Cold Weather Considerations
|"Every mile is two in winter."|
The Cold Weather Challenge
IMPACT ON MILITARY FORCES
The cold has been identified as an enemy of military forces and equipment since the beginning of recorded history. When employed in a cold region, a force actually faces two enemies--the tactical enemy and the environment that also aggressively attacks and can destroy equipment and men. The impact of cold weather on combat forces can readily be seen during decisive campaigns in history. Napoleon's disasterous march into Russia, Germany's failed conquest of Russia during World War II, and the operations of United Nations forces in Korea are modern examples. With United States (US) reliance on global force projection, Army forces must prepare to operate in a variety of climates, including extreme cold.
Army forces may be required to conduct sustained operations in temperatures as low as -65° Fahrenheit (F). Under such conditions, personnel are subject to decreased efficiency and cold casualties, equipment is prone to breakdowns, supply problems are increased, and operations are restricted and complicated by the environment.
It is the responsibility of unit leaders to ensure that personnel and equipment can withstand the challenges of cold weather. US Army equipment is among the best in the world for use in cold climates. However, soldiers and their leaders must understand the effects of cold weather and adapt operations and maintenance to overcome environmental conditions.
Since most US units are stationed in temperate or tropical climates, soldiers generally lack adequate training or experience in cold weather operations and maintenance. If troops stationed in temperate climates are to be expected to move to cold climates and perform their missions, they must be prepared for it.
A large part of a soldier's time and energy in cold weather is spent in self-preservation. This naturally reduces the efficiency of personnel when operating and maintaining materiel. Besides operating equipment, soldiers must learn to protect themselves against climatic factors by dressing properly and improvising protective measures and shelters.
LEVELS OF OPERATION
Operating equipment in temperatures no lower than 10° F presents few problems. Conditions are similar to those experienced during winter in the northern part of the continental United States (CONUS).
From 10° F to -25° F, operations become more difficult (Figure 1-1). At the warmer end of this range, lack of winterization results in only a slight loss of operating efficiency. Proper training prevents many failures of materiel and injuries to operators. Nevertheless, nonacclimated troops have difficulty at even the warmer temperatures above -10° F.
When temperatures drop below -25° F, operations become increasingly difficult. At temperatures nearing -50° F and lower, the maximum efforts of well-trained personnel are required to perform even the simplest tasks with completely winterized materiel.
EFFECTS ON MATERIEL
Since metals contract at lower temperatures and expand at higher temperatures, improper clearances may result in either binding or excessive looseness.
Cleaning and Preparing Equipment
Before operating vehicles, crews should review appropriate operator manuals for cold weather operations. These manuals all include a section subtitled Operations Under Unusual Conditions. Also, operators must know other basic skills, such as working with tire chains and slave-starting.
Soldiers must maintain equipment in the best mechanical condition to withstand the added difficulties and prevent failures during sub-zero operations. Commanders must place special emphasis on maintenance inspections.
Figure 1-1. Operational difficulty vs temperature range
Placing equipment in proper mechanical condition before the onset of cold weather requires time for necessary and careful disassembly, repair, cleaning, and reassembly. Low temperatures must be anticipated far enough in advance to permit completion of winterization. Refer to pertinent operator and unit maintenance technical manuals (TMs) for operation, lubrication, preventive maintenance checks and services (PMCS), and maintenance under unusual conditions. Operators must be very cautious when using equipment that has been inactive for a long time. For example, if lubricants congeal in various components, parts can fail.
Metals become brittle in severe cold temperatures; thus, parts cannot withstand the shock loads that they sustain at higher temperatures. Illustrations of such stress are at Figure 1-2. For example, at -20° F certain steels can withstand only 50 percent of the shock load that they can sustain at room temperature. For a given change in temperature, various metals will expand or contract by different amounts. These characteristics especially affect bearings in
which the bearings and shaft are of different metals, are of different metals bolted together, or meshing gears are of different metals. In cold weather, special care should be taken in adjusting parts of this type, especially when adjusting bearing clearances.
Besides natural rubber, there are hundreds of rubber substitutes. Synthetic rubbers look and usually react the same as natural rubber, although most do not attain a greater flexibility at high temperatures. As it cools, natural rubber gradually stiffens, but retains a large part of its elasticity until reaching temperatures below -20° F.
