Although industrial lighting has historically been a step behind technologies used for other building types, many of the advancements made over the past decade in lighting for other occupancies are finally taking hold in industrial spaces. It's only a matter of time before task-oriented lighting, energy-efficient alternatives, and bi-level lighting designs are installed regularly in industrial buildings across the United States.
Industrial lighting is following the trend in other sectors where “light the task” has become the popular mantra. While lighting designs for office spaces no longer light the top of the file cabinet and bookcase along with the desktop, warehouse lighting is no longer just concerned about horizontal footcandles to avoid forklift collisions. Vertical footcandles on the stored materials are also an important element of the design criteria. In addition, industrial spaces are no longer hanging 400W high-intensity discharge (HID) high-bay fixtures on 25-foot centers from wall-to-wall.
As “lighting the task” tends to reduce lighting levels overall, the levels of lighting for portions of industrial spaces need to increase. For example, raw material and finished goods staging areas may need only 30 footcandles for safe operation, while final inspection areas require more than 80 footcandles. However, a compromise of 50 footcandles everywhere is not the solution. Nevertheless, reasonable uniformity is necessary to reduce adaptation discomfort when processes require workers to look from one light level to another.
Proper lighting levels in industrial occupancies also have the highest relation to safety and lost time reduction when compared to just about any other occupancy. Low light levels at workstations, such as inspection stations, can lead to eyestrain and fatigue.
One solution is a simple strip fixture over the inspection station with a local switch to boost light levels only where and when it's needed (Photo). Improving on this simple approach, you can also install an occupancy sensor at the station for automated control. In fact, some may argue that task lighting was invented for industrial applications — the task light on the band saw was probably in service long before the task lights in office cubicles.
While not new, bi-level lighting can also be an effective industrial lighting design tool. Optical storage systems “pickers” and robotic systems need little, if any, light to perform their task. People, on the other hand, need lighting to perform maintenance and make inevitable repairs on equipment.
Bi-level lighting systems have long been in use in warehouse aisles. With the insignificant cost of occupancy sensors, the time has come to control lighting in more areas by occupancy. This technology should not scare facility managers — the horror stories associated with occupancy sensors can almost always be attributed to improper sensor application or adjustment.
Lighting in an industrial space should also offer flexibility, a characteristic lighting in other spaces generally does not have or need. For instance, if an office layout changes, the ceiling lighting is usually fairly uniform, and the office moves beneath the lighting. If the lighting is task-oriented, the lighting moves with the task. In an industrial setting, advances in technology now warrant flexibility as well.
If high-bay fixtures of any type are used, you should install them to be flexible. A few industrial spaces have the luxury of truly high (25-foot or better) ceilings, where the industry can evolve and move beneath the lighting. More recent industrial spaces, however, feature lower ceilings. Therefore, moving or updating the industrial equipment can often affect the lighting layout. For this reason, flexibility should be a key design component.
Lighting power bus rather than fixed power points can save money over the life of the occupancy when the delivery of a new generation of computer numerically controlled (CNC) machines means that 20 light fixtures have to be relocated. Multi-phase lighting power bus can also allow for the staggering of phases to help reduce the strobe effect of HID lighting systems used in large industrial spaces.
New lighting technology
Energy codes are forcing the use of higher lumen-per-watt light sources. HID givens excellent lamp life and acceptable color rendering index (CRI) for factories, but provides less-than-ideal lumen maintenance. However, as technology bullies its way out of the computer room and onto the shop floor, lighting technology must keep pace.
Ceramic metal-halide (CMH) lighting virtually eliminates the lumen maintenance issue, maintaining more than 95% of initial lumens over its published life. CMH will likely become on par with pulse-start metal-halide systems. Existing CMH products allow lamp-only replacement for HPS fixtures without expensive and cumbersome ballast retrofits.
Induction lighting is another technology that promises great things in terms of improved light sources, offering lamp life as long as 100,000 hours. While perhaps not yet a solution for general industrial space lighting, applications where lamp maintenance is dangerous or costly (such as towers) can benefit now. In spaces where reliability is a key factor, such as obstruction lighting, designers are also pursuing induction lighting options. However, it will be a few more years until induction lighting sources work their way into more fixture types and lumen output increases.
Finally, daylighting is also making a comeback in industrial facilities. Cinder block walls and rubber roofs are typically cheaper to install than glazing, and industrial facilities built over the last 75 to 100 years minimize glazing to save on construction costs. Pre-1900 era factories used the well-known saw tooth roof design with extensive roof glazing. Endless maintenance issues and rising heating costs drove builders away from this architecture, but it is making a comeback as more designers realize the lost benefits of natural daylight.
Quality and Quantity
Another factor known for years in retail lighting is finally reaching the industrial lighting arena: the quality of the light is just as important as the quantity. HID lamps with their marginal CRIs and poor lumen maintenance are being removed from service in favor of high lumen T8 and T5 fluorescent packages. Ceramic discharge lighting is offering high CRI with long life and exceptional lumen maintenance. More and more cathode ray tube (CRT) computer monitors and flat screen monitors are making their way onto the factory floor, and visual comfort and veiling glare are no longer issues confined to the office environment.
Quality lighting increases safety, productivity, and ultimately, product quality. Keep in mind, however, that “rebate-able” systems are not always the best choice, even from an energy standpoint. Many utilities rebate T5 lamp packages even though a properly implemented T8 package with a higher ballast factor can offer better energy efficiency.
Re-lamping, re-ballasting, and/or replacing fixtures can carry with it considerable up-front costs. Most facility managers will agree that while group re-lamping makes sense from a logistical and financial standpoint, few facilities actually implement the approach.
It is often difficult to convince the finance managers that preventive maintenance pays off, as they often cannot see past the initial cost, and ignore the payback over time. For the same reasons, facilities do not see the value in lighting systems upgrades. With increased global competition to cut costs across the board, spending money on the infrastructure is not always the first consideration. Between utility company rebates and soft cost factors, such as increased productivity and employee retention, moving toward a higher quality, lower energy lighting system makes sense.
The trend in green construction is also forcing improvements in industrial lighting. Building owners do not have to ask their consultants to include energy-efficient lighting sources in their design because the issue has become the norm. Sustainable design approaches are also cognizant of lighting quality. Sustainable design is not simply the reduction of raw materials and waste related to construction. It is the optimization of the entire facility, including lighting.
While trends in lighting may not always reach the industrial sector as quickly as other occupancies, design alternatives traditionally used in office, retail, and residential buildings are finally making their way to industrial buildings. As lighting technology further evolves for other occupancies, industrial facility managers will benefit from continuing to adopt these up-and-coming lighting concepts.
Nangle is a founding partner of Cronis, Liston, Nangle & White, LLP (CLN&W), a consulting engineering firm headquartered in Danvers, Mass.