10 Considerations for Pneumatic Conveying System Design: What Most Engineering Schools Didn't Teach You - International Powder & Bulk Solids ...
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10 Considerations for Pneumatic Conveying System Design:
What Most Engineering Schools Didn’t Teach You
International Powder & Bulk Solids
Rosemont, IL
April 24-26, 2018
David Kennedy
Business Development Manager
VAC-U-MAX
#AdvMfgExpo
Let’s start our journey… #AdvMfgExpo
“What Most Engineering Schools
Did Not Teach You”
Image courtesy of Psychologytoday.com
#AdvMfgExpo
Fluids or Fluid Dynamics
Typical Engineering School Curriculum: Materials or Materials Science
Polymer Science
Process & Plant Design
AICHe
Trade Shows such as Powder & Bulk Solids
Jenike & Johanson
Other Educators:
Kansas State University (K-State) Bulk Solids Innovation
Center
The Wolfson Centre for Bulk Solids Handling Technology,
School of Engineering at The University of Greenwich at
Medway, Kent, UK
#AdvMfgExpo
Vacuum Conveying System
Basics
• Transfer of bulk dry powders and granules from a 3
container to the customer’s process using vacuum
• Main components:
1) Pickup point
2) Material Convey Tubing
1 5
3) Filter Separator
4) Vacuum Tubing
4
2
5) Vacuum producer
• Mixture of conveying gas and powder (1-3)
• “Clean” air (3-5)
#AdvMfgExpo
#AdvMfgExpo
• Dilute Phase Vacuum
• Material is Entrained in Air Stream
• Up to 25,000 lbs/hr (11,000 kg/hr)
• Less then 300 ft (90m) convey distance
• Up to 6” (150mm) convey line
#AdvMfgExpo
Why Vacuum conveying:
• Eliminating hand scooping
• If it leaks, it leaks inward
• Delivers the powder in a closed
process from point A to B
• Discharges material with control
• Works with larger containers to
reduce frequent container changes
#AdvMfgExpo
10 things to know when designing a vacuum convey system
1. Bulk Density (#/ft3, PCF or gm/cc)
• Factor in calculating the size of the vacuum
receiver (Can Velocity)
• Factor in calculating the size of the convey line
vacuum power unit (Convey Velocity)
• Convey velocity must exceed saltation velocity
• gm/cc X 62.43 = #/ft3
• “More” velocity is not always better
#AdvMfgExpo
10 things to know…
2. Conveying Distance
• Horizontal and Vertical
• Number of 45- or 90-degree sweeps
(CLR)
• One sweep = 20 feet of linear tubing
or pipe
• For example: “20’ Vertically + 20’
horizontally and two 90-degree
elbows”
• Vertical legs: Beware of avalanches! A
line clearing valve is recommended.
#AdvMfgExpo10 things to know…
3. Convey Rate
• How many pounds per hour will be conveyed?
• Is it a batch operation?
• For example: customer wants to convey 2000
pounds per hour but they really want to convey
2000 pounds once an hour in 5 minutes. This is
really 24,000 pounds per hour.
#AdvMfgExpo10 things to know…
4. Material Characteristics “One man’s fumed silica…”
Shape: Powder, Pastille, Pellet, Flake, or Granule
Particle size / distribution
Free Flowing?
Moisture Absorption?
Abrasive?
Combustible?
Chemically compatible?
#AdvMfgExpo#AdvMfgExpo
10 things to know…
5. How Do You Receive The Raw Materials?
• Bag
• Fiber drums or barrels
• Bulk Bag a.k.a. Super Sac, FIBC
• RIBC (Rigid Intermediate Container)
• Silo/Day Bin
• Railcar
• Upstream process equipment
#AdvMfgExpoBulk Bag Unloaders with enclosed vacuum convey line (left) and Bag Dump Stations with integral dust collectors (right) #AdvMfgExpo
10 things to know when designing a vacuum convey system
6. Is The Material Coming From Upstream Process Equipment?
LIW or Weight-Loss Feeder
Volumetric feeder
Mixer
Extruder Hopper
Reactor
Other equipment
Up stream equipment effects down stream equipment
=> Know everything you can about your source.
#AdvMfgExpo10 things to know…
7. Headroom
How much headroom is above the equipment?
Even the smallest vacuum conveying system for powders will require
at least 30” of headroom.
I’m in over my head work-arounds:
Cyclones or Filter-less Vacuum Receivers
Scaling valves
Positive pressure system
#AdvMfgExpo10 things to know…
8. Batch Operation or
Continuous Conveying
Batch Operation: typical for
extrusion process
Continuous Operation:
Volumetric or LIW feeder
which then meter feeds the
material continuously into
the next process.
#AdvMfgExpoVacuum Conveyor refilling weight-loss feeder via
Discharge-On-Demand principal
#AdvMfgExpo10 things to know when designing a vacuum convey system
9. Geographic or Atmospheric Conditions?
Anything that changes the density of the conveying medium
Altitude: Denver CO or Mexico City vs. New Jersey
Electrical: US vs. International
Plant conditions: temperature controlled?
