Centrifugal pump viscosity limitation

These pumps are particularly useful when low volumes of low-viscosity liquids must be handled at higher pressures than are normally available with centrifugal pumps. Close clearances limit their use to clean liquids. For veiy high heads, multistage units are available. 

A forced circulation evaporator depends on the ability of a centrifugal pump to circulate the residue. This sets a limit of about 500 cP at working temperature on the viscosity of the bottoms and often requires that an appreciable amoimt of solvent must be left unrecovered to keep the residue mobile. In addition, the deliberate superheating of the mixture being circulated is the very opposite of what should be done to avoid exotherms, as discussed earlier in this chapter. 

Centrifugal pump Is used in majority of pump applications. However, It Is limited to liquid viscosity is 500 SSU (110 centistokes) or less. For liquid viscosity between 150 SSU (32 cts) to 500 SSU (HO cts), study is required to see whether it is still a good candidate for the service. For high viscosity fluid (>110 cts), consider using rotary or reciprocating pump. 

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