Lighting Standards makes steel and aluminum lighting
poles and related products at its 57,000-square-foot
plant in Warren, Michigan. The company, founded in
1971 as Wolmac Engineering, originally hand sprayed
its products with a primer and then applied an acrylic
enamel finish. Each coat took from 2 to 4 hours to
dry depending on the weather. Production was about
30 poles daily. In 1987, the company replaced liquid
paint finishing with powder coating, based on the
superior appearance and abrasion resistance powder
offered. However, the powder line, which included
an electric infrared oven, wasn't quite living up
to its promise, according to Robert Wesch, company
president. "Our capability was limited by the productivity
of our existing oven," he said. The oven failed to
completely cure large, light-colored poles, causing
slowdowns on the line. In addition, operators frequently
had to shut down the line for maintenance work and
search for a better curing system, headed by Bernie
Jenkins, general manager, focused on three options:
A new electric infrared oven, a catalytic system,
and a combination gas-fired infrared and convection
curing system. The company contacted vendors it was
familiar with to analyze the three types of oven systems.
Vendors took three criteria into account - capacity,
energy costs, and maintenance and replacement costs.
analyzing the needs of the lighting company, one vendor
determined that the company's existing electric IR
oven yielded the kilowatt (kW) equivalency of 1.18
million British thermal units per hour (Btuh). A vendor
for a new electric infrared system recommended a 1.4-million
Btuh system; a catalytic system vendor recommended
1 million Btuh. As for the combination gas-fired infrared
and convection system, the burner capacity for the
infrared section had to be 1.6 million Btuh to provide
for the 30 percent increase in productivity that United
Lighting sought. Taking into account engineering safety
and rapid heat-up capability, the vendor with the
combination oven recommended a system with a capacity
of 2 million Btuh to allow for growth in productivity.
"We realized we would need this additional capacity
to reach our increased production goals and to provide
for future needs," Jenkins said.
expenses were another factor. The engineers with the
vendor offering the gas-fired, infrared convection
oven compared the operating costs of an electric infrared
oven with the costs of the combination gas-fired infrared
convection system. First, they estimated the operating
costs of an electric infrared system with a capacity
of 392 kW of demand and an average usage level of
300 kW. When operated 8 hours a day, 22 days each
month, the estimated monthly electrical energy cost
was $7,168, of which about 60 percent was demand charge
- a surcharge on energy consumed during peak demand.
The remaining 40 percent was energy used during periods
of normal demand.
engineers considered a gas-fired infrared convection
system with a burner capacity of 1.6 million Btuh.
With the same amount of use per month as the electric
infrared system, engineers estimated that the gas-fired
infrared system would cost about $1,048 to operate.
(There are no utility demand charges when using gas.)
Broken down further, engineers figured that operating
the gas-fired infrared system would amount to a cost
of $6 per hour, compared with $41 per hour for the
electric infrared system. Working with an 8-hour-a-day
production schedule, the company could save up to
$82,000 a year with the gas-fired infrared system,
according to the vendor's figures, and $87,200 a year
on a 10-hour-per-day production schedule.
to Jenkins, replacing electrical heating elements
costs the company nearly $10,000 annually. Jenkins
rated the longevity of the elements at about 5,000
hours under the best conditions.
vendor of the gas-fired infrared convection oven advised
using heavy duty cast iron burners designed for long
service life under demanding operating circumstances.
According to the vendor, the burners last longer than
electric elements and less rugged formed-sheet metal
burners typically found in space heaters. The vendor
noted that the design of the burners permits them
to run on a premixed volume of air and gas, rather
than relying on atmospheric air for combustion. The
premix burners allow operators to control the oven
temperature and modulate heat input, even when work
loads fluctuate. With atmospheric burners, operators
can only turn the burners on or off.
