Scrap and Salvage

Hazards also result frommaintenance and decommissioning of process equipment. Some of these are  

Many of these hazards occur while handling the scrap and salvage materials produced by the following activities  

Decommissioning of inoperative equipment will make it nonhazardous to plant personnel. The equipment must be decommissioned in order to  

Essential features of an equipment cleaning/decontamination process are  

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An alternative to the foregoing process, which uses only physical methods of purification, is chemical recycling. Large amounts of PET film scrap are salvaged by a transesterification reaction. The scrap is treated with methanol in the presence of an acid catalyst to give ethylene glycol and dimethyl terephthalate, monomers that are purified by distillation or recrystallization and used as feedstocks for the production of more... 

In the fourth case, a plant or a piece of equipment has a limited use-Ril life. The primary reason for the decrease in value is the decrease in future life and the consequent decrease in the number of years for which income will be earned. At the end of its life, the equipment may be worth nothing, or it may have a salvage or scrap value S. Thus a fixed-capital cost Cpc depreciates in value during its useful life of s years by an amount that is equal to (Cpc S). The useful life is taken from the startup of the plant. 

A fourth method of computing depreciation (now seldom used) is the sinking-fund method. In this method, the annual depreciation A is the same for each year of the life of the equipment or plant. The series of equal amounts of depreciation Aq, invested at a fractional interest rate i and made at the end of each year over the life of the equipment or plant of s years, is used to build up a future sum of money equal to (Cpc S). This last is the fixed-capital cost of the equipment or plant minus its salvage or scrap value and is the total amount of depreciation during its useful life. The equation relating i Fc S) and Ao is simply the annual cost or payment equation, written either as... 

Ck is in excess of Cpc by an amount which, when compounded at an annual interest rate i for n years, will have a future worth of less the salvage or scrap value S. 11 the renewal cost of the equipment remains constant at (Cp S) and the interest rate remains constant at i, then Ck is the amount of capital required to replace the equipment in perpetuity. 

The operating cost includes items like fuel and other consumables. Maintenance costs are obviously repairs and periodic reworking of the structure. After the passage of years, nearly the entire aircraft structure has often been replaced part by parti The final category is the salvage value. What is the object worth at the end of its life Consider an aluminum airplane for which some scrap value exists at the end of its useful life. When the structure is no longer suitable to be flown, and there we... 

The lowest grade of plantation crepe rubber. It is made from earth scrap (rubber from latex which has fallen on the ground) and any other plantation salvage scrap. It was formerly called Rolled Brown Crepe. 

Aluminum scrap is one of the salvaged and recycled metals that is less expensive to reuse than it is to extract the metal from its ore. In other words, it takes much less electricity to melt scrap aluminum than it does to extract aluminum from bauxite. 

Salvage of Ammunitions The term salvage , as used in a military sense, includes those operations necessary to disassemble or break-down ammunition and its components so as to recover from them all materials or components which are or may be made serviceable, or which have a money value as scrap... 

Salvage value, scrap value, and service life are usually estimated on the basis of conditions at the time the property is put in use. These factors cannot be predicted with absolute accuracy, but improved estimates can be made as the property increases in age. It is advisable, therefore, to make new estimates from time to time during the service life and make any necessary adjustments in the... 

A piece of equipment originally costing 40,000 was put into use 12 years ago. At the time the equipment was put into use, the service life was estimated to be 20 years and the salvage and scrap value at the end of the service life were assumed to be zero. On this basis, a straight-line depreciation fund, was set up. The equipment can now be sold for 10,000, and a more advanced model can be installed for 55,000. Assuming the depreciation fund is available for use, how much new capital must be supplied to make the purchase ... 

A piece of equipment having a negligible salvage and scrap value is estimated to have a service life of 10 years. The original cost of the equipment was 40,000. Determine the following ... 

In order to make it worthwhile to purchase a new piece of equipment, the annual depreciation costs for the equipment cannot exceed 3000 at any time. The original cost of the equipment is 30,000, and it has zero salvage and scrap value. Determine the length of service life necessary if the equipment is depreciated (a) by the sum-of-the-years-digits method, and (b) by the straight-line method. 

A multiple-effect evaporator is to be used for evaporating 400,000 lb of water per day from a salt solution. The total initial cost for the first effect is 18,000, and each additional effect costs 15,000. The life period is estimated to be 10 years, and the salvage or scrap value at the end of the life period may be assumed to be zero. The straight-line depreciation method is used. Fixed charges minus depreciation are 15 percent yearly based on the first cost of the equipment. Steam costs 1.50 per 1000 lb. Annual maintenance charges are 5 percent of the initial equipment cost. All other costs are independent of the number of effects. The unit will operate 300 days per year. If the pounds of water evaporated per pound of steam equals 0.85 x number of effects, determine the optimum number of effects for minimum annual cost. 

Salvages sugar from candy scraps, especially with fondant creams from starch-molded candies and starch gum scrap. This facilitates solubility and filtration for reuse in sugar syrup for gum drop and other products. 

There comes a time when the plant is shut down and the equipment salvaged or scrapped. The engineering steps for equipment decommissioning can be as challenging as new construction. Important process design information is obtained by examining the equipment as it is moved out of service. 

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