D

DAP

Detroit Advisory Panel

Degree Day

A unit of temperature. Experience has shown

that, for buildings requiring an inside

temperature of approximately 70°F, the amount

of fuel or heat used per day is proportional to

the number of degrees the average outside

temperature falls below 65°F. The degree-day

is based upon this principle. The number of

degree-day (65°F base) for a given period is

the difference between 65°F and the United

States Weather Bureau daily mean

temperature, when the latter is less than 65°F,

multiplied by the number of days.

Degree Engler

A measure of viscosity. The ration of the time

of flow of 200 ml of the liquid tested, through

the viscometer devised by Engler, to the time

required for the flow of the same volume of water

gives the number of degrees Engler.

Density

The mass of a unit of volume of a substance.

DEO

Diesel Engine Oil

Detergent Oil

A lubricating oil possessing special sludgedispersing

properties usually conferred on the

oil by the incorporation of special additives.

Detergent oils hold sludge particles in

suspension and thus promote cleanliness

especially in internal-combustion engines.

Dielectric Strength

A measure of the insulating properties of

electrical insulating oils for use in cables,

transformers, circuit breakers and similar

apparatus (ASTM Method D 877).

Diesel Index

An expression for the ignitability of a fuel relative

to its aniline point:

Diesel index = aniline pint (°F) X API gravity

100

Diester Oil

A synthetic lubricating fluid made from esters;

also called ester oil.

DIN

Deutsche Industrie Norm

Dispersant

A dispersing agent, which holds a very finely

divided substance in a dispersed state in the

carrier fluid.

Distillate

Wide range of products produced by distillation.

DKA

Deutscher Koordinierungsausschuss

Dropping Point

In general, the dropping point is the temperature

at which the grease passes from a semisolid to

a liquid state. This change in state is typical of

greases containing conventional soap

thickeners. Greases containing thickeners other

than conventional soaps may, without change

in state, separate oil.

Dry-film Lubricant

Solid material left between two moving surfaces

to prevent metal-to-metal contact, thus reducing

friction and wear. Such materials are especially

useful in the region of boundary lubrication, and

for lubrication under special conditions of

extremely high or low temperature where usual

lubricants are inadequate. They may be applied

in the form of a paste or solid stick, or by

spraying, dipping or brushing in an air-drying

carrier which evaporates leaving a dry film.

Some examples are graphite, molybdenum

disulfide, boron nitride and certain plastics such

as tetrafluorethylene resins.

Dual-fuel Engine

A diesel engine which may be operated as an

oil diesel, a gas diesel, or a combination of both,

as it is equipped with controls or parts to permit

operating as one or the other