General Maintenance 4
5977B Series MSD Troubleshooting and Maintenance Manual 139
To Lubricate the Vent Valve O-Ring
Materials needed
• Cloths, clean (05980-60051)
• Gloves, clean, lint-free
• Large (8650-0030)
• Small (8650-0029)
• Grease, Apiezon L, high vacuum (6040-0289)
• O-ring, vent valve (0905-1217). Replace if the old O-ring is worn or damaged
The vent valve O-ring needs a thin coat of lubrication to ensure a good vacuum
seal and smooth operation. If the vent valve O-ring does not turn smoothly or
does not seal correctly, lubricate it using this procedure.
Procedure
1 Vent the MSD.
2 Completely remove the vent valve knob. (See Figure 21 on page 140)
3 Inspect the O-ring. If the O-ring appears damaged, replace it.
4 Use a clean, lint-free cloth or glove to spread a thin coat of high vacuum
grease on the exposed surface of the O-ring.
5 Use a clean, lint-free cloth or glove to wipe away excess grease. If the
O-ring looks shiny, there is too much grease on it
Vacuum seals other than the side plate O-ring and vent valve O-ring do not need to be
lubricated. Lubricating other seals can interfere with their function.
Excess grease can trap air and dirt. Grease on surfaces of the O-ring other than the
exposed surface can trap air, resulting in air spikes during operation.
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