Petroleum Products for Arctic Winter Use in Automotive Equipment: Encyclopedia Arctica 2b: Electrical and Mechanical Engineering
Petroleum Products for Arctic Winter Use in Automotive Equipment
EA-I. (Harold R. Porter)
PETROLEUM PRODUCTS FOR ARCTIC WINTER USE IN AUTOMOTIVE EQUIPMENT
CONTENTS
| Page | |
| Gasoline Engines | 2 |
| Diesel Engines | 5 |
| Starting Aids | 6 |
| Ice Prevention | 7 |
| Transmissions and Differentials | 7 |
| Grease-lubricated Chassis Parts | 8 |
| Cooling and Hydraulic Systems | 9 |
| Conclusion | 9 |
[EA-I. Harold R. Porter] ^✓^
PETROLEUM PRODUCTS FOR ARCTIC WINTER USE IN AUTOMOTIVE EQUIPMENT
In World War II large fleets of equipment powered with internal-combustion
engines were brought into the Arctic. This equipment included all varieties
— from automobiles to heavy tractors, as well as aircraft and marine engines
of all types. It had been general practice in the Arctic to halt the operation
of automotive equipment, with the possible exception of airplanes, during the
colder portion of winter. But it was mandatory to operate at all times
during the war emergency and many difficulties were encountered.
Starting of engines at extremely low temperatures was the major problem.
However, other problems were encountered even after the equipment was started,
such as solidification of gear oils resulting in locked transmissions and
differentials, and congealing of greases which made steering impossible.
It was soon recognized that solution of arctic operational problems in–
volved two major factors of equal importance: redesign of mechanical equipment,
and redesign of the fuels and lubricants. As the redesign of mechanical equip–
ment was more expensive and time-consuming than changes in petroleum products,
the major effort to provide immediate improvement in operation was directed to–
ward development of special arctic fuels and lubricants. As a consequence,
many new petroleum products were developed and introduced into the Arctic with
notable success.
EA-I. Porter: Petroleum Products
Following is a description of the requirements of petroleum products for
the various parts of automotive equipment when operated under extreme winter
conditions.
Gasoline Engines
. The primary problem in gasoline engines is starting, and
to accomplish successful starts the engine must be turned at not less than 25
r.p.m. Successful starting of engines is influenced by the following factors:
- ( 1 ) The temperature of the engine.
- ( 2 ) The mechanical condition of the engine. Engines in good mechanical condition are much easier to start.
- ( 3 ) Condition of the battery. Battery output is greatly reduced at sub– zero temperatures. This reduces both cranking speed and intensity of ignition.
- ( 4 ) Viscosity and fluidity of the lubricating oil.
- ( 5 ) Volatility of the fuel.
Turning the engine at the required speed to achieve starting is influenced
by the viscosity of the crankcase oil and the battery voltage, both of which are
adversely affected by low temperatures. The maximum allowable crankcase oil
viscosity for a successful start with a warm battery is in the order of 40,000
to 50,000 seconds Saybolt Universal (SSU). This critical viscosity varies over
wide limits for different engines and these figures should be considered only
as “order-of-magnitude” values. Allowable oil viscosity de
e
^
c^
reases greatly as
^
—^
the battery output diminishes with decreasing temperatures and is only some
15,000 SSU at −30°F. Starting at below −40°F. with a cold battery is virtually
impossible, regardless of the crankcase oil viscosity, due to the lack of
battery output. Typical temperatures at which cranking can be accomplished with
various grades of high-quality lubricating oil are given in Table I.
EA-I. Porter: Petroleum Products
| Table I. | ||
|---|---|---|
| Grade | Minimum starting temperatures. °F. | |
| Battery at ambient temperature | Battery at about 75°F. | |
| 5W | −30 | −45 |
| 10W | −15 | −20 |
| 20W | 0 | −5 |
| 30 | +10 | +5 |
Another important requirement of engine oils for low-temperature operation
is that they retain their fluidity. In other words, the stable pour point, the
minimum temperature at which the oil remains fluid, must be as low as the mini–
mum engine temperature. Although the initial solidification of an oil due to
the first precipitation of wax crystals has little influence on the engine
drag during starting, it is particularly important that this condition be avoided
because the congealed oil can
not be pumped to the engine parts and scoring may
^
—^
result if the engine is operated with oil in this state.
Other methods of achieving satisfactory starting with lubricating oils
are to dilute with kerosene or gasoline. The addition of 10% kerosene has
the same effect on viscosity as reducing the crankcase oil viscosity by one S.A.E.
viscosity grade, and, under moderate or intermittent operating conditions, the
kerosene remains in the oil reasonably well. Gasoline as a diluents has about
the same viscosity-lowering effect, but, being more volatile, is vaporized
from the crankcase much more rapidly. Experiments have shown, for example,
that operation for two hours will remove most of the gasoline dilution. The
use of gasoline as a diluents finds its principal use in ai
^
r^
craft where it is
^
—^
easier to control.
