Valve Gate and Bonnet Seal Replacement
Equipment and Notes
Equipment
Valve gate and bonnet seal replacement kit for Series 108, 6" UHV gate valve (order from VAT, should come with replacement valve gate and bonnet seal)
6 mm Allen key (attached to side of each gate valve)
Torque wrench with 6 mm Allen key bit (set to 45 Nm/33.5 lb ft)
Clean tweezers
Clean 10 mm Allen key
Clean foil
Clean kimwipes
Pouch for old valve gate
Notes
Manual:
Replacement procedure
Vent chambers on both sides of the gate valve and open the valve
Remove the 10 screws around the rectangular flange using 6 mm Allen key
Some of these are hard to reach
The assembly will still be held on to the flange by two pins, so will require some wiggling to withdraw
With P1 holding the actuator and P2 holding the valve body with clean gloves, lay flat on clean foil
Remove locking ring on the top side
We used three pairs of clean tweezers-- two to pull the ring open and one in the holes on the back side to tug it out
Put locking ring somewhere safe
Carefully flip the whole assembly over and pull the bolt out using clean tweezers
There is a locking ring on the other side, but that will stay attached to the bolt
Using a clean glove to hold the assembly pieces together can help
Put the bolt somewhere safe
The valve gate assembly and the actuator are now separate
The valve gate is held down with a spring that hooks onto the middle
P2 use a clean hand to lift up the side of the valve gate near the actuator while P1 inserts the clean 10 mm Allen key in between the valve gate and the ball guidance
Be careful when lifting the valve gate, it is quite strong and can pinch your fingers
Be careful not to let the locking balls escape. If they do, use a clean glove to carefully place them back in their spots.
Slide the valve gate off
Slide the new valve gate onto the spring
Withdraw the Allen key while P2 lifts the valve gate
Be careful when closing the valve gate to avoid pinching or snapping shut
Replace the bolt and the locking ring
This is difficult and needs a lot of force. We used three pairs of tweezers-- two to pull apart the locking ring and one to push it around the bolt.
Remove the old bonnet seal from the actuator side
It's best to replace the bonnet seal last to avoid bending it while getting the locking ring back on!
Clean the bonnet flange with a kimwipe if necessary
Place the new bonnet seal on the flange
The bonnet seal is not symmetrical, make sure the holes line up with the pin and bolt holes
Carefully insert the whole assembly back into the gate valve body
Replace the 10 screws and tighten down the accessible screws with torque wrench
Bring the chambers on either side of the gate valve back to UHV and let them pump for a while
Bring one chamber to rough vacuum to test if the gate valve holds UHV on the other side
If this goes well, bring the one chamber to N2 atmosphere to ensure the gate valve holds vacuum
Outgas the replacement parts
For Bravo's LC-BC gate valve repair, doing an LC bake caused the BC pressure to rise, indicating the gate valve was outgassing on both sides. We waited for the BC pressure to roll over while the LC lamp was hot before proceeding with normal use.