ANSI/ASTM F 571. Standard Practice for Installation of Exit Devices in Security Areas In addition, there are a series of ANSI standards for the preparation of standard steel doors and frames to receive hardwarethe Al 15 series, sponsored by the Door and Hardware Institute. A hinge is a device permitting one part to turn on another. In builders hardware, the two parts are metal plates known as leaves. They are joined together by a pin, which passes through the knuckle joints. When the leaves are in the form of elongated straps, the device is usually called a hinge (Fig. 11.70 and 11.71). This type is suitable for mounting on the surface of a door. When the device is to be mounted on the edge of a door, the length of the leaves must be shortened, because they cannot exceed the thickness of the door. The leaves thus retain only the portion near the pin, or butt end, of the hinge (Figs. 11.72 to FIGURE 11.73 Bearing butt hinge. FIGURE 11.74 Plain bearing butt hinge. 11.74). Thus, hinges applied to the edge of a door have come to be known as butts,

Certain manufacturing processes call for close control of temperature and relative humidity. A typical control system is shown in Fig. 13.45. The humidistat may be of the single-pole, double-throw type. On a rise in room humidity, the refrigeration compressor cuts in for the purpose of dehumidification. Since the sensible capacity of the cooling coil usually is much higher than the sensible load, whereas the latent capacity does not differ too much from the latent load, undercooling results. The room thermostat will then send enough steam or hot water to the reheat coil to maintain proper room temperature. A small drop in room relative humidity will cut off the compressor. A further drop in room relative humidity will energize the water or steam solenoid valve to add moisture to the air. The thermostat is also arranged to cut off all steam from the reheat coil when the room temperature reaches the thermostat setting. However, there may be periods when the humidistat will not call for the operation of the refrigeration compressor and the room temperature will climb above the thermostat setting. An arrangement is provided for the thermostat to cut in the compressor to counteract the increase in room temperature. When calculating the load for an industrial system, designers should allow for the thermal capacity and moisture content of the manufactured product entering and leaving the room. Often, this part of the load is a considerable percentage of

Bearing atop Webs. The sum of the compression stresses resulting from loads bearing directly on or through a flange on the compression edge of a plate-girder web should not exceed the following: When the flange is restrained against rotation, the allowable compressive stress, ksi, is F  5.5   (7.46) a (a/h)2 (h/ t)2 When the flange is not restrained against rotation, F  2   (7.47) a (a/h)2 (h/ t)2 FIGURE 7.36 Web crippling in a column at a welded joint with a beam. where a  clear distance between transverse stiffeners, in h  clear distance between flanges, in t  web thickness, in The load may be considered distributed over a web length equal to the panel length (distance between vertical stiffeners) or girder depth, whichever is less. Web Stiffeners on Columns. The web of a column may also be subject to crippling by the thrust from the compression flange of a rigidly connected beam, as shown at point a in Fig. 7.36. Likewise, to ensure full development of the beam plastic moment, the column flange opposite the tensile thrust at point b may require