Manual Cat

Caterpillar Inc.Marine AnalystService HandbookFebruary 1996 - 2nd EditionFebruary 1996LEBV4830This book contains a list of form ulas and term s for useby qualified C aterpillar M arine A nalyst. M any of the for-m ulas are R ules of Thum bbut they do provide guid-ance in their respective areas. These form ulas aregenerally accepted in the m arine field. This book isintended as an aid to the M arine A nalyst and NOT areplacem ent for professional ship design personnel.1Table of ContentsForm ula for C alculating H orsepow er . . . . . . . . . . . . 3 D isplacem ent H ull C alculation . . . . . . . . . . . . . . . . . 5H orsepow er R equirem ents forD isplacem ent H ulls . . . . . . . . . . . . . . . . . . . . . . . . . . 7H orsepow er R equirem ents forSem i-D isplacem ent H ulls . . . . . . . . . . . . . . . . . . . . 11H orsepow er R equirem ents for Planing H ulls. . . . . . 15H ull Speed vs W ave Pattern . . . . . . . . . . . . . . . . . . 19 B asic Propulsion Theory . . . . . . . . . . . . . . . . . . . . . 21 Propeller Pitch C orrection . . . . . . . . . . . . . . . . . . . . 33 Propeller Form ulas and R elated Tables. . . . . . . . . . 35 R ules of Thum b for Propeller Selection . . . . . . . . . . 53 R elated Propeller Tables . . . . . . . . . . . . . . . . . . . . . 55 O nset of ShallowW ater Effect. . . . . . . . . . . . . . . . . 59Ventilation SystemForm ulas . . . . . . . . . . . . . . . . . . 63Ventilation A ir D uct Sizing . . . . . . . . . . . . . . . . . . . . 65C om bustion A ir Form ulas . . . . . . . . . . . . . . . . . . . . 67Sizing C om bustion A ir D ucts. . . . . . . . . . . . . . . . . . 69Exhaust SystemForm ulas . . . . . . . . . . . . . . . . . . . . 71A PI G ravity C orrection for Tem perature . . . . . . . . . 77Fuel System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81Lubrication System . . . . . . . . . . . . . . . . . . . . . . . . . 95C ooling System . . . . . . . . . . . . . . . . . . . . . . . . . . . 113M ounting &A lignm ent. . . . . . . . . . . . . . . . . . . . . . 133Vibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141Sea Trial. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147C onversion Factors . . . . . . . . . . . . . . . . . . . . . . . . 167Physics Form ulas. . . . . . . . . . . . . . . . . . . . . . . . . . 183C om m on Term s and D efinitions. . . . . . . . . . . . . . . 185C orrosion A ppendix A . . . . . . . . . . . . . . . . . . . . 191D iagnostic C odes A ppendix B . . . . . . . . . . . . . 1992Formula for Calculating Horsepower2 TO R Q U E R PMH orsepow er =_____________________33000This form ula w as established by Jam es W att in the1800s and requires som e know n values:Average horse w alks at 212M PHAverage horse pulls w ith a force of 150 pounds1 m ile =5,280 feetW ith this background, w e w ill be able to establish theH orsepow er form ulas used today.5,280 feet212M PH=13,200 FEET per H O U R13200 FT/H R____________=220 FEET per M IN U TE60 M inutes220 FT/M IN 150 PO U N D S =33,000 FT. LB SperM IN U TE2 =6.283185333000__________=52526.2831853Thus w e get the fam iliar form ula used today in calcu-lating H p.Torque R PMH p =_____________or expressed another w ay as5252H p 5252Torque =__________R PM3Displacement Hull CalculationIf a vessels displacem ent is not know n, it can be deter-m ined fromthe dim ensions of the vessel, using the fol-low ing form ula.L B D C bW=________________MW here:W = The vessels displacem ent expressed in long tonsL = The length of the vessel, in feet, m easured at theactual or designed load w aterline (LW L)B = The extrem e w idth or beamof the vessel, in feet,at the designed load w aterline.D = The vessels m olded draft, in feet, m easured atits m idship section, exclusive of appendages orprojections such as the keel.C b = The block coefficient for the vessel.Light C argo, Fishing Vesselsand Sailing yachts .40 .55H eavy C argo, Fishing and Tugs .50 .65R iver TowB oats .55 .70Self-propelled B arges .70 .90B arges .85 .90M = The volum e of w ater (cubic feet) per long ton35 for sea w ater36 for fresh w ater5Horsepower Requirements forDisplacement HullsAdisplacem ent hull is define by having a taper at thebow , a taper at the stern, and a14beambuttock angleof 8 degrees or greater.The speed w hich corresponds to SL =1.34 is referredto as the displacem ent hull lim iting speed. A ttem ptingto pow er a displacem ent hull above this speed w illcause the stern of the vessel to dropinto its ow n boww ave troug h, exp osingthe oncom ingw ater to theunderside of the vessel and entraining air in the pro-peller. This w ill effectively cause the vessel to clim buphilland reduce the am ount of pow er the propeller iscapable of absorbing. This occurs at an SL =1.34 fora pure displacem ent vessel, and any attem pt to pow era displacem ent vessel in excess of this speed w ouldbe considered a w aste of fuel and m oney.N owthat the lim iting speed of a displacem ent hull isdefined, w e can predict the pow er requirem ents to pro-pel displacem ent hulls at different speeds.The am ount of pow er required to drive a displacem entor a sem i-displacem ent hull of a given w eight at a givenspeed can be approxim ated by the relationship of thew eight to the horsepow er (Lbs/H p). This is expressedas the form ula:10.665SL =______3Lbs____H pSL =Speed Length R atioH p =H orsepow er D elivered to the PropellerLbs =Vessel D isplacem ent in Pounds7This form ula can be rew ritten as :10.665______ 3 =Lbs/H p(SL)D ue to the boww ave lim itation discussed earlier, onlythe portion of the SL versus Lbs/H p relationship below1.34 applies to displacem ent hulls. This im plies that itw ould not be appropriate to pow er a displacem ent hullw ith m ore than 1 horsepow er delivered to the propellerfor each 504 pounds of vessel displacem ent.A n exam ple of howto apply this relationship w ill helpclear this up. C onsider a pure displacem ent hull w iththe follow ing characteristics:W aterline length = 200 feetVessel displacem ent = 440,000 pounds loadedD esired speed = 18 knots14beambuttock angle = 9 degreesW ith a14beambuttock angle of 9 degrees (greater than8), it can be assum ed that this vessel w ill be subjectto the speed lim it of 1.34.The next step is to see if the designed SL is w ithin thelim its established for a displacem ent hull, using theform ulaSpeed 18SL =______SL =_____SL =1.27W L 200 Since the 1.27 calculated SL is belowthe lim it of 1.34the speed of 18 knots for this vessel is attainable.8The next step is to determ ine the Lbs/H p relationship forthis boat using the design SL of 1.27. This is done usingthe follow ing form ula:10.665 10.665______ 3 =Lbs/H p______ 3=592 Lbs/H p(SL) (1.27)The pow er required to drive this vessel at 18 knotsw ould then be:440000 LbsH p =___________592 Lbs/H pH p =743This horsepow er requirem ent seem s low , but it m ust beconsidered that this is the required horsepow er deliv-ered to the propeller, and it does not account for lossesin the shafting, m arine gear, and engine. It also doesnot allowfor reserve horsepow er to allowfor addedresistance due to w ind and w aves, tow ing, draggingnets, pow er takeoffs, or other load increases, w hichm ay occur. In actuality, the installed horsepow er of thisvessel m ay be higher than the 743 H p requirem ent justcalculated.9Horsepower Requirements forSemi-Displacement HullsB ecause of the w ay these hulls ride in the w ater, thecalculations of required horsepow er uses a differentform ula. Asem i-displacem ent hull is defined as havinga point at the bowand tapers to a full beamat the m id-section and then partially tapers to a narrowsection atits stern. Asem i-displacem ent hull can be describedas a displacem ent hull w ith a portion of its after bodycut off, or a planing hull w ith a portion of a tapered afterb od y ad d edon. S em i-d isp lacem ent hulls can b eexpected to have a14beambuttock angle of betw een2 and 8.Sem i-displacem ent vessels have displacem ent hullcharacteristics in that they are som ew hat lim ited inattainab le sp eedb y the b oww ave p henom enon.H ow ever, sem i-displacem ent hulls also have som eplaning hull characteristics, w hich allowthemto par-tially clim bor plane out of the w ater at higher speeds.This partial planing characteristic causes the boww avelim itation to occur at higher speed length ratios. In gen-eral, speed-length ratios fall betw een roughly 1.4 and2.9 for sem i-displacem ent vessels. Effectively, sem i-displacem ent hulls operate at higher speeds than dis-p lacem ent hulls b ecause of their p artial p laningcharacteristics, yet are not as sensitive to w eight addi-tion as a planing hull, due to their partial displacem enthull characteristics. These com bined characteristicsallowfor relatively large cargo or passenger carryingcapacity at speeds higher than displacem ent vesselsof sim ilar size.To determ ine the pow er requirem ents for a sem i-dis-placem ent hull, the SL versus Lbs/H p relationship is uti-lized in the sam e m anner as w ith displacem ent hulls.The problemin applying this relationship to sem i-dis-placem ent hulls, how ever, lies in the fact that the lim it-ing speed-length ratios can vary betw een 1.4 and 2.9for different hulls. B efore attem pting a pow er require-m ent calculation for a sem i-displacem ent hull at a givenspeed, it is first necessary to determ ine the SL ratio lim it11for the vessel to ensure that no attem pt is m ade topow er the vessel to speeds higher than this lim it.The lim iting SL ratio for a sem i-displacem ent hull isdeterm ined by evaluating a factor referred to as theD isplacem ent Length R atio (D L). The D L ratio can bedefined by using the follow ing form ula:disp TD L =_________(.01XW L)3W here:D L = D isplacem ent-length ratiodisp T = displacem ent in long tons(1 long ton =2240 pounds)W L = W aterline length in feetO nce the D L ratio has been calculated for a sem i-dis-placem ent hull, the SL to D L relationship can be appliedto determ ine the lim iting SL ratio. This SL ratio w ill thendefine the m axim umattainable speed of the sem i-dis-placem ent hull. N o attem pt should be m ade to pow era vessel over this m axim umattainable speed, as this isthe point w here the boww ave lim itation occurs an asem i-displacem ent hull.The lim iting SL can be defined using the follow ingform ula:8.26SL ratio =_____D L.311W here:SL ratio = Speed-length ratioD L ratio = D isplacem ent-length ratio8.26 = constant used by C aterpillarfor this calculation12The follow ing exam ple w ill help explain howto applythe form ulas for calculating the horsepow er requiredfor a sem i-displacem ent hull.Lets use the follow ing for boat characteristics:W L = 62 feet14beambuttock angle = 3D isplacem ent tons = 44 Long tons(98,560 pounds)D esigned speed = 11.5 knotsB eamw idth = 18 feet at m id-section,tapering to 15 feet at thestern.B ased on this inform ation (3 and slight taper) w e canrecognize a sem i-displacem ent hull. Since this is asem i-displacem ent vessel and the D L ratio applies, theD L ratio m ust first be calculated in order to determ inethe