Drum Liners for the Petroleum Industry
History of Drum Liners
Industrial drum liners as we know them today, evolved from what once was a
mandatory component of type 2U packages.
Type 2U packages were the package of choice prior to the development of the
plastic drum for certain chemicals and foodstuffs.
The liners were specified by the DOT to be a minimum of .020 thick as they
were the primary source of containing the product.
These open-head 2U liners were mostly vacuum-formed.
History of Drum Liners cont.
In the mid to late 70’s a problem/ opportunity arose. Many companies that were
filling adhesives, paints and other products that were hard to clean out began
having trouble getting rid of their drums.
There was also an opportunity to help companies re-use their drums internally.
It was the combination of the technology used to make the 2U liners and these
new opportunities that spawned the lighter weight industrial liners that are used
fairly extensively today.
Benefits of Using Drum Liners
Provides product protection for new and reconditioned drums
Offers source and waste reduction
Reduces time and expense of cleaning and/or replacing drums
Promotes reuse of your drum internally, which keeps drums out of the waste
The above two reduces use of fuel and greenhouse gas emissions
Provides an after market value to either reconditioning network or recyclers
for steel drums
Recyclable – most liners are HDPE 2 and LDPE 4
Ships flat or nested for economical storage and shipping
Flat Seamed Drum Bags
Flat seamed bags are an economical solution, however they are not
recommended when mixing blades or follower plates are used.
Round Bottom Drum Liners
Liners provide an economic solution for protecting your products. These liners are
designed for easy installation and can be simply twisted and tied off to protect
Straight-Sided Drum Liners
Liners fit smoothly into new drums and are ideal when using a follower plate.
Accordion Drum Liners
Liners have flexible, pleated, side walls originally designed to accommodate
variations in reconditioned drum heights and also ship economically .
Combination Drum Liners
Liners combine a straight-sided design with a band of accordion pleats to
accommodate both drum height variations and follower-plate use.
Vented Drum Liners
Liners have four holes near the top to vent trapped air during a fill, allowing drums
to be filled with the lid on. Only recommended for high viscosity products.
Anti-stat Drum Liners
Anti-stat acts as a dissipater of an electrical charge.
Anti-stat liners have an anti-static additive made of low-
molecular-weight materials that attract water from the
environment, forming a thin film on the surface of the
plastic. The anti-stat additive continuously blooms to the
surface with a typical shelf life of 12 months. Typical industry
standards meet NFPA-99 and MIL-B-81705C.
Anti-stat liners should not be used as the sole means to
dissipate any charge. They only act to reduce the charge in
the polyethylene liner itself.
Anti-stat Industry Standards
MIL-B-81705C standards require static decay and surface resistivity testing
as follows: first the material must be conditioned for 24 hours at 12% +/- 3%
relative humidity. The material must meet the 2.0 seconds or less static
decay time at 12 +/- 3% relative humidity at a temperature of 73°F +/- 5°F
and a surface resistivity of 1012 or less according to ASTM D257.
NFPA-99 (National Fire Protection Association) standards require the
material to be conditioned for 24 hours at 50% +/- 2% relative humidity prior
to testing and then must meet the static decay time of 0.50 seconds or less
at 50% +/- 2% relative humidity at a temperature of 23+/- 1°C./p>.
Blown Film Liners
Very thin- typically 3, 4, 8 & 10 mil
Barrier films can be used (high
temperature above 180ºF, oxygen and
moisture barrier commonly used)
Typically not recommended when
follower plates, mixing blades and fill
and dispense wands are used.
Heat Seal technology is used to produce flat seam and round bottom liners.
Films that can be heat sealed:
Polyethylene (LDPE & HDPE)
Metallized polyester and foil laminates for moisture protection
Conductive laminates and anti-static films for volatile materials
Nylon and co-extruded films for chemical resistance
Polypropylene for high-temperature requirements
How Heat Sealing Works
In heat sealing, a thin clear thermoplastic film is bonded by heat, time and
pressure to form a closure.
Heat sealing technology is simple in concept and provides cost-effective products,
but the process is not trivial. Tight tolerances, proven materials, precise timing and
temperature control all play key roles in providing products that meet demanding
Uniformity of wall thickness
Flexibility vs. Strength vs. Price
Straight side or Accordion
Thermoforming or vacuum forming, produces strong, semi-flexible, seamless
(leak-proof) liners in a range of thicknesses designed to withstand the rigors of
most demanding applications.
In deep-draw thermoforming liners up to 40" deep can be produced in a variety of
shapes (cylindrical, tapered or rectangular).
Can be run with multi-cavity tools.
How Thermoforming Works
In thermoforming, extruded sheets of plastic are carefully heated to soften the
material. The sheets are then pressed into a mold and a vacuum is drawn to force
the plastic into the shape of the mold. It is critical to maintain an even distribution of
material during this process.
Sheets that can be thermoformed:
Polypropylene for high temperature resistance
Anti-static polyethylene for use with volatile materials
EVOH for oxygen resistance
Thin and Thick Gauge Thermoforming
There are two general thermoforming process categories. Sheet thicknesses less
than 0.038 inches are usually delivered to the thermoforming press in rolls. Sheet
thicknesses from 0.038 inches through 0.120 inches typically come in sheets cut
to final dimensions and stacked on pallets. These thin-gauge thermoforming
applications are dominated by rigid or semi-rigid disposable packaging. Sheet
thicknesses greater than 0.120 inches are considered heavy- or thick-gauge, cut
sheet thermoforming applications, which are primarily used as permanent
Blow Molded Liners
Very precise gauge control
Used with mixer, follower plate
Typically produced one at a time
Blow molding technology provides extra performance in maintaining package
integrity and durability. Wall thickness and lip design can be carefully controlled.
With this technology drum liners are typically cylindrical, but square or rectangular
shapes can be made.
How Extrusion Blow Molding Works
In Extrusion Blow Molding (EBM), plastic is melted and extruded into a hollow tube
(a parison). This parison is then captured by closing it into a cooled metal mold. Air
is then blown into the parison, inflating it into the shape of the hollow bottle,
container or part. After the plastic has cooled sufficiently, the mold is opened and the
part is ejected. EBM processes may be either continuous (constant extrusion of the
parison) or intermittent.
Compared to injection molding, blow molding is a low pressure process, with
typical blow air pressures of 25 to 150 psi. This low pressure process allows the
production of economical low-force clamping stations, while parts can still be
produced with textured surface finishes. The resulting low stresses in the molded
parts also help make the containers resistant to strain and environmental stress
Although Injection Molding is probably the most popular form of plastics processing, it is
not conducive to liner manufacturing. In order to form a part as tall as a drum, the walls
would have to be much thicker than is needed in thermoforming or blow molding, which
would increase the part cost. Thicker parts also mean longer cycle times, also
increasing costs. Injection molds are also typically more expensive and generally need
more taper than thermoforming molds, so the liner will not fit the drum as well.
There are some technical issues with injection molding related to liners. There are
inherent stress points at the sprue and gate (injection points), which may cause a
fracture point and consequently a leak point.