Goulds Pumps 3498 - IOM - Manual (Page 29)

DISCHARGE PIPING
If the discharge piping is short, the pipe diameter can be the
same as the discharge opening. If the piping is long, the
pipe diameter should be one or two sizes larger than the
discharge opening. On long horizontal runs, it is desirable
to maintain as even a grade as possible. Avoid high spots,
such as loops, which will collect air and throttle the system
or lead to erratic pumping.
A check valve and an isolating gate valve should be
installed in the discharge line. The check valve, placed
between pump and gate valve, protects the pump from
excessive back pressure, and prevents liquid from running
back through the pump in case of power failure. The gate
valve is used in priming and starting, and when shutting the
pump down.
PRESSURE GAUGES
Properly sized pressure gauges should be installed in both
the suction and discharge nozzles in the gauge taps
provided. The gauges will enable the operator to easily
observe the operation of the pump, and also determine if
the pump is operating in conformance with the
performance curve. If cavitation, vapor binding, or other
unstable operation should occur, widely fluctuating
discharge pressure will be noted.
STUFFING BOX LUBRICATION
Contaminants in the pumped liquid must not enter the
stuffing box. These contaminants may cause severe
abrasion or corrosion of the shaft, or shaft sleeve, and rapid
packing or mechanical seal deterioration; they can even
plug the stuffing box flushing and lubrication system. The
stuffing box must be supplied at all times with a source of
clean, clear liquid to flush and lubricate the packing or seal.
The most important consideration is to establish the
optimum flushing pressure that will keep contaminants
from the stuffing box cavity. If this pressure is too low,
fluid being pumped may enter the stuffing box. If the
pressure is too high, excessive packing or seal wear may
result; and extreme heat may develop in the shaft causing
higher bearing temperatures. The most desirable condition,
therefore, is to use a seal water pressure 15-20 psig above
the maximum stuffing box pressure.
If the pump system pressure conditions vary, packing
adjustment becomes difficult. Consideration should be
given to using a mechanical seal (See Mechanical Seals).
PACKING
!
Packed stuffing boxes are not allowed in an ATEX
classified environment.
Pumps are normally shipped with the packing set loose. If
the pump is installed within 60 days after shipment, the
packing will be in good condition with a sufficient supply
of lubrication. If the pump is stored for a longer period, it
may be necessary to repack the stuffing box. In all cases,
however, inspect the packing before the pump is started.
NOTE: Packing adjustment is covered in the
Preventive Maintenance section of this manual
On some applications, it is possible to use internal liquid
lubrication (pumped liquid) to lubricate packing. Only
when all of the conditions prevail, can this be done:
1. Liquid is clean, free from sediment and chemical
precipitation and is compatible with seal materials.
2. Temperature is above 32° F and below 160° F.
3. Suction pressure is below 75 psig.
4. Lubrication (pumped liquid) has lubricating qualities.
5. Liquid is non-toxic and non-volatile.
When the liquid being pumped contains solids or is
otherwise not compatible with packing materials, an
outside supply of seal liquid should be furnished. In
general, external-injection liquid (from an outside source)
is required when any of the above conditions cannot be
met.
The standard stuffing box consists of six (6) rings of
packing and a split type gland. A shaft sleeve which
extends through the box and under the gland is provided to
protect the shaft.
A tapped hole is supplied in the stuffing box directly over
the seal cage to introduce a clean, clear sealing medium.
The stuffing box must, at all times, be supplied with sealing
liquid at a high enough pressure to keep the box free from
foreign matter, which would quickly destroy the packing
and score the shaft sleeve.
Only a sufficient volume of sealing liquid to create a
definite direction of flow from the stuffing box inward to
the pump casing is required, but the pressure is important.
Apply seal water at a rate of approximately 0.5-1.0 GPM at
a pressure approximately 15 to 20 psig above the suction
pressure. (Approximately one [1] drop per second).
26
3498 IOM 12/04