lim iting SL ratio for this vessel. The D L ratio is cal-culated in the follow ing form ula:44D L =__________(.01 62)3D L =184.6 1858.26SL =_______(185).311SL =1.628 1.63A ny speed used in predicting a pow er requirem ent forthis vessel m ust correspond to an SL less than 1.63.1.63 SL ratio corresponds to the m axim umpossiblespeed of this vessel due to boww ave lim itation.Since the m axim umSL ratio is 1.63 has been calcu-lated the next step is to determ ine the pow er requiredto drive the vessel 11.5 knots. A s a check before pro-ceeding, the SL ratio corresponding to the design13speed of the boat should be calculated to ensure thatit is less than the m axim umattainable SL of 1.63.11.5SL =_____62SL =1.46Since 1.46 is less than 1.63, it is appropriate to try topow er this vessel for 11.5 knots. If the SL had beengreater than the 1.63 m axim umattainable SL then thedesign speed of the vessel w ould have to be reducedbefore attem pting a pow er prediction.K nowthat w e have the design SL (1.46) w e can go tothe form ula used in the displacem ent hull problem . Thatform ula w as:10.6653LB /H p =______(SL)10.6653LB /H p =______(1.46)LB /H p =389.8 39098560 Lbs for vesselH P =___________________390 LB /H pH p =252.7 253 H pSo to pow er this vessel to the 11.5 knots design speedit w ould need 253 H p to the propeller. This is only for them ovem ent of the vessel through the w ater and doesnot take into account auxiliary driven equipm ent, roughseas, or strong currents. There for the actual H p of theengine in the boat m aybe larger than this calculation,due to the reserve H p requirem ents.14Horsepower Requirementsfor Planing HullsAplaning hull is a hull of a formw hich allow s it to clim bup on a full plane at high speeds. W hen up on a fullplane, the reduced draft of the vessel causes the boww ave to becom e very sm all, and they do not lim it thespeed of the boat as w ith displacem ent and sem i-dis-placem ent hulls. B ecause of the reduced draft and lackof a boww ave lim itation w hile up on plane, planing hullscan achieve very high speeds. H ow ever, their perfor-m ance is very sensitive to the addition of w eight to theboat.Aplaning hull begins w ith a point at its bow , and tapersto full beamat its m idsection, then continues aft w ithno taper or at m ost a slight taper. The planing hull alsohas a14beambuttock angle 2 or less.Very fewaccurate m ethods exist for determ ining pow errequirem ents and speed predictions on full planinghulls. O ften tim es, planing hulls are equipped w ithengines based on past experience and tested duringsea trials to determ ine their level of perform ance. O nesim ple m ethod in existence for estim ating planing hullsp eedpotential is referred to as C rouchs PlaningSpeed Form ula. The form ula is:CSpeed =_______Lbs/H pSpeed = B oat speed in knotsC = C oefficient D efining H ull SpeedLbs = Vessel W eight in PoundsH p = H orsepow er D elivered to the Propeller15This form ula develops a pow er to speed relationshipfor planing hulls, and experim entation has determ inedw hich coefficients should be utilized to obtain accept-able results. The typical coefficients used at C aterpillarare:150 =average runabouts, cruisers, passenger vessels190 =high speed runabouts, light high-speed cruisers210 =race boatsThe follow ing exam ple w ill help explain howall of thisw orks.Lets use a boat w ith a displacem ent of 14,000 pounds.The boat has a narrowbeam , deep vee planing hullpow ered by tw o (2) 435 H p diesels. The boat is equippedw ith perform ance propellers and lowdrag stern drives,so w e can consider the boat a race type. It w ill there-fore have a C coefficient of 210.First lets take the H p of the engines 435 2 =870.Then w e m ust take into account the reduction gear effi-ciency, typically 3% . 870 H p .97 =844 H p availableLbsto the propellers. Then w e determ ine the____byH pdividing the boat displacem ent by the horsepow er14000 Lbsavailable. In our case Lbs/H p =_________or844 H pLbs/H p =16.59. N owthat w e have our Lbs/H p w e cancalculate the speed of the boat using C rouchs PlaningSpeed Form ula.210Speed =_______Speed =51.56 K nots16.59Lets say this custom er w ants 60 knots. W e can calculatethe needed H p by using the inform ation fromthe pre-vious form ula and w orking out the answ er. The form ulaCfor this w ould be______=X. Then Lbs/ H p =X2Speed16Putting the data in fromthe previous form ula w e get thefollow ing:210____=3.50260 Lbs/H p =12.25Since the w eight of the boat is 14,000 pounds, w e candivide the w eight of the boat by the Lbs/H p ratio of12.25 to get the H p needed to operate the vessel at the60 knot speed.14000 Pounds_____________=1,143 H p required.12.25 Lbs/H p17Hull Speed vs Wave PatternM iles per H our 1.15 =K notsK nots 101.3 =Feet per M inuteM iles per H our 88 =Feet per M inuteVSPEEDLEN G THR ATIO(SLR ) =______LW LW here:V = Vessel SpeedLW L = Loaded w aterline lengthThe generally accepted SLRlim its are as follow s:D isplacem ent type hulls = SLR1.34Sem i-displacem ent type hulls = SLR2.3 2.5Planing hulls = N o specific highlim it, but not goodbelowa SLRof 2.0The m axim umvessel speed can be calculated usingthe follow ing form ula:V =SLR LW LThe m axim umvessel speed can also be estim ated byw atching the w ave action along a displacem ent hulltype of the vessel. W hen the crest to crest distance ofthe boww ave is equal to the LW L of the vessel, the hullis at its optim umspeed. If the boww ave crest to crestdistance is equal to12the LW L then the vessel is atapproxim ately12the optim umhull speed.Econom ical speed for displacem ent type vessels is inthe SLRrange of 1.0 to 1.2. The crest to crest distancefor an SLRof 1.0 is (.56)(LW L). The crest to crest dis-tance for an SLRof 1.2 is (.8)(LW L)19Basic Propulsion TheoryThe essence of m arine propulsion is the conversion ofengine pow er into thrust through som e type of propul-sion device. B ecause of its sim plicity and efficiency,the screwpropeller basically an axial flowpum p hasbecom e the m ost w idely used propulsive device.PropellersThe ability of a propeller to m ove a vessel forw ard,through the w ater, depends upon several factors:1. The rotational speed of the propeller, w hich corre-sponds to the propeller shaft R PM ;2. The angle or pitch of the propeller blades;3. The diam eter and blade area.These factors, in com bination im pose a thrust force onthe propeller shaft. This thrust is transm itted through theshaft to the thrust bearing, the principle point w herethe forces generated by the rotating propeller act uponthe hull, and cause forw ard m otion.21FIGURE 1Figure 1 show s a typical 3-bladed propeller. To m oreintelligently understand the operation of a screwpro-peller, it is necessary to define the parts of a propeller:The blade does the w ork; it pulls w ater. N aturally, thew ider the blade face, the m ore w ater it can pull. Them ore w ater that can be pulled, the stronger the thruston the vessel and therefore, a greater am ount of w orkcan be done.Propeller diam eteris the diam eter of the circle describedby the tips of the rotating propeller blades.22B lade A ngle is the angle the blade m akes in relationto the center line of the hub. It is norm ally expressedas the distance, in inches. Pitch is the distance theblade w ould advance in one revolution, if it w ere ascreww orking in a solid substance.A n im portant concept in understanding propellers isthe pitch ratio. The pitch ratio expresses the relationbetw een the pitch and the diam eter of the propeller;often it is referred to as the pitch/diam eter ratio. It isobtained by dividing the pitch by the diam eter. Forexam ple, if a propeller is 60 inches in diam eter and has42 inches of pitch (w ritten as 60" 42") then the pitchratio is 42/60 =0.70.Ageneral guide for the selection of approxim ate pitchratio values is show n, by vessel application, in Figure 2.PITCH RATIO BY VESSEL APPLICATIOND eep w ater tug boat .50 .55R iver tow boat .55 .60H eavy round bottomw ork boat .60 .70M ediumw t. round bottomw ork boat .80 .90Planing hull .90 1.2FIGURE 223The propeller m ay be view ed as an axial pum p that isdelivering a streamof w ater aft of the vessel. It is thisstreamof w ater, equivalent in size to the diam eter ofthe propeller, that is the pow er that provides thrust tom ove the vessel through the w ater. H ow ever, to pro-duce thrust, the propeller m ust accelerate the m ass ofw ater it pulls against. In so doing, a portion of the pitchadvance is lost to the w ork of accelerating the w aterm ass. This is know n as propeller slip; Figure 3 illus-trates this concept.FIGURE 3Apropeller w ith a fixed pitch theoretically has a pitchvelocity or linear speed it w ould travel in the absenceof slip. H ow ever, because of the w ork needed to accel-erate a m ass of w ater, slip m anifests itself as the dif-ference betw een the pitch velocity and the velocity ofthe propeller through the vessels w ake or speed ofadvance.PITCH VELOCITY(THEORETICAL VELOCITY)VELOCITY OF THE PROPELLERTHROUGH THE VESSEL'S WAKESLIPAPPARENTSLIPWAKEVESSEL SPEED(SPEED OF ADVANCE)24A s a vessel m oves through the w ater, hull resistance,w ave form ation and converging w ater at the stern havea tendency to followthe hull. This results in a m ovem entof w ater under the stern in a forw ard direction know nas w ake. The added factor of w ake reduces slip to w hatis know n as apparent slip. It also adds to the speed ofadvance to produce the actual vessel speed. It is obvi-ous fromthis that propellers function in a very com plexm anner. There are m any factors to be considered w henselecting a propeller. The point to realize is that there isno form ula that w ill autom atically provide the ideal pro-peller size for a given vessel and application. This canonly be approxim ated to various degrees of accuracy.The only true test is trial and error under actual operatingconditions. R em em ber, all propellers are a com prom ise.The general practice is to use the largest diam eter pro-peller turning at the best speed for the vessels appli-cation w ithin practical lim its. These lim itations are:1. The size of the aperture in w hich the propeller is tobe installed.2. The application or type of w ork the vessel w ill bedoing tow boat, crewboat, pleasure craft, and soforth.3. Excessive shaft installation angles that m ay be re-quired w hen using large diam eter propellers.4. The size of shafting that can be accom m odated bythe structural m em bers of the hull w here the shaftpasses through.5. C om parative w eight of propellers, shafts and m arinegears w ith respect to the size of the vessel.6. The size of m arine gears w hich the hull can accom -m odate w ithout causing an inordinate degree ofshaft angularity.7. The vessels inherent ability to absorb the high torquethat results fromthe use of large slowturning propellers.8. C om paring the cost of using large diam eter propellersagainst any increases in efficiency or perform ance.25Number Of Propeller BladesIn theory, the propeller w ith the sm allest num ber ofblades (i.e. tw o) is the m ost efficient. H