Document DD6r5BGyBDE3Y006X2gQ22wBN

Small fats Pressure i _L Ring ofjets---.* Suction*. Coulee Hits 1,000,000 Kw Groin- Use suction and pressure................ not suction alone 1 Parallel jet* of steom ot riser top 4 Necessarily larger jets of steom must expand freefy toward tank, propci- create more suction not only to lift ling ash; section lifts only to riser top ash but to bring it around elbow to tank 3 Remember that rebounding wear curt beyond elbow to ample prattc* tlon b needed there os well at in elbow Tips for Pneumatic Ash Conveying As told to Managing Editor L H Rowley By Eugene Hahn, Hahn Equipment Co. To the basic problem of handling ash, changes In firing methods have added the job of handling flyoah in many plants. Presence of precipiutore, dust collectors, cinder traps and other points of flyash deposit consider* ably complicates layout of ash convoy* ors, making good design more essential than ever. Fortunately, the flexibility of pneu matic or "pipeline" construction fovors the proper solution of the frequently tortuous and difficult layouts encount ered, provided it is kept in mind thsi even flyash, let alone elinkery ash, con* sists of highly abrasive solids moving at high velocities in the pipeline. This means that resistance through unneces sary elbows and luma should be avoided. Resulting free-flowing design also prevents clogging end reduces steam consumption and maintenance to a minimum. When designers forget this, they produce layouts that would be more proper for water or gas lines, where velocities ore much lower and abrasion Is o problem. Once the best layout for given condi tions has been established, it is im portant to arrange outlets for osh and flyaab to the intake orifices of tho con veyor so charging into the latter will be most convenient. This keeps down steam consumption. It also reduces volume and velocity of exhaust steam, which Is responsible lor carrying flyash Into the atmosphere. II not eliminated entirely, this must be held to o nonobjectionablo minimum. The next problem U the convenient sod so-called "dustiest" unloading of ash end flyash from the storage tank. This is never perfect, as the disinte grated mass--fines and lumps of dusty osh and clinkers--It more difficult to handle dustlessly than uniformly fine or granular material. The first require ment is that the tank be of dischargeefficient and self-clearing design. This fooilitates gradual and uniform flow instead of dropping out irregularly with a cloud of dust and without possi bility of efleetive sprtying to allay dust. Although most steam-operated equip ment now boasts higher efficiencies, pipeline conveyors still tend to be the "steom hogs" of yore, when steam cost was Immaterial as long os the ash was removed. In contrast to skillful ex ploitation of thermo dynamics in other fields, engineers often ignore the sim ple fact that the jet of steam should be properly expanded and propel the ma terial irt the line by pressure as well as suction, reducing exhaust velocity to a minimum. Exhausting the steam, without first expanding it sufficiently, carries oil more flyash than necessary. In Fig. 1, parallel jets of steam st riser top expond freely toward the tank, propelling the material for this distance. Suction created by the jets needs to lift material to the riser top only. In contrast, necessarily (srger jets of steam in Fig. 2 must create tnore suction. They must not only lift sib within the riser -but must else bring It around the elbow and then to tho itk, which may be quile distant Highvelocity exhaust is wasted to iloosphere, carrying flyash with it ai so objectionable byproduct. The objection may be raised that contact of steam end ash post the steam jets of Fig. I may couse the ash to be-, come moist and hence leu easy to, clear from the lank. As this coaUct.U a matter of a split second, moisture ab sorbed by the ash is hardly perceptible There should he no problem with s properly designed tank. In fact, the' small amount of absorbed moisture will help seduce the dust nuisance wbes emptying the tank. From the maintenance ongle, remem ber that, unlike low-velocity liquids sod. gases, solids at high velocity acquire momentum and thus cause rebouad* wear beyond tho elbow as well ai im* pingement in it, Fig. 3. Thu* ampl* protection should be provided beyoad every elbow or turn in the line readily accessible aad Inexpensive li* ere. Also, since conveyors Iot difficult materials such as sih end flyash should logically be rugged and simple. c0' plicated "gadgets" should be avoided If low-cost maintenance is desired. U (352) POWER J-"* Ifo neueve the Northwest serious K shortage, Bureau of Reclamation gifSnecers iruus."h a--n a---d--d--i-tion to Grand Ice Oam' west powerhouse. Photos generator L.-6 assembly nearing ipletion. Plant's continuous copaeity girili then be over 1 jQOO.OOQ kw. n. ^teh generator is rated 108,000 kw nt uflity pi, but 1-L to 6-1, in operation during the war, have been loaded eon. ftiatrously to 130,000 kw. When a Power editor visited the plant last July, each V<he six machines was loaded to )2S,. 000 kw, or 750.000 kw total. Thus, j'vHen L-8 goes into service, the plant girili have a continuous rating of over ^1,000,000 kw with some overload capoeijy to spare- L-9 is being erected for aopeniion the early part of 1946. This F.vfll complete the plant, except one tO,. 1000-kw service unit, end give it 1,145,. fllOO-kw capacity, largest of any group sl geaorators in the world. Six of ^sbs uaits for the east powerhouse are so order for 1949 and 1950 installation. mg CRAHI5 CARRY HUGE- ROTOR. Sup. ported by two 350-ton. crones this giant rotor (above) is moved toward Its .stotor on right for newest generating unit in west powerhouse, now nearing completion at Grand Coulee Oam On Columbia River in Northeast Washington. Hero ' rotor * posses over unit 1-7, roted.108,000 kw but goad for over 125,000, which went into servico lost October to aliovioto Pacific Northwest's power shortoge ROTOR IS LOWIRIO INTO STATOR. Rotor (left) of unit U-8 has dia of about 31 ft, weigh* 587 tons. Workmen hold thin pieces ol wood In air gap between rotor polepleces 'end stator core whifo two cranes slowly'lower rotor. Clearance between Its potopieccs and stator core It lets than one Inch. This unit, which engineers of'the U. S. Bureou of Recla mation put into operation recently, brings the continuous copedty of the sta tion to over 1,000,000 kw