be defined as "major adjustments and
instructions", a charge will be made for the
additional time required. Should the request
for additional service involve an unscheduled
overnight stop-over or other unanticipated
expense, the customer w ill also be billed for
the added expenses involved.
3. Stokes servicepersons are specialists. Their
primary functions are to demonstrate, to
identify sources of trouble and to instruct
customers' operating and maintenance
personnel in methods of prevention and
correction. To obtain maximum unilization of
the servicepersons, customers should provide
all necessary assistance in the form of movers,
mechanics, operators, etc. Customers should
also provide any standard tools and facilities
that may be required and that cannot readily be
carried by a serviceperson such as lifting
equipment, electric drills, etc.
REBUILDING, REPA IRIN G AND REBU ILDING, REPAIRIN G A ND
M ODIFYING STOKES EQU IPM ENTM ODIFYING STOKES EQU IPM ENT
Customers interested in major overhaul and/or repair
w ork on their existing machines should first consider
the age and general condition of the equipment under
consideration, the current cost of comparable new
equipment and comparable design features. If it is
deemed advisable to rebuild rather than replace, the
equipment should be returned to the Stokes factory.
Pumps being rebuilt are thoroughly disassembled,
cleaned and reassembled with new parts. The rebuilt
pump is put on the test block and checked for
performance. Only w hen acceptable performance is
demonstrated, is the pump released for shipment.
Pumping units are available for rental, subject to
availability, by customers who need additional pumping
capacity for short periods or to fill in while the regular
equipment is being repaired or rebuilt.
The cost of disassembling, cleaning and inspection is
included in the price. The parts for the major repair kit
used are included in the parts section of this manual. If
the additional parts required or if repairs are found to be
so extensive that rebuilding is considered
uneconomical and the project is dropped, the customer
w ill be invoiced a previously established fixed fee.
PUM PING HAZARD OU S GASESPUM PING HAZARD OU S GASES
Pumping certain gases or gaseous mixtures is
hazardous. Consequently, w e cannot assume
responsibility for the operational safety of our pumping
components. We can only alert you to this hazard and
suggest procedures to minimize the possibility of an
explosion.
1. The mechanical pump should be located in a
safe area so that the reactive gas is unlikely to
be present in the atmosphere surrounding the
unit.
2. It is essential that the vacuum system,
including discharge line, be free of air leaks, so
that gases w ill not leak into or out of the
system.
3. The pump should be purged with nitrogen (or
other suitable inert gas) prior to, during and
after operation. Purge port connections should
be made at tw o locations: Port A - to be at the
pump inlet on the pump side of the inlet line
valve; Port B - to be in the discharge of the
pump.
Port A (at inlet) is to be used with the inlet
valve closed, but with the pump in operation.
This will help reduce the percentage of reactive
gas present in the unit and the discharge.
When the inlet valve is open, Port A should be
closed. After the evacuation is complete, the
inlet valve should be closed and Port A
reopened to purge the pump and to fill all voids
in the pump and discharge line.
Port B (discharge) is to be used while the unit
is in operation, with inlet valve open (but with
Port A closed). this w ill assure a continuous
positive flow of inert gas though the pump’s
discharge section to safely carry off the
reactive gas being evacuated from the system.
the inert gas flow must be sufficient to prevent
exhaust gases from back diffusing through the
exhaust line into the pump.
4. The discharge line from the vacuum pump
should be vented to a suitable safe area
outside of any building where it is unlikely that
the reactive gas could accumulate. The w ork
area around the pumping equipment should
also be ventilated to avoid the possibility of
reactive gas accumulations.
5. A suitable flame arrester should be placed in
the discharge line. The discharge pipe should
be marked to avoid the possibility of w orkmen
w elding, or w orking near the area with open
flames or dangerously hot equipment.
6. While it is normally unlikely that the reactive
gas will be present in the work area, insurance
regulations in a given locality may require
special electrical components. Where stricter
electrical specifications are dictated, the main
control panel for the pump(s) can be located
outside the hazardous area w ith only the
vacuum sw itch with its associated time delay
and control relays located on the mechanical
booster pump. These small electrical
components do not require a very large
housing and can be assembled directly on the
pump in a safe enclosure. The various motor
and control leads can then be fed to the
pumps from a safe remote location.
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