Tecfluid TM Series - Manual (Page 6)

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These distances can be reduced by installing a flow straightener upstream of the turbine
at a distance equivalent to 5 DN.
3.5 Valves
Regulating or shut-off valves must always be installed after the turbine, in order to assure
that pipe is full of liquid.
3.6 Pumps
Pumps must always be installed before the turbine in order to avoid cavitation.
This way the presence of air pockets in the flowmeter is avoided, which could cause
unbalance of the propeller which could damage the turbine.
Note: To avoid cavitation the pressure at the outlet of the turbine should be higher than
twice the pressure loss of the turbine (see table Nº 2) plus 1.25 times the vapour pressure
of the liquid or its most volatile component.