EA-I. Porter: Petroleum Products
Gasoline volatility plays an important part in engine starting because
the gasoline must be sufficiently volatile so that the mixture which enters
the cylinder will contain enough of volatilized gasoline to be combustible.
From a practical standpoint, both with respect to handling and transportation
of the fuel and to prevent vapor lock in the vehicle fuel system at moderate
temperatures, the maximum allowable vapor pressure of a gasoline is about 15
p.s.i. How gasoline volatility influences starting is shown by the figures
in Table II. For purposes of simplification, gasolines of different volatilities
are classified in terms of vapor pressure, although this gasoline property as
such is only one of the characteristics affecting starting. As in the case of
| Table II. | |
|---|---|
| Vapor pressure, p.s.i. | Minimum starting temperature, °F. |
| 15 (Special winter) | −50 |
| 12 (Type c: 2-103C Spec.) | −35 |
| 10 | −30 |
| 8 (Type A: 2-1030C Spec.) | −20 |
the critical viscosity for cranking, these figures represent averages, and
wide variations between individual engines may be expected; the better the
mechanical condition of the engine and electrical equipment, the lower will
be the temperature at which it can be started with a given combination of
lubricating oil and gasoline.
Inasmuch as engine wear is excessive when cylinder temperatures are below
140°F., good practice for arctic operation is to set engine thermostats so that
the coolant operates at about 180°F. After warm-up, therefore, engine operating
EA-I. Porter: Petroleum Products
temperatures in the Arctic are essentially the same as in moderate climates, and with the low-viscosity oils necessary for starting, oil consumption is much higher than with the more viscous oils used in temperate climates. For this reason, engine bearings should be maintained in good condition and the crankcase oil level checked frequently. Those vehicles which are used in inter– mittent operation in the Arctic must of necessity operate at much lower than desirable engine temperatures. This is conducive to accumulation of water condensate in the crankcase with its attendant difficulties of corrosion and sludge. This necessitates frequent draining of the crankcase oil (at about 500-mile intervals) and short engine-overhaul periods of as low as 10,000 miles.
Diesel Engines
. The same general lubrication problems apply to diesel
engines as to gasoline engines; although the diesels are usually equipped with
more powerful starters, they require cranking speeds of 50 r
^
.^
p.m. or higher for
^
—^
successful starting. In fact, normal practice for diesel engines
are
is to employ a usually —
warm battery. Also, the bearing loads in diesel engines are usually
higher than in gasoline engines and, therefore, a higher-viscosity oil is
desirable. For this reason, 5W oils should be used in diesel engines only
under extreme conditions. All oils used in diesel engines should be of the
heavy-duty type to avoid excessive engine deposits. These oils are described
by Army Specification 2-104B or by the Navy 9000 Series.
The most important characteristic of a diesel fuel for arctic operation is
the pour point, because, if the temperature of the fuel falls below its pour
point, it will not flow due to the precipitation of wax particles and the
engine can no longer be operated. Fuels of normal diesel volatility, i.e.,
boiling between 300° and 700° F., are satisfactory for arctic use. However,
it is usually necessary to limit the boiling range in order to obtain satisfactory
pour points. Cetane number is not an important factor in starting at low
EA-I. Porter: Petroleum Products
temperatures because an improvement of 10 cetane numbers results in a decrease in minimum starting temperature of only 10°F. With most diesel engines, suc– cessful starting can be accomplished only down to 30° or 40°F. with a fuel of 50 cetane number. Even with a fuel of 80 cetane, which is considerably higher in ignition quality than generally available, starting could be accom– plished only at 0° to 10°F. For this reason starting aids are mandatory under arctic conditions.
Starting Aids
. With most automotive diesel engines, starting difficulties
come at about +30°F. and become progressively worse as the temperature decreases.
Maintaining the engine at temperatures above 30°F. is one method for eliminating
starting troubles. For conditions where this is not possible, other means have
been developed, including flame throwers which heat the intake air by burning
fuel and special starting fluids with very low self-ignition temperatures.
These fluids have an ethyl ether base and have been spectacularly successful
at starting diesel engines. For example, the addition of 1/3 ounce of starting
fluid reduced starting time in a typical diesel engine from 30 seconds to
1-1/2 seconds. Also, successful starts of diesel engines at subzero tempera–
tures, as low as
^
−^
50°F., have been achieved with 1-1/2 to 2-ounce applications
^
— minus sign^
of starting fluid. For these low temperatures, however, the application of
the starting fluid must be continued for a long enough period until the engine
becomes sufficiently warm to ignite the diesel fuel. Ethyl
[:
]
ether type
starting aids are also used for starting gasoline engines, but their effect
is less pronounced than for diesel engines. They become effective with typical
winter gasoline at about −20°F., and below this temperature assist materially
in achieving starts.