Below -20° F, certain peculiarities occur. When cooled gradually but continuously over a short time, rubber remains flexible until it reaches approximately -60° F. It then quickly loses its elasticity and becomes brittle. Also, if rubber is consistently kept at the relatively higher temperature of -20° F for a long time, an effect similar to crystallization occurs, causing it to become brittle. For example, hoses for fueling may crack, increasing the potential for spills.
Figure 1-2. Effect of cold on metal
Extreme care must be taken in handling cables at low temperatures. If the rubber jackets become hard, the cables must be protected from shock loads and bending to prevent short circuits caused by breaks in the covering. If cables are to be bent, they must first be warmed. Neoprene jackets on cables become brittle and break readily at low temperatures.
Tires become rigid in cold, causing flat spots on parts that come in contact with the ground during shutdown. At severe cold temperatures, sidewalls become brittle and crack.
Tires must be inflated to the appropriate pressure at cold temperatures. A tire inflated to 40 pounds per square inch (PSI) indoors will change to 25 PSI when moved outside at -50° F. Failure to properly inflate tires can result in tires slipping off rims. Generally, tires should be inflated 10 PSI over the normal pressure for winter operations.
Plastics expand and contract much more than metal or glass, causing them to be brittle in cold weather. Vehicular canvas covers with plastic windows may break due to a combination of cold and vibration.
Glass, porcelain, and other ceramics perform normally at low temperatures if handled carefully. However, cracking may result if heat is applied directly to cold windshields or other vehicle glass.
If kept dry, fabrics generally retain
their flexibility, even at extremely low temperatures. However, tarpaulins may shrink, and wrinkles are extremely difficult to smooth out at sub-zero temperatures. Whenever possible, tarpaulins should be unfolded in heated enclosures or kept installed on equipment.
EFFECTS ON MISSION FUNCTIONS
Severe cold adversely affects the capability of a unit to accomplish its mission. Understanding the specific impacts can assist a unit in planning measures to counter these effects.
Units are less maneuverable in icy conditions or deep snow. Deep snow reduces vehicle traction on hills and increases the chances of breakdown/damage caused by hidden obstacles. Motorized units are restricted almost exclusively to roads. Also, personnel have a tendency to operate close to vehicles, which is tactically unwise. Trailers and towed artillery pieces further reduce mobility. Emplacement of artillery pieces for fire missions is very difficult.
When planning for battle, leaders must realistically evaluate the impact that physical factors have on operations.
There is an increased need for ammunition in cold weather. This is because cold temperatures adversely affect firing, responsiveness, effectiveness, and accuracy. Also, it is often necessary to fire several light-to medium-zone rounds prior to maximum propellant charges to avoid stressing the hydraulic recoil mechanisms of howitzers. Support units must be prepared to handle and transport the added volume of ammunition. Because of the harsh conditions, it is also more difficult to prepare ammunition storage areas.
Units operating in a cold environment can expect a dramatic increase in petroleum, oils, and lubricants (POL) and fuel requirements due to movement difficulty, extended idling, and heating requirements. Special fuel and lubricants must also be used to prevent freezing and jelling.
Always consult the appropriate TM or lubrication order (LO). Remember to use antifreeze in coolant systems. Different grades of hydraulic fluids are also necessary. If vehicles come into theater with temperate grade automatic transmission fluids and become cold-soaked (when vehicle temperatures drop as low as the existing ambient temperatures), seals are likely to blow when transmissions are engaged.
Units may also consult the Defense Logistics Agency (DLA) publication, Environmental Products, Chemical Alternatives, Recyclers, Aircraft Cleaners and More, to choose environmentally preferred substitutes.
Operators and maintenance personnel must be proficient in the use of all winterization and arctic kit items, which include heating devices, insulated grill covers, and sometimes engine exhaust restrictors. When authorized, stationary engagement of hydromechanical transmissions can be used to facilitate engine warming.
