Installation
Principal
of Operation
All Oberdorfer Chemical Gear pumps are the positive displacement
type. A definite amount of liquid is displaced with each revolution
of the pump. The displacement capacity will vary directly with
the pump speed within specified limitations. These pumps will
produce a discharge pressure equivalent to the conditions of the
particular installation. If these conditions are in excess of
the design capability of the pump, the discharge pressure may
rise to a point where the pump will be damaged and/or the driver
overloaded.
Inspection:
Upon receipt of any pump or pump unit, check carefully for possible
damage or shortages. Be sure that the shaft has not been bent
or damaged. Rotate the pump by hand to be sure it is free and
without tight spots. If the pump is to be stored, it should be
kept in a dry location.
Mounting
Bases
Pump units should be mounted on either a concrete or metal foundation
of sufficient weight and strength to properly support the entire
pump unit. It should be located as close to the liquid source
as is practical, while allowing for accessibility for normal pump
maintenance. The foundation should be made flat and smooth to
ensure correct alignment of the pump. Provisions should be made
to bolt the unit securely in place.
Do
not locate the pump unit in a pit unless provisions have been
made for proper drainage and ventilation.
Alignment:
Correct alignment is absolutely essential for satisfactory pump
life. Complete pump units are set and aligned at the factory on
a flat surface plate and shims are inserted where necessary to
provide perfect alignment. However, all baseplates are somewhat
elastic and as a result we cannot assume responsibility for mechanical
operation unless the shop alignment is reproduced when the unit
is secured to its foundation. Since no foundation is perfectly
flat or level, it is therefore necessary to shim the baseplate
until the pump and motor shafts are level and parallel.
Recommended
drive arrangement for pump only is direct motor drive. For belt
or pulley drive application, pillow block bearing must be used
to achieve acceptable pump life. However, it is important to ensure
that the pump and motor shafts are parallel and in line. Recheck
the alignment after the piping has been connected to the pump.
After
the unit has been completely set and piped, check that the pump
rotates freely by hand before activating the driver.
When
pumps only are supplied for field mounting, it is important that
the proper alignment between pump and drive is maintained. The
baseplate should be secured to a flat surface plate and the driver
and pump set so that the shafts are level and parallel.
The
use of flexible coupling will not compensate for poor alignment.
Parallel alignment can be determined by use of a straight edge
across the rim of both coupling halves at four positions ninety
degrees apart. Couplings aligned in this manner should be true
to within .005" at any position. Angular alignment can be
check by gauging the coupling gap at several points.
It
is particularly important that pumps driven through a flexible
coupling be mounted in such a manner as to ensure sufficient gap
between the coupling components to allow for any end play in the
driver.
Suction
Piping: Chemical Gear pumps are capable of operating at
17.7 inches mercury suction (20’ water). If the static lift
plus pipe friction losses combine to exceed this figure, pump
operation will be erratic or no pumping at all will be realized.
The
most desirable pump installations are those with the shortest
suction lines. It is therefore important to locate the pump as
close to the liquid source as is practical. Suction piping should
never be less in diameter than the pump suction opening. When
handling thick liquids with appreciable viscosity, the suction
pipe should be increased to a greater size than the pump opening.
It
is particularly important that the suction line be air tight.
Use a good pipe joint compound or tape at all joints. If the suction
line is not tight and air is allowed to enter the pump capacity
will be noticeably reduced or it may not pump at all.
Be
sure that the suction line is completely clean and free of any
foreign matter. Avoid high spots in piping which will tend to
trap air. It is good practice to install either a foot valve or
check valve in the suction line to ensure that the pump will prime
quickly when started.
When
handling highly volatile chemicals, it is necessary to reduce
the suction height to a point where vaporization will not occur.
In some instances, a positive suction head will be required.
Suction
Strainers: Gear pumps are designed and fitted with very
close internal clearances. The entry of foreign material or abrasives
will cause rapid wear or extensive damage to the pump. It is therefore
necessary to install a strainer at the pump suction.
