Patent ID: 7520744

Claim:
A monitoring device for being mounted in a wall of a furnace of a type in which deposits may accumulate on the wall's surface that faces the furnace's interior, the monitoring device comprising: opposite inner and outer ends, wherein the inner end is for facing toward the furnace's interior; at least one housing; a monitoring element positioned in the housing and extending at least partially between the inner end and the outer end; a scraper unit including a scraper head mounted for moving along the housing between a retracted position and an extended position, and at least one drive for reciprocating the scraper head along the housing between the retracted and extended positions; and the scraper unit being adapted so that the scraper head is for contacting, and thereby removing, the deposits that accumulate proximate the monitoring element at the inner end, and so that the contacting occurs in response to the scraper head being reciprocated along the housing between the retracted and extended positions.