According to Southco Inc.’s Product Manager, Hinges and Positioning Technology, Jim Ford it’s important to identify industry standards (NEMA or IP sealing), load requirements, aesthetics, and environmental conditions early in the design. Taking the time to do so minimizes total product costs and maximizes hardware and enclosure performance.
“Concealed versus exposed hardware, internal or external hardware space requirements, corrosion resistance, material preferences and flammability ratings can all influence hinge selection,” says Ford. For example, when concealed hinges are necessary, minor changes to the door and frame in the early stages of design can allow use of a standard product. “This in turn, minimizes product costs while maximizing overall performance,” says Ford. “Internally mounted hinge hardware can also satisfy concerns about appearance as well as minimize vandalism opportunities. Typically they require more space on the inside of the enclosure, which can be a problem in small, tightly packed enclosures.”
Externally mounted hinge hardware offers other advantages, says Ford. “They are typically stronger, have more universal fit and there’s greater flexibility for removable hinges. And, it’s also easier to specify them later in the design cycle.”
Designers should always specify hinges to accommodate not only the basic door weight, but also the maximum anticipated load on the door, says Ford. “If weighing the door is not an option, it can be calculated by multiplying the height by width by depth and multiplying that by the density of the door material. CAD software can also be used to accurately determine door weight or center of gravity.”
To select appropriate hinges, especially in larger door installations, Ford recommends determining both the maximum load and the center of gravity. The center of gravity of a symmetrical door is typically at the center of the door. But other factors including the doorframe shape or added components (electronics, cooling equipment, etc.) can shift it. An easy way to find the center of gravity for an existing door is to hang the door from each corner and snap a chalk plumb line from each of those corners. The point where all four chalk lines cross is the center of gravity.
Mounting the hinges as far apart as possible along the longest edge of a door will deliver maximum strength, says Ford, while closer, more even hinge spacing helps maintain rigidity, reduces flexing on the door, and can ensure more even gasket sealing.
Detent hinges, constant torque hinges, or other positioning devices provide the option of maintaining doors open at a variety of pre-determined positions without requiring additional space-consuming hardware such as gas struts or door stays. “This can be particularly valuable outdoors where wind can blow doors closed, or in close-quarters where holding the door fully open prevents obstruction of passageways,” says Ford.
The designer might also consider the use of removable door hinges. “This style of hinge is also a valuable asset in situations where enclosures are shipped disassembled, where the door panel will ship from a different location than the main body of the enclosure, or the enclosure is frequently opened for routine maintenance, says Ford. “Lift-off hinges provide an easy solution that keeps both hands free while handling the door. Retractable pin hinges can be used in close-quarters where there is not enough room to lift and manipulate the door.”