Document d8pzGZX30NnoJdeEg9LX3DEb

COAL IS WEIGHED AS RECEIVED, DURING. jdNDUNG, OR AS DISTRIBUTED With fuel a major cost item, keeping track of quantity^' I'VTrsck scales, often automatic, weigh coal coming In by and quality it important. Total coal received may lx "f:*\ Truck deliveries may be checked by familiar platform weighed at unloading point or aomewhere in the handling v above, hit. Weighing devices are built into unloading system, or coal going to individual boilers may be weighed 'aA `itfiiipment - rotary cor dumpers, feeders, etc. -- and scales at fina) handling step. It often pays to do both. '^7.) installed between receiving hopper and conveyor. *;Cosl is weighed in transit, also. In the belt scale, above, CHUTE DESIGN FOR GOOD HOW >.& weigh beam connects to a suspended section of the -'tcrying run. An integrator relates running weights and travel to record amount of coal being handled. Rathollng and arching can be particularly troublesome at the final handling step -- but proper design of bunk* era, chutes and hoppers can lick them. Chutes, like the 23-in. at bottom). There should be no projections into the flow system, and it itde. sirable to use corrosion- end abrasion-resistant materials to keep the coefficient of l-^For weighing coal to each boiler, the time-honored tarry I 'jjjjU finds use. Suspended from overhead rails or running on .'door tracks, it is basically a means of distributing coal. 'Drive may be by hand or motor. When weighing equipment jj added to the basic lorry, it may be manual or automatic. vBuic element of many modern systems is on automatic one at left, should be steeply inclined, preferably round or oval, and should flare in di rection of flow (chute shown friction a minimum. To avoid segregation in firing-equipment hoppers, the special conical-design cicala of general type illustrated, right. Such units are .ucurate to about 0.5% under average conditions. One Vtbowa has multiple-scale lever system with weight carrier ?.ind multiple weights, motor-driven belt feeder, hopper and is 18-in. diameter at top and chute, hit, is often employed. wunter to record weighing of preset amounts. The final handling step, of which weighing is.. r %, often a part, is important to good operation In the Anal handling stage --from live storage to firing equlpmentr-conveying equipment just described is sometimes used, to feed any firing unit from any 'bunker section, or to transfer coal from one bunker section to another. But in most plonti, discharge from bunkers is bandied by chutea. Apparently sim ple. chutes can give rise to flow troubles unless properly designed. Recent stud ies (Powbr, June 1953. p 92; Aug 194$, p 70) yield practical tips. Chute Darien. Diagrams and cap tion above show some features of good practice. Also, chutes should change direction gradually, with, if possible, a breakaway, or larger-area section, to give coal a chance to realign itself. Where two streams of coal meat, keep angle of convergence to a minimum. Avoid constrictions, cramped layouts. Segregation. In talking about stor age, we stressed the need for avoiding segregation -- the tendency of fine and coarse particles to go their separate ways. This same problem crops up be tween storage and firing units. How serious it is depends on how much segregation the handling system pro duces. and on the firing equipment. Segregation can cause site of coal fed to pulverisers to change from minute to minute. Usually more serious is the effect on stokers, where segregation that reaches the fuel bed sets up big differ ences in resistance to air flow end an extremely spotty fire. First step, of course, is to ovoid, if possible, han dling-system conditions that cause segregation. Pinal answer, however, FUfl HANDLING AND 5TOIAOI seems to be some form of special nonsegregating chute. KEEPING TABS ON (OAL Chocking Cool. A frequent part of in-piant handling is keeping tabs on quantity and quality of coal fired. - -Just as scales check coal quantity, sampling for analysis Weighing, of feed to individual boilers -'ll '.keeps tabs on quality. Process of reducing a grots sample or of total receipts, is outlined briefly . by hand quartering and riffling can be eliminated by using above, with sketches of typical setups. .'*a automatic sampler. Unit illustrated (far right") has an In addition, there ore maaaurinf de- sAlditionai splitter: it con deliver the normal 5, 10 or 15% vices.working on volumetric principle*. `temple, or a faster-worked 5% sample of anyone of them. One has a vane or helix that projects . As we've seen, we also want to keep tabs on coal flow down into the center of a spout sad *ad level in bins, silos, bunkers, etc. This applies equally records movement of coal past it on to the Anal handling stage, where we want to check flow meter calibrated to read in pounds. nd level in chutes and hoppers. Two units designed for the Another employs an endless chain in- - .feb appeared on p 87, another It shown, right. It hat a stead ot a vane. Similar volumetric . 'inlew-steel sensing element, which is said to resist principle is used when revolution kiiidup of dust and wet coal. Acting through.a spherical countera are put on atoker thefts an* -Pivot and seal, the probe operates a microswitch. pulveriser feeders. These serve wU f6t Q rough check on unit consumption. fowl* "tClMSH 1953