Technical Conventions - Johnson Pump TG GS2-25 Instruction Manual

1.4

Technical conventions

Quantity
Dynamic
viscosity
Kinematic
viscosity
Note! In this manual only dynamic viscosity is used.
Pressure
Note! In this manual, unless otherwise specified - pressure is relative pressure [bar].
Net Positive
Suction Head
Note! In this manual, unless otherwise specified, NPSH = NPSHr
When selecting a pump, ensure that NPSHa is at least 1 m higher than the NPSHr.
A.0500.501 – IM-TGGS/05.01 EN (03/2013)
Symbol Unit
µ mPa.s = cP (Centipoise)
ρ = density
ν = µ
ρ
dm
ν = kinematic viscosity [ mm
p [bar]
∆p Differential pressure = [bar]
p Maximum pressure at discharge flange (design pressure) = [bar]
m
NPSHa Net Positive Suction Head is the toal absolute inlet pressure at
the pump suction connection, minus the vapour pressure of the
pumped liquid.
NPSHa is expressed in meter liquid column.
It is the responsibility of the user to determine the NPSHa value.
NPSHr Net Positive Suction Head Required is the NPSH determined,
after testing and calculation, by the pump manufacturer to avoid
performance impairement due to cavitation within the pump at
rate capacity.
The NPSHr is measured at the suction flange, at the point where
the capacity drop results in a pressure loss of at least 4%.
[kg]
3
2
] = cSt (Centistokes)
s
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