Intermittent Service

INTERMITTENT SERVICEĀ I019

This is the opposite of continuous service. We could be talking about batch operations, standby pumps, level control pumps, etc.

It takes five times as much power to start a pump as it does to run it. This start up torque produces frequent seal failures

Intermittent service requires heavy duty pumps and mechanical seals, because:

  • The pump is continually moving off the best efficiency point (BEP) during the start up procedure.
  • Break away friction of the seal dynamic elastomer and lapped faces contributes to the problem.
  • The thrusting of the shaft at start up can cause seal problems.
  • Frequent heating and cooling of the liquid in the stuffing box can cause some products to:
    • Solidify.
    • Crystallize.
    • Build a film on sliding seal components.
    • Become viscous.
  • We experience shaft axial movement and volute radial movement as the pump comes up to operating temperature.
  • The frequent heating up and cooling down of the bearing case can cause bearing problems because of moisture condensation and aspiration.
  • Batch operations sometimes require a flushing of the lines and pump to clean out the old pumpage. The cleaners and solvents used for this cleaning can sometimes affect one or more of the seal components.

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Posted

  • On February 16, 2018