FACTORS IMPACTING LOGISTICS
Vast distances, major climatic or terrain obstacles to air or ground movement, or a combination of these factors often separate combat service support (CSS) elements from supported forces. As a result, logistical planning must be continuous and aggressive, making use of all modes of transportation. Unit standard operating procedures (SOPs) and training plans should address the following:
- Unit distribution is the rule and not the exception.
- Many munitions have known firing and/or function limitations as a result of cold temperatures, snow, and soft ground conditions. Multioption fuzes should be selected whenever available to provide for seasonal changes.
- Economic order quantities (EOQ) and ammunition required supply rates (RSR) should be computed on a seasonal basis rather than on the standard 180-day demand criterion.
- Special training and emphasis is required for using heat sources and keeping water and other liquids (especially medical items) in a liquid state when temperatures drop below 32° F.
At temperatures below 32° F, heated storage must be provided for power sources, command and control centers, dining facilities, aid stations, maintenance shelters, and critical supplies (i.e., medicines, batteries, and POL).
When preparing for sustained operations in remote, cold regions, logistical planners must understand the following environmental characteristics:
- Unrelenting hostile climate.
- Formidable and virgin terrain.
- Great distances.
- Extensive water obstacles.
- Acute movement problems.
- Poor lines of communication.
- Low population densities.
- Lack of shelter and developed resources.
Planning is critical to the success and survival of units operating in cold weather. Planners should consider the following:
- Plans must be both detailed and flexible.
- Personnel must be properly trained and prepared.
- A potential increase in medical problems (i.e., injuries from frostbite and hypothermia) must be anticipated.
- Prolonged exposure to cold and extended hours of darkness will lead to increased psychological stress.
- All units, especially mechanized and motorized, will require more time to accomplish tasks; cold will increase fuel consumption and the demand for lead acid and dry cell batteries.
- Although equipment is designed to function in the cold, it will be less reliable, thereby increasing maintenance, time, and supply problems. Maintenance, supply, and engineer units may require augmentation.
- Cold conditions tend to increase security problems because soldiers want to keep warm and sleep indoors. Cold will also make command and control more difficult. Flank units must work harder to keep up with the main body and require frequent rotation.
HOST NATION SUPPORT
Logistics support can be decisive to mission accomplishment during cold weather operations. Host nation (HN) personnel are critical to identifying sources of food, shelter, warmth, supplies, and services. Leaders must incorporate all available HN support into their planning to reduce the impact of cold weather on logistics operations. HN personnel should identify specific environmental restrictions pertinent to cold weather operations (i.e., specific chemical substitutions, spill response, and corrective actions).
The importance of maintenance, especially PMCS, must be impressed on all cold region soldiers. Maintenance of mechanical equipment is exceptionally difficult in the field during cold weather. Added time is needed to complete tasks. Even shop maintenance cannot be completed at normal speed. Mechanics must allow equipment to thaw out and warm up before making repairs. This time lag cannot be overemphasized and must be included in all planning. Personnel efficiency also is reduced by the bulky and clumsy clothing worn in extremely cold areas. Because it is dangerous to handle cold metal with bare hands, operators/mechanics must wear mittens or gloves at all times. Losing the sense of touch further reduces the soldier's efficiency. Even the most routine operations, such as handling latches or opening engine compartments, become frustrating and time-consuming when performed with protected hands.
At temperatures below -20° F, maintenance may take five times as long. Complete winterization, diligent maintenance, and well-trained crews are the keys to reducing the adverse effects of cold weather.
Listed below are several requirements that affect maintenance directly and require planning and preparation before a cold weather operation:
- Heated shelter for equipment maintenance.
- Proper clothing and tools for mechanics.
- Adequate portable heaters.
- Capability to store and issue antifreeze materials, fuels, hydraulic fluids, and lubricants.
- Adequate lighting.
- Supply of repair parts.
- Sufficient equipment for snow and ice removal.
PROVIDE PROPER VENTILATION IN HEATED SHELTERS TO AVOID THE DANGER OF CARBON MONOXIDE POISONING CAUSED BY EXHAUST GASES FROM RUNNING ENGINES AND CONTAMINATED HOT AIR FROM DEFECTIVE HEATERS.
The availability of maintenance facilities can be critical to the maintenance mission. Without some type of permanent or temporary shelter, even routine maintenance can become extremely difficult.
