winterzation and winter operation of automotive and construction equipment

7/27/2019 Winterzation and Winter Operation of Automotive and Construction Equipment

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CAREL's Cold Regions Technical Digests areaimed at communicating essential technicalinformation in condensed form to researchers,engineers, technicians, public officials and others. They convey up-to-date knowledge concerning technical problems unique to cold regions. Attention is paid to the degree of detailnecessary to meet the needs of the intendedaudience. References to background information are included for the specialist.


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COLD REGIONS TECHNICAL DIGEST No. 92-1, September 1992USA Cold Regions Research and Engineering LaboratoryHanover, New Hampshire 03755-1290

The author, aphysical scientist, is a

member ofCRREL'sApplied Research

Branch.

Winterization andWinter Operation ofAutomotive andConstruction Equipment

Deborah Diemand

Winterizing equipment involves applying any measure that willpromote proper operation at the lowest temperatures in which it willbe called upon to function . Figure 1 shows the cold regions of NorthAmerica and the minimum temperatures likely in three zones. ZoneI includes the coldest areas, where temperatures may reach -60Cor below from time to time. The temperatures in Zone II, whichincludes most of Canada and a large area of the northern UnitedStates, sporadically reach the range shown on the graph for two tothree months each year, as will locations within Zone III. Thedegree of winterization required will, of course, be greater in themore severe climatic zones. These zones represent the worst case,the most severe conditions likely during the year. The period duringwhich these conditions may prevail is fairly short-perhaps two tothree months-and a machine that is not to be used during this timemay not need to be fully winterized.

The use of equipment in low temperatures involves two mainareas of concern: starting the engine and a i ~ t a i n i n g a sufficientlyhigh temperature in the engine and other components for properoperation. This often involves applying heat, frequently from anexternal source. In general the power train, brakes and auxiliary


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2

1. Coldest regions ofNorth America. Theregions shown on the

map indicate areas wherethe lowest temperatureslikely to occur will fallwithin the ranges shown

in the graph.

COLD REGIONS TECHNICAL DIGEST NO. 92-1

0o-1o~

~ -2or--+-........eti~ -30F--+---.....E

~ -400800 1600Time (hr) 2400

systems may perform well enough if suitable fluids and lubricantsare used.

Engine performance deteriorates at low temperatures because ofthe adverse effect on fuel quality, lubricant behavior, materialdeformation, battery effectiveness and other factors. In general, theremedy is to make the engine warmer. A number of types of heatersand starting aids are available to increase the probability of successful starting at very low temperatures. These are discussed brieflybelow and at greater length by Diemand ( 1990). Ways to retain heatgenerated by the engine are covered in the following section.

Table I lists a numberofwinterization measures and the need fortheir implementation in the various zones. These rough guidelinesmay not apply in all circumstances. For example, equipment inZone I that is kept in a heated garage may need less protection thana unit that will be left outside in Zone III. The degree of winterization required for machinery in areas south ofZone III isminimalthe use of antifreeze is a good idea, but nothing else should beneeded.


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WINTERIZATION AND WINTER OPERATION OF EQUIPMENT

Table 1. Recommended winterization measures. Zones refer to thoseshown in Figure 1.Climatic zonesIII II I Impact

Ensure a proper concentration of antifreeze R R R sTune-up before the onset of winter 0 R R S,NEngine enclosures 0 R R S,NEngine preheaters 0 R R sCoolant heaters 0 R R sIntake air heaters 0 0 R S,NStarting aids 0 R R sChange engine oil to arctic grade 0 R S,NChange other lubricants to arctic grades 0 R R NAdjust tracks 0 R NIncrease tire pressure R NDiesel fuel heaters 0 R R S,NHeated fuel filter R R R NBattery heat or insulation R R S,NIncrease battery power 0 R R S,NHigh-temperature thermostats 0 R R NWinterfronts or radiator shutters 0 R NEngine insulation 0 R NUnder engine protection R R NThermostatically controlled fans 0 R NInstall air dryer and alcohol evaporator R R R NInstall arctic-grade seals and hoses 0 RSupplemental cab heaters 0 R R NDowngrade hoists and winches R R N0-optional S-stalt-upR-required N-normal operation

The frrst step toward eliminating cold-weather equipment problems is to ensure that the machine is in the best possible mechanicalcondition. The engine should be tuned and the oil changed beforethe onset of cold weather, and the radiator should be drained andrefilled with a suitable mixture ofantifreeze. Heat-retention devicesshould be installed such that the engine will be able to maintain atemperature between 85 and 93C. Cold-starting aids, such as fuelprimers and special batteries or other external power sources, maybe installed, as well as winterization kits, which primarily includeheaters of one sort or another and an insulated covering. Modif ications to the equipment, such as installing wider tracks, altering theexhaust system or moving the ai r intakes, may improve machineryperformance. Operators should be familiar with techniques of

Preseasonpreparation

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4

2. Freezing tempera-tures for ethyleneglycol solutions. The

lowest freezing point is a60% mixture ofglycol.

Near the freezing point,slush is formed, which

may adversely affect thepeiformance of the

cooling system.


20 40 60 80 100Proportion of Ethylene Glycol by Volume(%)

equipment operation at low temperatures and should scrupulouslyfollow a routine maintenance schedule.

Coolant In all areas where temperatures drop below the freezing point ofwater, antifreeze should be added to the cooling system. The mostcommon fluid used for this purpose is ethylene glycol, and in asuitable concentration it will prevent freezing of the coolant downto -55C. However, it is extremely important to use the correctproportions of water and glycol. A 66% solution of glycol willfreeze solid at about -60C (ice crystals will be present betweenabout -45 and -60C). A concentration greater or less than this willfreeze at a higher temperature. Always use clean water with lowmineral content in the cooling system, preferably deionized ordistilled. Otherwise deposits may form, obstructing the flow of thecoolant and forming hot spots in the system. The freezing points ofvarious concentrations of ethylene glycol are given in Figure 2.

Antifreeze, like other automotive fluids, thickens at low temperatures. Also, at temperatures just below the coolant freezingpoint, slush may form, which can collect in filters and in smallcoolant passages, such as those leading to auxiliary heat exchangers. This can lead to local hot spots in the engine, which can stressor warp engine parts. This problem can be mitigated by using acoolant preheater equipped with a pump and by running the engineslowly until it has warmed somewhat.

