Ulvac EGL-206M Instruction Manual page 49

SECTION 6
the inside wall of the crucible water path, not only deteriorating heat
conductance and lowering the cooling effect, but also melting the crucible
locally and perforating it.
9. The multi-hearth type electron beam gun uses an O-ring for the shaft seal to
seal water and vacuum. To the O-ring is applied vacuum grease as lubricant,
but there can be a leak due to shortage of grease or plastic deformation of the
O-ring even within the warranty period. It is recommended to change the
O-ring and apply grease to the shaft seal area once every six months for
caution's sake.
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