User manual

1
Instructions for Use
Loss of Sensitivity at High Leak Rates
26/36 Variable Leak Valve User Manual / 87-400-085-01 (D)
Loss of Sensitivity at High Leak Rates
Repeated bakeouts at 450°C will result in partial annealing and a loss
of tension in the spring washers that provide the force to open the
valve. This will be evidenced by decreasing sensitivity of control at
high leak rates. This is not a common situation, but may occur after
months of use under high-temperature conditions. Replacement of
the spring washers and adjustment are required.
1. Disassemble drive mechanism.
a Open the valve four counterclockwise turns of the knobs.
b Withdraw the two Phillips head screws on the upper part of the
valve body and remove the cover.
c Remove the roughing screw.
d Remove the two pivot rods by grasping each with a screw. Lift
out the handle.
2. Replace spring washers.
e With a 3/4" hex-socket wrench, remove the nut above the spring
washers.
f Remove and replace the spring washers.
g Replace the 3/4" hex nut.
3. Adjust tension.
h With a /4" hex-socket-wrench, tighten the nut above the spring
washers just enough so that there is no clearance between the
washers and the nut.
4. Reassemble.
i Replace the handle, pivot rods, roughing screw, and cover.
j Repeat the closure adjustment to reposition the handle and
knobs.