Modifications In API Separator Design
R.   N.   SIMONSEN
Senior Engineer, Technical Service Division
The Standard Oil Company  (Ohio)
Cleveland, Ohio
In the past seven years, The Standard Oil Company of Ohio has
spent nearly $2,000,000 on the construction of three new gravity type
oil-water separators. The first of these new separators was designed
and built strictly in accordance with the recommendations of the
American Petroleum Institute. Succeeding separators were modified
in certain respects but still followed the fundamental API design
principles. Each separator built has been an improvement over its
predecessor.
It should be clearly understood that a gravity separator has but
one function—to separate those materials that will float or sink from
the waste stream under quiescent conditions. A gravity separator can
neither break emulsions, remove materials having a specific gravity
closely approaching that of water, or remove dissolved chemicals.
The gravity separator is widely used in refineries as an efficient,
economical means of reducing oil and suspended solids contents of the
plant waste water effluent to a reasonable value. It is undoubtedly the
most important single piece of waste disposal equipment available.
Obviously, the use of a gravity separator is not always the answer to
a refiner's waste disposal problem. There are cases where, because of
local conditions, some means of secondary treatment is required to
produce a satisfactory effluent.
However, even in those cases, the gravity separator does not lose
its importance, since it has been found that secondary treatment
processes work most efficiently if they are preceded by an efficient
gravity separator.
The API has worked for many years on the development of
separator design methods. These methods have been published in
manuals, the first of which appeared in 1930 (1). The fifth revision
of this same manual is now being prepared for publication to include
the results of their latest research work.
In discussing the modifications incorporated in our newest separators, it would be well to first briefly describe the conventional
API separator. Those of you who were here last year heard an
excellent paper,   "Oil-Water  Separation"   (2),  presented  by  Dr.   R.
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