Other types of antifreezes have been tested, some for temperatures below -55C, but they are not commonly used. Alcohols havea very low freezing point, but their use requires massive modifications of the cooling system, and their low boiling points are adisadvantage. Other types of glycols have also shown promise, butagain they require system modifications and are not in widespreaduse. Table 2 gives some of the thermal properties of some common


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WINTERIZATION AND W ll.JTER OPERATION OF EQUIPMENT 5

Table 2. Properties of some commonly used cooling fluids. (After Smolin 1968.)Coefficient

Freezing Boiling Specific heat of thermal Coefficient ofpoint point at100C conductivity( oC) ( oC) (cal/gm C ) (callscmC)Water 0 100 1.01 1600Ethylene glycol - ll.5 to 198 0.65- 17.5Glycerol +17 290 0.58Ethyl alcohol - 117 79 0.58DowthermJ - 73 181 0.379*(alkylated aromatic) 0.721tMethyl alcohol - 98 65* At-73CtA t 181 C

coolants. In general water is the best choice in terms of specific heat(theamountofheatthatcan be absorbed by a given volume of fluid),thermal conductivity (the rate at which heat can be transmittedthrough the fluid) and volumetric expansion (how much the fluidwill expand when it is heated). Unfortunately water cannot be usedby itself because of its high freezing point and low boiling point,which is why mixtures of ethylene glycol and water are normallyused.

600

600300

400

volumetricexpansion

400500

50011003600

In areas where low temperatures are accompanied by high winds Blowing snowand snow on the ground, the snow crystals are broken down to a veryfine powder, which will be driven by the wind into the smallestcracks. In extreme cases these spaces can become completelyblocked with tightly packed snow with a consistency similar toStyrofoam. Even a moderate degree of snow accumulation in avehicle can cause difficulties if it is not removed before operation.I f it melts during operation without completely evaporating, thewater produced may cause short circuits or other problems, andwhen it freezes after shut-down, further problems and failures mayoccur.

When preparing equipment for winter use, operators shouldcarefully seal all compartments, not only to prevent snow infiltra-


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6 COLD REGIONS TECHNICAL DIGEST NO. 92-1

tion but also to reduce drafts and heat loss. This is usually notpossible for engine compartments, so it is important when startingthe equipment after a period of blowing snow to check for snowblockage in this area and remove it before attempting to start themachine.

To prevent snow from being sucked in with the engine air, the airintake should be located inside the cab or in some other shelteredpart of the vehicle. I f possible the intake air should be drawn froma warm area such as the cab or the engine compartment to assureproper combustion in the cylinders.

Heaters There are three methods commonly employed in winterizationkits for preheating cold engines: circulating heated engine coolant,warming the engine internally using electric heating elements in thecylinder block and crankcase, and circulating heated air around theengine exterior. The first method often involves the use of anauxiliary heating unit, either another vehicle or a device specificallydesigned for the purpose. There are also many on-board heaterswith pumps that can circulate heated coolant through the engine andany other heat exchangers that have been plumbed into the system.This type of system is the most effective of the three because it canheat all parts of the engine evenly and thoroughly, as well as othercomponents indirectly. Electric heating elements located withinspecific areas of the engine are useful for heating only those specificareas and may result in the development of hot spots and unevenheating of the engine. Hot air circulation is often used to heat not justthe engine but the entire machine. This is a good idea if practicable,but it is a long process and requires a great deal of energy.

There are electric heaters available for virtually all systems andcomponents of construction machinery, and there are fuel-firedheaters for many of the more important applications. In most casesit is a good idea to install at least a battery heater, a block heater anda pan heater. Also, special attention should be given to windowdefrosters. Other useful heaters are available that warm the fueltank, hydraulic reservoir, rear-view mirror, axles and transmission.Always disconnect electric block and pan heaters before trying tostart the engine. Types of heaters in common use are discussed byDiemand (1991b).

Cold starting Cold starting is the first and most difficult hurdle in successfullow-temperature operations. To start an engine without damagingit, the following conditions must be met:

Sufficient electric power must be available to operate thestarter motor effectively.


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In a diesel engine enough heat must be produced on thecompression stroke to ignite the fuel.

The oil along the cylinder walls must be sufficiently fluid toallow the engine to tum over. The oil in the sump must be sufficiently fluid to pump readilyand immediately to all parts of the engine.

The fuel must be free of wax and have a low enoughv i s c o ~ i t y to atomize properly in the combustion chamber.This is not usually a problem in gasoline engines.

At very low temperatures, some preheating will almost certainlybe required, especially for diesel equipment. In some cases, startingat extremely low temperatures may be hampered when certainmetal parts deform or contract differentially, causing them to bind.For example, aluminum contracts at a much greater rate than steel,so assemblies that contain both materials and have very closetolerances may seize up. This may become more of a problem asaluminum becomes more common in engine manufacture. I f thisappears to be a problem, the only solution is to warm the affectedparts. Further information on problems of materials in low-temperature operations is given by Diemand (1991d).

In diesel engines the heat required for ignition is produced by the Ignitioncompression of the air in the cylinder on the compression stroke. I fthe intake air is too cold, the fuel cannotbum and the engine will notstart. Even a small increase in the temperature of the intake air cancause a substantial temperature rise in the cylinder. Several types ofintake air heaters are available, and one of these should be used,especially if the machinery is to be used in very harsh conditions.These devices are discussed further by Diemand ( 1991 b).

Once the engine is running, the intake air heater may not beneeded any further unless the air intake is located in a cold place.However, if the air is drawn in at a low temperature, the heatershould be used during operation to ensure proper fuel combustion.Even gasoline engines can suffer ignition problems when the airintake draws in low-temperature air. This can be remedied byinstalling a protective shroud around the intake and exhaust manifolds.

When the engine oil thickens at low temperatures, the engine Engine oilbecomes more difficult to crank since the pistons cannot moveeasily in the cylinders. More cranking power is required to tum overthe engine at a time when the battery output is reduced from the cold.Even if the engine can be started, the cold lubricant will notadequately protect the cylinder walls, and scuffing may result, such

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3. Engine scuffing,caused by inadequatelubrication of he

cylinder walls. Thisfrequently happens whenan engine is started andthe oil is too cold to flow

properly.as that shown in Figure 3. For this reason block heaters arecommonly installed to ensure that the oil along the cylinder wallswill be sufficiently fluid to allow the engine to start and to protectthe cylinder walls immediately afterward. But this is only half thestory. I f the oil in the sump is too thick to pump, the bearings andother engine parts will be inadequately lubricated, which can causeserious damage, including bearing seizure. For this reason, preheating of both the block and the pan is highly recommended.

