Original Date: 08/08/1994
Revision Date: 01/18/2007
Best Practice : Replacing LOPS in Magnetic Particle Inspection
By replacing a Low Odor Base Paraffin Solvent (LOPS) with conditioned water as the particle carrier in magnetic particle testing, CSTA has been able to reduce hazardous waste generation, reduce its process costs, and increase worker safety. Magnetic particle testing is used in non- destructive testing on magnetizable materials to detect surface and slightly subsurface discontinuities. Magnetic particle testing consists of three processes including establishing a suitable magnetic flux in the test object, applying magnetic particles in a liquid suspension, and examining the test object under suitable lighting conditions.
CSTA previously used the LOPS petroleum suspension agent in the second step of magnetic particle testing. This agent caused several problems in the inspection process. For example, LOPS had to be collected after the inspection and disposed of as hazardous waste, and LOPS had a flash point of 140 degrees F presenting a constant danger of flash fires. Finally, the inspection personnel were continually exposed to vaporized LOPS which posed a health hazard at high concentrations.
CSTA solved these problems by replacing LOPS with conditioned water as the suspension agent for the magnetic particle inspection process. Water eliminated the generation of hazardous waste, eliminated the chance of flash fires, and eliminated the breathing hazard associated with LOPS. Further, the cost of using this inspection process decreased because conditioned water costs of $1.28/gallon replaced the $2.72 for LOPS -- and there was no disposal cost for the water.
CSTA continued to improve the magnetic particle inspection process by switching from traditional contact probes to larger clamps with copper brush contacts. This change more than doubled the contact surface of the inspected item which reduced the amount of heat generated by the process, allowing higher energy levels to pass through the clamps. In turn, greater spacing could be used between contact points reducing the number of shots required and thus the cost to inspect an object.
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