Goulds Pumps 3408 - IOM - Manual (Page 23)

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Mechanical Seals
Mechanical seals are preferred over packing on some
applications because of better sealing qualities and
longer serviceability. Leakage is eliminated when a
seal is properly installed, and normal life is much
greater than that of packing on similar applications. A
mechanical shaft seal is supplied in place of a packed
stuffing box when specifically requested. The change
from packing to an alternate arrangement may be
made in the field by competent service personnel.
Conversion parts may be ordered from your Goulds
Pump Sales Representative.
Just as with packing, the mechanical seal chamber
must be supplied, at all times, with a source of clean,
clear liquid to flush and lubricate the seal. The most
important consideration is to establish the optimum
flushing pressure that will keep contaminants from the
seal cavity. If this pressure is too low, fluid being
pumped may enter the stuffing box. If the pressure is
too high, excessive seal wear may result.
When contaminants are present in the pumpage, an
external source of clean seal water must be supplied.
Supply approximately .25 GPM at a pressure
approximately 15 to 20 psig above the suction
pressure.
Fig. 14 shows the recommended “Controlled Pressure
System” for a mechanical seal. Seal water enters the
seal chamber, lubricates the seal face, and exits into
the pump itself. Positive flow in the seal water line
indicates adequate seal water pressure.
Cartridge Seals
Follow the appropriate lubrication directions for
mechanical seals given in this section. Most cartridge
seals provide flushing connections on their glands.
Use the cartridge seal gland flushing taps (if provided)
for your seal water connections instead of the stuffing
box tap. The quench taps on the glands (if present)
are normally only used in chemical applications.
Consult seal manufacturer’s literature for more
detailed information.
Cyclone Separator
If the fluid being pumped contains sediment and there
is no external, clean water source available to flush
the mechanical seals, a cyclone separator can be
used to remove most of the sediment from the liquid
being pumped so it can be used to flush the seals.
The separator is placed in the seal water piping line
and removes the sediment to an external drain
(normally back to the pump suction line).
3408 IOM 03/99
21
Fig. 14
Pump
Casing