CHAPTER 14MISCELLANEOUS EQUIPMENTMixing equipment, drilling equipment, compressedair equipment, and miscellaneous construction andmaintenance equipment are procured for the NavalConstruction Force (NCF) to support specificconstruction and maintenance operations.This chapter covers the characteristics and basicprinciples of operations of mixing equipment, drillingequipment, compressed air equipment, and mis-cellaneous construction and maintenance equipment.These types of equipment play a vital part in NCFoperations; therefore, as an equipment operator, youshould become familiar with the capabilities of theequipment and how it can be used to serve thepurpose for which it was designed.CONCRETE TRANSIT MIXERA concrete transit mix truck, sometimes called aTM, is a traveling concrete mixer (fig. 14-1). The truckcarries a mixer and a water tank from which the operatorcan, at the proper time, introduce the required amountof water into the mix. The operator picks up the dryingredients at the batch plant along with a chit that tellshow much water is to be introduced to the mix. Themixer drum is kept revolving en route and at the jobsite,so the dry ingredients do not segregate.When a TM is used for mixing concrete, 70 to 100revolutions of the drum at the rate of rotation,designated by the manufacturer as mixing speed, areusually required to produce the specified uniformity.No more than 100 revolutions at mixing speed shouldbe used. All revolutions after 100 should be at the rateof rotation designated by the manufacturer asagitating speed. Agitating speed is usually about 2to 6 revolutions per minute, and mixing speed isgenerally about 6 to 18 revolutions per minute.Mixing for long periods of time at high speeds, about1 or more hours, can result in concrete strength loss,temperature rise, excessive loss of entrained air, andaccelerated slump loss.Concrete, mixed in a transit mixer, should bedelivered within 1 1/2 hours or before the drum hasrevolved 300 times after the introduction of water tocement and aggregates or the cement to the aggregates.Mixers and agitators should always be operated withinthe limits of the volume and speed of rotation designatedby the manufacturer.DISCHARGE CHUTESThe operator must have the proper chutes at thedelivery site or on the truck before delivering concrete.Open-trough chutes should be of metal or metal-lined,Figure 14-1.—Concrete transit mixer.14-1
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