Engineers who design large-diameter storage tanks primarily concern themselves with hot button issues such as calculating shell thickness for the desired fluid height, insulation, air venting and even wind resistance and seismic requirements.
Unfortunately for the people who maintain the tank interior after construction, illumination is nowhere on that priority list. Texas-based Larson Electronics’s solution has a new cart mounted explosion proof LED light that provides 8,500 square feet of work area coverage, said company co-owner Rob Bresnahan.
“In the past, maintenance workers had to string lights to see,” he said. “The problem is the lights were heavy. Each light head is about 10 pounds. Add to that a junction box between each light and an average 10-light string could weigh nearly 160 pounds.”
Making matters worse, the 280 feet of cord needed to hang those 10 lights is in the way of much of the work that needs to be done, Bresnahan said.
Larson’s EPL-C-2X70LED-250 replaces all of that with two 70 watt LED light heads that produce 11,600 lumens of light. The detachable heads make the unit small enough to fit through any standard manway or entry passage found in the petrochemical or marine industries.
With handles like a wheel barrow, the cart can be easily moved and the lights repositioned. When attached, the light heads offer 360 degrees of rotation and 90 degrees of tilt. And a cart with a low center of gravity has stability that light stands lack.
“Folks can bang into it and not knock it over,” Bresnahan said.
Larson’s new tank light design is only the latest in an evolution of lightning solutions for interior tank work.
“Back before LEDs came along, we made a 400 watt metal halide version which is still pretty popular,” Bresnahan said. “But the light heads on that weigh more than 85 pounds each.”
By comparison, the entire LED unit, cart and lights together, weights 75 pounds. Switching to LEDs make the unit so light that it can be shipped by overnight package delivery in two boxes instead of loaded on a pallet to wait for a heavy freight connection, Bresnahan said.
As opposed to the problems with the earliest generation, LED today is outpacing incandescent, fluorescent and compact fluorescent as the light source of choice for industrial settings, he said.
“We get an awful lot of output for little wattage,” Bresnahan said. “The heat problems have been solved. The biggest benefit is weight and light density. It is also more resistance to damage from vibration.”
The added cost of LED must also be balanced against the advantages of longevity. Maintenance issues for ordinary lighting such as changing light bulbs and ballasts do not exist for LED.
“LEDs are just a plastic cover coated with phosphor and soldered to a computer board,” Bresnahan said. “Most of your LEDs today are going to last 60,000 hours plus and still retain 80 percent of its lumen output. Metal halides may last 10,000 to 12,000 hours. An incandescent bulb may last only 25 to 100 hours.”
Measured in lumens, the LED fixtures are almost one-third times brighter than a halide fixture, Bresnahan said.
To make the unit explosion proof, also known as intrinsically safe, the cart is fabricated from non sparking aluminum mounted atop solid rubber wheels. The unit is multi-voltage capable and can be configured to operate on 120-277 volts 50/60 Hz. Power is drawn via 250 feet of explosion proof SOOW cord provided with the unit.
“Typically it only takes one unit to get the job done or two units if you want to crisscross the beams to take away shadowing,” Bresnahan said.