Fuels Winter-grade gasolines should not cause any problems, even inthe extreme cold, except those resulting from water in the fuel.However, diesel fuels are a frequent source of trouble,. mainlybecause ofwax formation. This can be prevented or mitigated eitherby the use ofarctic-grade fuel, which is basically kerosene, or by theuse of heaters for the fuel tank, fuel line, fuel filter or any of thesetogether. More information on fuels for cold regions use is availablein Diemand (1991a).

Cold-starting aids A low cranking speed is often responsible for starting problemsDiesel engines at low temperatures. This may be because of low battery power or

cold-thickened lubricants or both. The problem can be mitigated bythe use of engine disconnects if the machine is so equipped, butfailing that, other remedies must be sought. Several types of starterscan crank the engine at higher speeds than achievable with thecommon electric type. Compressed-air starters are one example.When this type of starter is activated, air at high pressure is directedthrough each cylinder in firing-order sequence. This system requires a compressor and a reservoir to store compressed air. The


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Russians regard compressed-air starters as very effective coldstarting aids. However, they are seldom used in North Americanequipment except in some very large engines in stationary or marineequipment.Hydraulic starting motors, which require a system similar to thatof compressed-air starters, are another type of starter that improvesvehicle cranking capabilities. These might not be a good choice ina very cold environment since hydraulic systems themselves are acommon source of trouble.

In the past, large diesel engines were commonly started using agasoline engine (called a pony engine) that was integral to themachine. There are many advantages to this arrangement. First, ingeneral it is much easier to start a gasoline engine in the cold thana diesel engine, requiring less battery power and only a modestamount of preheating. Second, once the pony engine is operatingnormally, its excess heat can be used to warm the diesel enginethrough a shared cooling system before any attempt to start thediesel. Third, when starting the diesel engine is attempted, crankingcan go on for as long as necessary without fear of depleting thebattery or overheating the starter motor, although extended cranking should not be undertaken until the diesel engine oil is fluidenough to pump readily.A general problem encountered when using any improved cranking system at low temperatures is that the engine lubrication may beinsufficient to prevent damage from high-speed cranking. I f he oilis essentially frozen along the cylinder walls, high-speed crankingwill add to engine wear. In some situations the amount of enginewear incurred during crankingcould be reduced by complementinga fast-cranking starter with a prelube device.

The use ofglow plugs, spark plugs and plasma plug igniters maysignificantly improve the likelihood of a successful start. Preheatersfor the intake air have also been used with considerable success.These devices are discussed by Diemand ( 1991 b).

In general, gasoline engines require little adjustment and modi- Gasoline enginesfication for normal operation at low temperatures beyond theinstallation of block, pan and battery heaters and a degree ofinsulation. Electronic control systems, which are becoming in-creasingly common, are usually reliable at even very low tempera-tures. There are some exceptions to this, but there are too manymakes and models of vehicles equipped with such systems toenumerate all known problems and suggested remedies. In somevehicles the central processing unit may malfunction if it is allowedto become cold-soaked. In this case the remedy would be to apply

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a small amount ofheat to the unit itself or to heat the area where theunit is located, for example, the cab. In other cases the sensing units,located in remote parts of the machine, may be affected. Remedieswill depend on the nature of the problem and the location of thesensors. Often these sensors will not affect the starting process andwill function normally when the machine achieves operating temperatures. In any case, problems of this sort are not common.

However, a few measures may improve the engine's performance somewhat:

Magneto or distributor interrupter point gaps should bereduced 2 ~ 2 5 % (while at a temperature of 20C [70F])relative to the adjustment recommended by the enginemanufacturer for temperate-climate operation. Spark plug air gaps recommended for temperate climatesmay prove to be excessive at the reduced voltagesof ignitionsystems that may prevail at subzero temperatures. Gaps,therefore, should be reduced 0.005 in. from the specificationfor temperate conditions.

Spark plugs of the next hottest range to that recommendedfor temperate climates ordinarily give better low-temperature results, especially those with smaller electrodes.

It may prove helpful to retard the ignition timing 3 from theengine manufacturer's recommendation. The condenser may be replaced by one oflower capacitance

to avoid pitting during low-temperature use. The capacity ofcondensers is usually set by engine manufacturers as a range,for example, 0.18-0.26 mF. In this case, a condenser of0.25-mF capacitance should be replaced with one with acapacitance of 0.17-0.21 mF.

Engine disconnects In some large construction equipment, engine disconnects aid

Warm-upprocedures

starting by disconnecting the transfer case or the transmission fromthe crankshaft and thereby reducing cranking resistance. Once thetransfer case is disconnected, the alternator and fan pulleys are nolonger driven and the resistance through the transmission need nolonger be overcome. This allows higher cranking speeds to bereached.

In machinery with manual transmissions that do not have enginedisconnects, the clutch should be disengaged before starting, evenif the machine is not in gear.

Once an engine is started, it is important to allow it to warmthroughout before a heavy load is placed on it. One way to do thisis to allow the engine to idle for about 5 minutes and then to operate


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it with a light load for an additional 10-15 minutes. Another way isto idle the engine for about 10 minutes and then tum itofffor another10 minutes. This allows the heat built up in the upper cylinder areato spread through the engine, reducing the likelihood of thermalstress build-up. When the engine is started the second time, it shouldbe run at moderate speed until its operating temperature is reached.The second method is useful for stationary engines where operatingunder a light load is not practical. Never race a cold engine.

All lubricants become thicker in the cold. Many become so thick Lubricantsthat they prevent the vehicle from operating normally, causingmoderate to severe damage to the affected parts. Some are specifi-cally designed for low-temperature use and are only slightly af-fected by the cold. Wherever possible these should be used in arcticoperations. Lubricants for low-temperature use are discussed ingreater detail by Diemand (1990).

Before equipment is used at low temperatures, all systemsshould be drained and flushed with arctic-grade fluids. All oil, fueland hydraulic filters should be replaced after flushing the system.All filters should be located within the engine compartment. It maybe useful or necessary to heat or insulate fuel, hydraulic and oillines.There are some general and obvious areas of concern, whichwill be discussed in the following paragraphs. However, there arealso many inconspicuous Jubricated components that may stiffen orbecome inoperable in the cold, such as cables, control knobs andlevers and instruments. In some cases merely removing the existinglubricant may assure smooth operation. In others it may be worthwhile to relubricate with a suitable light oil.

