Insulation costs

Optimal economic insulation thickness may be determined Iw various methods. Two of these are the minimum-total-cost method and the incremental-cost method (or marginal-cost method). The minimum-total-cost method involves the actual calculations of lost energy and insulation costs for each insulation thickness. The thickness producing the lowest total cost is the optimal economic solution. The optimum thickness is determined to be the point where the last dollar invested in insulation results in exactly 1 in energy-cost savings ( ETI— Economic Thickness for Industrial Insulation, Conservation Pap. 46, Federal Energy Administration, August 1976). The incremental-cost method provides a simplified and direcl solution for the least-cost thickness. 

There will be exceptions to this rule, such as thicker insulation where electric power is expensive, or thinner insulation for a chamber only used infrequently. Ceiling panels may be thicker to give added structural strength. In cases of doubt, the insulation costs must be resolved as the optimum owning cost. 

Electrical properties not adequate for primary insulation Cost... 

Examine how jc varies with the different parameters in (d), and confirm that the trends are physically meaningful. Note that the heat transfer area A does not appear in Equation (d). Why Could you formulate/as a cost minimization problem, that is, the sum of the value of heat lost plus insulation cost Does it change the result for jc How do you use this result to select the correct commercial insulation size (see Example 1.1) ... 

Insulation thickness x (cm) Insulation cost ( > Value of fuel saved ( /year) Payback period (years) Return on investment (% per year) Net present value ( > Internal rate of return (%)... 

Objective functions that allow only discrete values of the independent variable ) occur frequently in process design because the process variables assume only specific values rather than continuous ones. Examples are the cost per unit diameter of pipe, the cost per unit area for heat exchanger surface, or the insulation cost considered in Example 1.1. For a pipe, we might represent the installed cost as a function of the pipe diameter as shown in Figure 4.2 [see also Noltie (1978)]. For... 

The first example was formulated by Stoecker to illustrate the steepest descent (gradient) direct search method. It is proposed to attach a vapor recondensation refrigeration system to lower the temperature, and consequently vapor pressure, of liquid ammonia stored in a steel pressure vessel, for this would permit thinner vessel walls. The tank cost saving must be traded off against the refrigeration and thermal insulation cost to find the temperature and insulation thickness minimizing the total annual cost. Stoecker showed the total cost to be the sum of insulation cost i = 400jc° 9 (x is the insulation thickness, in.), the vessel cost v = 1000 + 22(p — 14.7)1-2 (p is the absolute pressure, psia), and the recondensation cost r = 144(80 — t)/x (t is the temperature, °F). The pressure is related to the temperature by... 

Forty-six case studies of hydrate plug formation and remediation are recorded in Hydrate Engineering (Sloan, 2000). In every case, hydrate plugs were remediated. In addition, a rule of thumb is that most of the offshore flowline shut-ins are less than the 10 h no touch time, which requires no antihydrate operation before restart (J.E. Chitwood, Personal Communication, August 1, 2003). However, hydrate prevention methods are very expensive, as shown in the above Canyon Express and Ormen Lange examples, or in the fact that deepwater insulation costs are typically U.S.Sl million per kilometer of flowline. 

When very high or very low temperatures are involved, insulation factors can become important, and it may be necessary to estimate insulation costs with a great deal of care. Expenses for equipment insulation and piping insulation are often included under the respective headings of equipment-installation costs and piping costs. 

It should be apparent that insulation does not eliminate heat transfer it merely reduces it. The thicker the insulation, the lower the rate of heat transfer but also the higher the cost of insulation. Therefore, there should be an optimum thickness of Insulation that corresponds to a minimum combined cost of insulation and heat lost. The determination of the optimum thickness of insulation is illustrated in Fig. 7-38. Notice that the cost of insulation increases roughly linearly with thickness while the cost of heat loss decreases exponentially. The total cost, which i.s the sum of the insulation cost and the lost heat cost, decreases fir.st, reaches a minimum, and then increases. The thickness corresponding to the minimum total co.st is the optimum thickness of insulation, and this is the recommended thickness of insulation to be installed. 

Total cost = Insulation cost -T Heal loss cost = 1085 -P 615 = 1700... 

Insulation thickness Heat loss, Btu/h Lost fuel, therms/yr Lost fuel cost, /yr Insulation cost, Total cost, ... 

Incremental investments, 315-329 Index name, 893 subject, 897 Indexes, cosf 163-166 Indirect costs, 210 in capital investments, 160, 167 Inflation, 295 strategy for, 408-413 tax effects on, 410-413 Informal reports, definition of 453- 454 Infringements of patents, 102 Installation costs for equipmenf 171-172 Instrumentation cost of 172-173, 812-814 plant requirements for, 97 Insulation cost of 172 for pipe, 513 Insurance, 262-265 as a cost, 253, 262 cost of 205, 210 Intalox saddles, 688, 690, 694 cost of 710 Interest ... 

Pipe insulation, cost of, 513 Pipe painting, cost of, 514 Pipe roughness, equivalent, 480, 482 Piping standards, 492-494 Piping systems cost of, 173-174, 497-510 design of, 494-497 Plant ... 

The dilution of the acid catalyst by the condensate formed in the heating process and in maintaining the reaction temperature stresses the importance of having the reactor thermally well insulated. Against this background, it must be kept in mind that a good thermal insulation, costing very little,... 

The amortized insulation cost, capital cost of the insulation, Zj, and the amortization factor, ip ... 

The cost of calcium silicate insulation is a function of the nominal diameter of the pipe and the insulation thickness. Costs for several pipe diameters and thicknesses (in half-inch increments) were obtained from quotations from a reputable insulation vendor. These estimates established the functional dependence, Zj(Dn,0), of insulation cost on thickness and pipe diameter. 

Figure 8. Piping system costs as functions of nominalpipe diameter for 6 — 3.5 in. (1 in. — 2.54 cm) (X)> total cost (%), pipe cost fl), friction cost (-)-), insulation cost and (A), heat loss cost.

The heat-loss and insulation costs are small compared to the friction and piping costs only 5.6% ([ 1.74/ft-yr + 2.14/ft-yr]/ 67.13/ft-yr) of the total cost for the optimal piping system. Furthermore, the effect of increased insulation thickness is not great. Figure 7, which shows total cost curves at selected insulation thicknesses (0 = 1.0, 3.5, and 7.0 in.), illustrates this effect. When the heat-loss and insulation costs are of secondary importance, the insulation thickness might well be dictated by a safe-surface temperature criterion. 

Insulation Costs. Where very high or very low temperatures exist foi precise conditions, insulation costs may become a significant factor. Foi normal temperature levels the insulation expense is included undei equipment installation costs, amounting to 6 to 10 per cent of deliverer equipment cost with 40 per cent of the cost charged to materials, th(... 

Design of Underground Piping. Laying a pipeline in a tunnel (1) reduces the heat losses and insulation costs, (2) does not occupy valuable overhead space, and (3) protects the piping from mechanical injury and freezing. However, it is a good rule to consider some of the disadvan-... 

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