Upload
others
View
47
Download
0
Embed Size (px)
Citation preview
Product quality, operational safety and energy efficiency are of prime im-
portance. Conveying distance, throughput, configuration of the system
and the order of processes are decisive when considering whether to use
over or negative pressure.
Pneumatic conveying systems have established themselves in all kinds of
sectors of bulk material processing. Both conveying systems – pressure
and suction conveying – have undergone consistent development. Today
both systems provide possibilities to transport product gently from A to
B with minimum attrition. That is why a plant manufacturer may find it
difficult to decide on which conveying method suits his process best.
Pneumatic Conveying: Pressure or Suction Conveying?
Pressure Conveying
Loading of product in normal atmos-•
pheric conditions, e.g. directly from
open hopper
Transport from several loading points •
to one receiving vessel is possible
Limited contamination of work envi-•
ronment if leakage occurs
Discharging of product from receiving •
vessel in normal atmospheric condi-
tions
From one starting point to several re-•
ceiving vessels
Dense phase conveying•
Long conveying distances•
Smaller tube diameters•
Smaller air compressors and filters•
Not necessarily suitable for dense •
phase conveying
Conveying over short distances (ap-•
prox. 80 m) limited
Larger tube diameters•
Larger compressors and filters•
Product can be compacted long-term •
if pressure is too high
Space required when loading can be •
quite large depending on selection
of pressure conveying process (rotary
valve – pressure vessel)Dis
adva
ntag
es
Suction Conveying
Adv
anta
ges
For further information: www.gericke.net
Trials carried out at our Test Centre
provide valuable information
The material to be conveyed can be
tested with both conveying systems
in realistic conditions at our Gericke
Test Centre. Laboratory tests provide
information concerning general flow
characteristics such as fluidisation ca-
pacity or compressibility of a product
and facilitate selection of the right
system.
Trend-setting configuration
The number of places in total where the conveying process begins and
ends can determine the type of conveying selected. If for example several
systems are to be supplied from one silo, one would probably decide on a
conveying process with overpressure the reason being that several recei-
vers can be supplied from one point.
If however one machine is to be filled from several reservoirs, this is a case
where suction conveying comes into play. This process means that the ma-
terial can be suctioned to one point from various loading points.
Modification of product characteristics
Varying forces affect the material to be conveyed depending on whether it
is conveyed using suction or pressure. Negative and positive differences in
pressure can have an impact on central product characteristics. The forces
during the conveying process as well as the residence time in the vessel
(pressure conveying) or in the receiving vessel (suction conveying) must be
taken into consideration.
Pressure as physical difference between suction and pressure systems
There are advantages in connection with both systems. One difference
remains: The suction pneumatic system has a maximum usable pressure
difference of 1 bar whereas pressure conveying systems can theoretically
use unlimited pressure. In practice, most pressure conveying systems ope-
rate with 1-4 bar overpressure.