Rebuilding
the
Welch 1402
Vacuum Pump
Reassembly
(Revised)
R1
Begin reassembly with the large end plate.
R2
Place the intake ring on the end plate.
R3
Tighten 5 bolts to attach the intake ring to the end plate.
R4
Put in the intake filter and the intake chamber cover gasket. Both gaskets should be new.
R5
Loosely tighten the large end plate cover without compressing the gasket.
R6
Apply vacuum oil to the inside of the intake ring and the part of the large end plate inside the
intake ring. The oil lubricates the pump when you start it for the first time after rebuilding it.
R7
Apply vacuum oil to the shaft, move the intake rotor to put oil on the shaft under it, both
spring holders and both large vanes. Be sure the woodruff key is in place. When you do this turn
the intake rotor back and forth to see if the intake rotor turns with the shaft. There
should be little or no play. If there is play replace the woodruff key and repeat. If there is still
play check the slot for the woodruff key in the shaft. If the woodruff key does not fit tightly in the
slot replace the shaft.
R8
Put the intake rotor inside the intake ring by gently pressing in the large vanes, put the thrust
washer on the shaft first.The space between the intake rotor and the intake ring is very important. If the space is too large
there will be no vacuum. If the space is too tight the motor may not be able to turn the shaft on
start-up. The correct spacing is about the thickness of a sheet of aluminum foil.
If there is too much or too little space loosen the bolts holding the intake ring and move it
slightly.
See the Supplement on Tolerance for more detail.
R9
Apply vacuum pump oil to the side of the center plate facing the intake rotor. The oil lubricates the pump when you start it for the first time after rebuilding it.
R10
Put the center plate on the shaft and align the holes with the holes in the intake ring.
R11
Apply vacuum pump oil to the other side of the center plate, both small vanes and the small
vane spring holder. The oil lubricates the pump when you start it for the first time after rebuilding it.
R12
Put the two small woodruff keys on the shaft.
R13
Put the exhaust rotor on the shaft, put vacuum pump oil on the shaft. When you do this turn
the exhaust rotor back and forth to see if the exhaust rotor turns with the shaft. There
should be little or no play. If there is play replace the woodruff key and repeat. If there is still
play check the slot for the woodruff key in the shaft and if the woodruff key does not fit tightly in the
slot replace the shaft.
R14
Put the exhaust vane spring holder on the shaft and put the 2 exhaust vane springs and the 2
exhaust vanes on the exhaust vane spring holder.
R15
Apply vacuum pump oil to the inside of the exhaust ring. The oil lubricates the pump when you start it for the first time after rebuilding it.
R16
Gently squeeze in the exhaust vanes and put on the exhaust ring and align the holes with the
holes in the center plate. The space between the exhaust ring and the exhaust rotor is very important. If the space is too
large there will be no vacuum. If the space is too tight the motor may not be able to turn the
shaft on start-up. The correct spacing is about the thickness of a sheet of aluminum foil.
Maintain this adjustment when you put the end plate on the exhaust ring.
See the Supplement on Tolerance for more detail.
R17
Apply vacuum pump oil to the inside of the small end plate. The oil lubricates the pump when you start it for the first time after rebuilding it.
R18
Install the small end plate and align the holes with the holes in the exhaust ring.
R19
Apply vacuum pump oil to the steel ball.
R20
Install the pressure release duct and the pressure release valve.
R21
Put the top of the pressure release duct onto the base of the pressure release duct.
R22
Be sure the small spacer is on the inside of the end cap.
R23
Put the vacuum pump oil on the end of the shaft and install the end cap.
Optional:
To find out whether or not everything is going together okay but before you add oil and have
to drain it out to get back inside the pump please put the pulley and woodruff key on the shaft for a
quick test. When the pulley is on the shaft try to turn the pulley in the direction of the arrows
imprinted on the pulley and see if the pulley turns easily and smoothly. If it does not it is much easier to
fix now than after the pump is all put together. For example, in one case, the pulley did not turn easily
because the bolts holding the small end plate were too tight, when they were loosened the pulley
turned fine and the pump pulled vacuum fine.
R24
Get the oil case assembly.
R25
Put a new oil case gasket on the oil case assembly (see the Supplement on Gaskets) and bolt the large end plate to the oil case
assembly.
Please be sure both surfaces are clean or the pump may leak.
R26
Put a new seal gasket on the shaft.
R27
Apply vacuum pump oil to the shaft. The oil lubricates the pump when you start it for the first time after rebuilding it.
R28
Please put a new shaft lip seal on the shaft.
R29
Attach the vacuum pump to the metal base using 4 bolts and an allen wrench.
R30
Attach the belt guard to the base with 4 bolts and an allen wrench.
R31
Put the woodruff key for the large pulley on the shaft.
R32
Install the large pulley. It may be easier to remove the large pulley if the set screw is facing
out instead of in. The photo shows the set screw facing in.
R33
Install the guard around the motor shaft.
R34
Install the woodruff key for the small pulley.
R35
Install the small pulley and the belt, use a straight edge to be sure that the small pulley and
large pulley are aligned on the same flat surface. The outer edges of both sides of both pulleys should be flat on the straight edge, no spaces.
It may be easier to install the small pulley if the
set screw is facing out.
There should be about one half inch deflection in the belt. If there is too
much deflection loosen the bolts holding the motor and move the motor to reduce the deflection.
R36
Manually test the vacuum pump by turning the large pulley with your hand and placing your
other hand over the vacuum inlet, you should feel suction.
R37
Add 2.25 quarts of vacuum pump oil to the pump. Consider running the pump and then draining the oil to flush out any remaining debris and then refilling the pump with oil again.
If the vacuum pump is
pulling solvent vapor there may be certain types of vacuum pump oil that are recommended for
use with the solvent vapors you are pulling, please check.
You should measure the vacuum with a vacuum gauge (see the Supplement on Vacuum Gauges).
R38
Congratulations!
You did it !
Your pump is now ready to plug-in and test.