Instruction 2111.80B 04/05 10
a. Water Seals: On pumps handling liquids with solids, a water seal is used principally to flush the
packing and prevent entrance of solids or grit which would score the shaft or shaft sleeve. It also
serves to cool and lubricate packing, and in the case of suction lift applications it is required as a seal
against entrance of air. Non-Clog pumps are furnished with water seals for external or outside
connection to a clear water supply having a pressure approximately 3 to 10 lbs. (7 ft. to 23 ft. head)
greater than the pump discharge pressure. If the available pressure is too high (20 pounds or more above
the operating head of pump) or if gland leakage is excessive a pressure reducing valve should be used.
If available pressure is below operating head of pump, or when required, it is often necessary to
employ a small water seal pumping unit. The most economical consumption of sealing water is
obtained by installing a solenoid valve in the water seal line, wired with the pump circuit to open
automatically when the pump operates.
Note: As a precaution against contamination, State Departments of Health do not permit connecting
the water seal line of a sewage pump directly to the city supply.
b. Grease Seals: When water is not available a grease seal is recommended. For grease seals to be
effective, a constant pressure of water-proof grease must be maintained on the packing, for which purpose
a spring loaded grease cup (see Fig. 2) is usually employed. This spring loaded grease cup is designed for
controlled lubrication. The cup has a knurled adjusting screw at the top that permits the operator to decrease
or increase the tension on the spring and thus assures a precise regulation of a constant lubricant flow.
The reservoir of the cup is filled with lubricant through the Alemite Fitting located at the cup base. As the
lubricant is forced into the reservoir, the cup leather and the pressure spring are elevated until the spring
stops at the safety shoulders where the top of the cup slopes inward. The pressure is then extended
downward through the cup channel, flushing the packing and refilling it with fresh, clean lubricant. The cup
is fitted with a special type tapered valve stem which moves in a tapered delivery channel. As the spring
expands by its own tension, the valve stem descends. This combination of tapered stem and tapered
channel automatically compensates for the decreasing tension of the spring and an exact uniform
pressure of lubricant is effected.
When the spring loaded grease cup is used for this purpose, the cup must be kept loaded at all
times with a recomended grease. It is imperative that grease be forced through the packing at a rate of
at least 1 oz. per day. For high head pumps (over 100 ft. head) a water seal is required.
Regardless of the type of lubrication system employed, the stuffing box gland should be quite loose
when the pump is first put into operation. After the pump has been found to operate properly, the stuffing
box gland may be evenly tightened very slowly. Packing should not be pressed too tightly as this may
result in burning the packing and scoring the shaft or shaft sleeve. The gland should leak a slow steady
weepage of fluid (either outside flush water or pumpage) when the pump is operating. When weepage can
no longer be controlled by adjusting the gland, all rings of packing should be replaced. The addition of a
single ring to restore gland adjustment is not recommended.
If the pump is to be left idle for a period of one month or more, the packing should be removed. Refer to
the "Repairs" section of this manual for packing installation procedure.
5. Mechanical Seal Box
Pumps may be furnished with a mechanical seal. The standard seal arrangement consists of a double
mechanical seal (two single seals mounted back to back) and a suitable sealing medium which is
introduced into the sealing chamber. Each seal consists of a rotating element and a stationary element. The
sealing faces are highly lapped surfaces of materials selected for low coefficient of friction and
resistance to corrosion by the liquid being pumped. The faces have a minute running clearance and
normally run on a very thin film of liquid. The sealing liquid may be clear water, or if the
application permits, filtered liquid taken directly from the pump discharge.
a. Flow Through Clear Water Lubrication
Clear water is injected into the seal box cartridge through a tapped connection at a pressure higher
than that which would exist in the box, thereby isolating the sealing faces from the liquid being pumped.
If sufficient sealing pressure is not maintained, the pressure within the pump will force open the lower seal
and allow the liquid being pumped to enter the box, ruining the seal. A flow of 2 GPM per pump at 5 psi
above the shutoff pressure is required for satisfactory seal operation. Consult the typical performance
curve to determine shutoff head, or contact your CHICAGO PUMP representative. A solenoid
installed in the downstream side of the seal box should open the seal water line at the mechanical seal
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