The difference between layered and non-layered approaches in the calculation of adiabatic workloads
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In accordance with the requirements of the Construction and Acceptance Specifications for Insulation of Industrial Equipment and Piping GBJ126-89, when the insulation thickness is greater than 100 mm and the cooling insulation thickness is greater than 80 mm, construction should be carried out in layers, with the volume of work being calculated on a layer-by-layer basis. According to Page 47 of the 98R419 atlas. So, what is the difference between hierarchical computation and non-hierarchical computation? Today let’s do a comparison. Suppose we have an industrial pipeline with a diameter of 529 mm, a length of 1000 m, and an insulation thickness of 100 mm; the insulation material is fibrous type.1. First, calculate based on the assumption of no layers. Using the formula: 3.1415926*(0.529 + 1.033*0.1)*1.033*0.1*1000 = 205.20 m³. Applying the rates from “Henan Province Comprehensive Unit Price for Installation Projects (2003)” under item 11-1855 for the installation of fibrous products (pipes/shells) for pipelines with a diameter of less than Φ529 mm and an insulation thickness of 100 mm, the direct cost is 11,714.86 yuan.
2. Next, calculate by considering separate layers. For the first layer, with a thickness of 60 mm, the insulated volume is calculated using the formula: 3.1415926*(0.529 + 1.033*0.06)*1.033*0.06*1000 = 115.07 m³. For the second layer, with a thickness of 40 mm, the diameter is first calculated as follows: (529 + 2.1*60) + 8.2 = 663.2. [Note: Since both the pipeline diameter and the insulation thickness are given in millimeters, 0.0082 also needs to be converted to millimeters, i.e., 8.2.] The insulated volume for this layer is then calculated using the formula: 3.1415926*(0.6632 + 1.033*0.04)*1.033*0.04*1000 = 91.45 m³. Applying the rates from “Henan Province Comprehensive Unit Price for Installation Projects (2003)” under item 11-1851 for the installation of fibrous products (pipes/shells) for pipelines with a diameter of less than Φ529 mm and an insulation thickness of 60 mm, the direct cost is 10,184.84 yuan. Then, applying the rates from item 11-1857 for the installation of fibrous products (pipes/shells) for pipelines with a diameter of less than Φ720 mm and an insulation thickness of 40 mm, the direct cost is 9,569.46 yuan. The total cost for these two items is 19,754.30 yuan, which is 8,039.44 yuan more than the cost calculated assuming no layers. ====================================================================== This leads to another question: when we carry out construction in layers, the thickness of the two layers is sometimes not consistent – some layers are thinner while others are thicker. So, should we build the thinner layers first, or the thicker ones first? Taking the project above as an example, let’s make a comparison: the method described in the post upstairs is 60mm + 40mm, resulting in a total insulation thickness of 100mm. Let’s calculate the result again using 40mm + 60mm, with the insulation thickness also being 100mm. No more nonsense, let’s get to work! For the first layer, with a thickness of 40 mm, the insulated volume is calculated using the formula: 3.1415926*(0.529+1.033*0.04)*1.033*0.04*1000 = 74.03 m3. For the second layer, with a thickness of 60 mm, the diameter is first calculated using the formula: (529+2.1*40)+8.2 = 621.20; then the insulated volume is calculated as: 3.1415926*(0.6212+1.033*0.06)*1.033*0.06*1000 = 133.03 m3.
1. First, apply the rates from “Henan Province Installation Project Unit Comprehensive Base Prices (2003)” under item 11-1849, which covers the installation of fiber-based products (tubes and shells) for pipes with a diameter of Φ529 mm or less and a thickness of 40 mm. The direct cost in this case is 8320.23 yuan.
2. Next, apply the rates from the same document under item 11-1859, which covers the installation of fiber-based products (tubes and shells) for pipes with a diameter of Φ720 mm or less and a thickness of 60 mm. The direct cost here is 11076.08 yuan.
The total cost for these two items is 19396.31 yuan. It can be concluded that the cost for a thickness of 60 mm + 40 mm is 19754.30 yuan, while the cost for 40 mm + 60 mm is 19396.31 yuan. The difference between these two amounts is 357.99 yuan. Conclusion: The results obtained by calculating first for a thicker value and then for a thinner one are slightly higher