Using graphite insert materials to improve pump

The use of graphite, graphite-impregnated, or graphite-filled insert materials has
gained wide acceptance as an option in improving pump performance in both
original equipment and after-market upgrades.

These graphite-based materials, are considered to be "self-lubricating" to the
extent that they can survive momentary upset conditions where loss of lubrication
occurs between wear parts without seizing, such as when a pump unexpectedly
stops running.

This property makes them ideal as "inserts" in case wear rings, throttle bushings,
and other non-rotating wear parts, to reduce the running clearances between the
mating parts. The reduced clearances, some as much as 50% of the standard
clearances, can result in significant improvement in pump performance:

  • reduced clearances can minimize the leakage across the mating parts,
    which in turn will result higher efficiency; typical improvement is about 2 to
    3 points depending on pump type and size

  • reduced leakage can help slightly increase the discharge head at the
    same discharge flow rate

  • reduced clearance can help dampen the pump vibration

  • graphite, and graphite-impregnated materials, are ideal in applications
    handling low specific gravity liquids that are considered to have poor
    lubricating properties, such as butane, propane, liquid carbon dioxide, etc.

There are many commercially available graphite, graphite-impregnated, or
graphite-filled materials. Among the commercial trade names are graphalloy,
peek, pure carbon etc. Consult their respective manufacturers for application
recommendations. Some of these materials may not be suitable in abrasive, high
temperature, or high-stress application.

File: graphite inserts

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