Wearfacing is commonly known in the NCF ashardfacing. The purpose of hardfacing (fig. 5-15) is toinsulate many working parts of equipment from thedestructive forces that cause metal wear. The selectionof a hardfacing alloy for a certain application is basedon the capacity of the alloy to withstand or resist impactand abrasion. Impact refers to a blow or series of blowson a surface that results in a fracture or gradualdeterioration. Abrasion is the grinding action that resultswhen one surface slides, rolls, or rubs against another.Under high compressive loads, this action can result ingouging.Alloys that resist abrasion well are poor inwithstanding impact, whereas those that withstandimpact well are poor in resisting abrasion; however,there are many alloys whose hardfacing properties fallbetween two extremes. These alloys offer someprotection against abrasion and withstand impact fairlywell. The hard-faced welding procedures, the typematerial the part is manufactured from, and the primaryand alternate electrodes to perform the hardfacingprocedures are all outlined in NAVFAC P-433.Hardfacing operations must be approved by themaintenance supervisor.MaintenanceOften, maintenance is put off to a later date becauseof production. This may satisfy the immediateproduction demands of the unit, but it is not good for theequipment and creates a lax attitude toward scheduledmaintenance. When this occurs, a precedent is set thatleads to putting maintenance second to production.Should this happen, it is not long before production ratesdecline because of equipment breakdowns.BLASTING OPERATIONSBlasting operations are usually necessary whenworking a quarry containing materials that cannot beremoved with construction equipment, such as front-endloaders, bulldozers, and hauling equipment. Should thisbe the case, blasting will come under the directsupervision and control of a qualified blaster who carriesthe NEC-5708. All other quarry personnel assignedmust follow written and oral instructions, carry outassigned duties, and observe all safety precautions.Limiting the number of personnel handlingexplosives lessens the risk of accidents occurring. Thismeans one or two blasters have a definite assignment toconduct several of the tasks involved in loading andfiring a blast. These tasks include the following:carrying explosives and detonators, opening cases,priming, loading, stemming, connecting blastingcircuits, and firing. The entire quarry crew must knowexactly what the blaster’s duties are. With such a systemobserved, everything is accomplished in a precise andorderly manner with no haphazard assumption of thevarious tasks to be performed.5-16
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