Document 6Rpk30gqq6K8vDJwZYjDVan8m

PLANT PROBLEMS put your know-how to work the other auv tore his headaches mil HIOCS* Aiaxfafe ttBor Question No. 1: Why Is Diesel Piston Worn ? IICRE ARE THE FACTSi One pltlon of our 4-cyela 8-ejl lOOO-hp dletel ( worn oval about 0.015 In. on iho ihruit Ide, and the rings are worn ih'e itme way. Liner thowt normal wear with no Korlng. Recenily we put In a new piston and ran for three hours. Then the wrlsi pin got hot and the piston scored the liner. Cheeking the engine we found outside lubricator sup- plying oil to pistons was working right when scoring oc curred. We now gel a noise from this cylinder that sounds like a piston slap. Sinee engine Is only 11 months old and oil pistons are correct site, what Is eautlng our trouble? Why did piston weor oval in such a short time? What's best way to repair piston and liner? How can w avoid tropblo In this engine?--BB, March Power Here Are the Answers fgYS CHICK piston (or roundness .driving in a wrist pin. When o |i out of round it wears more pidly. A few hearty whacks with a hammer usually cures this trouble iir plant. (^wrist-pin clearance and connectLmd side play are normal, pin heat* `results from laek of lubrication. oil bore in rod, holes in wrist pin ersnkbox.. You may find a rag or Uni in cfankbox oil hole, tj p Tillies' Mexico City, Mex. [ALIGNMENT between piston and ii is causing SB's trouble, not faulty station. Oval wear of piston thrust de shows that misalignment is the cub V Check liner for wear in fore and ('direction of engine, coring shortly after new piston was _jlled could not be beamed on the pen If Us dimensions were correct and er was in good condition. agrees with manufacturer's recommen dation. It should be free of score marks. Also, check rod for straightness. If liner isn't worn excessively, you ean be cer tain connecting rod end its bearings are at right aogles with crankshaft. Consult engine manufacturer for beat repair methods when you expect to do a large job on your diesel engine. Henhy Grbinea Anoka, Minn. LAROE LINER BORE and small piston al low piston to wobblo la cylinder. Small bore with a large piston causes overheat ing, scoring and possible seizing. Pis ton that has too much clearance wears oval, and causes liner to wear oval in a shorter time than normally expected. When fitting rings to out-of-round cylinders, be sure they are fitted to the largest diameter of cylinder to prevent ring binding, distortion, overheating, etc. Renew the liner, insleod of reboring it. Fit new piston. John Ceist Brooklyn, ff. Y. HOT WRIIT PIN suggests it may bo fitted loo tightly. This could cause unequal wear in cylinder. Re sure wrist-pin ends fit piston and bearing properly. Wrong ly fitted wrist pin ctn run hot, seize, and lorce piston sides out against liner, acoring |L Check pin carefully. Petr Teller Chicago, HI. SLIGHTLY BENT connecting rod causes this trouble. Beni rod throws an unbal anced load on wrist-pin bearing; oil dis tribution la poor. Rod causes piston to slap cylinder wall on dead center. A heavy fuel eharge in this cylinder during eotd starting might cause con necting rod to bend, especially If start is sudden and engine has a large fly wheel. Cylinder relief valves, If fitted to engine, should pop when fuel charge is excessive. Since a good job is important I'd eall in the manufacturer's engineer to get the.best advice possible. Art Belton Montreal, Can. THESE PHOTOS show piston scoring from abnormal thrust, caused by engine overload, and fatigued crown resulting from continued overload. An unbalanced and overloaded cyl inder leads to abnormal thrust pressure on piston. This may overload wrist pin and bushing, or distort connecting rod. More heal must be rejected to cooling water when engine ia overloaded. Higher heat load may break down oil film. Laek ol good lubrication can lead to seixure and acoring. Cood corrections include: (1) Hone or rebore liner. If maximum bore 11mitationa ore exceeded, renew liner. (2) Clean the piston; renew if under min* Imum diameter or if distorted. Remem* ber, using a liner with maximum bore and d piston with minimum diameter may produce too targe o clearance. (3) Check rod alignment and straighten or renew H necessary. (4) Re* fit or renew wrist ond pin bushing. (S) Renew piston rings. (6) Check connect* ing rod bearings, adjusting os needed. (7) Clean cylinder cooling-water pas sages. (8) Reassemble engine and lake eotd compression readings on cylinders. (9) Run engine at no load, checking compression and exhaust. (10) Reset fuel racks. Run engine under load while, adjusting fuel system to give equal ex-, hauat