Useful life

The treatment of expenditures will be specified by the fiscal system set by the host government. A typical case would be to define expenditure on items whose useful life exceeds one year as capital expenditure (capex), such as costs of platforms, pipelines, wells. Items whose useful life is less than one year (e.g. chemicals, services, maintenance, overheads, insurance costs) would then be classed as operating expenditure (opex). 

A further advantage is the Selenium halflife of 120 days, which is 60% more when compared to iridium and a factor of approx. 4 when compared to Ytterbium. These differences turn out to be an important economical aspect when comparing the different sources, as they are a direct measure of the useful life of sources. The short halflife and the very high costs for Ytterbium sources have been the main factors for the rather low importance of Ytterbium in the full range of gamma radiography. 

Antioxidants markedly retard the rate of autoxidation throughout the useful life of the polymer. Chain-terminating antioxidants have a reactive —NH or —OH functional group and include compounds such as secondary aryl amines or hindered phenols. They function by transfer of hydrogen to free radicals, principally to peroxy radicals. Butylated hydroxytoluene is a widely used example. 

Reactions on Adsorbents. To permit the recovery of pure products and to extend the adsorbent s useful life, adsorbents should generally be inert and not react with or cataly2e reactions of adsorbate molecules. These considerations often affect adsorbent selection and/or require limits be placed upon the severity of operating conditions to minimi2e reactions of the adsorbate molecules or damage to the adsorbents. 

Benefits depend upon location. There is reason to beheve that the ratio of hydrocarbon emissions to NO has an influence on the degree of benefit from methanol substitution in reducing the formation of photochemical smog (69). Additionally, continued testing on methanol vehicles, particularly on vehicles which have accumulated a considerable number of miles, may show that some of the assumptions made in the Carnegie Mellon assessment are not vahd. Air quaUty benefits of methanol also depend on good catalyst performance, especially in controlling formaldehyde, over the entire useful life of the vehicle. 

A typical catalyst bed is very shallow (10 to 50 mm) (76,77). In some plants the catalyst is contained in numerous small parallel reactors in others, catalyst-bed diameters up to 1.7 and 2.0 m (77,80) and capacities of up to 135,000 t/yr per reactor are reported (78). The silver catalyst has a useful life of three to eight months and can be recovered. It is easily poisoned by traces of transition group metals and by sulfur. 

Depth filters are usually preferred for the most common type of microfiltration system, illustrated schematically in Figure 28. In this process design, called "dead-end" or "in-line" filtration, the entire fluid flow is forced through the membrane under pressure. As particulates accumulate on the membrane surface or in its interior, the pressure required to maintain the required flow increases until, at some point, the membrane must be replaced. The useful life of the membrane is proportional to the particulate loading of the feed solution. In-line microfiltration of solutions as a final polishing step prior to use is a typical apphcation (66,67). 

The use of these sHmicides may result in an appreciable increase in the cost of producing paper. However, thein use often reduces downtime that is caused by slime and, therefore, increases production which more than compensates for the initial cost of the sHmicides. White water systems also often contain proteolytic microorganisms which attack the machine felts and reduce thein useful life. Control of this problem may be accompHshed by treating the felts with a sHmicide foUowed by cleaning with a mild acid (see INDUSTRIALANTIMICROBIALAGENTS). 

Responsible Care is the incentive sponsored by the Chemical Manufacturers Association (CMA). Any CMA company must embrace the philosophy of continuous improvements of health, safety, and environmental efforts accompanied by an open communication to the pubHc about products and their production. Thus the total impact of any product on the environment, from the extraction of raw materials, their beneftciation, transportation, production of final product, and disposal of the product at the end of its useful life, must be taken into consideration. 

Glass is a material having properties that provide attributes for many commercial products. As some of these products reach the end of thek useful life and are discarded, there is often the opportunity to have the glass recycled into other useful products. In many respects, this alternative is preferred over the glass entering a municipal waste stream for landfill disposal. 

Dicyandiamide fluidifies various adhesives and glues. In the presence of dicyandiamide, the initial viscosity of the adhesive formulations is lowered and maintained at a lower range for longer periods of time, thus preventing premature gelling and extending the useful life of the adhesive (see Adhesives). 

The advantage of this process over other xerographic processes using conventional photoconductors is that the most sensitive part of the photoconductor is protected from the corrosive environment. This helps to increase the useful life of the device. The process itself, however, is rather comphcated. 

The trend in the xerographic copying and printing industry is to expand the use of organic photoconductors which are typically inexpensive and have a useful life. However, the a-Si H photoreceptors, even though more expensive to manufacture, may ultimately have an advantage in greater durabihty. 

The useful life of the emissions control system is expected to be five years or 80,000 km, unless otherwise noted. 

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... 

Useful life 1 trip 1 trip 10 trips 15 years 5 years 25 years 10 years... 

Lease cost is based on a period equal to the useful life. 

Microbiological analysis of material removed from corroded areas showed high aerobic and relatively high anaerobic counts (Table 6.7). Fungi counts were also elevated, indicating relatively high die-off of aerobic bacteria that is, the coolant was approaching its useful life. 

Frequently a piece of equipment is used in different processes during its lifecycle. This could result in process conditions that exceed the safe operating limits of the equipment. Equipment inspection may provide a poor prediction of the equipment s useful life and reliability, due to the change of material handled or change in process chemistry over the life of equipment. Batch operations are also characterized by frequent start-up and shut-down of equipment. This can lead to accelerated equipment aging and may lead to equipment failure. This chapter presents issues and concerns related to the safe design, operation, and maintenance of various pieces of equipment in batch reaction systems, and provides potential solutions. 

Implement pH monitoring to determine useful life of scrubbing solution... 

Too many gland adjustments will cause the packing to crystallize and burn, which will shorten the packings useful life and damage the shaft or pump sleeve. 

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