EA-I. Porter: Petroleum Products
Ice Prevention
. Gasolines and diesel fuels have the ability to dissolve
about 0.01% water. Even when the fuels leave the refineries in a completely
dry condition, they almost invariably pick up this much water in transit or in
storage. When the fuels containing the small proportion of dissolved water
are exposed to very low temperatures, some of this water comes out of solution
in the form of ice crystals which have the very adverse effect of clogging
fuel filters and carburetor jets. This can be avoided by adding to the fuel
small proportions, 0.3% or less, of low-molecular-weight alcohols. The heavier
alcohols are less effective for this purpose. The lighter alcohols are very
soluble in water but sparingly soluble in the fuel; therefore, when the tempera–
ture of the fuel is lowered and water comes out of solution, it takes with it
about a proportional amount of alcohol and has the very low freezing tempera–
ture of an alcohol-water blend.
Transmissions and
D
^
d^
ifferentials
are not equipped with devices for keeping
^
—^
them warm during operation and, consequently, the only degree of heating in
these units above ambient is that caused by friction. For this reason, in
very cold operations, gear lubricants of low viscosity must be used. Army
Specification 2-105, Grade 75 lubricants are designed specifically for this
purpose. This specification requires that the lubricant be suitable for use
at −50°F. particularly with respect to low-temperature flow. The most critical
condition for gear lubricants is during initial operation after exposure to
low temperatures, and, if the lubricant is not sufficiently fluid, it will not
flow to the gears and is said to “channel.” This channeling consists of the
gears pushing the lubricant away from the metal and running dry. Gears so
operated often score and for this reason Specification 2-105 requires that the
EA-I. Porter: Petroleum Products
Grade 75 not channel at −50°F. Another difficulty encountered with gear lubricants at low temperatures is hard shifting. It has been established that, with a shifting force of 25 pounds on the gearshift lever, shifting can be accomplished readily when the oil in the gear case has a viscosity not exceeding 100,000 SSU. Typical examples of temperatures at which shifting can be accomplished easily with various grades of gear lubricants are shown below:| Grade | 75 | 80 | 90 | 140 |
| Minimum temperature of easy shifting, °F. | −30 | −5 | +20 | +40 |
Gears can be shifted at lower temperatures than those listed above, but
it becomes very difficult at about 10°F. below these temperatures.
The Grade 75 oil has viscosity limits of 150 to 190 SSU at 100°F., or
near those of an S.A.E. 10 grade motor oil.
,
Although it contains an extreme
^
—^
pressure additive, it is considered too low in viscosity for gear lubrication
at moderate ambient temperatures and should not be used when prolonged opera–
tion at atmospheric temperatures above +30°F. is expected.
Grease-lubricated Chassis Parts
. It is characteristic of greases that
they are less sensitive to temperature changes than lubricating oils. How–
ever, in no case can a grease become more fluid than its constituent lubricat–
ing oil. (Greases are composed of about 90% lubricating oil plus about 10%
soap.) Special greases prepared from selected light lubricating oils are
described by Army Specification AXS-1169 (Rev. 1) and are designated as “Grease
O.D. No. 00.” This grease is sufficiently fluid to provide lubrication at
temperatures as low as −65°F. and can be used on all chassis parts, including
wheel bearings, steering gears, distributors, etc. It is also sufficiently
fluid for application through grease guns at low temperatures.
EA-I. Porter: Petroleum Products
Due to the adverse effects of snow and ice formation on various chassis
parts, greasing should be frequent under low-temperature conditions. Five
hundred miles is a recommended interval.
Cooling and Hydraulic Systems
. It has been found that conventional
radiator antifreezes and hydraulic fluids are unsatisfactory in Alaska at ex–
tremely low temperatures. In the first case, adequate protection against
freezing of the equipment is not provided, and, in the second case, excessive
thickening of the fluid occurs. By addition of heavy alcohols, the effective–
ness of both fluids at low temperatures may be greatly increased.
Antifreeze solutions of the permanent type must be
[:
]
inhibited against
rusting, and these inhibitors become ineffective with continued use. Therefore,
it is the best policy to drain and discard permanent-type antifreezes after
each season’s use.
Conclusion
. Petroleum products described above have alleviated the prob–
lem of arctic operation to a large extent when used in conjunction with the
mechanical aids and devices now available. However, much research remains to
be done on the development of equipment designed specifically for arctic use
if totally successful year-round operation is to be achieved.
Harold R. Porter
Loading...