Notes On Suction And Delivery Lines - Graco 333466E Manuel D'instructions

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NOTES ON SUCTION AND DELIVERY LINES

DELIVERY
EFFECTS ON Length and diameter of pipe, fl w rate of dispensed liquid,
FLOW RATE accessories fit ed, can create back pressures above those allowed.
In this case, the pump mechanical control (bypass) will trip to re-
duce the fl w rate.
HOW TO REDUCE To avoid these problems, system fl w resistances
EFFECTS ON
using shorter and/or larger diameter pipes, as well as line accessories
FLOW RATE
with low resistances (e.g., automatic nozzle for higher fl w rates).
NOTICE The delivery pipe must have the following technical
characteristics:
CHARACTERISTICS
- recommended minimum nominal diameter: ¾"
OF DELIVERY PIPES
- recommended nominal pressure: 10 bar (145 psi)
SUCTION
FOREWORD Diaphragm positive-displacement pumps are self-priming and
feature good suction capacity.
During the start-up phase, when the suction pipe is empty and the
pump is wet, the electric pump unit is able to suck liquid from a
maximum vertical distance of 2 mt. (6.5 ft)
NOTE Priming time can last a few minutes. We suggest
performing priming operations without automatic
nozzle and making sure the pump is properly wet.
NOTICE Always install a foot valve to prevent the suction pipe
from being emptied and to keep the pump wet at all
times. In this way, the pump will always start up im-
mediately the next times it is used.
CAVITATION The pump is able to work with vacuums of up to 0.5 bar (7 psi) at the
suction mouth. Over this value, CAVITATION can occur that causes a
fall in fl w rate and increase in noise levels.
HOW TO It is important to ensure low vacuums at suction mouth by using:
PREVENT - short pipes with larger or identical diameter to that recommended
CAVITATION - reduce bends to the utmost
- use large-section suction fil ers
- use foot valves with minimum possible resistance
- keep the suction fil ers clean because, when they become clogged,
they increase the resistance of the system.
NOTICE
The vertical distance between the pump and the fluid
must fall within the 2 mt. (6.5 ft) maximum required
for priming. If the distance is greater, a foot valve
must be installed to allow the suction pipes to fill up
and the diameter pipes must be larger. It is recom-
mended that the pump not be installed at a vertical
distance greater than 2 meters.
NOTICE If the suction tank is higher than the pump, an anti-
siphon valve should be installed to prevent acciden-
tal product leaks. Size the installation to contain the
back pressures caused by water hammering.
NOTICE
It is a good system practice to immediately install
vacuum and air pressure gauges at the inlets and
outlets of the pump which allow verification that
operating conditions are within anticipated limits.
To prevent the suction pipes from being emptied
when the pump stops, a foot valve should be
installed.
NOTICE The suction pipe must have the following technical
specifications:
CHARACTERISTICS
OF THE SUCTION - recommended minimum nominal diameter: ¾";
PIPES - recommended nominal pressure: 10 bar (145 psi);
- use pipes suitable for low vacuum operation (e.g.
M0309
with metal core)
must be reduced
EN
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