Method of identifying defective roll on a strip processing line

A method of identifying the location of a defective roll in a strip processing line wherein a defective roll causes a visible repeating mark on the material being processed, said strip processing line including a plurality of laterally spaced pairs of rolls between which the strip material is carried, means for opening and closing roll pairs, an inspection station downstream of the rolls to inspect for visible marks on the strip emerging from the rolls, data processing means for selectively opening and closing pairs of rolls in timed sequence, and actuating means associated with the inspection station for actuating the data processing means,

• said method comprising actuating the data processing means when a mark on the strip material passes the inspection station thereby starting the timed opening and closing of said rolls and stopping the timed opening when the absence of a mark is detected at the inspection station, recording the lapsed time between the timed opening and the detection of the absence of a mark, and comparing the lapsed time to a data base indicating the location of a roll relative to the lapsed time thereby identifying the defective roll.