There are two ways to ensure adequate fluidity of the engine oil. Engine oilThe first is to use an arctic-grade oil such as OW20 or OW30, whichcan be pumped at temperatures as low as -40 or -50C. Most smallequipment, such as automobiles and pick-up trucks, can use theselight oils without significant problems. Oil consumption may beslightly higher than normal using these arctic-grade oils since theyare more volatile than those used in warmer conditions, but if oillevels are checked frequently, this should not cause any trouble.Some heavy equipment, however, may not be able to tolerate themand will need 20- or 30-weight engine oils at all times. In these casesboth block and pan heaters must be used to ensure successfulstarting and prevent engine damage. See Diemand ( 1991 b) for moreinformation on the types and capacities of heaters available andrecommendations for their use.

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Gear assemblies The gears and bearings of axles and other gear cases depend fortheir lubrication on oil carried or splashed from the oil reservoir.When this oil thickens in the cold, it is not effectively distributed,especially to parts at some distance from the reservoir, and localoverheating and consequent damage may ensue. Transmissions anddifferentials are not usually equipped with devices for keeping themwann before or during operation (and in many cases they are notaccessible). The oil in these assemblies should therefore be replacedwith a lighter grade, or if this is not possible, means should be foundto apply heat to them before the machine is moved. Initially it shouldbe moved very slowly in any case until the parts are warm and goodlubrication is assured.

Chassis and Stiff grease at temperatures of -37C (-35F) and below mayrunning gear prevent the bogie wheels on tracked vehicles from rotating easily.This can cause serious wear, and in extreme cases the bogies maybecome sufficiently worn to require replacement.

Tracks break more easily at very low temperatures because themetal becomes more brittle. In addition, because metal contracts atlow temperatures, the track tension should be adjusted to allow 50%greater slack than that specified for temperate climates. It is best tomake adjustments at temperatures above freezing to avoid possiblebreakage; however, if the adjustments are made on a cold machine,only the normal amount of slack should be allowed, as any contraction of the metal will already have taken place. Track failure may bereduced in some cases by loosening the end connector nuts on alltracks before they are used at low temperatures. The equipmentshould then be left to cold-soak for about a day before beingproperly torqued. After this the torque should be checked daily.

Hydraulic systems Hydraulic systems are a frequent source of difficulty in coldregions. Leakage is common, both because seals tend to becomestiff or are easily damaged and because of differential shrinkage ofthe various components of the system. The high operating pressuresmake mitigation measures more difficult. It is essential to use awinter-grade fluid at low temperatures. I f the oil is too thick, thepump will cavitate and may be severely damaged. For this reasonit is especially important to operate a cold system very slowly at firstuntil the fluid has warmed slightly by circulating through the pump.It is also a good idea to heat the reservoir at temperatures below-25C. Once the fluid viscosity has decreased to a workable level,most equipment can be used normally because the fluid will becirculated through all circuits fairly constantly and will flush in andout of the cylinders thoroughly enough to maintain a satisfactory


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working temperature. This is not true in some equipment, however,such as graders where the blade will be set and not moved for a longperiod. When it is necessary to change the blade orientation again,the system must be treated as cold-soaked and operated with thesame care as when the equipment was first started.

Another special case is machinery such as cranes in which someof the cylinders are so far from the reservoir that they are nevercompletely flushed and therefore are always at the air temperature.In some cases these can be used with winter-grade fluid if they areoperated very slowly, but in extreme conditions aircraft hydraulicfluid is used in these systems. This fluid retains a workable viscositydown to about -60C, but it is more reactive than the standard fluidand may damage the seals or other parts of the system. It also has avery low lubricity and may reduce the life of the pump, and it willleak more than the standard fluids. Hydraulic fluids are discussed ingreater depth by Diemand (1990).

The most common problems with fuels at low temperatures are Fuels and fuelassociated with water content. When liquid water collects in the systemsbottom of the fuel tank, it can freeze in the fuel line, forming ablockage and preventing the fuel from reaching the engine. But asmall amount of water can also be dissolved in the fuel at highertemperatures. This water will then come out of solution in the formof ce crystals when the temperature drops. These crystals will lodgein the fuel filter and in constrictions in the fuel line and will alsoobstruct fuel flow.

The first line of defense against such problems is to ensure thatwater does not get into the fuel in the first place. Don't usecontaminated fuel. Clear all snow away from the filler tube beforeadding fuel. Leave the fuel tank as full as possible at the end of theday or when taking the vehicle into a warm garage; this will reducethe amount of condensation that can form in the tank. To avoidpossible ice clogging, a bleeder valve or drain cock can be insertednear the lowest point of the fuel system to allow easy drainage ofanyfuel remaining in the fuel tubing system after the engine is stopped.If water contamination is possible or likely, small amounts ofalcohol or similar compounds can be added with the fuel to keep thewater in solution so it cannot block the fuel lines and filter. This isdiscussed further by Diemand (1991a).

The starting capabilities and operating performance of vehiclesare greatly affected by both the fuel used and the system by whichit is delivered to the combustion chamber, especially in dieselvehicles. Inadequate vaporization or atomization can cause incomplete combustion, leading to rough running, poor fuel efficiency

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14

Electric andelectronic

componentsBattery power


and loss of power. Some trouble can be averted by enclosing thediesel fuel supply line and the fuel return line within a commoninsulated covering so that the incoming fuel will be warmedsomewhat before reaching the injectors.

Standard diesel fuels are not suitable for arctic use because oftheir high wax content. The wax crystals collect in flow restrictionssuch as elbows and also clog the fuel filter. Fuel filters are normallylocated close to the engine and may be kept warm enough to preventthe wax crystals from accumulating, but if they do form, the remedyis to remove and clean the filter, replace it with a new one or applysufficient heat to melt the wax. There are diesel fuels intendedspecifically for arctic and winter use that are designed such that theviscosity at low temperatures remains low, while at the hightemperatures met during normal engine operation the viscosity ismaintained above the minimum level required to ensure adequatelubrication of the injectors. These fuels are essentially kerosenes,and waxing is not a problem because all the wax has been removed.

Low-temperature problems of batteries were discussed at somelength by Diemand ( 1991 c), and that discussion will not be repeatedhere in any detail. In short, though, batteries experience an apparentpower loss proportional to the drop in temperature, and this powerloss coincides with the greatest power requirements for starting,lighting, heating and so forth. There are several ways to ensure thatenough battery power is available for engine starting and operation.These measures may be used singly or in combination, dependingon the severity of the conditions and the special needs of theequipment:

Use an insulated battery box with a stand-by battery heater,and make sure that the battery is fully charged on shut-down.

