Selecting a High-Speed Door
Before making a choice among the proliferation of high-speed doors, know what you're looking for in a high performance door.
The use of high-speed doors has grown dramatically since their introduction the United States a decade ago. The technology that goes into these doors was developed in Europe in response to high overseas energy costs. As the doors gained in popularity here, more high-speed door manufacturers entered the market, each touting its product line as the perfect line of high-tech doors. A basic understanding of the high-speed door market and the applications for which these doors are intended will help simplify the selection process.
Types of high-speed doors
There are two basic types of high-speed doors: rolling and folding. Both are intended to limit the amount of time a door remains open, reducing energy costs and increasing productivity.
Rolling or roll-up doors operate vertically, similar to a window shade. They are constructed with a durable, lightweight synthetic fabric within a metal frame, and provide a tight seal between joining rooms or exterior doorways. In a well designed door, the fabric is fully tensioned to withstand high exterior winds or interior negative pressure. Many exterior applications also include a heavier door that is shut at the close of the day for greater security.
Some rolling doors on the market utilize springs and pulley systems built into the frame in order to function. Others use technology that eliminates springs which further reduces maintenance.
Roll-up doors operate at speeds ranging from 3 to 8 feet per second. A key feature of some rolling doors is a release system or break-away bar on the bottom. If the door is hit, the bar breaks free, fabric flexes, and the operating motor automatically shuts off. The bar, usually made of extruded aluminum, is easily reset without tools and the door is restored within minutes.
High-speed folding doors open horizontally like an accordion. The most popular folding doors consist of flexible, transparent PVC panels that overlap to ensure a tight fit. Folding doors are extremely effective in freezer applications. As in the case of roll-up doors, the most popular folding doors are capable of taking a hit from a forklift, due to swivel hinges connecting the door to the top of the frame, which give upon impact, avoiding damage to the door. The top selling folding doors open at up to 7 feet per second.
Analyzing the need
High-speed doors are designed to be placed in doorways that accommodate a considerable amount of traffic. Heavy traffic requires durable doors that can automatically open and close quickly, cycle after cycle, with minimum maintenance. They are probably not suitable for doorways that are usedinfrequently or primarily by pedestrian traffic. Nor are they necessary where a barrier is not required to eliminate dust or noise, or to maintain temperature set points.
Prior to the selection process, a study of the doorway itself would be wise. Make a flowchart illustrating how the doorway interacts with overall traffic patterns. Determine the primary purpose for which the door is used. Is the traffic one-way or does it flow evenly in both directions? What type of vehicles pass through and at what rate of speed? Are all vehicles being delayed by the existing door and, if so, for how long? Acting as a barrier, what is the door's purpose? Is the doorway used more during certain periods of the day, and less other times? Such observations will give the plant engineer a better overview of what is to be expected in the performance of a high-speed door.
Using high-speed doors to manage energy costs
Since high-speed doors are very effective in conserving energy and reducing operating costs, they are used frequently in coolers and freezers and to maintain separate set points in adjoining rooms or to maintain ambient interior temperature. In high traffic areas, high-speed doors are more effective in controlling energy costs than slower-moving metal or wooden overhead doors or insulated metal freezer doors. High operational speeds minimize the humidity that infiltrates the refrigerated room or allows heat to escape through an exterior opening.
It may be advisable to conduct an energy audit of the facility prior to installing the high-speed door and again upon completion of the installation. An energy audit will not only identify areas with a significant energy loss, but will provide verifiable savings in terms of real dollars. In many states, the local utility companies may assist the plant engineer in conducting an energy audit and even allow for energy rebates. In some cases, rebates can more than cover for the cost of the new door.
The government's Office of Industrial Productivity and Energy Assessment (OIPEA) will assist industries conducting an energy audit at no cost to the manufacturer. OIPEA works with 20 universities throughout the country through its Department of Energy's (DOE) Energy Analysis and Diagnostic Center program (EADC) for small and medium sized manufacturing firms. The audits are performed by teams of faculty and students from engineering schools. For more information on this program, contact the Office of Industrial Technology at the U.S. Department of Energy in Washington, DC.
Reducing maintenance costs
Traditional overhead doors constructed of metal or wood rely on a system of springs and counterweights to function. These heavy doors place a great burden on moving parts, supports and motors. Frequent breakdowns are virtually inevitable. A well designed high-speed door is lighter and has fewer moving parts, contributing to greater reliability. High maintenance costs and related down time is a major reason plant engineers opt for high-speed doors.
A Milwaukee-based manufacturer of auto parts, for example, was plagued with maintenance and material cost overruns resulting from 20 older overhead doors. To determine the cost of maintaining these older doors, the plant engineer decided to analyze the actual costs spent on maintaining just one of these overhead doors over a 26 week period.
Cost analysis helps justify replacing old doors
Maintenance and materials expenses, one old door:
Total labor costs, per 26 week season: $14,560
Calculated as labor costs for two men, 4 hours each time,
4 times/week = 32 hours
32 hours @ $17.50 per hour = $560 per week
$560 x 26 weeks = $14,560
Total material costs, per 26 week season: $2,215
Calculated as costs for:
New door springs: $1,200
New door motors: $360
New door panels: $500
New gear box: $155
Material costs total: $2,215
Total of labor and material costs: $16,775
The results of the cost analysis showed that the savings possible with high-speed doors would more than justify the replacement of the older doors. In a four month trial, the newly installed high-speed door performed 74,088 cycles without a breakdown.
Increasing plant productivity
Another major contribution that high-speed doors make is increased productivity. Many doors must be opened hundreds of times per day. Assuming that a traditional door opens at a rate of 8 inches per second, it takes 15 seconds for a 10-foot high door to fully open. If a single worker transporting material passes through 25 times per hour, he collectively spends 15 minutes per 8 hour work shift waiting for a door to open. In addition, doors that fail to operate or are damaged while in the shut position can be a major disruption to work flow.
Classic methods of activating vehicular traffic doors call for the approaching driver to operate either a pendant pushbutton control or a pullcord-operated switch as he nears the door. Operating efficiency of high-speed doors is further enhanced by going beyond these basic actuation methods.
Motion detectors and photoelectric controls can be applied to open and close the door as the driver approaches and passes through. Hand-held radio controls are another option. Several operating methods can be combined and are programmed through a wall-mounted controller. One such system can be programmed to let the door open only high enough to accommodate pedestrians when actuated by persons walking.
The most effective system utilizes an induction loop embedded in the floor to sense metallic objects passing over it to activate the door. The control is tuned to discriminate between vehicular traffic and objects of lesser metallic mass. The permanence of this type of actuating system is superior to portable devices that can get misplaced. An induction loop can be installed in existing floors as well as in new construction, positioned at whatever distance and in whatever configuration is optimum for the application.
The purpose of most doors in industrial receiving, shipping, warehousing and manufacturing areas is not to control access, but to provide a seal between adjacent areas. Slow operating doors compromise this role with increasing migration of dust, fumes and noise between areas; and by reduced effectiveness in maintaining desired temperatures. Installing high-speed doors may not be a sure path to fame and fortune. But selection of the right door and options can make a big difference in plant operating efficiency.
For more information on the selection and specifications of high-speed doors, contact a Rytec representative at 888-467-9832.