Document OzVQk4odz8n5o3opn8ZQmew6j

EXHAUST temperatures ora quickly checked by this engineer TEST pyrometer by piocing thermocouple In pot of molten from pyrometer inttolled on the control ond olorm panel here leod. Check reading when leod starts solidifying or 620 F FOUR-CYCLE liners ore checked for blow, DILUTION TEST is mode by compering by by looking up from Insrde cronkcose boll's trove) through new ond uteri oil "Log Pyrometer Readings," says C Morgan Jones, Diesel Engineer, . and end diesel mysteries. A pyrometer takes most goesswork out of froub/e-shoofrng. tog rtf readings ond do away with headachesHere's bow to "read," bow to maintain one Mac a omits he knows more about haven't smoked." So another mystery diesel engines thin anyone else. When of diesel gossip Harts going round. Then I asked why he didn't log his individual it's entered in the maintcnonce log book cylinder temperatures, he said, "What's for posterity*--to be thrown at some the use? I cen tell bow she's running by unsuspecting salesman. Exhaust pyrom just looking si the stack, or feeling the eter would hove found this trouble also. exhoust headers." Again, If a cylinder showa a very What he didn't know wos that indi high exhaust temperature, you might vidual exhoust* temperature readings check fuel pump, injector, even the fuel, often tip you off about trouble, long and stitt not find cause of high reading. before exhaust smoke ond touch method Thinking everything la all right, you do. They might tell, for example, when start engine, blaming pyrometer. Then water jackets need cleaning, or if fuel you forget It, but before long you lose injection Is early or late. your plant. How could this happen? Operator naturally knows everything Well, you should have checked liner Isn't OK when exhaust is smoky. and piston, also. Careful check shows Trouble might be one cylinder overload- first signs of scoriog, causing overheat ing from faulty injection. Rut one cyl ing registered by pyrometer. No break inder can be overloaded without engine down if ibis had been cheeked and lube- smoking. How? Because combustion is oil service overhauled. completed in hot exhaust headers, where it does no good. Pyrometer will find / (HINOS TO CHECK that In a hurry. Scale can form in engine jackets if Carbon builds up in combustion you don't keep Water hardness to s min spaces of that cylinder, hut moy not imum. It forms slowly and robs engine be bad enough to smoke st once. In the of its efficiency. Scale gathers slowly, meantime. If cylinder heads sre lifted, but the exhaust pyrometer tells ell about Mac will be surprised and say, "Look at iL Temperature of cooling water might this. AM other cylinders ere clean and decrease as thin layer of scale prevents cylinder heat passing to coulittg water. Uut gradual increase for all cylinders lips you off to need of a descaling job. Quick check of 2-cycle engine's cool-. ing system without draining is to tike off air-box hand doors. Then bar en gine over slowly. Check rings with a strong flashlight as they slowly pan . ixiris. first blackened ring that passes . marks lowest point blowby has readied. All rings should be polished. Stop bar ring, push ring with wooden wedge. Ten to one, it will be stuck. Lie on your back and shine torch upward through port. ITien, as engine ' is jacked over, you esn see es/feon streamers on otherwise shiny liner. You. can even see injector lip. Rings will be gummed from lack of oil. Lube oil burns off from high temperatures caused-by poor cooling. Blowby might take place for wholo length of piston, front crown to skirt edge, far ss you can see. Remove crankcase doors If 4-cycla en gine. Don't jam clothing or yourself in webs while engine is barred over care-, fully. Piston skirt's bottom and liner's lower part can often be Inspected for ' blowby indications, sketch. If blowby ahews for liner's full length, smell tho lube oil. It msy reek of fuel oil. If so, toke aamplo and pises in tube, sketch. Toke same amount of* unused oil in another tube o! asm* length snd diameter. When both are same temperature, use two steel ball* (ballbearings) of same weight, slightly mailer than tube. Drop one ball into each tube, at lime. If ball In used sample slokt. Isster, oil is diluted. This tost is *erj practical. The faster the ball travels I* used oil, the greater the dilution. Here agoin, carefully logged exbsui*- temperatures could hove saved tro' e' So keep an accurate log. Dont skjP degrees and say reading Is "^0* ., snd so." There must be no "about --' must be exact to tell true story- MB 'UN! OPElAflON AND MAINTENANCE SECflON `ake case of a 2-cycle engine where cylinder does most work because It too much fuel. Pyrometer ehows reading for this cylinder, but it's islly ignored. But trouble in this [jnder can spread to others, j overheating from overload con ies, carbon forms in ring grooves combustion spaces. That distorts [ectlon spray. Some nozxles also clog, Wbon builds up fast. Then carbon # i exhaust ports. So cylinder works on less oir supply. More carbon gjos, clogging ports. Then temperasoars as less air enlera cylinder. 