Ensure that the battery is warm during operation so that it canbe charged while the engine is running. This can be done bylocating it in a warm area such as the cab or the enginecompartment or by enclosing it in an insulated box suppliedwith thermostatically controlled heat from a coolant heatexchanger.

Use a heavier electrolyte than normal, up to a specificgravity of 1.300. This will improve the performance of thebattery and reduce the likelihood that it will freeze.

Use the largest battery that is practical for the equipment orinstall an extra one. The internal resistance of the battery isinversely proportional to the plate area, so this should beincreased as much as possible.


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should be used to maintain an acceptable level ofheat in the engine,as well as to warm many areas of the machine, such as the cab,batteries, hydraulic reservoir and so forth by the use of heatexchangers in the cooling system.

I f the engine is allowed to achieve normal operating temperatures under arctic conditions, the engine life will be considerablylengthened and the maintenance requirements much reduced. Lowoperating temperatures can result in oil dilution from unburned fuel,as well as sludge deposits in the crankcase; these problems areespecially pronounced h e n the jacket and crankcase temperaturesare low.

The optimum design of heat retention devices should enable theengine to reach a temperature range of85-93C ( 185-200F) underthe worst possible conditions. During most of the operating time,therefore, there should be excess engine heat. Instead of rejectingheat by circulating coolant through the radiator, however, it can beused to advantage by pumping the hot coolant to other heat exchangers to warm other components, such as batteries, fuel, rearview mirrors and personnel, as well as to defrost the windshield.

Retaining the heat produced by a running engine is the mostimportant factor in increasing the engine operating temperatures.Engine temperatures can be increased through the use of insulation,grille covers, controlled cooling fans, exhaust restrictors and hightemperature thermostats. Air circulation should be limited to onlythat needed for engine cooling. These measures decrease the rate ofheat transfer from the engine to the environment and can therebyenable it to reach higher temperatures while operating. Thermostatsrated at190-195F (88-91 C) are commonly used on arctic equipment, and 205F (97C) thermostats are available. The use of suchthermostats will raise the temperature the engine can reach beforethe coolant is diverted to the radiator. Howev.er, installing a hightemperature thermostat will not by itself increase the engine temperature. It can only regulate the highest temperature the engine canreach. I f he engine is not generating enough heat to open a lowertemperature thermostat, it will not get any warmer with a hightemperature unit.

Permanent Closed-cell vinyl insulation 6 mm or more thick is a popularinsulation choice for use in cabs and can be used in the engine compartment

as well if treated with a flame retardant. A protective steel liner isalso a good idea. Many vehicles are equipped with sound-insulatingfoam in the engine compartment, which also serves as thermalinsulation to a degree.


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Other types of insulation have been tested for use as vehicleinsulation. A 3-in. layerofpolyurethane foam applied to the exteriorof the vehicle provides excellent heat retention, although its application and removal are very labor-intensive and it is easily damaged. Gluing styrofoam boards to the vehicle is inexpensive butagain labor intensive due to the large number of shaped sectionsrequired for good coverage. Again this is easily damaged.

Many single components may also be insulated to good effect aswell, such as the heater hose, battery box, hydraulic reservoir andso forth.

Hood blankets, formerly used in arctic service, were usuallymade of heavy canvas and were sometimes filled with kapok orother insulating material to protect the engine and help retain engineheat during shutdown periods. Because of their bulkiness, however,canvas hoods were difficult to handle and install, and because theyaccumulated dirt and grease, they represented a fire hazard. Also,while the engine was operating, the blankets absorbed moisturefrom melted snow, and during shutdown periods they shrank andbecame stiff. Woolen blankets were also used with modest success.These have largely been replaced by layers of foam as describedabove or by the "arctic jacket." The latter, which is used by themilitary as well as by some private-sector operators, is composed ofa p.ylon outer shell and a l-in. rayon or Fiberglas batting fill andprovides about 10% of the insulating properties of the foam. It cannevertheless reduce heat losses by 25%. The importance of insulating all parts of he equipment intended to retain heat is demonstratedby Table 3.

Cold air blowing into an engine compartment affects the operating temperature of the engine and various other components within

Temporaryinsulation

17

Table 3. Effect of varying degrees of insulation on the heat loss ofa vehicle. The air temperaturein the personnel compartment was maintained at l5C, while the outside air temperature was-40C. (From Stupich 1987.)

Heat loss (kW) Internal wall temperature (C)Degree of insulation Meas. Calc. Roof Walls Floor

Uninsulated vehicle 9.5 8.9 -40 -39 -40Vehicle with arctic jacket 7.1 4.3 -9 -11 -40Arctic jacket and floor insulation 3.3 -3 -6 -11Double arctic jacket and floor insulation 2.1 4 2 -1Quadruple arctic jacket and floor insulation 1.2 9 8 6


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18

5. Loader equippedwith winterfront and

side blankets.


the compartment. This effect can be reduced through the use of aradiator grille cover (or winterfront), side blankets, a diaper or acombination of these. A winterfront covers the radiator grille, andside blankets cover the open sides of the engine compartment ofconstruction machinery, as shown in Figure 5. A diaper is a metalor fabric covering used to shelter the underside of the engine.Devices of this sort should always be used at temperatures below-25C and are often beneficial in warmer conditions.

The most common winterfronts have been made ofcanvas. Theyare, however, difficult to roll and unroll because of absorption andfreezing of moisture. Many winterfronts now in use are made ofPVC or other elastomers resistant to low-temperature cracking.They may be insulated or not and are frequently equipped with azipper or some other means of opening them partially in case ofwarmer weather.

Metal shutters that can open and close to control the air flowthrough the grille to optimize engine operating temperatures aresuccessfully used in the trucking industry. The shutters are oftentemperature-controlled, remaining fully closed until the enginesurpasses by 3-5C the temperature at which the thermostat becomes fully open. Other more elaborate grille covers are made of


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metal, canvas or plastic with more or less complex control mechanisms. Some types can be adjusted from inside the cab.

The chief disadvantage of some types is their inability to withstand severe vibration. Like all systems for low-temperature use,the mechanism should be as simple as possible. The more sophisticated the linkages and controls, the greater the likelihood thatsome part of it will fail.