Buildings and Shelters
Heated buildings or shelters are
necessary for cold weather maintenance. Proper and satisfactory servicing is difficult unless personnel are working in reasonably comfortable temperatures. Maintenance of many components requires careful and precise servicing. Without the use of heaters, the increase in maintenance man-hours is from 25 percent to 200 percent above normal.
When buildings are not available, maintenance tents are a temporary expedient. If possible, tents should have wood flooring and be heated by portable duct heaters or tent stoves.
WHEN VEHICLES, GENERATORS, AND POL CONTAINERS ARE BROUGHT INTO WARM STORAGE FROM THE COLD, THE FUEL TANKS/CONTAINERS SHOULD ONLY BE FILLED THREE QUARTERS FULL. IF THIS PROCEDURE IS NOT FOLLOWED, THE EXPANSION OF THE COLD POL PRODUCTS IN THE FUEL CONTAINERS COULD CAUSE SPILLAGE AND CREATE A SERIOUS FIRE HAZARD.
In the absence of buildings or maintenance tents, tarpaulins may be used to create overhead shelter and windbreaks. A framework of poles erected around a vehicle can support the tarpaulin.
Parachutes can also make temporary shelters. The parachute should be deployed over the vehicle, securely staked down at the bottom, and then inflated by the air from a portable duct heater. If parachute shelters are used, extreme care should be taken to avoid the danger of carbon monoxide poisoning by ensuring proper ventilation.
PERSONNEL MUST BE CONSTANTLY ON THE ALERT TO DETECT VEHICLE DEFICIENCIES THAT EXPOSE PERSONNEL TO CARBON MONOXIDE POISONING. PASSENGER AND CREW COMPARTMENTS OF WHEELED AND TRACKED CARRIERS MUST BE INSPECTED AND TESTED IN ACCORDANCE WITH (IAW) TECHNICAL BULLETIN (TB) MED 269 AT REGULAR INTERVALS. THE PURPOSE OF THE INSPECTION AND TEST IS TO DETECT ANY SIGN OF AIR CONTAMINATION FROM EXHAUST GASES CAUSED BY LEAKING GASKETS, IMPROPER EXHAUST INSTALLATIONS, CRACKED EXHAUST PIPES, DEFECTIVE PERSONNEL HEATERS, AND AUXILIARY GENERATORS. WHEN VEHICLES ARE IDLING, ALLOW FOR FRESH AIR ACCESS TO PREVENT CARBON MONOXIDE HAZARD.
Daylight can be scarce in cold climates. Lighting equipment must be available to furnish adequate illumination for maintenance services. Lights with ample cable extensions, attachment plugs, connectors, and spare bulbs are essential.
Maintenance Personnel, Tools, and Equipment
More mechanics are needed to maintain equipment in cold weather operations (Figure 1-3). At a minimum, a highly organized, more intensive effort is required of mechanics. Providing heated buildings or shelters for maintenance of materiel increases work efficiency and morale.
An added supply of battery chargers must be available to meet the heavy requirements for battery maintenance in sub-zero temperatures. Soldiers must check battery charges using hydrometers and testers.
Handwear may become saturated with fluids when soldiers perform maintenance on fuel and cooling systems. Saturation reduces the insulating value of the handwear, causing cold injuries. Soldiers should carry extra handwear when performing maintenance under arctic winter conditions.
Figure 1-3. Normal vs cold weather maintenance
Personnel should avoid leaning on cold-soaked equipment (equipment that has been standing in sub-zero temperatures for an extended period) or kneeling and lying on the ground. Rapid body cooling caused by heat transfer to the equipment or ground may result in cold injury.
Mechanics should place insulating material--such as fiber packing material, corrugated cardboard, rags, or tarpaulins--between themselves and cold-soaked equipment.
When performing maintenance under arctic winter conditions, a box or pan should be used to hold small parts. A tarpaulin should be placed under each vehicle to catch parts that may be dropped. This prevents the parts from becoming lost in the snow (Figure 1-4).
Vehicle recovery in cold, snowy conditions can be extremely dangerous. Every precaution must be taken to maintain soldier safety and ensure equipment is functioning properly.
