5. Magnetic seal replacement procedure*
5.1.1. Rotating anode (RA) assembly
5.1.2. Magnetic seal removal
5.1.3. Bearing assembly removal
5.1.4. Installation of magnetic
5.1.1. Rotating anode (RA)
Figure 22.214.171.124 Special tool "compass"
Switch the x-ray generator off, close the chilled water supply
to the Haskris water chiller, however, maintain the water circulation to
the generator and wait for 1/2 hour.
Shut the rotating anode (RA) off, if it is not already off,
and shut down the vacuum pumps. Switch off the main powers at the gray
breaker box on the wall and switch off the Haskris water chiller and wait
for another 1/2 hour.
Using the special tool (flat steel
plate with a wedge) loosen the vacuum release valve underneath the front
cover of the anode chamber and let in air slowly. Once the anode chamber
is equilibrated with outside pressure, tighten back the vacuum release
valve to the same tension (hand tight).
Figure 126.96.36.199 Special tool for vacuum release
Place a plastic tray underneath the water connections to
the RA assembly and to the anode housing and disconnect the two sets of
water hoses. Remove quick-connects of the two sets of hoses and reconnect
them in such a way that the flow will resume without interruption. However,
this time the path of the flow should not contain the RA assembly.
Remove the v-belt protection plate and the rotation sensor
from the anode assembly. The v-belt protection plate is a perforated steel
plate that is attached in front the anode rotation motor. The rotation
sensor is a small device with a black cable and attached to the assembly
with two Phillips screws.
Using a #2 Phillips screw driver loosen, in cycles, the four
Phillips screws found on the rotating anode assembly and remove all
but one of them completely. The last screw should be removed ONLY after
firmly holding the anode assembly by hand; otherwise, the surface of the
anode assembly will get damaged.
Take the RA assembly to a room with minimum dust, as the
magnetic cassette assembly is very sensitive to dust and place it on a
smooth spongy surface.
To remove the magnetic seal the following materials are required:
New magnetic seal
Phillips screw driver (M40)
Minus screw drive
5.1.2. Magnetic seal removal
Figure 188.8.131.52 Magnetic cassette seal and RA flange
Place the rotating anode assembly on a smooth thick sponge
and using either a vacuum hose or a compressed air supply remove all the
water in the water ports. There are three water ports: one for anode in/out,
one for housing in/out and the third main target in-out. Consult Figure
184.108.40.206 for details.
Figure 220.127.116.11 Rotating anode (RA) assembly with
v-belt in place
Figure 18.104.22.168 RA assembly with v-belt, water
cooling main port and water sealing shaft removed
Remove the separator lock nut (See Figure
22.214.171.124) with the help of the "compass".
This has a left hand threading.
Disconnect the water cooling main port by removing the three
screws (two long and one short Phillips screws (See Figure
126.96.36.199) and pull out the water-cooling port main body. Flipping the
water-cooling main port assembly reveals the water seal (a rubber seal
underneath a brass ring).
It is a good idea at this point to replace the water seal
by first removing the brass ring using the "compass" and then removing
the water seal. These two can be seen in Figure
Figure 188.8.131.52 Water-cooling main port with brass
ring and rubber water seal
Take a fresh water seal and fill the grooved portion of the
seal with silicone vacuum grease. Then place the steel washer on the side
of the grease (and the groove).
Flip the seal with the washer side facing toward the opening
and gently place it on the opening. The water seal needs to be installed
tight and flat and therefore requires the special tool "Plunger".
Take the plunger and insert the thinner part in a press (or in the drilling
machine at workshop) and tighten it to the press. Now slowly and uniformly
lower the plunger while applying pressure on the water seal with wider
part of the plunger in such a way that the seal gets inserted flat. Place
the brass ring on top of the inserted water seal and hand tighten it using
Figure 184.108.40.206 Special tool "Plunger"
Going back to the magnetic seal replacement, now remove the
four counter-sunk Phillips screws seen on the water-sealing shaft. Thread
in two long screws into the water-sealing shaft and gently pull it out.
See Figure 220.127.116.11 for details.
Figure 18.104.22.168 Rotating anode assembly after removing
water-cooling main port
Now remove the pulley fixing ring (Figure
22.214.171.124) with the help of the "compass" and pull out the pulley (Figure
Figure 126.96.36.199 Copper target, magnetic cassette
seal and pulley
Detach the target drum by gently pushing the top stem by
hand while holding underneath the copper drum with another hand over a
soft sponge. If it is hard to remove the target drum gently tap the copper
drum with a rubber mallet and pull it out.