'o maintain speed, governor advances rack, causing other cylinders to 'pond. But large cylinder gets more also. Then higher temperatures 9 piston to drag snd score. [More fuel is injected os governor a to make up power loss. Other pisititrain and pull in response to throl.Then these cylinders start overheatSame eycle starts all over again, ibustlon spaces carbon>up, rings t, ports plug, fuel spray is distorted, lobe oi) burns. IOOK TOR TROUBLE (When engine is stopped, you find fUader damaged and about to seize. Pi connecting rods may be damaged Jfhtly, end other damaged parts may unnoticed. Don't kid yourself. j,la*ge will show up--and how! ^ule Infection to any cylinder is eas< found with a pyrometer. It means btr temperatures, incomplete com mon, carbonization. Early Injection esuse detonation ns piston posses Wgh top dead center. Then pyrom. 1 reading Is low. 'Botfly, a pyrometer showing high iperelure also tells: (1) need for dog injection timing (2) need for luting fuel supplied to any overloadfinder (3) If one cylinder Is getting ` much fuel. Rut if temperature is low, it showa: (I) need to advance'injection (2) if rings or valves are leak-, ing, or (3t if cylinder isn't getting' enough fuel. When temperatures are high in all cylinders: (1) engine ia overloaded, or (2) exhaust backpressure is too high from muffler or silencer being plugged, or (3) exhaust turbine Is dirty, or (4) exhaust piping is too long or small. Pyrometer hat only four ports: Indi cator, thermocouples, switch and exten sion wires. Indicator is actually small millivoluneter. TfisnastDvpIi for diesels is two wires of different metals; Iron snd constantan. Wires are welded together at one end, connected to Indicator's! other to serve all cylinders. Welded end is "hoi" junction, other "cold." When "hot" end Is heated, e small voltage is generated. Voltage travels along wires through.switch to indiealor, where it's measured. But in dicator scale is calibrated in degrees of temperature. Hotter the temperature, higher the reading. To lest, plaee thermometer at "cold" end (this end Is ai switch when alloy wire eonneeta thermocouple to Indica tor, at thermocouple when wire is cop per). Leave thermometer there for 40 to 60 minutes. Then take reading and compare with (hat given on indicator dial. If not same, adjust indicator with small knob or screw provided for this purpose. Indicators, fitted with cold-end compensators, need no adjusting. If you know engine temperature is going up while pyrometer says it's going down, wires aro reversed at switch con nection or terminal. Reverse, and read ings will be OK. Set indicator dial at room tempera* ture, not zero. And don't test Indicator with dry battery or other power source. Smallest current slammed across termi nals will damage coil, springs, and per haps bend pointer. So be careful. Thermocouple wires must not touch engine. Keep dry, ond protect against vibration. If extension wires are of standard type, look for fraying at benda or at flexes. Thermocouples sre mounted In pro tecting tubes or "wells." For this pur pose, seamless steel is preferred to wrought iron--steal responds to tem perature changes quicker. Clean tubes at regular Intervals. Don't scrape-- wipe. Tips of thermocouples should projeet into center of exhaust header. KEEP INDICATOR IN SHAPE Indioetors get sluggish from dirt. Clean with carbon tetrachloride. Don't adjust internally. Oil Indicator bear ings (often jeweled) with light ma chine oil on pipe cleaner. Causes of pyrometer trouble are: damage to indiealor, loose or broken contacts or connections, dirty contacts, grounded wiring. Fluctuating pointer indiooles loose wiring. If connection be tween elements (iron end constantan) breaks, remake using electric welding. Slightest rupture in wiring insulation means complete loss of current through grounding. If no reading, ond insula tion Is all right, check for switch dam age. Bypass swlieh with two short leads lo indicator terminals. Some indicators Have simple looking device to short-circuit moving coil dur-. ing transit. It's connected lo terminal posts and must be removed before indi cator can operata. Don't forget this when fitting s new one. Chock pyrometer's accuracy every year. Place thermocouple's welded-end in bath of molten lead. `When lead Is at point of solidifying, temperature Is about 620 F. sketch on facing page. Compare reading with indicator's. After years of trouble-shooting around diesels, both at sea and ashore, I hove found that a pyrometer is one of the best Investments an owner can moke. to IfJJ FIANf operation and maintenance section 119