ow ever, in m ostcases, diam eter and technical lim itations necessitatethe use of a greater num ber of blades.Three-bladed propellers are m ore efficient over a w iderrange of applications than any other propeller. Four andsom etim es five-bladed propellers are used in casesw here objectionable vibrations develop w hen using athree-bladed propeller.Four-bladed propellers are often used to increase bladearea on towboats operating w ith lim ited draft. They arealso used on w ooden vessels w here deadw ood aheadof the propeller restricts w ater flow . H ow ever, tw o bladespassing deadw ood at the sam e tim e can cause objec-tionable hull vibration.A ll other conditions being equal, the efficiency of a four-blade propeller is approxim ately 96%that of a three-blade propeller having the sam e pitch ratio and bladesof the sam e proportion and shape. Arule of thum bm ethod for estim ating four-blade propeller requirem entsis to select a proper three-blade propeller frompro-peller selection charts, then m ultiply pitch for the three-b lad e p rop eller b y .914. M axim umd iam eter of afour-blade propeller should not exceed 94%of the rec-om m ended three-blade propellers diam eter. Therefore,w e m ultiply diam eter by .94 to obtain the diam eter of afour-blade propeller.For exam ple, if a three-blade recom m endation is:48 34M ultiply pitch (34") by .914 =31"M ultiply diam eter (48") by .94 =45"Four-blade recom m endation 45" 31"26A s a w ord of caution, rem em ber that this is a generalrule...for estim ating only. D ue to the w ide variation inblade area and contours fromdifferent propeller m an-ufacturers, consult your particular m anufacturer beforefinal specifications are decided upon.AR ule of the Thum bfor all propeller selection is:Tow boats big w heel, sm all pitchSpeedboats little w heel, big pitchA ll other applications can be shaded betw een thesetw o statem ents of extrem es.Propeller Tip SpeedTip speed, as the nam e im plies, is the speed at w hichthe tips of a rotating propeller travel in m iles per hour(M PH ). The greater the tip speed, the m ore pow er con-sum ed in pure turning. As an exam ple, a 30 inch propellerw ith a tip speed of 60 M PHabsorbs approxim ately 12horsepow er in pure turning effort. This is a net horse-pow er loss because it contributes nothing to the for-w ard thrust generated by the propeller.The follow ing form ula can be used to calculate tipspeed:D SH A FT R PM 60 T =_________________________12 5280W here:T = Tip speed in M PHD = Propeller diam eter in inches27CavitationW hen propeller R PMis increased to a point w here suc-tion ahead of the propeller reduces the w ater pressurebelowits vapor pressure, vapor pockets form , inter-rupting the solid flowof w ater to the propeller. This con-dition is know n as cavitation.O ne of the m ore com m on causes of cavitation is exces-sive tip speed, a propeller turning too fast for w ater tofollowthe blade contour. C avitation can usually beexpected to occur at propeller tip speeds exceeding130 M PH . C avitation results in a loss of thrust and dam -aging erosion of the propeller blades.1:1 1.5:1 2:1 2.5:13:1 4:1 4.5:1 5:1 6:1 7:1 8:1 9:1 10:1TYPICAL REDUCTION RATIOSLOWSPEEDPLANINGBOATSLOWSPEEDDISPLACEMENTBOATS28Reduction GearsThe reduction gear enables the propulsion engine andpropeller to be m atched so they both operate at theirm ost efficient speeds.The proper selection of the reduction gear ratio is anim portant decision in preparing a m arine propulsionsystem . There is a range of com m ercially availablereduction ratios that can help assure optim umvesselperform ance under a given set of operating conditions.It is difficult to discuss the selection of reduction gearratios w ithout m entioning som e of the other factors thatcan influence the selection. The m ajor influencing fac-tors are:Expected vessel speed Type of vesselVessel duty cycle Pitch R atioPropeller tip speed Engine horsepow erOUTBOARD TURNING PROPELLERSLWLLEFT HANDROTATIONRIGHT HANDROTATIONAHEADROTATIONINBOARD TURNING PROPELLERSRIGHT HANDROTATIONLEFT HANDROTATIONAHEADROTATIONLWL29Propeller OverhangThe m axim umdistance fromthe stern bearing to thepropeller should be lim ited to no m ore than one shaftdiam eter. Propeller shafts are apt to vibrate and pro-duce a w hip action if these lim its are exceeded. Thiscondition is greatly accelerated w hen a propeller is outof balance due to faulty m achining or dam age.Propeller RotationPropeller rotation is determ ined frombehind the ves-sel, facing forw ard. The starboard side is on the rightand the port side on the left. R otation of the propeller isdeterm ined by the direction of the w heel w hen the ves-sel is in forw ard m otion. Thus, a clockw ise rotationw ould describe a right-hand propeller and a counter-clockw ise rotation w ould be a left-hand propeller.R ight-hand propellers are m ost frequently used in sin-gle screwinstallations. Tw in screwvessels in the U .S.are norm ally equipped w ith outboard turning w heels.H ow ever, there are som e installations w here inboardturning w heels w ill be found. Arotating propeller tendsto drift sidew ays in the direction of the rotation. In a sin-gle screwvessel this can be partially offset by thedesign of the sternpost and the rudder. In a tw in screwvessel this can be com pletely elim inated by usingcounter-rotating propellers. A lthough the question ofinboard and outboard rotating propellers has beendebated m any tim es, authorities on the subject agreethat there are no adverse effects on m aneuverabilityw ith either rotation. In fact, there are those w ho feel thata gain in m aneuverability is obtained w ith outboardrotating propellers. O ne point in favor of inboard rota-tion is a decreased tendency for the propellers to pick-up debris off the bottomin shalloww ater.30Multiple PropellersThe m ost efficient m ethod of propelling a vessel is bythe use of a single screw . H ow ever, there are other fac-tors w hich, w hen taken into consideration, m ake theuse of a single propeller im possible. If a vessel has tooperate in shalloww ater, the diam eter of the propelleris lim ited. Therefore, it m ay be necessary to install tw oand som etim es three propellers to perm it a proper pitchratio for efficient propulsion.Another condition requiring m ultiple propellers is encoun-tered w hen higher speed yachts need m ore horse-pow er than a single engine can develop and still beaccom m odated in the engine space. A s a general ruleto followfor calculations in this text, the total SH P of allengines is used w hen m aking estim ated speed calcu-lations. For calculating propeller size, SH P of each indi-vidual engine is used.31Propeller Pitch CorrectionA n overpitched propeller w ill overload the engine. Toperm it the engine to reach its Full pow er and speed theload m ust be rem oved. The load m ust be reduced byam ount proportional to the engine R PMratio. This canbe defined by the follow ing form ula:R PM 1LF =______R PM 2W here:LF = %of LoadR PM 1 = The engine R PMw hile overloaded W hat youhave.R PM 2 = The anticipated engine R PMW hat you w antto have.EXAMPLE FORMULAThe M /V C at has an engine that produces Full pow erat 1800 engine R PM . W hile being tested the enginew ould only turn to 1750 R PM . A pplying the above for-m ula w e get the follow ing equation:1750LF =_____1800LF =.97 100LF =97%This m eans to get the engine to turn the correct R PMw ew ould have to reduce the load by 3% . If the overloadis due to an overpitched propeller then the am ount ofpitch to be taken out of the current propeller can bedeterm ined using the follow ing form ula:R PM 1Pr =Pp ______R PM 233W here:Pr = Propeller pitch requiredPp = Present propeller pitchR PM 1 = The engine R PMw hile overloaded W hat youhave.R PM 2 = The anticipated engine R PMW hat you w antto have.Ducted propellersD ucted propellers are best used on vessels such astraw lers, tugs, and tow boats w ith tow ing speeds of 3-10knots. D ucted propellers should not be used on vesselsw ith relative high speeds.To help assist in the selection of a ducted propeller, youcan performthe follow ing calculation. If the resultantB p is < ( less than) 30, the use of a ducted propellershould not be considered as it m ay result in a net lossof vessel perform ance.SH PB p =SR PM ______(Va)2.5W here:B p = B asic Propeller D esign VariableSR PM = Propeller Shaft Speed, R PMSH P = Shaft H orsepow erVa= Velocity of A dvance of the propeller (knots)generally equals 0.7 to 0.9 tim es boat speed.34Propeller Formulasand RelatedTables(5252 H p) H p =H orsepow erTorque =____________R pm Rpm= Revolutions per m inutePropeller Horsepower Curve FormulaPH p =Csm R pmnCsm= summ atching constantn= exponent from2.2 to 3.0, w ith 2.7 being usedfor average boatsR pm = R evolutions per m inuteDisplacement Speed Formula10.665SL R atio =______3LB____SH PW here:SL R atio =Speed-Length R atioandK nts.SL R atio =_____W LK nts = Speed in knots =B oat speed or VSH P = Shaft H orsepow er at propellerLB = D isplacem ent in poundsW L = W aterline length in feet35Displacement Length Ratio Formuladisp TD L R atio =___________(00.01XW L)3W here:disp T = D isplacem ent in long tons of 2,240 pounds,m t =1.016 long tonsW L = W aterline length in feetMaximum Speed-Length Ratiovs DL Ratio Formula8.26SL R atio =______3.215D L R atioW here:SL = Speed-length ratioD L = D isplacem ent-length ratioCrouchs Planing Speed FormulaCK nts =________Lb/SH PW here:K nts = Speed in knots =B oat Speed =VC = C onstant chosen for the type of vessel beingconsideredLB = D isplacem ent in poundsSH P = H orsepow er at the propeller shaftThe speed predicted by this formula assumes a pro-peller has been selected that gives between 50%and 60% efficiency, with 55% a good average.36Analysis Pitch Formula101.33VaP0=________N0W here:Va= Speed in knots through w ake at zero thrustN0= Shaft R pmat zero thrustPitch Ratio FormulaPitch R atio =P/DW here:P = PitchD = D iam eterTheoretical Thrust FormulaThrust =Force =FWF =M Aor F =__ (V0V1)gW here:W = W eight in pounds the colum n of w ater acceler-ated astern by the propellerg = the acceleration of gravity, 32.2 ft/sec.V0= velocity of w ater before entering the propeller infeet per secondV1= velocity of w ater after leaving propeller in feet persecondM = M ass in slugsA = A cceleration in feet per second squared37Developed Area to Projected Area FormulaA p___=1.0125 (0.1 PR ) (0.0625 PR2)A dW here:A p___=A pproxim ate ratio of projectedarea to developed areaA dPR =Pitch ratio of propellerMean-Width Ratio FormulaM ean-W idth R atio =M W RAverage B lade W idth,M W R=____________________orDExpanded A rea of O ne B ladeM W R=___________________________ DB lade H eight fromR oot to TipW here:D=D iam eterDisc-Area RatioD2D isc A rea =____or 0.7854D24D isc-A rea R atio =D A RExpanded A rea of all B ladesD A R=__________________________D isc A reaW here:D = D iam eter 3.141238Disc-Area Ratio vs Mean-Width RatioD A R=N um ber of B lades 0.51 M W RorD A RM W R=________________________N um ber of B lades 0.51W here:D A R = D isc-area ratioM W R = M ean-w