Select
a strainer of proper size and material with as fine a mesh as
is practical, being careful that the pressure drop through the
strainer will not add to the suction lift to exceed the suction
capability of the pump. Install the strainer as near the pump
suction as is practical and in such a manner that it can be easily
opened and cleaned. Be sure to arrange a regular inspection on
the strainer basket to avoid clogging.
Discharge:
Select pipe of sufficient size to ensure that the resulting
friction loss does not add to the discharge head an amount that
will exceed the design capability of the pump or motor. It is
advisable to install a fitting in the discharge line adjacent
tot he pump to allow for priming or venting and installation of
a pressure gage for both system and pump performance evaluation.
To avoid excessive pressure build-up due to a closed or blocked
discharge line, ore due to an increase in liquid viscosity, it
is often necessary to install a relief valve in the pumping system.
Chemical
Gear pumps are not available with a relief valve built onto the
pump. When required, it is necessary that the relief valve be
installed in the discharge piping and piped back tot he source
of supply. Heat is better dissipated over large surface areas.
The relief valve should be set at a pressure of approximately
10 PSI in excess of the designed operating pressure, but not so
high as to overload the drive or the pump itself.
Product
Contamination:
All Chemical Gear pumps are assembled and tested using a suitable
grade of machinery oil. Unless specified, this oil is left in
the pump during shipment. It ensures some lubrication during start-up.
If this oil is detrimental to the system, it will be necessary
to dismantle the pump and clean all parts thoroughly. Before starting,
be sure to fill the pump with a compatible liquid.
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Operation
Priming:
Before operating the pump, make sure that it is thoroughly primed.
If at all possible, use a good grade of light lubricating oil.
Failure to properly prime the pump could cause immediate damage
to the working parts.
Lubrication:
The internal bearings in all Chemical Gear pumps are lubricated
by the liquids being pumped. Outboard pillow block support bearings
and motor bearings should be lubricated as covered by the manufacturer’s
instructions.
Direction
of Rotation:
Upper shaft drive is standard and standard direction of rotation
is clockwise when facing shaft end of the pump. When rotated in
this manner and the pump and/or piping must be installed so that
the suction line is connected to the port on the left hand side
of the pump. If the right hand port is to be the inlet or suction,
the rotation must be counter clockwise when facing the pump from
the shaft end.
Chemical
Gear pumps are designed to operated in either direction of rotation.
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Repair
Disassembling
Pump:
Repair kits are available for all Chemical Gear pump models. Each
repair kit includes replacement gaskets, seal, gears, shafts,
and bearings.
Oberdorfer
Chemical Gear pumps are constructed of three sections – a
rear cover, a body section, and a front cover. The three sections
are bolted together with through bolts and nuts.
Remove
the through bolts and separate pump sections by tapping lightly
while forcing sections apart. Pump body and front cover are doweled
together. Ease body and front cover off dowel pins by lightly
tapping and forcing apart. Light tapping on exposed pump drive
shaft aids separation of pump section. Note that the all plastic
gear pump does not use any dowel pins.
Remove
rear bearings.
Slide
out idler gear and shaft assembly and the front idler bearing.
Slide
out the drive gear and shaft assemble.
For
mechanical seal models, the drive gear and shaft assembly also
includes thrust washer, seal retaining ring, and mechanical seal
head.
Two
set screws secure the seal head to the drive shaft. Loosen both
set screws and slide the seal head from the drive shaft.
Removal
of the seal retaining ring (snap ring) allows sliding off the
thrust washer and upper front cover chamber – seal wearface
and seal seat – can be pried out by using a hook tool or
by pushing a 1/8" diameter drift through the push-out hole
in the front cover.
Metal
gears are pinned or keyed to pump shafts and are normally provided
as gear and shaft assemblies.
Plastic
gears are driven via woodruff keys and are positioned and retained
over the woodruff keys by retaining rings. Plastic gear and shaft
assemblies are also normally provided as gear and shaft assemblies.
Replace
any parts where wear is evident.
Re-Assembling
Pump:
Carefully clean all parts and lubricate lightly.
-
Make sure pump body faces are clean and free of nicks or scratches.
-If
new bearings are used, try in body and on shaft before re-assembling
pump.
For
mechanical seal models:
Prepare the front cover for re-assembly by inserting the seal
wearface and seal seat into the cover’s seal chamber.