In addition to winterfronts or shutters, under-engine protection,or diapers, generally consisting of a sheet metal cover and aninsulating barrier, is a good idea, especially in situations where theoil pan is exposed to air blast from the wind, speed of movement orthe cooling fan. It should be designed to maintain a sufficiently highoil temperature for normal engine operation (about 72-93C) andshould be removed if the oil temperature exceeds this.

The flow ofcold air through a radiator and into an engine bay canalso be reduced through the use of a controlled cooling fan. Acommon way of controlling fail operation is with a clutch, either avariable-speed type or an on-off type. The variable-speed typesoften cannot be turned off entirely and even at their slowest speedwill blow some cold air into the engine. The on-off types usually donot operate at intermediate speeds and provide uneven air flow.Variable-speed clutches are superior to the on-off type because thefan speed continuously adjusts to the engine temperature to providethe required amount of cooling. Controlled fan operation increasesnot only the engine operating temperature but also the availableengine power since the power used by the fan drive (as much as 13%of maximum engine output in some cases) can be diverted to thedrive train when the fan is not in use.

Thermostatically controlled electric fans may be a better choicesince they provide a full variable-speed range as needed. These maynot be available for all equipment. Another approach is to usevariable-pitch fan blades so that the fan is always turning but is notalways blowing. The disadvantage of this is the excessive powerconsumption.

Controlled cooling fans that monitor and respond automaticallyto engine temperature avoid the problems of overheating that couldoccur if the fan was required to be manually switched on and off.Automatically activated fans are generally set to switch on once theengine becomes several degrees warmer than the temperature atwhich the thermostat becomes fully open. On vehicles that are alsoequipped with a shutter over the grille, the fan is activated only afterthe shutters have fully opened. I f a manually operated winterfront

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Controlled coolingfans


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is used with an on-off fan clutch, it should never be completelyclosed.

Exhaust restrictors An exhaust restrictor is a metal pipe with a restrictor valve-thepipe fits over the exhaust pipe and the restrictor valve creates a backpressure within the exhaust. This reduces the flow ofair through theengine and leads to higher engine operating temperatures when theair is cold. In addition, the temperature of the exhaust increases.Consequently exhaust restrictors can reduce the incidence of wetstacking, the condensation of combustion products within theexhaust pipe due to insufficient exhaust temperature.

Exhaust gases also have potential as a source of heat for variouscomponents. Systems for heating batteries, intake air, oil pans inunenclosed engine compartments and other components have beenused successfully . There are problems with using exhaust gas,though, because the fumes are poisonous and corrosive , requiringthat special precautions be taken and only certain material s, whichare usually expensive, be used. Moreover, there is a limit to theamount ofheat that can be extracted from the exhaust before seriousproblems with wet stacking develop.

Brakes A common problem with brakes in general is the tendency forfrost to form, especially on shoe brakes, preventing their release.Operators of semitrailers often paint radial marks on their tires sothat they can determine whether the wheels are turning when pullingaway after having stopped for a short time. For similar reasons it isalso recommended that chocks be used instead of the parking brake.To prevent the brakes from freezing on, it is sometimes helpful tobum offany moisture by dragging them slightly before parking. Alltypes of brakes are likely to be somewhat sluggish at first becauseof thickened fluid and slight frost build-up on the linings.In terms of the type of system used, hydraulic brakes shouldfunction normally at low temperatures if the system contains asuitable low-temperature fluid. Silicone brake fluid is widely usedby the U.S. military in cold regions and is reported to be effective.

Air brakes may experience problems with frost in the air lines,in addition to any problems that may exist with the compressor. Allair brakes produce water vapor, which can collect and freeze in thebrake lines and other parts of the mechanism. I f this happens, thebrakes can be frozen on or off. Some means of removing water orwater vapor from the system must be used in cold weather. There aremany systems on the market to accomplish this. Most of theminvolve the use of alcohol evaporators that require frequent additionof alcohol to the reservoir. Daily checks of the alcohol level are a


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good idea. Other types use a condenser that heats the incoming air,extracts the water from it and expels the accumulated water fromtime to time. Ice build-up on the expulsion port can be a problem inthese systems, and some modification may be necessary to assureproper operation. Also the main body of such air driers must beinsulated at temperatures below -25C. The best air driers includeboth alcohol injection and condenser components.

Many types of steel used in automotive construction lose theirability to withstand impact loads at low temperatures, and theirstrength at -40C may be reduced to as little as 50% ofnormal. Mostother metals retain their strength characteristics, but structural steelmembers that may be susceptible to brittleness damage should bestrengthened by installing reinforcing plates in areas most at risk.This is discussed in greater detail by Diemand (199ld).

For a given change in temperature, various metals will expand orcontract different amounts. For example, aluminum will contracttwice as much as steel for the same temperature drop. This willespecially affect parts with different metals bolted together, meshing gears of different metals, and bearings in which the bearing andshaft are of different metals. Special care should be taken inadjusting parts of this type for cold-weather operations, especiallywhen adjusting bearing clearances. In addition, gear boxes andassemblies likely to be affected by differential expansion should beequipped with some means ofheating if the equipment will be keptin a cold location.

Fluid leakage reaches epidemic proportions at low temperatures,especially in hydraulic systems, where the fluid pressures are higherthan in other systems. However, oil commonly leaks out of transmissions, power steering and other systems as well. Some of thisleakage may be due to metal contraction affecting the tjghtness offasteners and the clearances between mating parts. However, thegreater part of the problem is because the materials used in seals,gaskets and hoses shrink, crack and lose their flexibility. Arcticgrade seals and hoses should be used on all parts of the machine thatwill be exposed to temperatures down to -40C and below. Siliconerubbers have proven very useful in these applications, and a greatnumber of seals and hoses that use this material are commerciallyavailable. Above-40C, standard parts may be satisfactory in manyapplications and need not be replaced unless leakage problemsdevelop. These problems are discussed by Diemand (199ld).

Another factor that should be considered in selecting suitablematerials is their ozone resistance. In snow-covered regions, ozone

MaterialsMetals

Nonmetals

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22

Low-temperatureequipmentoperations


concentrations are higher than normal , and many products willdegrade in its presence.

Operations in extremely cold conditions can be conducted fairlynormally i f a few precautions are taken. First, it is important to makesure that all systems are warm enough to function freely and assuresufficient lubrication of moving parts. This is especially true ofhydraulic systems. Second, because of the increased brittleness ofmaterials, abrupt movements, shock loads and any other action thatwould place great strain on structural and functional elements of theequipment should be avoided. In any case, increased down timeshould be expected because of the need for more frequent maintenance and the certainty of more breakage than normal.

