Page 587 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Be st Practice 1 0.12 The Post-Shipment Phase: Installation, Pre-Commissioning, Commissioning and Start-up Best Practices

A change in: Cavitation is possible only if a liquid vaporizes?
What can cause a liquid to vaporize? (Fig.)
Discharge Pressure
After a liquid vaporizes, it will change back to a liquid when ?
Suction Pressure (look at Fig 10.12.11.)
Specific Gravity This is cavitation, it sounds like rocks and can cause much
damage if water is the liquid. Oils act like shock absorbers.
What can happen in the process to cause these changes?
Change flow and pump damage is possible! Fig 10.12.7 What causes cavitaiton and what is cavitation?

Fig 10.12.6 What causes a change in pump flow?

Fig 10.12.8 -

A very confusing term indeed (see Fig 10.12.11.)
Therefore if the pressure drop (NPSHr) is greater than the
pressure above the liquid’s vapor pressure at the suction
If the pressure drop in the suction part of the pump reduces
the liquid pressure below it’s suction pressure, what happens? flange of the pump (NPSHa), we will have--------------?
That’s why if NPSHr (Net Positive Suction Head required)
To predict if-----------will occur, NPSHa is used to describe how
much above the vapor pressure is in feet (pressure). NPSHr is > than NPSHa, it’s bad!!
is the pressure drop inside the pump suct in feet What can cause cavitation?-------,-------,------------,--------,--------

Fig 10.12.9 NPSH anyone? Fig 10.12.10 NPSH? cont

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