Document K8083yY8rr4dMkoRpy203qQw

Get n^iv Got \ THE OAI is drown Into cylinder through inlet volvc, while omount of got 1% controlled by. metering valve |n thls'engirw GW/ofr# '(jj|talection valve must work freely, jjjriafc'riur* Pushing does not bind stem stapmHr port 9 Got VHt o iyfrtdw A*eO QAS metering valve of duet-fuel unit Is octuoted by the lever at the right OA5-MAIN hookup tor lorgo nglne is at top. for small angina at bottom fUll-OIBIEl duol-fuel unit, ccmprestion iparV-Ignltlon gat pressure can be anywhere between three and seven inches of water. But, egsin, Dual-Fuel Maintenance best operating figure depends oa engine and gas quality. Gas hookups for units, both small (about 150 hp) and large (to 5000 hp and more), are shown in sketch (right, facing page). Motoring Valve. Gas next passes to the metering valve. This valve (sketch, center on foeing . pege) ' it operated By C MOROAN JONES, 0*j*f fogMeer through a fuel-gas control shaft, oper ated in turn hy governor linkage. These valves are important. They can be in dividually adjusted for required gas flow to each cylinder. Both cas-ihci** end diesel men often regard the dual-fuel engine as something of e mystery. But, while dif ferent, it actually colls for no speciallied maintenance know-how or operat ing ability. There are soma equipment parts on a dual-fuel engine not found en the full diesel, though. These ere commonplace on the fuff gas engine. Scrubber. First of these extras is the gas scrubber, between the gas main, supplying the plant and the engine. If gas is corrosive, scrubbers remove trou blemakers, which greatly extends liner, piston and valve tife. Fit two scrubbers so you can clean one while the other lakes load. If only one Is used, operate engine as a full diesel while changing or cleaning scrubber. Reducer*. Meat are the gas pressurereducers. You must always use these even when ges pressure is low, as they maintain the right pressure. When gas pressure Is high, I've found that two When engine is running, compare ex reducers give better gat-pressure con haust temperatures. If there's a dif trol. Reduced gas passes to receiver. ference of more than 50 F at full load, Receiver pressure is important and adjust metering valres until exhaust receiver's capacity depends on engine temperatures are balanced and within 50 site. A good receiver capacity-formula F of each other. It's usually best to Is to allow 0.02 cu ft of capacity for reduce high temperatures instead of each 1000 Rtu contained in a cubic fool bringing el] readings up to-hlgb figure- of gas. Multiply answer by englno's Reduce unless they aro well below max fuif-lood horsepower, ff gas value it imum figure recommended for engine only 500 Btu, receiver capacity must be ' when running at full load. If below, doubted. So if engine Is rated 1000 bp admit more gas to low reading cylinder nd gas value is only 500 Btu, receiver to Increase exhaust temperatures. capacity will be 40 cu ft. Pay careful attention to liming of From receiver, gas passes to engine's gas-injection valve. Titfa valve admit* gas manifold. Manifold pressure is im metered gas into engine's air intakeportant. For supercharged engines, a manifold. Sketch above shows position- manifold pressure of 10 to 20 psl is Don't open gss injection-valve while best, but exact pressure depends on en- exhaust valve is open. In all modem gino Itself. Rarely will two'englnes burn, engines, exhaust, air-lnlei valves are ing the tame fuel give identical per both open briefly as piston passes formances under similar conditions. through top center, at end of exhatui, Instead, I find that trial and error often end beginning of air-inlet stroke. In* decide best operating pressure. ' jectlon valve opens the instant exits')1* For nonsupercharged engines, gas valve closes, ff gas fnjection-vsfve opens 114 NANI OPERATION AND MAINTENANCE SECIION ROWES Cites Burned to Diuffue) Entfm tod The)/ Vtlua ftleiare exhaust valve Is closed, get will `ij&s'ierMs combustion space and out of ij^ins Into exhaust manifold, where it 3$ born in exhaust line* or silencer. jfi|B|scrte vahrea ere often operated by pWr own individual camshaft, or by an ftfiilonsl cam. on main camshaft. If ' _ afikafi j correctly timed, then valves noil, also be correctly timed, so only `dittitment needed is at valve tappets. .^Sketch (left, above) shows one type of Hit* haot velvt tv ft n It ClOwUH Will ** CaeS 00* Cak-*a en Nehirvl en Ihi-ntir eai ou fti JwtW PrHftii ( IlntAwim eat C* ft ah 4.15 S.M 4.15 10.14 1,71 erv vatiw ft ta It f Miatata S.S vy.r HI 14.1 U.f V).} HJ 4S.J 14.7 * jHiinjetiion-vsWe. k-`*pno make of dual-fuel engine oper> 'ita.on high-pressure gas. Gas enters 'empnaaot from scrubbers and is de livered to cylinder-head valve at about MjdO. psl. Compressor is engine mounted Wdodspendently powered. Cas Is held justment. Always check gas metering- *;'s receiver (or delivery to engine. valve and fuel-injection pump linkages. ljj*Valre* run hotler on most dual-duel Make sure distances between linkage- lesgiDes than on full diesels. Often, you pin centers are correct at every over have to make slight tappet ad- haul. These dimensions can effect meter ^justmenis besides those manufacturer ing of oil fuel and gas. If engine 1'Veecmtncnds for best operating results. "hunts" (speed varies at constant lw.jll one cylinder continuolly-detonates, i[J^frtard hi loel-oil pump timing from one IVf'D.ihres degrees. This should help un- throttle setting) inspect linkage for binding and, if a long time has elapsed since last overhaul, for wear. '.'FM its cause Is something unusual, Trouble shooting in dual-fuel en at focreaaed compression rath for gines. Let's sey engine if running on c*^n,icr> CjT&k W4y* carry cooling-water tempera- high as manufacturer allows, oil, and control lever or wheel is turned to iJie gaa position. If engine loses speed, line valves In gas hookup may engine runs on full oil and ges be closed or only partly opened. i^.Wxture (with plenty of gas) but grod- If engine fails to pick up speed when l2aJ[*llMMrea jnto oil operating range so running on gaB-and-diesel fuel mixtuie, ^ IJpcentage of oil burned slowly In- check the gas metering-valves. They .v*'-*?***' css pressure at moln and may be Improperly set. Faulty setting t'^.'bfecehrer. Trouble may be dirty gas of valve can also lead to "hunting." ^Wf^sr or cleaner, or defective gas 1/ angina knocks when running on diesel fuel, and gas injection of "pilot" *54fiflTWrt' linkage needj accurate ad- ufuewl is isklng piece....l.o..o.....e..a..r..ly, rre--tard injection. Clearance. of gas injectionvalves may be too little, or Injection valve may be leaking. Often valve pack ing is too light and needs slackening back to' allow valve to move freely and admit full quantity of gas io cylinder. Knocking can also be from unbalanced cylinders. If engine alert* but runs'erratically when placed on gas fuel, check for: (l) low gas-fuel pressure (2) defective gas regulator! (3) Incorrectly adjusted gas throttle (4) incorrect gas-lnjection- vb!vq clearance. Should ongln* misfire in exhaust manifold, pilot fuel-injection jj taking place too laic. H pyrometer readings show tempera tures are too high in all cylinder*, check for fate injection of pilot oil li temperature la high in one cylinder only, trouble la often due to Injection valve sticking because valve-stem peck ing Is too tight. Check stem lor grooves. (Jo&i. 1933 fUNT OPEIATION ANO` MAINTENANCE SECTION ill