Jenkins: "When we looked at these design elements
and cost estimates, we realized that the additional
capital investment for the combination gas infrared
convection system was insignificant in comparison
with the operating and replacement costs of the electric
infrared oven." The company ordered the system, convinced
it could effectively and efficiently accommodate an
assortment of parts, substrates, powders, and line
vendor ran tests and troubleshooting exercises on
the oven before the system left the factory. For each
oven zone, the vendor mounted a complete gas-valve
train. The vendor's employees piped and wired the
system before delivery, which was done in three complete
sections to simplify installation. As a result, downtime
for oven installation at United Lighting Standards
lasted only 6 days.
company's light poles vary in length from 10 to 40
feet, are round or square in cross section, and are
usually tapered. Wall thicknesses vary from 1/8 to
1/2 inch. Employees weld the poles to heavy, 1/2-
to 2-inch-thick solid base plates that range in diameter
from 10 to 17 inches. Poles vary in weight from a
30-pound, 10-foot aluminum pole to a 1,100-pound,
40-foot steel pole. The company also powder coats
a range of associated flat, formed, and tubular hardware.
clean poles and parts with steel shot before loading
the items on a continuous overhead conveyor. The conveyor
moves lighting poles, with base plate at the rear,
through the application booth, where four coronacharging
guns spray TGIC-based polyester powders. Manual guns
are also available for touch-ups.
spray bronze-colored powder on more than 70 percent
of the poles, black on about 10 percent, white on
about 8 percent, and a number of other colors on the
remainder of the poles. Minimum film thickness is
2 mils. Maximum film thickness depends on several
factors. For example, one major factor is whether
or not the lighting pole will be placed in an area
where it will be exposed to atmospheric corosion,
such as salt spray at a seashore location.
then enter the cure oven, which is 32 feet long, 8
feet tall, and 5 feet wide. Assembled of structural
steel, the freestanding system includes 4-inch double-insulated
sheet metal wall, floor, and roof panels. High-intensity,
or long wavelength, gas-fired infrared and low velocity
convection rapidly fuses the powder to the substrate.
After the powder fuses to the part, IR and convection
elements continue heat application, maintaining the
substrate and powder at the curing temperature, usually
450°F. Cure times range between 2 and 7 minutes,
depending on base materials and coating thickness.
For example, steel poles take more time to cure than
aluminum ones because heat penetrates aluminum faster
heating acts as a supplement to the IR elements, according
to the company. The convection section of the oven
transfers heat accurately and uniformly along and
across the parts. This is especially important for
curing the underside of lighting poles. Operators
have the capability to control and direct airflow
so that heat reaches all areas of the part.
oven features a prewired main control panel that includes
all the necessary temperature, controllers, combustion
safeguards, push buttons, and lights for operation
of the curing system. Digital temperature controllers
in each zone modulate fuel input to the burners to
maintain desired setpoint temperatures. A digital
display provides a continuous reading. A noncontact
sensor measures pole temperature at the oven exit.
poles exit the oven, the overhead carries them laterally.
This moves the base plates through a supplemental
electric infrared section adjacent to the main oven,
completing base-plate curing. Operators then stack
and band the poles for shipment.
a mere 3 months of operation, company employees were
impressed with the gas-fired infrared convection oven.
Production was up from 30 poles to nearly 40 a day.
"We're confident we can easily raise that to another
50 or 60 percent," Jenkins said. This allows operators
to coat heavy, cast transformer bases, which were
previously farmed out. The oven allows for excess
capacity of the powder coating system, which means
the company can raise production rates with minimal
natural and supplemental convection heating enhances
product coating quality and curing system efficiency.
Oven efficiency - estimated as the ratio of the heat
input to the product, to the energy consumed by the
oven - has increased. Electric radiant elements typically
have a radiant efficiency of 60 to 80 percent; gas-fired
infrared burners, 40 to 60 percent. In each case,
the remainder of the energy input not converted directly
to infrared radiation appears as heated air within
company's combination oven makes use of this heated
air, using it as additional heat for parts, and offsetting
the unavoidable losses through the oven enclosure
and to the exhaust. This type of convection heating
system heats the poles faster and more consistently
than radiant heating alone.
can expect to reduce long-term operating costs by
more than 60 percent," Jenkins said. "And maintenance
and replacement costs should drop by better than 50