INTRODUCTION 



The Naval Civil Engineering Laboratory (NCEL) under Naval Facilities 

 Engineering Command (NAVFAC) and Bureau of Mines joint sponsorship has 

 investigated nondestructive test (NDT) equipment for the inspection of 

 wire rope. Conventional NDT equipment utilizes separate AC and DC units 

 to detect loss of metallic area (LMA) and local faults (LF) , respectively. 

 A representative device was tested and compared to a newly developed 

 type of NDT equipment that is a unitized AC/DC device. The two devices 

 were compared considering operational capabilities and ease of use. The 

 Magnograph equipment, the unitized AC/DC device, was recommended for 

 use by the Navy. It is more versatile than the separate AC and DC units, 

 as both LF and LMA data are recorded simultaneously on a 2-channel, 

 brush-chart recorder and on a cassette tape. The Magnograph uses Hall 

 effect sensors, which permit the wire rope speeds to vary from fpm to 

 over 800 fpm without any change in the reliability of the recorded LF 

 and LMA data". Figure 1 shows the Magnograph in operation. 



As a result of extensive field testing of these NDT devices, 

 inspectors stated that a need existed for a small, lightweight, and 

 inexpensive NDT wire rope inspection device. This inspection device would 

 be used to replace the "rag and visual" method for interim or preliminary 

 inspections when there is a question of broken wires. 



NCEL, under NAVFAC sponsorship, conducted a survey to find a NDT 

 wire rope inspection device that met these criteria. As a result of 

 this survey, the MT 75 Rope Tester was selected for test and evaluation 

 (Figure 2). This report presents the results of the test and the evalua- 

 tion program conducted on the MT 75 to determine its characteristics 

 before Navy field activities acquire the units and start NDT wire rope 

 inspection programs. 



MT 75 ROPE TESTER 



The MT 75 is a hand-held NDT wire rope inspection device that uses 

 the DC method of detection. The MT 75 is 6 inches long, 8-1/2 inches 

 wide, 1-1/2 inches deep, and weighs about 5 pounds. 



The DC method of detection is a well-established method for detect- 

 ing local faults such as broken wires. The DC NDT wire rope inspection 

 equipment uses strong permanent magnets to magnetically saturate the 

 wire rope to be inspected; this causes a magnetic flux field to radiate 

 from the wire rope into the surrounding air. Search coils are positioned 

 close to the wire rope inside this flux field. As the wire rope is 



r Naval Civil Engineering Laboratory. Technical Note N-1639: Test and 

 evaluation of the Magnograph unit - a nondestructive wire rope tester, 

 by L. D. Underbakke. Port Hueneme, Calif., July 1982. 