idth R atioNote:These ratios assume a hub that is 20% of over-all diameter, which is very close to average. Smallpropellers for pleasure craft may have slightlysmaller hubs, while heavy, workboat propellers, par-ticularly controllable-pitch propellers, may haveslightly larger hubs.Developed Area vs Disc-Area Ratio FormulaD2A d = __ D A R(2)Developed Area vs Mean-Width Ratio FormulaD2A d = __ M W R 0.51 N um ber of B lades(2)w here for both the above form ulas:A d = D eveloped A reaD = D iam eterD A R = D isc-area ratioM W R = M ean-w idth ratio 3.141239Developed Area for Any Hub Diameterand MWR FormulaDA d =M W R D (1 H ub% )__N um ber ofB lades2orD2A d =M W R __ (1 H ub% ) N um ber of B lades2W here:A d = D eveloped A reaM W R = M ean-w idth ratioD = D iam eterH ub % = M axim umhub diam eter divided by overalldiam eter, DBlade-Thickness Fraction Formulat0B TF =__DW here:B TF = B lade-Thickness FractionD = D iam etert0= M axim umB lade Thickness as Extended to ShaftC enterline40Rake Ratio Formula___B OR ake R atio =___DW here:___B O = D istance betw een tip of blade projected dow n tothe shaft centerline and face of blade extendeddow n to shaft centerlineD = D iam eterApparent Slip FormulaP__ R PM(K nts 101.3)(12)Slip A=__________________________P__ R PM(12)W hich can be restated as:K nts 1215.6P =_________________R PM (1 Slip A )W here:Slip A = A pparent SlipP = Propeller face pitch in inchesK nts = B oat speed through the w ater or V in K notsR PM = R evolutions per m inute of the propeller41Slip vs Boat Speed Formula1.4Slip =_______K nts0.057W here:K nts =B oat speed in knotsDIA-HP-RPM Formula632.7 SH P0.2D=______________R PM0.6W here:D = Propeller diam eter in inchesSH P = Shaft H orsepow er at the propellerR PM = Shaft R PMat the propellerOptimum Pitch Ratio FormulasAverage Pitch R atio = 0.46 K nts0.26M axim umPitch R atio = 0.52 K nts0.28M inim umPitch R atio = 0.39 K nts0.23These formulas have been found to check well witha wide variety of vessels.42Minimum Diameter FormulaDm in=4.07 (B W L Hd)0.5Dm in= M inim umacceptable propeller diam eter in inchesB W L = B eamon the w aterline in feetHd= D raft of hull fromthe w aterline dow n (exclud-ing keel,skeg or deadw ood) in feet(Hull draft is the depth of the hull body to the fair-body line, rabbet, or the hulls intersection with thetop of the keel. It thus excludes keel and/or skeg.)Dm infor tw in screw s = 0.8 Dm inDm infor triple screw s = 0.65 Dm inAllowable Blade Loading FormulaPSI =1.9 Va0.5 Ft0.08W here:PSI = Pressure, in pounds per square inch, at w hichcavitation is likely to beginVa= The speed of the w ater at the propeller in knotsFt = The depth of im m ersion of the propeller shaftcenterline, during operation, in feet43Actual Blade Loading Formula326 SH P ePSI =_______________Va A dW here:PSI = B lade loading in pounds per square inchesSH P = Shaft H orsepow er at the propellere = Propeller efficiency in open w aterVa= Speed of w ater at the propeller, in knotsA d = D eveloped area of propeller blades, in squareinchesThrust Formula326 SH P eTA=_______________VaW here:T = ThrustSH P = Shaft H orsepow er at the propellere = Propeller efficiencyVa= Speed of w ater at the propeller, in knots44Approximate Bollard Pull FormulaDTs=62.72 (SH P __)0.6712Ts= Static thrust or bollard pull, in poundsSH P = Shaft H orsepow er at the propellerD = Propeller diam eter in inchesThis form ula can also be expressed as:Tston =0.028 (SH P Dft)0.67Tston = Thrust in long tons of 2240 poundsSH P = Shaft H orsepow erDft= Propeller diam eter, in feetTaylor Wake Fraction FormulaV VaW t =______VorVa=V (1 W t)W here:W t = Taylor w ake fractionV = B oat speed through the w aterVa= Speed of the w ater at the propellerWake Factor FormulaW f =1 W t45Speed of Advance FormulaVa=V W fW here:V = B oat SpeedW f = W ake FactorW t = Taylor W ake FractionWake Factor vs Block Coefficient Formulasfor vessels with a SL Ratio of under 2.5Single ScrewW f =1.11 (0.6 C b)Tw in ScrewW f =10.6 (0.4 C b)W here:W f = W ake factor (percent of V seenby the propellerC b = B lock coefficient of the hull.Block Coefficient FormulaD isplacem entC b =_____________________________W L B W L Hd 64 Lb/cu.ft.W here:D isplacem ent = Vessel displacem ent, in poundsW L = W aterline length, in feetB W L = W aterline beam , in feetHd= H ull draft, excluding keel, skeg ordeadw ood, in feet46Wake Factor vs Speed FormulaW f =0.83 K nts0.047W here:W f = W ake FactorK nts = Speed in knotsPower Factor Formula(SH P)0.5 NB p =____________Va2.5W here:B p = Pow er FactorSH P = Shaft H orsepow er at the propellerN = N um ber of shaft revolutionsVa= Speed of advance of the propeller through thew akeAdvance Coefficient FormulaN Dft =_______VaorN D =_______12 Va47This m ay also be restated as: =Va 12D=___________,NW here: = A dvance coefficientN = Shaft R PMDft= Propeller diam eter in feetD = Propeller diam eter in inchesVa= Speed of advance of the propeller through thew akeDisplacement Speed with Efficiency Formula10.665SL R atio =______3LB____SH PW here:SL R atio = Speed-length ratioLB = D isplacem ent in poundsSH P = Shaft horsepow er at the propeller = Propeller efficiencyIf the speed in knots is already know n, w e can m ultiplythe speed directly by3____0.553____0.5548Planing Speed With Efficiency FormulaCK nts =______LB____SH PW here:K nts = B oat speed in knotsLB = D isplacem ent in poundsSH P = Shaft horsepow er at the propeller = Propeller efficiencyIf the speed in knots is already know n, w e can m ultiplythe speed directly by3____0.55Shaft Diameter Formula Solid TobinBronze Propeller Shafts 3321000 SH P SFD s =___________________St R PMD s = Shaft D iam eter, in inchesSH P = Shaft H orsepow erSF = Safety factor (3 for yachts and light com m ercialcraft, 5 to 8 for heavy com m ercial craft and rac-ing boats)St = Yield strength in torsional shear, in PSIR PM = R evolutions per m inute of propeller shaft3____0.5549Shaft Diameter Formula forMonel 400 Propeller Shafts 3321000 SH P SFD s =___________________ .80St R PMD s = Shaft D iam eter, in inchesSH P = Shaft H orsepow erSF = Safety factor (3 for yachts and light com m ercialcraft, 5 to 8 for heavy com m ercial craft and rac-ing boats)St = Yield strength in torsional shear, in PSIR PM = R evolutions per m inute of propeller shaftShafts made of Monel 400 should be reduced by20% the size shaft required for a solid Tobin Bronzeshaft.Shaft-Bearing Spacing Formula3.21 D s4EFt =_______________R PM D ensW here:Ft = Shaft-bearing spacing, in feetD s = Propeller shaft diam eter, in inchesR PM = Propeller shaft speed, in revolutions per m inuteE = M odulus of elasticity of shaft m aterial, in PSID ens = D ensity of shaft m aterial, in pounds per cubicinch50Propeller Weight Formulas (with 0.33 meanwidth ratio and a hub diameter of 20%)Three-Bladed Propeller WeightW gt =0.00241 D3.05Four-Bladed Propeller WeightW gt =0.00323 D3.05W here:W gt = W eight of propeller in poundsD = D iam eter of propeller in inchesBrake Horsepower vs LOA Formula TugsLO A4.15B H P =100 +_______(111000)W here:B H P = M axim umbrake horsepow er of engineLO A = Length overall of the tug at w aterline, in feelTowing Speed vs Brake Horsepower FormulaK nts =1.43 B H P0.21W here:K nts = Average speed in knots during average towB H P = M axim umbrake horsepow er of engine51D.W.T. of Barges Towed vs BHP FormulasLowD .W .T. =(1.32 B H P) 255.25Avg D .W .T. =(3.43 B H P) 599.18H igh D .W .T. =(5.57 B H P) 943.10W here:D W T = D eadw eight tons of barges tow edB H P = M axim umbrake horsepow er of engine52Rules of Thumb forPropeller Selection1. One inch in diameter absorbs the torque of twoto three inches of pitch. This is a good rough guide.B oth pitch and diam eter absorb the torque gener-ated by the engine. D iam eter is, by far, the m ostim portant factor. Thus, the ratio of 2 to 3 inches ofpitch equals 1 inch of diam eter is a fair guide. It isno m ore than that, how ever. You could not select asuitable propeller based only on this rule.2. The higher the pitch your engine can turn neartop horsepower and RPM, the faster your boatcan go. This is accurate as far as it goes. The greaterthe pitch, the greater the distance your boat w illadvance each revolution. Since top engine R PMisconstant, increasing the pitch m eans m ore speed.Then, w hy arent all propellers as sm all in diam eteras possible, w ith gigantic pitches?The answ er is sim ply that w hen the pitch gets toolarge, the angle of attack of the propeller blades tothe onrushing w ater becom es too steep and theystall. This is exactly the sam e as an airplane w ingsstalling in too steep a clim b. If the pitches and pitchratios selected are optim um , then w ithin these lim itsit is w orthw hile, on high-speed craft, to use the sm all-est diam eter and greatest pitch possible.3. Too little pitch can ruin an engine. This is quitetrue if the pitch and diam eter com bined are so lowthat it allow s the engine to run at speeds far over itstop rated R PM . N ever should the engine be allow edto operate at m ore than 103%to 105%of rated R PM ,w hile underw ay and in a norm aloperation. If yourengine exceeds that figure, a propeller w ith increasedpitch or diam eter is indicated.4. Every two-inch increase in pitch will decreaseengine speed by 450 RPM, and vice versa. This isa good rough guide for m oderate- to high-speedpleasure craft, passenger vessels, and crewboats.Like all rule of thum bs, though, it is no m ore than arough guide.535. A square wheel (a propeller with exactly thesame diameter and pitch) is the most efficient.This is not true! There is nothing w rong w ith a squarew heel; on the other hand, there is nothing specialabout it, either.6. The same propeller cant deliver both high speedand maximum power. This is true! Apropeller sizedfor high speed has a sm all diam eter and m axim umpitch. Apropeller sized for pow er or thrust has alarge diam eter. For som e boats you can com pro-m ise on an in-betw een propeller, but for either realspeed or real thrust there is little com m on ground.54Related Propeller TablesSuggested Shaft SpeedsRange ofType of Vessel SL Ratio Shaft RPMHeavy Displacement hulls(Tugs, Push boats,Heavy Fishing Vessels) Under 1.2 250 500Medium-to-LightDisplacement hulls(Fishing vessels, trawlers,workboats, trawler yachts) Under 1.45 300 1,000Semi-displacement Hulls(Crew boats, Patrol boats,motor yachts) 1.45 3.0 800 1,800Planing hulls (Yachts, fastcommuters and ferries,high-speed patrol boats) over 3.0 1,200 3,000 +Minimum Tip ClearanceMinimumTipRPM SL Ratio Clearance200 500 Under 1.2 8%300 1,800 1.2 2.5 10%1,000 and above over 2.5 15%High-speed Planing Craft over 3.0 20%55Shaft Material CharacteristicsYieldStrength inTorsional Modulus of DensityShear Elasticity Lb/Shaft Material PSI PSI Cu. In.Aquamet 22 70,000 28,000,000 0.285Aquamet 18 60,000 28,800,000 0.281Aquamet 17 70,000 28,500,000 0.284Monel 400 40,000 26,000,000 0.319Monel K500 67,000 26,000,000 0.306Tobin Bronze 20,000 16,000,000 0.304Stainless Steel 304 20,000 28,000,000 0.286Buttock Angle vs SL RatioButtock Angle Type Hull SL RatioLess than 2 Planing 