When using the winch, operate the vehicle engine at a reasonable speed IAW the operator's manual. High engine speeds are likely to damage the winch mechanism. Use a snatch block whenever possible to reduce the load on the winch.
Read all caution plates and estimate a 25-percent reduction in capacity when determining load. EXAMPLE: If capacity of the winch is specified as 5,000 pounds on "Winch Caution Plate," lower the rated capacity for cold weather operations by 25 percent, making capacity 3,750 pounds. This safety factor is essential to prevent damage to the winch.
Figure 1-4. Tarps used to protect from cold
and to catch dropped parts
Preparation for Operation
In preparing a winch for operation, the following steps should be taken:
- Remove mud, dirt, and rust from exterior of winch.
- Inspect cable for rust and apply lubricating oil (PL-S).
- Flush and clean gear housing, and fill to level with recommended seasonal gear oil (GO75W).
- Inspect safety brake for satisfactory operation.
- Check drum brake and adjust if necessary.
- Check for iced bleeder and selector valves, controls and linkage, and winch cable sheaves.
Recovery in Cold Weather
A cold-soaked/inoperable vehicle can present a maintenance challenge. Vehicle recovery is often extremely difficult due to reduced mechanical capacity, ice, snow, and limited approach routes. Exercise care when towing cold-soaked vehicles. Drive trains may have to be disconnected to prevent further damage.
Antifreeze, Fuels, Hydraulic Fluids, and Lubricants
The proper antifreeze materials are critical for cold operations. Antifreeze materials specified for protection of liquid-cooling systems are listed in Appendix A. Units can also consult DLA's publication (see DLA publication in references) for environmentally preferred antifreeze substitutes.
Arctic fuels for gasoline or diesel engines are selected to obtain the proper atomization necessary for a combustible fuel-air mixture. These fuels are listed in Appendix A.
Hydraulic fluids must be able to work in cold conditions. Hydraulic fluids specified for hydraulic systems, recoil mechanisms, and equilibrates are listed in Appendix A.
Lubrication required for Army equipment is specified in the LO or TM pertinent to the equipment. LOs are based on three anticipated ranges: above 32° F, from +40° to -10° F, and from 0° to -65° F.
NOTE: Oil, engine, arctic (OEA), is a synthetic SAE OW-20 lubricant intended for temperature range 40° F to -65° F for engine systems and 120° F to -65° F for transmission and hydraulic systems. This lubricant is approved for use in engines, power steering systems, and both automatic and standard transmissions. Although OEA can be used in most automatic transmissions, it is necessary to consult the LO prior to use. The use of OEA may void the warranty in some transmission applications.
The materials normally required to prepare equipment for operation in cold weather are listed in Appendix B. These items are listed in Department of Defense (DOD) Federal Supply Catalogs (FSC), FSC Groups 68 and 92. Consult these catalogs when requisitioning. Other items--with specification numbers, unit of issue, stock numbers, and issuing services--are listed herein for requisition through supply channels.
The provisions of Department of the Army (DA) LOs are mandatory and will be adhered to at all times, unless DA authorizes deviation.
Increased service scheduling from that specified on LOs is necessary to compensate for cold conditions that destroy the protective qualities of the lubricant. The incomplete combustion of fuels in a cold engine, and the piston rings not sealing tightly until the engine reaches operating temperatures, causes rapid fuel dilution of the oil. The commander may extend intervals during inactive periods, provided adequate preservation continues. During prolonged periods of extreme cold weather, it may be necessary to take oil samples more frequently for equipment registered in the Army Oil Analysis Program (AOAP). This precaution ensures the protection provided by the lubricating oils is adequate.
Military symbols for petroleum and related products indicated in the "KEY" on LOs are standardized in Military Standard (MIL-STD) 290. To identify the contents, container markings for these items include the North Atlantic Treaty Organization (NATO) and military symbols, the national stock number (NSN), and specification nomenclature.
Contaminated petroleum products and coolants must be disposed of in an environmentally safe manner IAW US and HN laws and regulations and unit SOPs. Units must identify US and HN requirements in advance.
One of the greatest hindrances to successful military operations in a winter environment is the effect of cold on batteries.
