Many field maintenance workers overfill excessive thermal conductive grease during thermocouple installation on YUDO and domestic multi-cavity precision hot runner, redundant high-temperature grease easily flows backward along sheath gap into open terminal inner cavity under long-term high-temperature softening, triggering terminal insulation decline, creep short-circuit and gradual measuring drift, which is a frequently overlooked human-induced hidden failure factor. Thermal conductive grease keeps semi-fluid status under continuous hot runner working temperature above 300℃; superfluous grease extruded out from probe mounting clearance creeps upward along tiny clearance between sheath outer wall and mounting hole inner wall, finally penetrating into terminal internal wiring cavity after long-term thermal migration. Ordinary grease contains mineral oil and low-molecular organic additive, these compositions gradually volatilize and decompose into conductive carbon residue under high-temperature aging, accumulated carbon powder adheres on bare copper terminal surface to form indirect conductive path between positive and negative wiring terminal, bringing intermittent creep short-circuit fault and irregular temperature jumping on controller display. In serious cases, carbonized grease residue completely fills terminal cavity clearance and directly causes permanent core-to-terminal short-circuit failure leading to full-channel zero display shutdown. In actual production, most operators pursue better heat conduction effect and blindly increase grease dosage without mastering standardized filling range, ignoring backward creep risk of high-temperature softened grease.
Unified standardized filling regulation clearly limits grease only coated on front 1/3 measuring section of probe outer circumference, and prohibits any grease daubing near sheath root and terminal transition position. Before filling construction, wipe probe surface residual dirt and old aged grease thoroughly with alcohol cloth to avoid mixed impurity accelerating grease carbonization speed. When replacing new thermocouple, clean mounting hole residual aged carbonized grease completely first before refilling matched grade thermal grease in limited standard dosage. Monthly equipment inspection spot-check terminal internal grease overflow carbonization condition channel by channel for hot runner equipment which suffered previous overfilling hidden trouble, disassemble and clean accumulated carbon residue timely once abnormal carbon deposition is found. Workshop compiles filling dosage comparison poster pasted beside maintenance tool cabinet to standardize operator's daily filling operation and cut overfilling-induced premature thermocouple scrap rate year by year.