2.5 or Higher2 8 Semi-displacement 1.4 2.9Greater than 8 Displacement 1.34 MaximumCrouchs Formula ConstantsC Type of Boat150 Average runabouts, cruisers, passenger vessels190 High-speed runabouts, very light high-speed cruisers210 Race boat types220 Three-point hydroplanes, stepped hydroplanes230 Racing power catamarans and sea sleds56Typical Slip ValuesSpeed PercentType of Boat in Knots of SlipAuxiliary sailboat, barges Under 9 45%Heavy powerboats, workboats 9 -15 26%Lightweight powerboats, cruisers 15 -30 24%High-speed planing boats 30 -45 20%Planing race boats, vee-bottoms 45 -90 10%Stepped hydroplanes, catamarans over 90 7%Typical Slip Values Twin ScrewSpeed PercentType of Boat in Knots of SlipAuxiliary sailboat, barges Under 9 42%Heavy powerboats, workboats 9 -15 24%Lightweight powerboats, cruisers 15 -30 22%57Onset of Shallow Water EffectA s all M arine A nalyst know , the desired depth of w aterto performa P.A .R . test is 212tim es the draft of the boat.This depth is a R ule of Thum bthat should keep youout of the shalloww ater effect. If, as is the case on m anyriver boats, the boat operates in w ater that is shallow erthan the desired (212), then the test is perform ed underactual w orking w ater depths. The follow ing inform ationw ill give you som e insight into howto determ ine if youare seeing the effects of shalloww ater on the load of theengine.The behavior of a boat in shalloww ater is am azing.There are tw o kinds of increases in resistance due torunning in shalloww ater.1. There is a slight, but m easurable, increase beginningw hen the boat advances into w ater w hose depth isone half to one quarter the length of the boat. A t highspeeds, it begins w hen the boat advances into w aterw hose depth is equal to the length of the boat.2. There is a phenom enal and sudden increase inresistance beginning w hen the speed of the boatequals 2.3 tim es the square root of the depth ofw ater in feet, or V =(2.3) H . In w hich, V =speedin knots and H=depth of w ater in feet. W hen V =(212) H , w e have alm ost reached the lim it at w hichthe boat can be driven in shalloww ater. W hen V =(3.36) H , w e are at the utm ost lim it of speed forthe boat unless the boat starts to plane, in w hichcase the boat begins to out run the w aves that nor-m ally w ould be produced in deep w ater. A s the boattravels faster than its w ave train, feww aves can beproduced; residual resistance decreases, and w ehave the phenom enon of full planing such as thecase of a sport fishing and pleasure craft.59V =2.3 HW here:V = Vessel speed in knotsH = W ater depth in feetCritical Speed at whichshallow water effect drops offV =3.36 HW here:V = Vessel speed in knotsH = W ater depth in feetLets take an exam ple of a 200 foot boat traveling at 15knots in deep w ater. A s it is m oving, it enters w aterabout 20 feet deep. Since w e knowthe boats speedand the w ater depth w e m ust solve for the unknow n =X. W e w ould use the follow ing form ula: V =(X) H or15 =(X) 20or =3.35. This m eans that the boatw ould slowdow n appreciably as the speed of the boatequals 3.35 tim es the square root of the depth of w ater.For our exam ple then this w ould be as follow s: V =(3.35) 20 or V = 14.98 knots. In other w ords, this boatis at the criticalspeed it can operate in the 20 foot w aterdepth. A t this point, unless the w ater depth increasesor the boat planes, it w ill suffer greatly fromthe effectsof shalloww ater.The w ake that is trailing the boat w ould be at approxi-m ately a 45 angle to the center of the stern, in deepw ater, w ill nowtake a position of 90to the centerline ofthe boat as it m oves into the shalloww ater. The enginesm ay begin to lug under the additional load and exces-sive vibration w ill becom e apparent throughout theboat.60B oat ow ners can w atch the angle of their w ake fromthestern to see w hen they are getting loading fromshal-loww ater effect. The sam e is true for the M arineA nalyst, w hen conducting a P.A .R . test. If you noticethe w ake is at a 90 angle fromthe stern of the boat,w hile conducting a N orm al O perationtest, then youshould operate the boat test in deeper w ater.Effects of shallow water on the wake of a boatSTERNSTERNGOOD WAKE DEEP WATER45 OR LESS ANGLEBAD WAKE SHALLOW WATER90 OR MORE ANGLE61Ventilation System FormulasA s a rule of thum b, the installer should provide ventila-tion air flowof about 8 cfm(.22656 m3/m in) per installedhorsepow er (both propulsion and auxiliary engines). Ifcom bustion air is to be draw n fromthe engine roomincrease that figure to 914cfm(.26196 m3/m in).If you w ish to com pute m ore exact engine roomairrequirem ents it is necessary to determ ine the follow ingfactors:H = H eat radiated to the engine roomThis data is available fromthe TM I systemforC aterpillar engines. Add in 4 Btu/m in per gener-ated 0.07032 kWfor the norm al m axim umaux-ilary generator load. M iscellaneous heat loadsfromother sources (pum ps, m otors, etc.) canbe ignored if they are not exceptional.Ta = M axim umam bient air tem perature the vessel isexp ectedto op erate in d uringits w hole life.[U sually assum e 110 F (43.3 C ).]Sa = D ensity of the air at the m axim umam bient airtem perature.Density of Air at Various TemperaturesF/C lbs/cu. ft./kg/m3F/C lbs/cu. ft./kg/m30/18 0.086/1.38 70/21 0.075/1.2010/12 0.084/1.35 80/27 0.074/1.1820/7 0.083/1.33 90/32 0.072/1.1530/1 0.081/1.30 100/38 0.071/1.1440/4 0.079/1.27 110/43 0.070/1.1250/10 0.078/1.25 120/49 0.068/1.0960/16 0.076/1.22 130/54 0.067/1.07dT = M axim umdesired air tem perature in the engineroom . (U sually assum e 10 F (5.6 C ) rise aboveam bient)63W hen these factors have been determ ined, the venti-lation air requirem nets in cubic feet per m inute (cfm )can be calculated by the follow ing form ula:HQ a =_______________Sa 0.24 dTHQ a =________________=M etricSa 0.017 dTQ a = Volum e of inlet air required in cfm(m3/m in)H = R adiated heat [btu/m in (kW )]Sa = Inlet air density [lbs/cu. ft. (kg/m3)]0.24 = Specific heat of air (btu/lbs/ F)0.017 = Specific heat of air (kW m in/kg C )dT = Tem perature rise fromam bient air to engineair [ F (C )]64Ventilation Air Duct SizingB efore the duct cross-sectional area can be calculatedyou m ust determ ine tw o elem ents.Q cfm = A m ount of Ventilation air and C om bustionair (com bine system ) in cfm .Va = D esired inlet air velocity [N ot to exceed2,000 feet per m inute (609.6 m /m in)]O nce these tw o elem ents have been determ ined thenthe follow ing form ula can be used to determ ine the m in-im umcross-sectional for both intake and exhaust ductsor openings.144 Qa39,365.7 QaAv =_________Av =______________=M etricVaVaAv = D uct cross sectional area in square inches (m m )Qa= Q uanity of air flowin cubic feet per m inute(m3/m in)Va= Velocity of air in the duct in feet per m inute(m /m in)65Combustion Air FormulasIf com bustion air is to be draw n fromthe engine room ,a slight m odification is in order. Since the air used forcom bustion takes som e engine roomheat w ith it, it canbe counted partially as ventilation air. This can beadded into the calculation by adding about half of thecom bustion air required (12Q c) resulting in the follow -ing equation:H 1Q a =_______________+__Q cSa 0.24 dT 2H 1Q a =________________+__Q c =M etricSa 0.017 dT 2Q a = Volum e of inlet air required in cfm(m3/m in)H = R adiated heat [btu/m in (kW )]Sa = Inlet air density [lbs/cu. ft. (kg/m3)]0.24 = Specific heat of air (btu/lbs/ F)0.017 = Specific heat of air (kW m in/kg C )dT = Tem perature rise fromam bient air to engineair [ F (C )]Q c = C om bustion air required in cfm(m3/m in)For com bustion air requirem ent a good rule of thum b isto m ultiply the horsepow er in the engine roomby 2.5.R em em ber to include all engines in the engine roomspace for this calculation. If you need m ore exact com -bustion air figures then you can get that inform ationfromthe TM I system . H ow ever, the 2.5 tim es rule is usu-ally adequate for sizing purposes.67If the rule of thum b of 8 cfm /.22656 m3/m in of air perinstalled horsepow er is applied, the m inim umductcross sectional area (A v) per installed horsepow erw ould be:Av =0.6 in2/H p (3.87 cm2/kW ) @Va =2000 fpm(609.6 m /m in)Av =0.9 in2/H p (5.81 cm2/kW ) @Va =1200 fpm(365.8 m /m in)If you included com bustion air into the ventilation sys-tem[used 9.25 cfm(.262 m3/m in)]:Av =0.7 in2/H p (4.52 cm2/kW ) @Va =2000 fpm(609.6 m /m in)Av =1.0 in2/H p (6.45 cm2/kW ) @Va =1200 fpm(365.8 m /m in)Remember air should enter the engine room freely.It is far better to have extra air than not enough.Thisinstallation parameter is second only to sufficientliquid cooling capacity in importance. If the rules ofthumb are adhered to they will normally be suffi-cient, however, they are not overly conservative Dont Cheat!68Sizing Combustion Air DuctsO btain the actual air requirem ent fromthe TM I systemor use the rule of thum b (2.5 H p) to calculate the airrequired. The form ula used to calculate the ventilationcross-sectional area can then be applied by using theappropriate com bustion air volum e and a velocity.(8000 fpmm axim um )This w ill m ost likely yeild a cross-sectional area sm allerthan that of the factory connection to the air cleaner,how ever, be sure to keep the duct size equal to, orgreater than, that of the factory connection.If the straight length of duct is long, (over 25 thediam eter or diagonal of the factory connection) orincludes m ore than tw o right angle bends, it w ould bew ise to calculate the pressure drop at full air flow . Thiscan be done using the follow ing form ula:Le S Q2Le S Q2dP =____________dP =_____________=M etric187 d53600000 d5dP = Pressure loss [inches (kPa) of w ater]Q = A ir flow[cfm(m3/m in)]d = D uct diam eter [inches (m m )]Le = Equivalent duct length [ft (m )]S = D ensity of com bustion air [lbs/cu.ft. (kg/m3)]U se the follow ing m ethod to determ ine Le:Standard elbow=2.75 d Long Sw eep elbow=1.7 d45 elbow=1.25 dd = value must be in inchesStandard elbow=0.033 d =m eterLong Sw eep elbow=0.020 d =m eter45 elbow=0.015 d =m eterd = value must be in mm69Exhaust System FormulasWater Cooled ExhaustThere are tw o basic types of exhaust system s used inthe m arine area. The tw o system s are w et(w atercooled) and dry exhaust system s. The m ain consider-ation is to design the systemto rem ove the exhaustgases fromthe engine roomand lim it the backpressureto a m inim um .The lim its for a given enginesexhaust backpressure canbe located in the TM I system . In general term s the back-pressure lim it is 27 inches of w ater for all C aterpillar turbo-charged/turbocharged aftercooled engines. 