2
8
➜
➜
➜
➜
2.4
2.5
36 2000
50 1500
70 800
95 400
115 300
155 100
Fig. 9
Fig. 10
RIGHTWRONG
INJECTION
NOZZLE
BACKPRESSURE
VALVE
Right
Right
Wrong
Siphoning.
Uncontrollable flow rate
.
Wrong
Failing a back pressure valve, the
flow in pipeline “A” draws the
product from the tank in an
uncontrolled way.
• When the free surface of the liquid in the suction side tank is above discharge-side tank level, an uncontrollable flow from the suction
side tank to the discharge side tank will occur.
• To prevent this natural passage of liquid, the discharge pressure must always be at least 0,3 Kg/cmq, higher than the suction pres-
sure, in case of small flow rates 0,5 Kg/cmq.
• If for any reason this condition cannot be complied with the plant it is necessary to create a backpressure by means of a suitable
valve, or better to highten the discharge pipe so as to prevent the siphoning effect (fig.10).
DISCHARGE LINE
RIGHTWRONG
Recommended
Recommended
Right
Wrong
Wrong
Wrong
S.P.M. cp max execution "A"
Table E
Relationship between strokes per minute "SPM" and
viscosity of the liquid "cp", valid for AISI 316L or PP.11
pump heads.
• Specific technical information is required for the installation of pumps intended for
metering viscous liquids.
- For this kind of application we recommend stainless steel pumpheads.
- The suction piping must have an adequate diameter; as a rule, for high-viscosity liq-
uids (2000 cps), select the size immediately above the diameter of the pump suction
connections.
- In any case, when viscous liquids are to be metered choose for the pipe at least the
same size as that of the pump connections.
Examples of installation for viscous liquids
INSTALLATION
SUCTION PIPING FOR VISCOUS LIQUIDS
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