Document 6B5k0NeRrmorzodJqMe2kBzzm

17--Building Construction and Maintenance ground structures The use of open-flame devices, such as solder pot furnaces and welding equipment, should not be permitted in or near manholes, tunnels, or trenches, in which tests indicate the presence of flammable gas Waste disposal facilities. Waste disposal trenches of reinforced concrete have been known to settle, the side walls separating from the bottom slab of the trench and allow ing water to seep out Such seepage carries earth with it so that the trench and building footings may be undermined and the support may be removed from the underside of the floor slab at ground level Structural failures may result also, if waste disposal trenches are not kept in good repair If trenches are lined with lead, acid-proof bnck, or other lining, they should be checked for leakage Other underground pipelines. When men are to work on an underground pipeline, it is important that its approximate location be known before digging is begun. The sides of all trenches more than 5 ft in depth should be shored unless they are sloped to the angle of repose or unless the trench is in solid rock No excavation should be made immediately adjacent to or below the level of a pipeline because of the danger of cave-in and of failure of the line, which may be carrying liquids or gases vital to plant operation Workmen cut ting into or working on a pipeline should know what the line is carrying and the dangers involved Before repairs are begun, pipelines should be completely drained, the connecting systems blanked off, and the valves closed and locked Whenever a workman opens a line or valve, he should watch for back pressure m the line Workmen should be cautioned to open valves slowly and to equalize pressures slowly Sudden changes in pressure can wreck equipment and endanger lives After a steam valve has been opened com pletely, it should be backed off at least onehalf turn so that thermal expansion will not lock the valve m the open position When pipe or trenches must remain open overnight, they must be protected by barri cades, signs, and lanterns Lighting systems All lighting systems--fluorescent, incandes cent, or mercury vapor--require regular main tenance to maintain maximum light output (For design factors, see section on Lighting m the preceding chapter ) To reduce the number of persons who might be exposed to flying glass and dust if lamps are broken, fixtures can be relampcd on weekends or at other tames when personnel are not m the aiea Gloves should be worn by those who handle the lamps To dispose of a few lamps, put them m special containers for regular rubbish removal or wrap m several thicknesses of newspaper or wiappmg paper, place outdoors m a dis posal container, and crush with a heavy stack or shovel Large numbers of tubes should be broken m commercially available machines and m a ventilated enclosure equipped with an exhaust and a dust collector Captured dust should be wet down and removed Lamp bum-outs and depreciation, dirt ac cumulation, voltage drops, and bght absorp tion by dirty walls and ceilings will cause a loss of bght Because dark or dirty surfaces absorb as much as 80 percent of the bght that stakes them, a regular cleaning schedule is important For duty aieas, this may be every two weeks A bght meter can be used to check condi tions, and the readings then can be checked with the minimum standards of illumination for industrial intenors, ANSI All 1, Practice for Industrial Lighting These standards, rec ommended by the Illuminating Engineenng Society, are summarized m the table entitled Levels of Illumination m Chapter 46, "Safety Engineenng Tables " These values can be used as a guide to formulate a regular main tenance program If cleaning lamps and replacing burnouts fail to increase the illumi nation to standard levels, then a qualified il luminating engineer should be called upon to make a complete survey of the present system Fluorescent fixtures should be of the type that locks the tubes m place Older fixtures should be equipped with shields or gnds beneath the tubes to prevent the tubes from falling if vibration should loosen them Where reflectors or glassware cannot be taken down, the current should be shut off and a cleaner that requires no rinsing should be 434