34 inchesof w ater is the lim it for naturally aspirated engines. The3600 series of engines have a lim it of 10 inches of w ater.Som e special rating, such as the 435 H p 3208 E ratinghave a lim it of 40 inches of w ater. You need to deter-m ine the lim it of your engine, rating and then size theexhaust systemto be belowthe lim it. R em em ber thatthe closer you get to the lim it the m ore affect the exhaustbackpressure w ill have on the perform ance of the engine.M any w etexhaust system s utilize an exhaust riser tohelp prevent sea w ater fromentering the engine throughthe exhaust systemw hen the engine is not operatingor w hen the boat is backed dow nquickly. As a generalrule of thum b the riser should be at least 22 inches abovethe level of the sea w ater to the low est portion of the riser.71The m inim umw ater flowrequirem ents to a w et exhaustsystemcan be calculated by using the follow ing form ula.Vd N e Vd N eFlow=________Flow=________=M etric66000 285.785Flow = G allons per m inute (L/m in)Vd = Engine displacem ent [cubic inches (liters)]N e = R ated speed (rpm )66,000 = constant for gallons285.785 = constant for litersA w ater lift m uffler is also com m on in som e of the sm allerpleasure craft. If a w ater lift m uffler is to be used thefollow ing are som e points to pay close attention to.1. Size the m uffler outlet for a m inim umexhaust veloc-ity (gas only) of 5000 ft/m in at rated engine pow erand speed. The follow ing form ula w ill give the m ax-im umpipe diam eter, D ethat can be used to insurethe 5000 ft/m in velocity.D e =0.19 Q e D e =28.67 Q e =M etric D e = The m axim umw ater lift exhaust outlet pipediam eter [inches (m m )]Q e = Exhaust flowrate fromthe m uffler [cfm(m3/m in)]2. The tank itself should be of sufficient size. Arule ofthum b w ould be at least 8 cubic inches per ratedhorsepow er.3. The inlet pipe to the tank should be truncated nearthe top of the tank.4. The outlet pipe should extend to near the bottomofthe tank (about 1 inch fromthe bottom ) and shouldbe angle cut (m itered) to increase exit gas velocityat low er loads and flowrates.5. Asiphon break should be installed betw een theexhaust elbowand the high point of the outlet pipefromthe m uffler.72Dry ExhaustThe dry exhaust systemhas som e typical points thatneed to be considered as w ell.1. Aflexible connection at the engine exhaust outlet.N o m ore than 60 pounds of exhaust piping w eightshould be supported on the flexible connection.2. Flexible connection(s) are installed on the horizon-tal portion and on the vertical stack of the exhaustsystem .3. H orizontal portions of the exhaust systemare slopedaw ay fromthe engine4. A spray shield/rain trap is used on the exhaust outlet.The exhaust gas flowrate for a given engine and ratingcan be obtained fromthe TM I system . It can be closelyestim ated by using the follow ing form ula.(Te + 460) H p (Te + 273) kWQ e =______________Q e =______________=M etric214 3126.52Q e = Exhaust gas flowrate [cfm(m3/m in)]Te = Exhaust gas tem perature [ F (C )]H p = Engine rated horsepow er (kW )A fter you have determ ined the exhaust gas flowratethe exhaust systembackpressure can be calculatedusing the follow ing form ula.Lte Se Q e2Lte S Q e2dP =_______________P =______________=M etric187 d53600000 d5P = Exhaust systembackpressure [inches of w ater]orkPaLte = Total length of piping for diam eter d[ft (m )]d = D uct diam eter [inches (m m )]73Lte is the sumof all the straight lengths of pipe for agiven diam eter d, plus, the sumof equivalent lengths,Le, of elbow s and bends of diam eter d. Straight flex-ible joints should be counted as their actual length iftheir inner diam eter is not less than d.Le =equivalent length of elbow s in feet of straight pipeStandard elbowLe (ft) = 2.75 d (inches)Long elbowLe (ft) =1.67 d (inches)45 elbowLe (ft) =1.25 d (inches)Note:Leresults are in feet but dmust be in inchesLe = equivalent length of elbow s in m eters of straight pipeStandard elbowLe = 0.033 d = (m etric)Long elbowLe =0.020 d = (m etric)45 elbowLe =0.015 d = (m etric)Note:Leresults are in meters but dmust be in mmQ e = Exhaust gas flow[cfm(m3/m in)]Se = Specific w eight (density) of exhaust gas[lbs/cu. ft. (kg/m3)]The specific w eight of the exhaust gas is calculatedusing the follow ing form ula.39.6 352Se =____________Se =____________=M etric(Te +460) F (Te +273) CSe = Specific w eight [lbs/cu. ft./kg/m3)]Te = Exhaust gas tem perature [ F ( C )]d = pipe diam eter [inches (m m )]The values of Lte, Se, Qe, and d must be entered inthe units specified above if the formula is to yieldvalid results for backpressure.74To get the total exhaust pressure you nust add to theansw er fromthe above form ula the pressure drop ofthe m uffler. The pressure drop for C aterpillar m ufflersis available in the TM I system .Exhaust gas velocity should also be checked. If thevelocity is too high, excessive noise or w histle m ayoccur and inner pipe and w all surfaces m ay erode at anunacceptable rate. A s a rule of thum b, the velocity isbest kept to 18,000 ft/m in or less. The velocity can becalculated using the follow ing form ula:183 Q e 1,270,691.83 Q eVe =_________Ve =_________________=M etricd2d2Ve = Exhaust gas velocity [ft/m in (m /m in)]Q e = Exhaust gas flowrate [cfm(m3/m in)]d = Pipe diam eter [inches (m m )]75APIGravity Correctionfor TemperatureA PI = A M ER IC A NPETR O LEU MIN STITU TESG = SPEC IFICG R AVITY141.5IF A PI =_____131.5SGTH EN141.5SG=____________(A PI +131.5)TH EN141.5 =SG (A PI +131.5)The m ean coefficients of expansion for different gravitym aterials up to about 400F are in a range of 0.00035 0.00090. For fuels in the range of 15 A PI to 34.9 A PIthe m ean coefficient of expansion is 0.00040. Fuels inthe range of 35 A PI to 50.9 A PI have a m ean coeffi-cient of expansion equal to 0.00050. Since m ost of thefuels w e deal w ith at C aterpillar are in these tw o ranges,the average of the tw o w ill be used to performthe cal-culation. (0.00045 m ean coefficient of expansion)*Lets set up an exam ple problem .You m easure the A PI gravity of a diesel fuel and find itto be 38A PI @100F. You w ould like to correct this tothe standard and determ ine the w eight of the fuel.* From the Physical Properties of Petroleum Oil77To solve for this w e w ill use the form ula:141.5SG=____________(A PI +131.5)141.5W here SG=____________(38 +131.5)SG= .8348.8348 is the Specific G ravity of the fuel at 100 F. W ew ant it at standard of 60 F. To correct the SpecificG ravity w e m ust do the follow ing:W e knowthat for every 1F w e w ill have 0.00045 m eancoefficient of expansion.Since w e are 40 F above the 60 F standard w e w illw ork it out as follow s:(40 F)(0.00045) =.0181.00** .018 =.982 C orrection FactorSpecific G ravity can nowbe corrected by the follow ing:.8348 SGM easuredC SG=____________________.982 C orrection FactorC SG=.8501N owthat w e have the C orrected Specific G ravity (C SG )you can answ er the original question by using the fol-low ing form ula:141.5A PI =_____131.5SG** 1.00 IS THE SPECIFIC GRAVITY OF FRESH WATER78A s follow s:141.5C orrected A PI @60 F =______131.5.8501C orrected A PI @60 F =34.95 ~35W e can also nowcalculate the w eight per gallon of thediesel fuel. First w e m ust realize that the w eight of freshw ater is 8.328 lbs per gallon. W e have said that ourSpecific G ravity C orrected is .8501 that of w ater. There-fore the w eight of our diesel fuel can be calculated by:(.8501)(8.328) =7.076 lbs/gallon.7981Fuel SystemFuel PropertiesDistillate Fuel ChartCaterpillarPreferred FuelRequirements(As DeliveredTo Fuel System)Aromatics, % Max. 35%(ASTM D1319)Ash. % Weight Max. .02%(ASTM D482)Carbon Residue on Max. 1.0510% Bottoms, %(ASTM D524)Cetane Number Min. 35 PC/40 DI(ASTM D613)Cloud Point, C (F) Max. Not Above(ASTM D97) AmbientCopper Strip Corrosion Max. No. 3(ASTM D130)Distillation 10% C (F) Max. 282C (540F)Distillation 90% C (F) Max. 360C (680F)(ASTM D86, D158 or D285)Flash Point, C (F) Min. Legal(ASTM D93)Gravity API Min. 30(ASTM D287) Max. 45Pour Point, C (F) Min. 6 (10)(ASTM D97) Below AmbientSulfur, Total %, Weight Max. 0.05% max over the road(ASTM D2788 or D3605 0.5% max commercialor D1552) See Page 95 to adjustengine oil TBNViscosity, Kinematic, cSt Max. 20.0(ASTM D445) Min. 1.4Water and Sediment, Max. 0.1% Volume(ASTM D1796)Water, % Volume Max. 0.1Sediment, % Weight Max. 0.05Fuel PropertiesBlended Fuel ChartPermissible Fuels As Delivered To The Fuel SystemFuel Propertiesand Characteristics 3500 3600Water and Sediment % volume Max. 0.5 0.5(ASTM D1796)Sulfur Max. 4% 5%(ASTM D2788 or D3605 or D1552)Viscosity Min. 1.4 cSt 1.4 cSt(Viscosity to the Unit Injector) Max. 180 20(ASTM D445) cSt/50Carbon Residue (CCR) Max. 15 22ASTM D189Vanadium PPM Max. 250 PPM 600 PPMAluminum PPM (ASTM D2788 or D3605) Max. 1 PPM 80 PPMSilicon (ASTM D2788 or D3605) Max. 1 PPM 80 PPMPPM = parts per million82Blended (H eavy) fuels are usually described by their vis-cosity, expressed either in centistokes(cSt) or SecondsRedw ood. The Redw ood scale at 100F is being phasedout and replaced by the centistokes scale at 50C . Thecentistoke viscosity m ay be preceded by the letters IF forinterm ediate fuelor IB F for interm ediate bunker fuel.For exam ple, IF 180 fuel has a viscosity of 180 cSt at 50C .The follow ing table gives the approximate relationshipbetw een the tw o scales.cSt at 50C Seconds Redwood at 100F30 20040 27860 43980 610100 780120 950150 1250180 1500240 2400280 2500380 350083Fuel PropertiesCrude Oil ChartFuel Properties and Characteristics Permissible Fuels As Delivered To The Fuel SystemCetane Number or Cetane Index Min. 35(ASTM D613 or calculated index) (PC Engines)(DI Engines) Min. 40Water and Sediment % volume (ASTM D1796) Max. 0.5%Pour Point (ASTM D97) Min. 6C (10F) Below Ambient TemperatureCloud Point (ASTM D97) Min. Not Higher than Ambient TemperatureSulfur (ASTM D2788 or D3605 or D1552) Max. 0.5% See Page 95 to adjust oil TBN forHigher Sulfur ContentViscosity at 38C (100F) (ASTM D445) Min. 1.4 cStMax. 