The storage battery's available energy decreases sharply when temperatures fall. Power requirements for starting an engine increase when the battery is least capable of delivering power. Current delivered at 15° F is
only 50 percent of that produced at normal temperatures. The amount delivered at -30° F is only a little over 10 percent of that produced at room temperature (Figure 1-5).
At -40° F and below, the available current is practically zero. A fully charged battery does not freeze in extreme cold climates, but a battery with specific gravity 1.100 freezes at 10° F. It is essential to keep batteries fully charged.
Figure 1-5. Battery efficiency at varying temperatures
Frozen batteries rupture and break internally and externally. Table 1-1 shows freezing points of batteries at various specific gravities. Unless a storage battery is warmed to about 35° F, it does not receive an adequate charge from the generator. In constant cold weather, storage batteries should be tested for state of charge every three days. Recharge batteries if the specific gravity is less that 1.1250.
Specific Gravity of Electrolyte (Corrected to 80° F)
Table 1-1. Freezing points of batteries at
various specific gravities
If the vehicle is equipped with a battery preheater, it should be used IAW the operator's TM. If the vehicle does not have a preheater, an insulated battery box can help maintain specific gravity at higher levels for longer periods. Batteries should be filled with 1.280 specific gravity electrolyte, not the tropical electrolyte of 1.250. Deployment of tactical vehicles from a hot to a cold region requires a change in electrolyte for maximum battery effectiveness.
For more information on operations and maintenance of lead-acid storage batteries, refer to TM 9-6140-200-14.
BATTERIES PRODUCE HYDROGEN GAS. HYDROGEN GAS CAN CAUSE A BATTERY CASING TO EXPLODE DUE TO BLOCKAGE OF THE BATTERY VENT BY ICE. SEE FIGURE 1-6 FOR PROPER JUMP-STARTING PROCEDURE.
Figure 1-6. Proper jump-start procedure
SMALL EQUIPMENT BATTERIES
For small equipment, alkaline batteries are far superior to carbon batteries. For example, flashlights (essential items in regions with long periods of darkness) using size D batteries should use the BA-3030/U rather than the BA-30. These same batteries should be used in artillery, mortar, and tank night-aiming post lights along with tactical telephones such as the TA-312/PT (see TB 43-PS-491, The Preventive Maintenance Monthly, October 1993, for more information).
When properly maintained, the nickel-cadmium (NICAD) batteries used in some Army equipment (such as range finders, some night vision sights, and ground surveillance radars) are very effective low-temperature power sources.
To get maximum effectiveness when charging NICAD batteries, one must destroy the charging memory characteristic of the battery. For example, if a NICAD battery is continually called upon to deliver an average of only 25 percent of its capacity before it is recharged, it will eventually "memorize" this fact and become incapable of supplying the remaining 70 percent capacity. Operators must discharge NICAD batteries down to their lowest operating levels, then recharge them fully, then discharge them again to their lowest operating levels, then once again recharge them fully to destroy the "memory."
The preferred cold weather batteries are lithium-based, but precautions must be taken in their storage and disposal. Mercury batteries should not be used below 0° F.
LITHIUM SULFUR DIOXIDE BATTERIES
The lithium sulfur dioxide battery is recommended for use in the AN/PRC-77 and single-channel ground and airborne radio subsystem (SINCGARS) radio sets when used in extreme cold weather areas. The lithium battery has unique characteristics that provide improved operational capabilities and extended battery life. Lithium sulfur dioxide batteries require special handling. Turn-in instructions must be followed carefully IAW host nation, federal, state, and local environmental laws and regulations.
Special equipment is provided for a vehicle when protection against cold weather is required. This equipment is issued in specific kits. Geographic location and ambient temperatures dictate the use of winterization equipment as per Supply Bulletin (SB) 9-16.
Where the temperature falls only a few degrees below freezing for a short period, only ordinary preparations are needed; for example, changing engine oil to a lighter grade and adding antifreeze to the cooling system.
For anticipated temperatures of -25° F or lower, personnel heater kits and hardtop closures are installed. Operations will not be attempted without winterization kits in areas where temperatures from -25° F to -65° F are likely. Since some winterization kits require use at temperatures warmer than -25° F, consult the TM for the correct starting procedure.
