Chemical Engineering January 2022 - 20

Facts At Your Fingertips
Flexible Intermediate Bulk Container (FIBC) Basics
Department Editor: Scott Jenkins
lexible intermediate bulk containers
(FIBCs), sometimes
known as bulk bags, are widely
used in the chemicals, pharmaceuticals,
F
food,
agriculture
and other
chemical process industries (CPI)
sectors, to transport and store dry,
flowable bulk-solid materials, such
as granules, powders, grains, clays,
cement, resins and others. This onepage
reference provides basic information
on FIBCs to aid in their selection
and use.
FIBC bag construction
Most FIBCs in use in the CPI are
made of polypropylene extruded in
threads or ribbons and interwoven in
a longitudinal-and-transverse pattern.
When filled, FIBCs can be handled by
forklift trucks, cranes or hoists, and
are designed to be lifted from the top
by means of permanently attached lift
loops, sleeves or stevedore straps.
Generally, FIBCs in use at industrial
sites are one of the following types:
U-panel. U-panel bags have one
panel forming two opposite sides and
the bottom, creating a " U " shape.
Circular. A circular bag (also known
as a tubular bag) is made from fabric
woven on a circular loom that is then
cut to the proper length for a specified
bag height. This eliminates the vertical
seams on each of the bag's sides.
Four-panel. Four separate pieces of
fabric are sewn together to create the
body of the bag.
Baffle. In a baffle bag, pieces of fabric
or other material are sewn across
each corner of a tubular or four-panel
bag to help stabilize the load and
more efficiently utilize storage or shipping
space.
Linings. FIBCs can be used with or
without liners. Two common liner
types are form-fit and tubular. Formfit
liners will allow improved filling and
complete discharging of product. Tubular
liners are straight cylinders that
may have one end heat-sealed.
FIBC selection and use
FIBCs are lightweight (5-7 lbs), offering
a low package-to-product weight
ratio and the ability to hold one metric
20
ton of product. With a standard filled
diameter of 45-48 in., FIBCs are designed
to fit two across in a truck or
a shipping container, although specially
configured containers are available
(Figure 1).
To ensure that an FIBC will meet
the requirements for handling a specific
product, users should seek to
answer the following questions on
product details:
* What is the product's bulk density
(lbs/ ft3 or kg/m3)?
* What is the safe working load (SWL;
the amount of load that a FIBC is designed
to carry) and the net fill weight
needed per FIBC?
* Is the product considered a hazardous
material or dangerous good?
* Does the FIBC need to meet pharmaceutical
or food-safety requirements?
* What is the product's mesh size
(particle size)?
* What is
the
product's
moisture
content?
* Are there special barrier needs (is the
product hydroscopic, for example)?
* What are the product's flow characteristics
(free-flowing, dust-forming,
bridging, static buildup)?
* What is the filling temperature?
* What are the product's sensitivities
to agglomeration, clumping, mechanical
deformation, vibration?
FIBC safety
Handling FIBCs involves safety considerations,
including the following:
Load. The SWL is determined by
the design of the FIBC, along with
the sewing method used and the
strength of the fabric.
Antistatic. FIBCs made from plain
woven polypropylene and other
non-conductive materials (Type A
FIBCs) offer no static protection.
Type B FIBCs are made from plain
woven polypropylene fabrics that
have a low breakdown voltage to
prevent the occurrence of highly
energetic propagating brush discharges
that can ignite a dust-air
mixture, according to ABC Polymer
Industries, a maker of FIBCs. However,
Type B FIBCs do not have any
mechanism for dissipating static
FIGURE 1. FIBCs have a standard filled diameter of
45-48 in. and are designed to fit two accross in a
truck or shipping container
electricity. Type C FIBCs are made
from non-conductive polypropylene
fabrics interwoven with conducting
threads, normally sewn in a grid pattern,
that connect the bag to ground
via a grounding point. Type D FIBCs
are made from antistatic and staticdissipative
fabrics that are designed
to safely prevent the occurrence of
incendiary sparks, brush discharges
and propagating brush discharges
without the need for a connection
from the bulk bag to the ground.
Type D FIBCs are designed to safely
package combustible products and
to handle products in combustible
and flammable environments.
Stacking. FIBCs should only be
stacked if they are designed to be
stacked, if their stability is assured
and if they are stacked using a " pyramid "
or " supported " stacking method.
In pyramid stacking, each bag above
the first layer must sit on at least four
lower bags. Each layer is subsequently
tiered inward, forming a pyramid
structure. Supported stacking refers
to placing FIBCs against two retaining
walls of sufficient strength.
Filling and unloading. Filling and
discharging options are shaped by
the filling method (conveyer, gravity,
bulk bag filler), clearance, desired
fill rate, discharge method (gravity,
screw, conveyor, bottom cut, full
dump) and whether or not controlled
discharge is required, as well as
whether bag handling is available. n
Refences
1. ABC Polymer Industries LLC, " What are the differences between
Types A, B, C and D FIBC fabrics, Newsroom, Dec. 10, 2014,
www.abcpolymerindustries.com, accessed Dec. 2021.
2. Flexible Intermediate Bulk Container Association, Resource
Center, www.fibca.com, accessed Dec. 2021.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
JANUARY 2022
http://www.abcpolymerindustries.com http://www.fibca.com http://WWW.CHEMENGONLINE.COM
Chemical Engineering January 2022

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