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Centrifugal Pumps Design and Application 2nd ed - Val S. Lobanoff, Robert R. Ross (Butterworth-Heinemann, 1992)

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Reliability<br />

Mechanical Seal Reliability 567<br />

Once the potential problems of selection, installation, <strong>and</strong> operation<br />

are address<strong>ed</strong>, mechanical seals can provide reliable sealing for many<br />

years. Many large refineries <strong>and</strong> chemical plants have obtain<strong>ed</strong> a gross<br />

average mean time between pump failures that is greater than two years.<br />

(This statistic includes all causes of pump repairs <strong>and</strong> not just mechanical<br />

seals.)<br />

Some services will always be more difficult than others <strong>and</strong> have a correspondingly<br />

lower reliability. Higher pressures, higher temperatures,<br />

higher solids content, <strong>and</strong> increas<strong>ed</strong> corrosion rates will generally result<br />

in a lower pump <strong>and</strong> seal reliability. Similarly, large seals <strong>and</strong> high shaft<br />

spe<strong>ed</strong>s may have lower reliability. Rather than accept lower reliability,<br />

many users elect to use special purpose seals <strong>and</strong> sealing systems that are<br />

engineer<strong>ed</strong> for these specific applications.<br />

Considering the wide variety of designs, arrangements, <strong>and</strong> materials<br />

available, it is no wonder that the mechanical seal is the most popular<br />

device for sealing modern centrifugal pumps.

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