20 cStAPI Gravity (ASTM D287) Min. 45Max. 30Specific Gravity (ASTM D287) Min. 0.8017Max. .875Gasoline and Naphtha Fraction Max. 35%(Fractions Boiled off below 200C)Kerosene and Distillate Fraction Min. 30%(Fractions boiled off between 200C and cracking point)84Fuel PropertiesCrude Oil Chart (cont.)Fuel Properties and Characteristics Permissible Fuels As Delivered To The Fuel SystemCarbon Residue (Ramsbottom) (ASTM D524) Max. 3.5%Distillation 10% Max. 282C (540F)Distillation 90% Max. 380C (716F)Distillation Cracking % Min. 60%Distillation Residue (ASTM D86, D158 or D285) Max. 10%Reid Vapor Pressure (ASTM D323) Max. 20 psi (kPa)Salt (ASTM D3230) Max. 100 lb per 1000 BarrelsGums and Resins (ASTM D381) Max. 10 mg per 100 mlCopper Strip Corrosion 3 Hrs 100C (ASTM D130) Max. No. 3Flashpoint C/F (ASTM D93) Must be legal limitAsh % Wt. (ASTM D482) Max. 0.1%Aromatics % (ASTM D1319) Max. 35%Vanadium PPM (ASTM D2788 or D3605) Max. 4 PPMSodium PPM (ASTM D2788 or D3605) Max. 10 PPMNickel PPM (ASTM D2788 or D3605) Max. 1 PPMAluminum PPM (ASTM D2788 or D3605) Max. 1 PPMSilicon (ASTM D2788 or D3605) Max. 1 PPM85Density and Specific GravitySpecific Gravities and Densities of FuelGravity DensitySpecificDegrees Gravity PoundsAPI at at per15C (60F) 15C (60F) gallon25 .9042 7.52926 .8984 7.48127 .8927 7.43428 .8871 7.38729 .8816 7.34130 .8762 7.29631 .8708 7.25132 .8654 7.20633 .8602 7.16334 .8550 7.11935 .8498 7.07636 .8448 7.03437 .8398 6.99338 .8348 6.95139 .8299 6.91040 .8251 6.87041 .8203 6.83042 .8155 6.79043 .8109 6.75244 .8063 6.71345 .8017 6.67546 .7972 6.63747 .7927 6.60048 .7883 6.56349 .7839 6.52686Fuel API Correction ChartAPI Gravity Corrected to 60F(Measured Fuel Temperature F)MeasuredAPI 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150GravityAPI Gravity At 60F29 33 32.5 32 31 30 30 29 28 28 27 26.5 26 25 24.5 24 23.530 34 33.5 33 32 31.5 31 30 29 29 28 27.5 27 26 25.5 25 24.531 35 34.5 34 33 32.5 32 31 30 30 29 28.5 28 27 26.5 26 2532 36 35.5 35 34 33.5 33 32 31 30.5 30 29 29 28 27.5 27 2633 37 36.5 36 35 34.5 34 33 32 31.5 31 30 29.5 29 28.5 28 2734 38.5 38 37 36 35.5 35 34 33 32.5 32 31 30.5 30 29 29 2835 39.5 39 38 37 36.5 36 35 34 33.5 33 32 31.5 31 30 29.5 2936 41 40 39 38 37.5 37 36 35 34.5 34 33 32.5 32 31 30.5 3037 42 41 40 39 38.5 38 37 36 35.5 35 34 33.5 33 32 31.5 3138 43 42 41 40.5 39.5 39 38 37 36.5 36 35 34.5 34 33 32 3239 44 43 42 41.5 40.5 40 39 38 37.5 37 36 35 34.5 34 33 32.540 45 44 43 42.5 41.5 41 40 39 38.5 38 37 36 35.5 35 34 33.541 46 45 44.5 43.5 42.5 42 41 40 39.5 39 38 37 36.5 36 35 34.542 47 46 45.5 44.5 44 43 42 41 40.5 39.5 39 38 37.5 37 36 3543 48.5 47.5 46.5 45.5 45 44 43 42 41.5 40.5 40 39 38 37.5 37 3644 49.5 48.5 47.5 46.5 46 45 44 43 42 41.5 41 40 39 38.5 38 3787Fuel API Correction Chart (cont.)MeasuredAPI 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150GravityAPI Gravity At 60F45 50.5 49.5 49 48 47 46 45 44 43 42.5 42 41 40 39.5 38.5 3846 52 51 50 49 48 47 46 45 44 43.5 42.5 42 41 40 39.5 3947 53 52 51 50 49 48 47 46 45 44.5 43.5 43 42 41 40.5 4048 54 53 52 51 50 49 48 47 46 45 44.5 44 43 42 41 40.549 55 54 53 52 51 50 49 48 47 46 45.5 45 44 43 42 41.550 56 55 54 53 52 51 50 49 48 47 46.5 45.5 45 44 43 4251 57.5 56 55 54 53 52 51 50 49 48 47 46.5 45.5 45 44 4352 58.5 57.5 56 55 54 53 52 51 50 49 48 47 46.5 45.5 45 4453 60 58.5 57 56 55 54 553 52 51 50 49 48 47.5 46.5 46 45Tooling: Fuel Therm o-hydrom eter 1P7408 Test B reaker 1P7438Distillate Fuel TemperatureM axim umFuel Supply Tem perature: W ithout Pow er R eduction: 85 F (29 C )Pow er is reduced 1%for each 10F (5.6C ) above 100F (38C ) if engine is running against fuel stop. W ithout Injector D am age: 150 F (65 C )88Performance Analysis Rules of ThumbCorrection Factors:Fuel TemperatureCorrection FactorsFuel CorrectionTemp F Factor10 .9055 .9100 .9155 .92010 .92515 .93020 .93525 .94030 .94535 .95040 .95545 .96050 .96555 .97060 .97565 .98070 .98575 .99080 .9958511.00090 1.00595 1.010100 1.015105 1.020110 1.025115 1.030120 1.035125 1.040130 1.045135 1.050140 1.055145 1.060150 1.065155 1.070160 1.0751Standard value.89Fuel Density (API)1Correction FactorsAPI Correctionat 60F Factor32.0 .98732.5 .98933.0 .99133.5 .99334.0 .99534.5 .99835.021.00035.5 1.00336.0 1.00536.5 1.00837.0 1.01137.5 1.01438.0 1.01738.5 1.02039.0 1.02439.5 1.02740.0 1.03140.5 1.03541.0 1.03941.5 1.04342.0 1.04742.5 1.05243.0 1.05643.5 1.06144.0 1.06644.5 1.07245.0 1.07745.5 1.08346.0 1.08946.5 1.09647.0 1.10247.5 1.10948.0 1.11648.5 1.12449.0 1.13149.5 1.13950.0 1.1481The measured fuel API and corresponding temperature must becorrected to 60F before selecting an API correction factor. Usethe Fuel API Correction Chart on pages 87 and 88 to determinethe API at 60F.2Standard value.90Air PressureCorrection FactorsAir Pressure Correction" Hg Factor31.0 .99630.511.00030.0 1.00429.5 1.00729.0 1.01128.5 1.01528.0 1.01927.5 1.02327.0 1.02726.5 1.03126.0 1.03625.5 1.04025.0 1.04524.5 1.04924.0 1.05423.5 1.05923.0 1.06422.5 1.06922.0 1.07521.5 1.08021.0 1.08620.5 1.09220.0 1.098130.5"Hgisusedasthestandardvaluetoaccountfortheaircleaner restriction and vapor pressure (humidity).91Power Calculation:Fuel R ate (G PH )Fuel D ensity H P =_____________________________________B SFCFuel R ate (L/H R )Fuel D ensity kW=______________________________________B SFCBSFCC SFC(G R A M S/kWH R )_____________________=LB S/kWH R454LB S/kWH R_____________________=B SFC(LB S/H P H R )1.34TolerancesPerform ance curves represent typical values obtainedunder norm al operating conditions. Am bient air conditionsand fuel used w ill affect these values. Each of the valuesm ay vary in accordance w ith the follow ing tolerances:Exhaust Stack Tem perature 42 D EGC 75 D EGFIntake M anifold Pressure-G age 10 kPa 3 in H gPow er 3 PercentFuel C onsum ption 6 g/kW -hr .010 lb/hp-hrFuel R ate 5 PercentG R A M_______(kW H R)G R A M______(LITER)LB_______(H PH R)LB_____(G A L)92ConditionsR atings are based on SA E J1349 standard conditionsof 100 kPa (29.61 in H g) and 25 C(77 F). These rat-ings also apply at ISO3046/1, D IN6271 and B S 5514standard conditions of 100 kPa (29.61 in H g), 27 C(81 F) and 60%relative hum idity.Fuel Rates are based on fuel oil of 35API [16C(60F)]gravity having an LH V of 42 780 kJ/kg (18,390 B tu/lb)w hen used at 29 C(85 F) and w eighing 838.9 g/liter(7.001 lbs/U .S. gal).Additional Formulas Usedto Develop Marine Par CurvesFor Torque C heck G PHproceed as follow s:Torque C heck G PH=TQC O R . Fuel R ate (G /M IN ) 454 60 =LB S/H RLB S/H R 7.076 =G PHFor B SFCproceed as follow s:B SFC=A djusted C SFC(G /kWH R ) 454 =LB S/kWH RLB S/kWH R 1.34 =B SFC(LB S/H P H R )93Lubrication SystemOil TBN vs. Fuel Sulfur ContentG raph for determ ination of necessary TB N . Find thefuel sulfur percentage on bottomof the graph. Findpoint w here the newoil TB Nline intersects the sulfurcontent line, and read the required TB Nat the left sideof the chart.Rule of Thumb: N ewoil TB Nshould be 10 tim es fuelsulfur content. C hange oil w hen TB Ndrops to 12its orig-inal value w hen using A PI C F-4 oil and you are using aD I engine.95AdditivesThere are chem ical substances added to a petroleumproduct to im part or im prove certain properties.A dditives strengthen or m odify certain characteristicsof the base oil. U ltim ately, they enable the oil to m eetrequirem ents quite beyond the abilities of the base oil.The m ost com m on additives are: detergents, oxidationinhibitors, dispersants, alkalinity agents, anti-w earagents, pour-point depressants and viscosity im provers.H ere is a brief description of w hat each additive doesand how .D etergents help keep the engine clean by chem icallyreacting w ith oxidation products to stop the form ationand deposit of insoluble com pounds.O xidation inhibitors help prevent increases in viscos-ity, the developm ent of organic acids and the form a-tion of carbonaceous m atter.D ispersants help prevent sludge form ation by dispers-ing contam inants and keeping themin suspension.A lkalinity agents help neutralize acids.A nti-w ear agents reduce friction by form ing a filmonm etal surfaces.Apour-point depressant keeps the oil fluid at low tem -peratures by preventing the grow th and agglom eration(the gathering together into a m ass) of w ax crystals.Viscosity im provers help prevent the oil frombecom ingtoo thin at high tem peratures.96Anti-Wear AdditiveThis is an additive in a lubricant that reduces frictionand excessive w ear.API (American Petroleum Institute)This is a trade association of petroleumproducers,refiners, m arketers, and transporters, organized for theadvancem ent of the petroleumindustry by conductingresearch, gathering and dissem inating inform ation, andm aintaining cooperation betw een governm ent and theindustry on all m atters of m utual interest. O ne A PItech-nical activity has been the establishm ent of A PIEngineService C ategories for lubricating oils.API Engine Service CategoriesG asoline and diesel engine oil perform ance levels areestablished jointly by A PI, SA E, and A STMcalled A PIEngine Service C lassifications. A PI Service C ategoriesare as follow s:Diesel Engine OilsAPI LetterDesignation API Engine Service DescriptionKey:X Obsolete Test TechniquesO Active Test TechniquesCA X Diesel Engine Service (Obsolete)CB X Diesel Engine Service (Obsolete)CC X Diesel Engine Service97CD O Diesel Engine ServiceThe category CD denotes service typical ofcertain naturally aspirated, turbocharged, orsupercharged diesel engines where highlyeffective control of wear and deposits is vitalor when using fuels of a wide quality range,including high sulfur fuels. Oils designed forthis service were introduced in 1955 andprovide protection from bearing corrosionand from high-temperature deposits in thesediesel engines.CD-II O Severe Duty Two-Stroke CycleDiesel Engine Service typical of two-strokecycle diesel engines requiring highly effectivecontrol over wear and deposits. Oils designedfor this service also meet all performancerequirements of API Service Category CD.CE X 1983 Diesel Engine ServiceService typical of certain turbocharged orsupercharged heavy-duty diesel enginesmanufactured since 1983 and operated underboth low-speed, high-load and high-speed,high-load conditions. Oils designed for thisservice may also be used when API EngineService Category CD is recommended fordiesel engines.CF-4 O 1990 Diesel Engine ServiceService typical of certain turbocharged orsupercharged heavy-duty diesel enginesmanufactured and operated under both low-speed, high-load and high-speed, high-loadconditions. Oils designed for this service mayalso be used when API Engine ServiceCategory CD and CE are recommended fordiesel engines.CG-4 1995 Diesel Engine ServiceService for engine wear and deposits issueslinked to fuel specifications and enginedesigns that are required to accommodate1994 EPA emission regulations for low sulfurfuel (0.05%).98Gasoline Engine OilsAPI LetterDesignation API Engine Service DescriptionSA (No test Formerly for Utility Gasoline andrequired) Diesel Engine Service (Obsolete)SB X Minimum Duty Gasoline EngineService (Obsolete)SC X 1964 Gasoline Engine WarrantyMaintenance Service (Obsolete)SD X 1968 Gasoline Engine WarrantyMaintenance Service (Obsolete)SE X 1972 Gasoline Engine WarrantyMaintenance Service (Obsolete Startingin 1989)SF X 1980 Gasoline Engine WarrantyMaintenance ServiceSG O 1989 Gasoline Engine WarrantyMaintenance ServiceThe category SG denotes service typical ofpresent gasoline engines in passenger cars,vans, and light-duty trucks operating undermanufacturers recommended maintenanceprocedures. Category SG quality oils includethe performance properties of API ServiceCategory CC. (Certain manufacturers ofgasoline engines require oils also meetingthe higher diesel engine Category CD). Oilsdeveloped for this service provide improvedcontrol of engine deposits, oil oxidation, andengine wear relative to oils developed forprevious categories. These oils also provideprotection against rust and corrosion. Oilsmeeting API Service Category SG may beused when API Service Categories SF, SE,SF/CC, or SE/CC are recommended.SH O API category for use in service typical ofgasoline engines in present and earliervehicles. These oils have been testedaccording to the CMA product approval codeof practice and may be used where APIcategory SG and earlier categories havebeen recommended. They must meet allAPI SG requirements and use Multiple TestAcceptance Criteria (MTAC).99Anti-Wear AdditiveThis is an additive in a lubricant that reduces frictionand excessive w ear.Ash ContentThis is the noncom bustible residue of a