defect signals which can be lost in the background noise. This limita- 

 tion was first observed during a field test on an elevator wire rope 

 taken from a mine and known to have a 1/8-inch gap. When the sensor head 

 was moved slowly or rapidly over the broken wire, the break signal was 

 totally lost in the background noise. 



Further Tests 



Consequently, a laboratory test track was built to accommodate a 

 loop of wire rope 100 feet in length. Different sized wire ropes were 

 tested that contained broken wires having various gap spacings. This 

 work was planned for the defect catalog, but became an investigation of 

 the minimum-sized gap which produces an observable break signal. 



Field studies also indicated that used wire rope gave off consid- 

 erably more background noise than new rope. It became apparent that a 

 used wire rope would need to be taken apart to correlate the defect 

 signals to the actual wire rope conditions. This work was done, and the 

 results are presented in this report. 



Magnograph Development 



The Magnograph unit has only recently become available for purchase 

 from the manufacturer (Heath and Sherwood Limited, Ontario, Canada). 

 The manufacturer's discussion on engineering principles and operation of. 

 the equipment is presented in the Appendix (the manufacturer's operation 

 manual) . 



It is important to mention that as limitations of this new equip- 

 ment arise, the developers (Noranda Research Centre, Montreal, Canada) 

 and Heath and Sherwood work to solve the problems. For example, during 

 the NCEL tests it was observed that the LMA recordings were drifting 

 with time. Part of the problem was an electronic component failure, but 

 another part was the temperature sensitivity of the Hall sensors. Both 

 developer and manufacturer solved the problem and have upgraded subse- 

 quent equipment." Noranda has improved the calibration method for LMA 

 readings. Thus, the equipment is evolving and improving as problems are 

 noted and solved. 



TESTING 



Scope 



New wire ropes of 6x25 right-regular-lay, fiber-core construction, 

 having diameters of 1/2, 3/4, 1-1/8, 1-1/2, 2, and 2-1/2 inches, were 

 tested with manmade broken wires. The broken wires had gap spacings 

 that varied from to 1/2 inch in 1/16-inch increments. A used wire 

 rope of 6x31 regular- right- lay, fiber-core construction, having a 

 1-1/8-inch diameter, was tested and disassembled to compare LF signals 

 with the actual condition of the wire rope. Other tests investigated 

 signal size as a function of gap configuration, orientation, and rope 

 speed. 



"'NCEL's equipment has not been upgraded with this feature. 