After start-up, all cold-soaked systems should be exercisedslowly with no load for up to 30 minutes to avoid excessive wear andbreakage. First, with the engine operating at low speed, the hydraulic attachment should be moved a few centimeters and then returnedto its original position. Then it should be moved a little farther andreturned. This process should be continued until all circuits becomesufficiently warm to operate freely. The transmission and powertrain should be treated similarly , first shifted from forward toreverse a few times without moving the equipment, and then movedbackward and forward for increasing distances until all linkagesmove smoothly and readily.

Windchill is a very important factor in maintaining sufficientlyhigh temperatures for normal operation ofboth the engine and othercomponents. While an object cannot become any colder than the airtemperature, wind significantly increases the rate of heat loss.Therefore, it is very important to insulate or shelter any part of theequipment that must remain warm for proper operation. Similarly,on shut-down a machine exposed to the wind will cool much morerapidly than one that is sheltered, even by a tent or makeshiftwindbreak. A snow shelter can be used to good effect in remoteareas, as it can provide a degree of insulation as well as protectingthe equipment from the wind. Temporary shelters will also protectthe equipment from blowing snow and are also useful, and oftennecessary, for performing simple maintenance and repair operations.

I f the engine is to be started and stopped frequently or idledextensively, carbon deposits will tend to form, which will ultimately cause improper valve operation and engine damage (Fig. 6).To prevent this the engine should be run until the coolant temperature reaches about 65C before it is shut down or the idling speed


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should be increased to achieve this. Figure 6 shows a valve withmoderate build-up and one that is relatively clean.An engine should not be turned off immediately after being run

hard, as this will result in thermal stresses in the engine, which maycrack or warp the block or pistons. This is especially important intwo-cycle engines or those with aluminum castings. It is worthtaking the time to idle the equipment briefly to allow it to coolsomewhat before shut-down.

I f the machine is to be shut down for an extended period (forpractical purposes, 16 hours or more), it is a good idea to leave asmany controls as possible in the position in which they will beneeded on start-up. For example, leave the choke closed, thewindshield defroster on, the gearshift in neutral and so forth.

In general, maintenance procedures for low-temperature operations are the same as those in temperate areas except that they aremore frequent. It is very important to implement maintenanceprocedures on a predetermined schedule. The consequences offailing to do so can be costly and sometimes dangerous . Oneexperienced manager suggested attaching a control device to thehour meter that would tum on a warning light when maintenance isdue. I f the time is exceeded by 10 hours, the controller wouldreduced the engine' s power by half. I f the time is exceeded by 20hours, the heater would shut down. This suggestion was made halfin fun, but in some circumstances this approach or a similar onecould prevent excessive engine wear or corrosion requiring verycostly repairs.

23

6. Valve with a fairlyheavy carbon depositcaused by a chronicallycold engine and a valvefrom an engine thatreached normaloperating temperaturesmost of he time.

Maintenance andfield repairs


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24

Comfort andsafety


The following are a few suggestions dealing with aspects that areespecially important in the cold or specific for these conditions:

Check the oil level frequently and change the oil when anysigns of sludge formation appear or every 200-300 hours. Lubricate when the machine is still warm to ensure maxi

mum lubricant penetration. Store lubricants in a warm placeor warm them before using.

Do not wipe grease fittings clean-leave a small smear ofgrease to prevent ice formation.

Add icing inhibitors to the fuel in the recommended concentration at the time fuel is added to the tank.

Fuel tanks should be topped up as often as possible toprevent condensation build-up in the fuel, and sedimentshould be drained daily.

Keep batteries warm and fully charged. Check daily for signs of coolant in the crankcase oil-if

found, repair the problem immediately and change the oil. Keep the tire valve stems covered to prevent ice build-up. A void sudden blasts of hot air on the windshield or other

glass surfaces, which can crack the glass. In vehicles with air brakes, check the level of the alcohol in

the air dryer regularly and fill as required. Use chocks under the wheels instead of the hand brake to

avoid freezing up the brakes. Park the vehicle on a dry surface or on branches, lumber,

cardboard or similar material to prevent the vehicle fromfreezing to the ground.

It is useful to maintain records of all adjustments, modificationsand repairs done on each vehicle. These can provide an indicationof the types ofvehicle preparations or maintenance inspections thatshould be performed prior to deployment at future times or maysuggest the need for longer or shorter routine maintenance intervals.

The comfort of the operator is very important-in the success andefficiency of low-temperature operations. An operator who is coldwill be less alert and less efficient and may suffer impaired judgement. This in tum may result in needless equipment damage andavoidable down time. In addition, lost time due to illness maybecome a significant factor. For all of these reasons, improving thepersonnel compartment of the cab is well worth the expense.

First, the doors and windows must be tightly sealed with amaterial that will keep a seal at low temperatures. Some equipmentcan be provided with double-paned side windows, with the addedbenefit that they will reduce frost. These two measures prevent


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drafts. Second, the walls, roof and floor should be insulated. Last,the heater should be both adequate to maintain a comfortabletemperature within the cab, which should not be difficult in aninsulated cab, and installed so that it will not blow directly on theoccupants or produce major hot spots. To ensure that carbon dioxidelevels do not get so high as to endanger personnel, a small amountof ventilation, or infiltration of air, may be needed.

Cabs should be sufficiently wide to seat personnel in arcticclothing comfortably. They should have a good windshield defroster, have provisions for a quick emergency escape, and bearranged or constructed to keep out exhaust gases.

Most machinery is not designed to be used by operators wearingbulky arctic clothing, boots and mitts. Many equipment accidentscaused by the operator's foot or hand slipping when wearing arcticclothing can be avoided by providing nonskid walking or standingsurfaces and oversized handles on the equipment. Grated types ofplatforms, running boards and walkways are self-cleaning for snowand ice. Standard equipment can also be made nonskid by applyingpaint mixed with emery dust to all foot surfaces. All control knobs,handles, keys, levers etc. that the operator uses should be of asuitable shape and should be spaced so that they can be workedwithout the operator removing his gloves. A further safety featureis the coating of control handles with a cold-resistant or nonconducting paint so that bare hands will not freeze to the handles.