lubricating oilor fuel. Lubricating oil detergent additives containm etallic derivatives, such as barium , calcium , and m ag-nesiumsulfonates, that are com m on sources of ash.A sh deposits can im pair engine efficiency and pow er.See detergent.ASTM (American Societyfor Testing and Materials)This organization is devoted to the prom otion of know l-edge of the m aterials of engineering and the stan-dardization of specifications and m ethods of testing.Apreponderance of the data used to describe, identify,or specify petroleumproducts is determ ined in accor-dance w ith A STMtest m ethods.Base StockB ase stock is a prim ary refined petroleumfraction, usu-ally a lube oil, into w hich additives and other oils areblended to produce finished products.Bid OilThis is oil produced by an oil com pany w hich just m eetsthe m inim umof the diesel engine oil perform ance spec-ifications. These oils are usually the least expensivebecause they have only the m inim umam ount of addi-tives to just get by. These oils m ight be acceptable forlightly loaded applications but could cause problem s inm ore severe m achine application.100Blow-ByThis com es froman internal com bustion engine w hereseepage of fuel and gases past the piston rings andcylinder w all into the crankcase, results in crankcaseoil dilution and sludge form ation.BMEPB rake m ean effective pressure is the theoretical aver-age pressure that w ould have to be im posed on thepistons of a frictionless engine (of the sam e dim ensionsand speed) to produce the sam e pow er output as theengine under consideration; a m easure of howeffec-tively an engine utilizes its piston displacem ent to dow ork.Borderline Pumping Temperature C(ASTDM D3829)This is the tem perature at w hich the oil becom es tooviscous (thick) and cannot be m oved w hen force isapplied. The oil, how ever, is not yet a solid (pour point).Bulk DeliveryThis is a large quantity of unpackaged petroleumprod-uct delivered directly froma tank truck, tank car, orbarge into a consum ers storage tank.ColloidAcolloid is a suspension of finely divided particles 5to 5000 angstrom s in size in a gas or liquid, that do notsettle and are not easily filtered. an A ngstromis a unitof w ave length of light equal to one ten billionth of am eter w hich carries a positive or negative charge.101C olloids are usually ionically stabilized by som e formof surface charge on the particles to reduce the ten-dency to aggolom erate (gather into a ball or m ass). Alubricating grease is a colloidal system , in w hich m etal-lic soaps or other thickening agents are dispersed in,and give structure to, the liquid lubricant.Color ScaleThese scales serve prim arily as indicators of productuniform ity and freedomfromcontam ination. The scaleis a standardized range of colors against w hich the col-ors of petroleumproducts m ay be com pared. There area num b er of w id ely usedsystem s of color scales,including: A STMscale (test m ethod A STMD1500), them ost com m on scale, used extensively for industrial andprocess oils.Crude OilC rude oil is a com plex, naturally occurring fluid m ixtureof petroleumhydrocarbons, yellowto black in color, andalso containing sm all am ounts of oxygen, nitrogen, andsulfur derivatives and other im purities. C rude oil w asform ed by the action of bacteria, heat, and pressure onancient plant and anim al rem ains, and is usually foundin layers of porous rock such as lim estone or sandstone,capped by an im pervious layer of shale or clay thattraps the oil. C rude oil varies in appearance and hydro-carbon com position depending on the locality w here itoccurs. C rude is refined to yield petroleumproducts.Demerit RatingThis is an arbitrary graduated num erical rating som e-tim es used in evaluating engine deposit levels follow -ing testing of an engine oils detergent-dispersantcharacteristics. O n a scale of 0-10, the higher the num -ber, the heavier the deposits. Am ore com m only usedm ethod of evaluating engine cleanliness is m erit rating.See Engine D eposits.102DetergentThis is an im portant com ponent of engine oils that helpscontrol varnish, ring zone deposits, and rust by keep-inginsoluble particles in suspension and in som ecases, by neutralizing acids. Adetergent is usually am etallic com pound. B ecause of its m etallic com posi-tion, a detergent leaves a slight ash w hen the oil isburned. Adetergent is norm ally used in conjunctionw ith a dispersant.DispersantAdispersant is an engine oil additive that helps pre-vent sludge, varnish, and other engine deposits bykeeping soot particles suspended in a colloidal state(prevents these particles fromgathering into a ball orm ass).Engine DepositsThese are hard or persistent accum ulations of sludge,varnish, and carbonaceous residues due to blow -by ofunburned and partially burned (partially oxidized) fuel,or frompartial breakdow n of the crankcase lubricant.W ater fromcondensation of com bustion products, car-bon, residues fromfuel or lubricating oil additives, dust,and m etal particles also contribute. Engine depositscan im pair engine perform ance and dam age enginecom ponents by causing valve and ring sticking, clog-ging of the oil screen and oil passages, and excessivew ear of pistons and cylinders. H ot, glow ing deposits inthe com bustion cham ber can also cause pre-ignitionof the air-fuel m ix. Engine deposits are increased byshort trips in cold w eather, high tem perature operation,heavy loads (such as pulling a trailer), and over-extendedoil drain intervals.103EPA (Environmental Protection Agency)The EPAis an agency of the federal executive branch,established in 1970 to abate and control pollutionthrough m onitoring, regulation, and enforcem ent, andto coordinate and support environm ental research.Fighting Grade OilSee B id O il.FlashpointThis is the low est tem perature at w hich the vapor of acom bustible liquid can be m ade to ignite m om entarilyin air. Flash point is an im portant indicator of the fireand explosion hazards associated w ith a petroleumproduct.LubricationLubrication is the control of friction and w ear by theintroduction of a friction-reducing filmbetw een m ovingsurfaces in contact. The lubricant used m ay be a fluid,solid, or plastic substance.Merit RatingThis is an arbitrary graduated num erical rating com -m only used in evaluating engine deposit levels w hentesting the detergent-dispersant characteristics of anengine oil. O n a scale of 10-0, the low er the num ber,the heavier the deposits. Aless com m on m ethod ofevaluating engine cleanliness is dem erit rating. SeeEngine D eposits.104Mineral OilThis is any petroleumoil, as contrasted to anim al orvegetable oils. A lso, a highly refined petroleumdistil-late, or w hite oil, used m edicinally as a laxative.OSHA (Occupational Safety and HealthAdministration)OxidationO xidation is the chem ical com bination of a substancew ith oxygen. A ll petroleumproducts are subject to oxi-dation. This degrades their com position and low erstheir perform ance. The oxidation process is acceler-ated by heat, light, m etal catalysts (agents w hich bringabout a chem ical reaction) and the presence of w ater,acids or solid contam inants.These substances react w ith each other to formsludges,vanishes and gum s that can im pair equipm ent operation.To m inim ize oxidation and its effects, carefully select agood base stock oil, insure an oxidation inhibitor isadded to the base stock and m aintain equipm ent andchange oil to prevent contam ination and excessive heat.Oxidation InhibitorThis is any substance added in sm all quantities to apetroleumproduct to increase its oxidation resistance,thereby lengthening its service or storage life; alsocalled anti-oxidant. A n oxidation inhibitor m ay w ork inone of three w ays (1) by com bining w ith and m odify-ing peroxides (com pounds high in oxygen) to renderthemharm less, (2) by decom posing the perioxides, or(3) by rendering an oxidation catalyst (m etal or m etal-ions) inert; that is, lacking in a chem ical reaction. SeeO xidation.105Oxidation StabilityThis is the resistance of a petroleumproduct to oxida-tion; hence, a m easure of its potential service or stor-age life. There are a num ber of A STMtests to determ inethe oxidation stability of a lubricant or fuel, all of w hichare intended to sim ulate service conditions on an accel-erated basis. In general, the test sam ple is exposed tooxygen or air at an elevated tem perature, and som e-tim es to w ater or catalysts (usually iron or copper).D epending on the test, results are expressed in term sof the tim e required to produce a specified effect (suchas pressure drop), the am ount of sludge or gumpro-duced, or the am ount of oxygen consum ed during aspecified period.Pass-OilSee B id O il.Pour PointPour point is the low est tem perature at w hich an oil ordistillate fuel is observed to flow , w hen cooled underconditions prescribed by test m ethod A STMD 97. Thepour point is 3C(5F) above the tem perature at w hichthe oil in a test vessel show s no m ovem ent w hen thecontainer is held horizontally for five seconds. Pourpoint is low er than w ax appearance point or cloud point.It is an indicator of the ability of an oil or distillate fuelto flowat cold operating tem peratures.Ring LandThis is the area on the surface of the piston that isbetw een either the top of the piston and first ring grooveor betw een tw o adjacent ring grooves.106Ring StickingR ing sticking is freezing of a piston ring in its groove, ina piston engine or reciprocating com pressor, due toheavy deposits in the piston ring zone. This preventsproper action of the ring and tends to increase blow -by into the crankcase and to increase oil consum ptionby perm itting oil to flowpast the ring zone into the com -bustion cham ber. See Engine D eposits.SAE (Society of Automotive Engineers)The Society of A utom otive Engineers review s the totalautom otive engine and lubricant situation and definesthe requirem ent for newoil specifications.SAE Oil Viscosity ClassificationB ecause of the im portant effects of oil viscosity theSociety of A utom otive Engineers (SA E) has developeda systemfor classifying lubricating oils in term s of vis-cosity only; no other physical or perform ance charac-teristics are considered.The viscosity num bers w ithout the letter Ware basedupon 210 F viscosities. Viscosity at that tem peraturecorrelates w ith oil consum ption and other oil perfor-m ance characteristics influenced by viscosity at nor-m al eng ine op eratingtem p eratures. The viscositynum bers w ith the letter Ware based on 0F viscosities.The 0F viscosities for W -num bered oils w ere selectedbecause they correlate w ith the cranking characteris-tics of m otor oils in the average autom obile engineunder low -tem perature starting conditions.107Viscosity Grades for Engine OilsBoderline(b)SAE Viscosity (cP)(a)pumpingViscosity(c)Viscosity at temp. (C) temp.at 100C (cSt)grade max (C) max min max0W 3250 at 30 35 3.8 5W 3500 at 25 30 3.8 10W 3500 at 20 25 4.1 15W 3500 at 15 20 5.6 20W 4500 at 10 15 5.6 25W 6000 at 50 10 9.3 20W 5.6 < 9.330W 9.3