6
Notes on Delivery and Suction Lines
Delivery Line - Effects on Flow Rate:
Length and Diameter of Pipe, Flow Rate of Dispensed Liquid and
Accessories fitted, can create back pressures above those allowed. In this case, the Pump mechanical control
(bypass) will trip to reduce the Flow Rate.
How to Reduce Effects on Flow Rate:
To avoid these problems, system flow resistances must be reduced
using shorter and/or larger diameter pipes, as well as line accessories with low resistances (ex. Automatic
Nozzle for higher Flow Rates).
Characteristics of Delivery Pipes:
The delivery pipe must have the following technical characteristics:
•
Recommended Minimum Nominal Diameter: 3/4” (19mm)
•
Recommended Nominal Pressure: 145 PSI (10 bar)
Suction Line:
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 Pump unit is able to suck
liquid from a Maximum Vertical Distance of 10 ft. (3m)
Note:
Priming time can last a few minutes. We suggest performing priming operations without Automatic
Nozzle and making sure the Pump is properly wet.
Note:
Always install a Foot Valve to prevent the Suction Pipe from being emptied and to keep the Pump wet
at all times. This would ensure the Pump will always start up immediately next time it is used.
Cavitation:
The Pump is able to work with vacuums of up to 7 PSI (0.5 bar) at the Suction Mouth. Higher
pressure than 7 PSI (0.5 bar) can cause Cavitation, which causes a fall in Flow Rate and increase in Noise
Levels.
How to Prevent Cavitation:
It is important to ensure low vacuums at the Suction Mouth by:
• Using
Short Pipes with larger or identical diameter
•
Reduce bends to utmost on the Pipes
•
Using Large-section Suction Filters
•
Using Foot Valves with minimum possible resistance
•
Keeping the Suction Filters clean because, when they become clogged, they increase the
resistance of the system.
Note:
The Vertical Distance between the Pump and the Fluid must fall within the 10 ft. (3m) 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 recommended that the Pump not be installed at a Vertical
Distance greater than 10 ft. (3m).
Note:
If the Suction Tank is higher than the Pump, an Anti-siphon Valve should be installed to prevent
accidental product leaks. Size the installation to contain the back pressures caused by water hammering.
Note:
It is a good 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.
Characteristics of the Suction Pipes:
The Suction Pipe must have the following Technical Specifications:
•
Recommended Minimum Nominal Diameter: 3/4” (19mm)
•
Recommended Nominal Pressure: 145 PSI (10 bar)
•
Use Pipes suitable for low Vacuum Operation (e.g. with metal core)
Duty Cycle:
The Pumps have been designed for intermittent use and a 30-minute duty cycle under conditions
of maximum back pressure.
Note:
Functioning under by-pass conditions is only allowed for short periods of time (Max. 3 minutes).