Visibility is often a problem at very low temperatures because ofthe prevalence of ice fog, frost and exhaust plumes. Engine exhaustshould be directed away from the operator's line ofvision. Between-30 and -50C, visibility can be sufficiently reduced by ice foggenerated by internal combustion engines to restrict operations andbring about hazardous conditions (Fig. 7). In a situation wheremany machines will be working in a small area, it is a good idea touse ice fog control devices of some sort. Two approaches to thishave been studied and tested. The first and easiest is to disperse theexhaust by attaching a long perforated metal tube to the exhaustpipe, which allows the exhaust to escape through the widely spacedperforations rather than as a single dense plume. The fog is notremoved but rather diffused, resulting in a thinnerhaze. The secondmethod is to condense the exhaust gases in a heat exchanger,removing the greater part of the water (and incidentally many otherwater-soluble combustion products) and thereby entirely suppressing the exhaust plume.

Lights should be carefully located to prevent them from restricting the vision of the operator or becoming packed with snow thrownby the tracks or wheels.

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26

7. Ice fog generated byequipment operating atvery low temperatures.


Caution plates on winch housings indicate maximum safe loads.These load markings should be changed to indicate a reduced loadlimit at low temperatures. Such a reduction prevents hazardouswinch and cable failures at low temperatures. Because of theincreased likelihood of structural failures at low temperatures, themaximum load limits of cranes and lifts should be downgraded by1% for every 1op below 0F. I f possible it is a good idea to suspendheavy equipment operation entirely at temperatures below -40C,especially in high winds.

At low temperatures, fire extinguishers do not function satisfactorily. The fire is not blanketed, extinguishing materials do notadhere to ceilings or overhead fires, the temperature of burningmaterial is not reduced, extinguishingmaterials do not carry throughthe air without dangerously high pressure, and all classes of firesClass A (Solids), Class B (Liquids) and Class C (Electrical)cannot be fought with the same extinguisher. Fluorinated hydrocarbons, dibromodifluoromethane and dibromotetrafluoroethane arethe most effective for all classes of fires at temperatures down to-55C ( 65F).

Fire trucks, pumps and stored water should be kept in heatedshelters. Pumps operated by the truck engine should circulate thewater enroute to the fire. Piping should be insulated. Trucks shouldbe winterized and equipped with front-wheel drive and low-pressure mud and snow tires.

Conclusions The operation of equipment in extremely cold regions will resultin higher maintenance costs, increased down time, decreased pro-


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ductivity and increased fuel consumption over similar operations intemperate areas. This is inescapable. However, by implementingsuitable winterization measures, many of these problems can bekept to a minimum. In general the areas of concern are as follows.Lubricants should be changed from summer-weight products tothose suitable for temperatures in the range of expected operation,including lubricants for all parts of the equipment: engine oil, gearoil, greases, hydraulic fluids and so forth.

Sufficient battery power should be provided to assure sufficientpower for reliable start-up and operation of accessories such aslights, heaters and fans.

Cooling system components should be carefully inspected before the onset of cold weather, and any impaired elements cleaned,repaired or replaced. Hoses should be firm but not rigid. Theradiator, auxilliary heat exchangers and all passages should beclear. All valves, seals and controls should be in good condition.

Many standard seals become hard or brittle at low temperatures,severely reducing their effectiveness. These should be replacedwith arctic-grade products, which will remain flexible at very lowtemperatures.

The engine and cab should be insulated to a degree consistentwith the expected minimum operating temperatures. Fuel tanks andhydraulic reservoirs exposed to ambient air should be insulated orprotected from wind, as should lubricated components of the drivetrain, if possible.

Any necessary equipment modifications should be implementedbefore the onset ofcold weather, such as moving the air intake underthe hood, installing a high-temperature thermostat or altering the fan.Bugelski, W.G. (1975) Preparation and operation ofdiesel engines Referencesin construction and industrial machinery for operation in coldclimates. Society of Automotive Engineers Transactions, 84(2):1273-1289.Canada National Defence Department (1982) Preparation andoperation of vehicular equipment in extreme winter areas. CanadaNational Defence Department, C,.04-010-005/MG-OOO.Coutts, H.J. and R.K. Turner (1976) Research on practicalmethods of reducing automotive ice fog. The Northern Engineer,8(2): 29-39.Coutts, H.J. (1984) A simple device to improve low temperaturedriving. The Northern Engineer, 16(1): 36-37.Diemand, D. (1990) Lubricants at low temperatures. USA ColdRegions Research and Engineering Laboratory, Cold RegionsTechnical Digest 90-1 .

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Diemand, D. (1991a) Automotive fuels at low temperatures. USACold Regions Research and Engineering Laboratory, CRREL Technical Digest 91-2.Diemand, D. (1991b) Automotive and construction equipment forarctic use: Heating and cold starting. USA Cold Regions Researchand Engineering Laboratory, Cold Regions Technical Digest 91-3.Diemand, D. (1991c) Automotive batteries at low temperatures.USA Cold Regions Research and Engineering Laboratory, CRRELTechnical Digest 91-4.Diemand, D. (1991d) Automotive and construction equipment forarctic use: Materials problems. USA Cold Regions Research andEngineering Laboratory, Cold Regions Technical Digest 91-5.Newton, W.S. and C.G. Makrides (1954) Effect of climate andenvironment on ground support equipment. Study by Corvey Engineering Co. for Wright Air Development Center. Air Research andDevelopment Command, USAF. Wright-Patterson Air Force Base,Ohio., Technical Report 54-132.Northrop Services, Inc. (1980) U.S. Marine Corps cold weathercombat operations. Arlington, Virginia: Northrop Services, Inc.Pipeline and Gas Journal (1974) Special winterization programdeveloped for arctic use trucks. 201(14): 65.Smolin, A.P. (1968) Operation of construction machinery underwinter conditions. Translated from Ekspluatatsiya Stroitel nykhMashin v Zimniky Usloviyakh bu, U.S. Army Foreign Science andTechnology Center, 1970.Stupich, T .F. (1987) Cold regions operation ofdiesel vehicles withspecial consideration for the M 113A 1 armoured personnel carrier.Defence Research Establishment Suffield, Ralston, Alberta, SuffieldReport No. 408.U.S. Army (1989) Operation and maintenance of ordnance materiel in cold weather (0F to -65F). Departments of the Army andthe Air Force, Washington, D.C.U.S. Navy (1955) Arctic engineering. Department of the Navy,Bureau of Yards and Docks, Technical Publication Navdocks TPPW-11.

'C.S. GOVER.'\"XDIT PRINTING OfFICE : l99 5 -60 0-080 /00 52 7

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