Flip over the assembly and remove four cassette fixing Phillips
screws (Figure 188.8.131.52) and pull out the magnetic
seal. Once again, if the seal does not come out easily, tap it gently with
a rubber mallet.
Wipe out oil and dirt sticking to the flange. Also, thoroughly
wipe out water drops that may remain on the circumferences of the magnetic
cassette seal and in the o-ring groove.
Now one can install the magnetic seal. However, this may
be the time to replace the bearing assembly as well, if it has been more
than 5000 h since the last change or you hear vibration while the RA is
running. A new bearing assembly hardly makes audible sound. Please refer
to section 5.1.3 for bearing assembly removal
5.1.3. Bearing assembly removal
5.1.4. Installation of magnetic
If you are only removing bearing assembly you have to consult
section 5.1.2 and should at least perform steps
1 through 9 before you begin this section. However, if you have already
performed steps 1 through 12 in section 5.1.2 you can continue.
Flip the RA flange (RA assembly's main steel housing), if
it is not already flipped correctly, such a way that the bearing assembly
is facing you. Notice that the bearing assembly's two ends look different.
The side facing you now has a flat surface (inner tube and outer bearing
is flush with each other, see Figure 184.108.40.206),
where as the side facing away from you and toward the magnetic seal has
a recessed inner tube.
Figure 220.127.116.11 Bearging unit, bearing fixing ring
and RA flange
The side facing magnetic seal is called the vacuum side and
the side facing you is called the water side (according to Rigaku engineer
Steve Kirkorian). Using the compass remove the brass ring and slide out
the bearing assembly.
Wipe clean the interiors of the RA flange with lint-free
wipe and remove all traces of water.
Slip in a new bearing assembly ensuring that the face with
recessed inner tube goes in first. This is very critical since the recessed
portion of the bearing has to lock in with the inner tube of the magnetic
seal to provide proper rotation of the magnetic seal.
Flip the RA flange such a way that bearing assembly faces
away from you and clean the inside of the flange if you have not already
done so as described in section 18.104.22.168.
One should see two holes for cooling water in/out and a wedge
on which the magnetic seal will seat with an o-ring. This o-ring is very
critical and is NOT supplied with new magnetic seal. Notice that there
are two o-rings in the magnetic seal itself. One on the steel face (#3)
and another (#5) just above the rim for the water grooves. The third o-ring
(#6) is what I have referred to above. Place this o-ring (S42) first and
then place magnetic cassette seal.
Figure 22.214.171.124 Magnetic cassette seal
Tighten the seal with four Phillips screws cyclically ensuring
the pressure is applied uniformly. Properly installed seal should sit tightly
mating with the back of the bearing and flush with the brass surface.
Insert the target drum, while making sure that the o-ring
on the steel face is intact (#3).
Flip the RA flange and slip in the pulley (#11) onto the
stem of the target drum and insert it in such a way that the groove in
the stem and the wedge inside the pulley match properly and fit snuggly.
Slip in the pulley-fixing nut (#13) and tighten it with the
compass. The pulley-fixing nut has threads inside.
Grab a new water-sealing shaft (#15) and slip in a new S15
o-ring (#14) with little vacuum grease inside the shaft.
Slip in the water-sealing shaft onto the stem and press it
firmly and match the four counter sunk holes in the shaft to that on the
pulley. Tighten all four Phillips screws, as before do this cyclically
to ensure uniform pressure.
Do not forget to apply the v-belt to the pulley at this stage,
since we have come to a stage where the RA assembly can be mated with the
water cooling port.
From section 5.1.2 step 6 you would have installed a new
water seal onto the water cooling port. Now install water cooling port
onto the RA assembly. While doing this pay attention to the v-belt and
do not allow either to slip out or get caught.
Another essential point is that the pin on the target stem
has to match correctly with the groove in the water cooling port. It can
go only in two ways. However, only one of them is correct. To find out
which one is correct, first insert a screw driver in to the main water
port marked "IN" and make a mark on the stem of the screw driver flush
with the surface of the cooling port. Now take the screw driver and insert
it in to the port marked "OUT" and mark again. If the stem is installed
correctly in the "OUT" port screw driver should have gone more
and in the "IN" port less. If installed wrong, pull out the
water port and rotate the stem 180° and repeat the procedure.
Insert the three Phillips screws in the water cooling port
and tighten them evenly there by attaching the port to the RA assembly.
Insert o-ring KS-8(#21) outside the stem and before nut (#22).
Using the compass tighten the nut. Notice it is a left hand threaded nut.
This completes the installation of new magnetic seal, bearing
assembly, new water shaft and water seal. The RA assembly can be attached
to the generator and all water connections restored.