Generally, vehicles using gasoline as fuel provide ample heat through personnel hot-water heaters until the ambient temperature drops below -25° F. Below this temperature, fuel-burning heaters are normally used to provide more heat. Personnel heaters in military vehicles are only required to maintain a temperature of 41° F IAW MIL-STD-1472C.
Present personnel heaters have pot-type vaporizing burners. This means the pot must get hot enough to vaporize fuel at -65° F. Fuel carbonizes if the combustion chambers do not get hot enough. This accelerates heater failure by carbonizing the wick, igniter, burner, related burner components, or heat exchanger. Contaminated fuel can block the flow of fuel to the heater burner causing low heat output and/or numerous heater stoppages. This blockage also can lead to premature igniter failure due to excessive start attempts. Fuel burning heaters are generally unreliable because of--
- Contaminated fuel.
- Low voltage.
- Inexperienced operators and mechanics.
- Design characteristics of the heaters.
PERSONNEL AND CREW CAB HEATERS SHOULD BE SHUT OFF AT LEAST 20 MINUTES PRIOR TO ENTERING ANY SHELTER. THIS PROCEDURE WILL HELP PREVENT THE FIRE HAZARDS CREATED FROM ACCIDENTAL PUMPING OF FUEL ON BUILDING FLOORS AND EMISSION OF GASOLINE VAPORS FROM HOT HEATER COMPONENTS IN THE EVENT OF FAULTY HEATER COMPONENTS.
POWER PLANT HEATERS
The present generation of power plant heaters are water coolant type, thermostatically controlled to heat the engine block and the water pillow below the batteries. These heaters are multifuel, pot-type burners. Because they are not used often, problems surrounding these heaters include:
- Low voltage.
- Contaminated fuel.
- Inexperienced operators and mechanics.
- Inattentive operators and mechanics.
PORTABLE FUEL-BURNING HEATERS
In some geographical locations, DA has approved the use of the NATO standard heater because of its improved arctic operating capability and lower maintenance requirements.
The swingfire heater (Figure 1-7) is a pulse jet engine that burns gasoline with less carbon buildup. It uses no external power in the run cycle and needs only 6 amperes at 24 volts for starting.
Figure 1-7. Swingfire heater
The heater can be used in 12 various exchangers, making it a versatile and useful tool. An operator can externally heat gear boxes, drive trains, transmissions, and oil pans on vehicles prior to operations.
HARDTOP CLOSURE KIT
A hardtop closure kit is provided for some vehicles. It must be added to protect the driver and assistant driver where colder temperatures are expected. All-around vision is provided by a glass window on each side and to the rear.
QUICK HEAT SYSTEM
Quick heat is a technique that allows quick warmup and reliable starting when vehicle temperatures drop as low as the existing ambient temperature. Just prior to vehicle operation, heat is applied to the engine, batteries, and components, raising their temperatures enough to ensure starting.
The time from initiating quick heat to achieving reliable starting temperatures can vary from a few minutes to one hour. The military objective is to achieve reliable starting within a maximum of one hour regardless of ambient temperature.
STANDBY HEAT SYSTEM
The standby heat concept does not allow vehicle components to fall below a certain minimum temperature. For this to happen, the fuel-burning heater is continuously operated during the standby period. Continuous operation maintains engine and battery electrolyte temperatures at levels that provide adequate cranking and battery recharging potential.
The standby system includes an engine coolant heater, hoses, control valves, fuel pump, battery heat exchanger (commonly known as a battery pad), and miscellaneous hardware. This system is not designed to
start a vehicle engine after it has been cold-soaked for an extended period in extreme sub-zero temperatures (-25° F to -65° F). However, in an emergency, the standby system can assist in getting an engine start if adequate time and auxiliary power are available.
AUXILIARY POWER (SLAVE) RECEPTACLE
The auxiliary power (slave) receptacle is an electrical outlet located at a readily accessible place on the vehicle. It receives current from other tracked or wheeled vehicles. This provides direct boosting of the cold vehicle current when starting an engine in cold weather. See Figure 1-8 for sample auxiliary power receptacles.
Figure 1-8. Auxiliary power (slave) receptacle and terminals
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