Page 159 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

SOLID-LIQUID SEPARATION AND INTERCEPTORS

SOLID-LIQUID SEPARATION AND INTERCEPTORS 3.27

FIGURE 3.9 Typical oil interceptor. (Courtesy of Rockford Co.)

Smaller Systems. Oil separators for small flows usually take the form of a single unit
consisting of a drain grating into which the effluent flows and inside which the oil remains
to be drawn off manually. Another type of unit uses an overflow arrangement which sends
the trapped oil to a remote oil storage tank.
Because there is the possibility that the vapor given off by the flammable liquid could
also ignite, it is important to provide a separator vent that terminates in the open air at an
approved location above the highest part of the structure. Some codes require that a flame
arrester be installed on the vent.
The most common material used for an oil interceptor is cast iron, although steel can be
used for less severe service. Gratings must have the strength for the type of vehicle expected.
Refer to Fig. 3.9 for an illustration of a typical small oil interceptor. Figure 3.10 shows the
installation of a typical oil interceptor with gravity oil draw-off for garage floor drains.

Sand
Whenever a potential source of solids discharges into the drainage system, a sand intercep-
tor, or trap, should be provided. A mechanical hazard could be created, since the sand could
create a blockage in the piping system.
Since the solids are heavier than water, these traps operate on the principle of settle-
ment, permitting the solids to accumulate at the bottom as the effluent flows through the
device. The outlet from the sand trap should be located so that the accumulated material
is prevented from being discharged. The solids must be removed from the trap by hand.
Sufficient space must be available around the trap to make this easy to accomplish.
Sand traps are commonly constructed of masonry, but prefabricated units made of cast
iron or steel are also used. Refer to Fig. 3.11 for an illustration of a typical sand interceptor.

Precious Metals

The most common source of gold, silver, or platinum is from jewelry establishments. The
small amount of metal discharged would not be detrimental to any drainage system, but it
should be recovered because of its value.
A solids interceptor for this type of service is a small, in-line unit, using either a fine
wire mesh screen or stainless steel wool as a filter inserted inside a small housing. This
housing is installed instead of a trap on a fixture.

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