Next,
prepare the drive gear assembly by sliding on the front bearing,
gasket and thrust washer.
Install
seal retaining ring into the groove provided on the shaft.
Slide
the mechanical seal head onto the shaft-metal end first –
and position against the seal retaining ring.
Tighten
the two seal head set screws to insure it will rotate with the
shaft and carefully insert the complete drive gear and shaft assembly
into the pump body.
Next
assemble the lower front carbon bearing into pump body.
Insert
idle gear shaft assembly and remaining bearings into the pump
body section.
Assemble
front cover by engaging dowel pins into body.
Insert
all (8) cover bolts into front cover and body, assemble rear cover
with gasket and (8) acorn nuts. Tighten bolts carefully drawing
the three pump sections together. Tighten bolts in diagonal sequence.
Rotate drive shaft by hand to insure alignment and pump looseness.
Note:
Chemical Gear pump internal tolerances are held extremely
close. Pump parts are manufactured to precise dimensions and most
rigid quality control standards. The smallest foreign particle
or damage in the form of a nick or gouge could jam the gears and
bind the pump. Extreme cleanliness and care is essential for proper
pump assembly.
Operating
Temperatures and Pressures:
For metal Chemical Gear pumps (stainless steel and Alloy C) several
gear options are available. A combination of Alloy C drive gear
and Teflon idle gear offers maximum corrosion resistance with
limits of 100 psi pressure and 1000 F temperature.
Drive and idle gears of W88 stainless steel are suitable for 150
psi pressure and 4500 F temperature. Drive gear and
idle gear of Teflon offer excellent corrosion resistance, low
noise level and economy, but are limited to 50 psi pressure and
1000 F temperature. Teflon gears have lower life expectancy
than metal gears.
For
Plastic Chemical Gear Pumps: Temperature extremes are detrimental
to service life and should be avoided. Basic materials of construction
allow temperature range of –40 to 1800 F and pressures
up to 100 psi. High pressures accelerate pump wear and reduce
service life.
When
handling products with temperature in excess of 2000
F, care should be taken to avoid sudden temperature shock by introduction
of high temperature to a cold pump or reverse. It is advisable
to bring the temperature up gradually. Freezing liquid in pumps
can deform or damage pumps.
Starting:
Never start or run the pump dry. This will inevitably cause galling
or seizing of the internal parts. Always prime the pump with a
clean, light lubricating oil or with liquid to be pumped.
Before
starting, rotate the pump by hand. It should rotate freely without
tight spots.
Check
that all suction and discharge valves are open and that any relief
valves have been "backed off".
After
priming, start the driver and allow pump to operate at a reduced
load while observing for unreasonable noise, heat, or vibration.
Check to be sure pump is delivering liquid. If not, shutdown immediately
and review foregoing instructions.
Gradually
bring pump up to operating pressure by tightening relief valve
adjustment until the pressure gauge indicates that the system
design pressure has been reached. Again check pump for excessive
noise, heat, or vibration. Check that the pump is delivering the
required capacity and that the vacuum is not in excess of design
conditions. If it is determined that the pump is meeting the required
conditions, it is important to check that the driver I not overloaded.
Be
sure that the overload protection for the electric motor is properly
sized. Check that the electric motor is operating within the nameplate
amperage limitations.
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Maintenance
General:
Chemical Gear pumps are designed to be lubricated by the liquid
being pumped and therefore do not require lubrication maintenance.
Barrel type carbon bearings are self-lubricating.
Lubrication
for reduction gear drives, outboard bearing supports and electric
motors should be maintained as specified in the manufacturer’s
instructions furnished with the shipment.
Stuffing
Boxes:
Pumps equipped with packing will require adjustment periodically
to avoid excessive leakage. The packing gland should be tightened
as needed, but only when the shaft is rotating.
Do
not attempt to tighten gland to the point where leakage is completely
stopped.
Allow
for a small continuous leakage of approximately one drop per minute
to ensure lubrication and cooling at the packing area. Eventually
all the packing in the pump will become deteriorated and will
have to be replaced.
Pumps
equipped with mechanical seals require no adjustment.
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