#AdvMfgExpo10 things to know…
10. Material of Construction of the Equipment
Mainly a product contact concern:
Carbon Steel with coatings
Stainless Steel: 304 or 316L
Pharmaceutical Grade
Aluminum
“Who cares?”
Maintenance and QC cares!
#AdvMfgExpoBasic components of a Vacuum Convey System
Pick Up points
Wands: Used in drums. Operator
manipulation…Great for minors
Feedbins: Great for mixers or grinder
output
Bag Dump Stations
Bulk Bag Unloaders. Great for
automation of the system
#AdvMfgExpoBasic components…
Tubing or Flexible Hose
• Static grounding…NFPA 77, 652, 654
• Food-grade?
• Smooth-bore…sweep elbows,
couplings
• Metallic tubing.. aluminum or
stainless steel…no plastic!
• Aluminum on clean air side.
#AdvMfgExpoBasic components…
Filter Receiver
• A steep angled hopper will make
sure the material discharges in
mass flow…60- or 70-degree
cones…or 90-degrees!
• Hopper geometry: concentric,
offset, tube-style
• Discharge opening / type: 50%+
#AdvMfgExpo“A 90-degree cone???”
• Tube Hopper
• Tube hoppers are straight
vacuum receiver, no cone.
Best solution for non free
flowing powders.
#AdvMfgExpo#AdvMfgExpo
Vacuum Conveying System
Basics
• Transfer of bulk dry powders and granules from a 3
container to the customer’s process using vacuum
• Main components:
1) Pickup point
2) Material Convey Tubing
1 5
3) Filter Separator
4) Vacuum Tubing
4
2
5) Vacuum producer
• Mixture of conveying gas and powder (1-3)
• “Clean” air (3-5)
#AdvMfgExpoBasic components…
Vacuum Source
• Venturi.
Runs on compressed air. No
moving parts. Simple.
Low initial cost…utility costs?
Excellent for hazardous
environments.
“Up-and-In”…up to 3,000lb/hr
#AdvMfgExpoRegenerative Blower
Medium Vacuum, High Air Flow.
Good for pellets and granules
#AdvMfgExpoPositive Displacement Vacuum Pump
Straight-line curve…@12”Hg – 16” Hg
Great for conveying everything !
#AdvMfgExpoBasic components…
Controls
• Simple timer boards or pneumatic controls
• Automation and communication are the
trends
• Local Mini PLC
• DCS PLC Based
Know your area classification!
#AdvMfgExpoBasic components…
• Air-To-Cloth Ratio
• Amount of air (CFM) moving
through the system related to
the amount of filter area (ft2)
in the vacuum receiver.
• Lower air-to-cloth ratio
means higher efficiency
filtration and less HP
requirement (“Face Velocity”)
• “Can Velocity” is…..
• “Interstitial Velocity” is….
“Permeability” is…ft3 / ft2 / min
#AdvMfgExpoBasic components…
Filter Elements
• Sock-type bag filters
• Pleated bags
• Cartridges
Filter Media
• PTFE Static-Conductive
• SBPE Static-Conductive
#AdvMfgExpoA pleated bag filter has 5X more filter area than a sock-type filter bag/cage #AdvMfgExpo
Filter Maintenance and Access Top-Load with Swing-Away Cover (upper left) Top-Removal Filter Plate (center) Side Access Hinged Doors (right) #AdvMfgExpo
Types of Convey Systems for LIW Feeders • Convey on Demand • Discharge on Demand #AdvMfgExpo
Convey on Demand
• The feeder or process, in
gravimetric and or volumetric
mode, calls for material by
sending a signal to the convey
system to transfer and deliver
material.
• Volumetric feeder signal: typically
a level control.
#AdvMfgExpoDischarge on Demand
• Vacuum receiver is full of material and needs
a refill
• The feeder or process sends a refill signal to
the vacuum receiver….
• The vacuum system will then convey more
powder to the vacuum receiver and will wait
in standby mode until another refill signal is
sent.
#AdvMfgExpoDesign Factors that Affect the $$ of a Vacuum Conveying System
• Convey rate
• Material characteristics, including combustibility & chemical compatibility
• Sanitation or Cleanability Requirements
• Distance from pickup point to discharge point
• Electrical classification
• Overhead space above the process being fed
• Automation and/or communication
• Material handling
• Accuracy
• Elevation
#AdvMfgExpoTesting Materials and Powders
Last but not least..
• Get your powders evaluated by your
pneumatic conveying equipment supplier
before you place a purchase order. Have them
run a full scale test. Don’t rely on Google for
your information!!!
• Don’t skimp on value added items. These could
make or break the system
Remember your goal is to make more product to a high standard.
The last thing you need is to tinker with the system. Make sure
your supplier fully understands your goals.
#AdvMfgExpoThank you for your time!
Questions?
Booth 1316
P&BS 2018
VAC-U-MAX
69 William Street
Belleville, New Jersey 07109 USA
Tel: 1-800-VACUMAX
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