Feeling the Heat
Six important factors manufacturers must consider when heating drums and totes
By Laurie Benko Hull
Manufacturers throughout the process industries have traditionally utilized a
variety of methods to heat their drums and totes, including band heaters, immersion
heaters, steam jackets and homemade, in-plant hot rooms. Over the years, operators
in the chemical, food and pharmaceutical industries have turned to drum warming
ovens as a safe, cost-effective way to heat those 55-gallon drums.
But before a manufacturer commits to one specific technology, it’s important to
understand the considerations that should go into selecting the proper heating
technology for their specific needs. There are six important factors that all operators
should consider prior to selecting a heating method, starting with the material that
is being heated.
1. Material
When heating drums and totes, it is critical to fully understand all of the
characteristics of the material to be heated. Operators should consider the following
questions:
• Is the material flammable?
• Is the material caustic or corrosive?
• What happens when the material is heated?
• Does the material have an autoignition temperature?
• Will excessive heat burn or degrade the material?
• Will heating the material produce a dangerous or foul fume or vapor?
If the material is flammable, an NFPA (National Fire Protection Agency) Class A
oven, hazardous duty band heater or water bath may be necessary. Caustic or
corrosive materials may require special coatings or stainless steel construction.
Spill containment may be needed as certain materials expand when heated. The
bungs on the drum may also need to be loosened to relieve pressure caused by
heating.
Autoignition temperature of a material is the lowest temperature at which it can
spontaneously ignite in a normal atmosphere without an external source of ignition,
such as a flame or spark. The temperature at which a chemical will ignite decreases
as the pressure or oxygen concentration increases. It is critical that operators take
the proper steps to ensure the material being heated never reaches the autoignition
temperature.
Precise temperature control and temperature uniformity are critical requirements
to ensuring excessive heat doesn’t burn or degrade the material. Some fragile
materials, such as honey, will burn when subjected to excessive heat. Band heaters,
which concentrate intense heat on a small section of the drum, should not be used.
If heating the material will create a dangerous fume or vapor, operators must take
steps to ensure the proper exhaust.
2. Environment
Environment encompasses the area where the drum heating will take place. When
considering environment, all hazards and classifications in the area must be known.
If it is an explosion-proof area, the heater must be properly designed for the hazard
classification. This may require the use of steam heat, hazardous duty rated heaters
and NEMA 7/9 controls.
Within that established environment, operators must consider whether or not the
heat created by the heating of drums will impact the temperature of the room. This
consideration may require the implementation of a process designed to prevent
heat from escaping during the heating process. Operators can properly utilize
insulated ovens with door switches to prevent heat from being blown out of the
oven when the doors open, or even exhausting the oven prior to the doors being
opened. Special construction and controls are necessary for use in wet areas such as
outdoor applications and washdown areas.
3. Heat-Up Times
A third factor to consider when heating a drum is the heat-up time. How quickly a
drum must melt or reach a certain temperature will dictate the heating method to
be used, as well as the quantity of drums to be heated. Certain methods produce
faster heat-up times than others. For example, a prefabricated drum oven will
generally melt a drum faster than a band heater.
Factors to consider when predicting heat-up times include the material’s starting
temperature, its melting point, specific heat, heat of fusion and the maximum
temperature the material can be exposed to. A reputable supplier of drum heating
equipment will be able to estimate heat-up times and may even guarantee them.
4. Energy Use
Energy efficiency must be a top consideration for operators as stricter legislation
has dictated the implementation of more environmentally friendly equipment
worldwide. Certain methods of drum heating are more energy-efficient than others.
One example would be a compact, fully insulated drum oven, which is much more
energy-efficient than a large homemade, in-plant hot room.
Plants will build dedicated hot rooms to heat drums. Sizes can vary greatly, but
traditionally these rooms are large enough for a forklift to maneuver in and out of
with ease. Some hot rooms can fit as many as 100 pallets in them but are typically
inefficient from an energy perspective due to their tall ceilings and large surface
areas. The entire room must remain heated, even if the space is partially full. Drum
ovens, by comparison, are compact and only heat the space directly around the
drum.
