must be supported with a pressurized fluid lubrication loop. For more information,
see Section 4.2.
If a significant problem is observed during operation, the pump should be stopped so that corrective action can
be taken. The observed problem could have several possible causes, and multiple remedies for each cause.
For help with problem solving, refer to the Troubleshooting Guide given in Appendix 5.
1.6
Maintenance & Repair
Pumps with packing require periodic lubrication or tightening of the gland screws over time. Pumps with a
double mechanical seal require maintenance of the fluid in the lubrication loop. Repair is necessary when the
gland screws cannot stop the packing from leaking excessively, or when the mechanical seal starts to leak, or
when a decrease in head is observed. O-rings and gaskets should always be replaced when rebuilding the
pump.
The main factors affecting the physical wear of the pump are operating speed, differential head, fluid viscosity,
duty cycle, starting and stopping frequency, abrasives in the fluid and the wear properties of the materials.
These factors can cause pump lifetimes to vary significantly from one application to another, making it difficult to
predict when the pump will require maintenance. Therefore, the maintenance schedule for the pump is typically
based on the maintenance history of the specific application. The main indicators that a pump may require
maintenance are the following: (1) decreased flow rate or head, (2) fluid leakage, (3) unusual noise or vibrations
and (4) increased power consumption.
The common repair items of the pump due to erosion wear are the seal components (i.e., packing rings, gland
plate or mechanical seal) and the shaft. Possibly, other pump parts, such as the impeller, volute and seal
housing, may require replacement due to abrasion wear, corrosion wear or cavitation wear.
Before performing maintenance on the pump, review the safety precautions and follow the included instructions.
1.7
Replacement Parts
Replacement parts for the pumps can be purchased from your local Liquiflo distributor. Refer to Appendices 3
& 4 for individual parts information.
Centry
Model 620 – Sealed
6
®
Series Centrifugal Pumps
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