temperatures in each cylinder. Excessive skirt clearance causes pis ton slop, but a simitar sound may come Irom loo early Injection of fuel. To iso late and eliminate fuel noise, shut oS- supply to cylinder In question while engine is running. If noise stops, i* time fuel pump. Cam. J Sarne /faverioum, Pa. CRANKSHAFT BEARINOS aren't at fault because BB reports no trouble with them. Wrist pin is at fault. Its clear ance may be less than manufacturer recommends. This will cause overheat ing. Rebore liner and fit an overeixe pis ton. Same wrist pin may he used, but check to see that pin ends fit piston and bearings with right clearances. A J DnsuccLMAits Neto York, N, Y, CHECK CRANKSHAFT alignment. We had similar trouble in o 5-cylinder en* gine. There was 0.005-in. distortion at No. 4 crank. Piston end rings In this cylinder wore os BB describes. Refit, ting the main bearings.and lowering outboard bearing stopped wear in No. 4, but then it showed up in No. 5. SB's trouble is from misalignment. Rest cure is to align engine as carefully as possible. Repair a worn cylinder by rehoring to a larger else ond fitting an oversize piston. Or build up liner sur face with porous chromo to standard size, ond use a new piston. A M Damrrow Elk River, Minn. CONNECTING-ROD bearing U fined 100 low on one side. This pulls rod fool down, causing excessive side thrust o piston. Insert o shim of right thickness to align rod foot correctly. Check clMr1 once of the beoring after Suing Rbl- F A Butler Dallas, Texas 114 PUNT OPERATION AND MAINTENANCE SECTION pown Question No. 2: Is This Stack the Right Size? SB ARE THE FACTSi The steel slack fur our new loir Is to be SO In. din, 150 fi high above boiler-room ?*r- Boiler Is rated at 20,000 lb per hr, 125 pslg, 5S3 F. wd temperature Is 212 F, goe leaves boiler 01 583 F. U no heat recovery. CO* leaving furnace is 14%, hiring boiler 13.5%. $Lomcs expected a ret dry gas 12.5%, Its and moisture In (Clverited-eoa) fnel 4B, moisture In air 0.80, unbornad mabntilble 1-5, radiation 1.2, unoeeounted far l.S% Guaranteed boiler efficiency 1 78.4% | overage draft loss through boiler Is 0.60 In. IliOi required draft at entrance to first pass 0.15 In. IlfOt furnace draft needed el min imum rating 0.05 In, DiO. Proximate fuel analysis tsi moisture 2A8%, volatile 36.0, carbon 52.36, ash 8.76%. ( don't think stack also recommended Is right. What's best way to cheek staek sleet Is site recommended ton reel?--K.IC, March Power fere Are the Answers__ BACK HEIGHT, DIAMETER depend on 30. mount of fuel to be burned (2) Ad type (3) ges temperature (4) type Ptle. (5) design of boiler end breech(6) Hub arrangement (7) plant fUfede, and (8) atmospheric air temp. Amount of fuel that will be burned fctermlnea flue-gas quantity. Gas tern- Mature and plant altitude fix gas volj** You must know these factors to Ueek diameter. Amount of fuel ond its properties, ^ther with grate type and boiler deSQ (number of pnsses, turns, etc) MtTmine draft intensity required. Css Ml atmospheric eir temperatures ere Mdcd to find thermal head available. Though GfCs data are incomplete, ** computed slack size, using several ^enable assumptions. Pm sssumiag is stoker fired because pulverized is generally not considered eco- nomical (or outputs of less than 50,000 lb of steam per hr. Also, with pulverized-fuel firing, air heaters generally supply hot air for heating and tranaporting the fuel. CK mentions no beat recovery, another reason for assuming stoker firing. From the proximate analysis, com putations show his fuel has a healing Belter Heat Balance % Btu/(6 fuel Input 100 Output 78.4 Energy losaes: Dry flue gas 12.5 H* and HiO In fuel 4.8 H0 in air 0.3 Unburned combus tible 1.5 Radiation 1.2 Unaccounted 1.5 13,100 10,250 1635 628 39 I9S 157 196 value of 14,910 Blu per lb on a molslure-and-asb-free basis. On the orig inal basis It la 13,100 Btu per lb. Boiler heal balonce Is In table, left. At an output of 20,000 lb of steam per hr, quantity of fuel burned when boiler runs at guaranteed efficiency of 78.4% ia 1970 lb per hr. Theoretical amount of air needed (or firing ibis fuel with a beating value of 13,100 Blu per lb, Is found by calculation to be 10 lb of air per lb of fuel. Therefore, total amount of air theoretically needed la 19,700 lb per hr. From the dry gas loss expeeted, 12.5%, wo can compute weight of dry gas per lb of fuel as 13.S lb. Total dry flue gas from combustion is (1970) (13.5) -- 26,600 lb per hr. Using the dry flue gss quantity and theoreticol air for combustion, excess air Is 35%. Dry gas leaviag boiler Includes all 1953 flANT OPERATION AND MAINTENANCE SECTION 135