Most in-plant hot rooms are poorly insulated as well. Temperatures fluctuate
greatly due to their size and lack of adequate airflow. Doors in these hot rooms can
also be left open for long periods as forklifts drive in and out, pushing heat out of the
hot room and onto the plant floor.
The heating medium used will also dictate energy use, and the heating medium used
will depend on what is available at the plant. If an abundance of steam is available, it
can be utilized as an efficient method of heating. Electricity is also convenient and
efficient if the oven or hot room is properly sized, insulated, temperature-controlled
and features adequate air circulation.
5. Material Handling
Drum handling is very important to consider when deciding on a heating method.
The entire drum heating process must be thought out to ensure the least amount of
drum handling as possible. Hot drums are inconvenient and unsafe to handle and
may even leak or spill when transported far distances.
One way to eliminate transportation concerns would be to have the drums heated
near the process they are going to be implemented. Whether the drum is simply
dumped into a tank or requires a more controlled removal method, such as pumping
or metering, it is convenient and practical to have the drum heater near the process.
The advantage of having a drum next to its destination is that there is less handling
required and less time for it to cool down. If pumping is required, it is critical to
keep the drum warm as this process can take a long time. If operators choose this
option, drum ovens, band heaters, drum wraps and immersion heaters are ideal.
They can be located near the drum filling line, tanks or pumping station for
convenience.
Other considerations in the material handling process should be convenience and
flexibility. Drum ovens and smaller heating methods, such as band heaters, provide
greater flexibility as they can be turned off when not in use. It is also easier to heat
the drums or totes to various temperatures when not utilizing a large hot room.
For example, if 16 drums need to be heated quickly to 200° F, a 16-drum capacity
oven can be easily set to the desired temperature. This is not an option in a large,
central hot room environment where varying materials are stored. Some may not be
able to take the heat. If large numbers of drums must be heated, band heaters and
other single drum heaters will be time consuming and labor intensive to use. A
properly sized drum oven or in-plant hot room makes more sense.
6. Cost
While cost shouldn’t be a top consideration, operators must consider equipment
that will perform their jobs at an economically acceptable level. Initial purchase
price as well as lifetime running costs must be weighed. Plants can utilize band
heaters, which represent the least expensive heating option, or they can invest in
homemade, in-plant hot rooms, which represent a substantial cost to the company.
It is expensive and time-consuming to build a hot room. In this process, someone is
required to design it, procure the materials and then build it.
There are other costs to consider beyond the initial purchase price. This includes the
cost involved with downtime as various heating options aren’t as reliable as others
and require frequent maintenance. Durability and dependability also tie into
maintenance costs as drum heaters, for example, have a well-earned reputation for
providing the reliability manufacturers demand.
Conclusion
When manufacturers consider methods for safely heating their valuable products,
they must consider the material, heat-up times, energy use, material handling and
costs. While band heaters, homemade hot rooms and immersion heaters can meet
traditional heating needs, each technology has disadvantages that make them an
inefficient option in many applications.
Drum warming ovens have become a popular choice in industry as they offer the
energy efficiency and safety other heating methods cannot, protecting employees
and the environment from dangerous, ignitable vapors while providing costeffective heating in less time.
Laurie Benko Hull is Sales Manager with Benko Products, Inc. She can be reached at
440-934-2180 or at lhull@benkoproducts.com. Benko Products, Inc. is a privately held
company based out of Sheffield Village, OH. Benko Products was founded in 1983 by
pioneer John Benko, the inventor of many breakthrough products such as the Sahara Hot
Box® drum warming oven, the G-Raff Elevating Tank Truck Platform and the Protect-OGate line of Mezzanine Safety Gates. Benko Products’ leading product lines include
drum and tote ovens, industrial ovens, mezzanine safety gates and chemical storage
systems. Benko Products is also the parent company to GREEN Access & Fall
Protection, a leading manufacturer of access and fall protection platforms and gangways
for tank trucks and rail cars.
For more information on Benko Products, go to www.benkoproducts.com.