Book - School of Science and Technology

Provision for thermal expansion 259Table 9.9 Fabricated expansion loops (see Figure 9.17 for symbols)Pipework dimensions (m)Total thrust on anchors (kN)Nominalbore(K)Pipe run Loop System temperature ( C)T L W H 80 110 14025 21 4 1.00 0.66 0.34 0.49 0.6332 24 5 1.25 0.71 0.50 0.71 0.9140 27 6 1.50 0.75 0.72 1.01 1.2950 30 8 1.75 0.88 1.02 1.41 1.8065 34 11 2.00 1.10 1.54 2.10 2.6580 38 14 2.25 1.16 2.16 2.90 3.65100 43 19 2.50 1.58 3.15 4.16 5.16125 48 25 2.75 1.79 4.54 5.87 7.20150 52 30 3.00 2.14 6.03 7.69 9.36. A symmetrical offset or loop, between guides, produces the least thrust at the anchors.. Anchor points in long runs of pipework may be subjected to equal thrust from eachdirection and thus to a balanced force of compression.. Least thrust is imposed upon anchor points when the height of a rectangular loop isboth twice its width and equal to the distance between the associated guides.. When loops are fabricated, short radius elbows should be used rather than wide bends.The latter offer stiffness, and consequent increased thrust on anchor points, in theirtendency to assume an oval cross-section.The leading dimensions necessary to initiate calculation of the forces and momentsacting as a result of thermal expansion are identified in Figure 9.17 and, from these,results such as those listed in Table 9.9 may be produced. These latter are not, it must beemphasised, recommended values but no more than a collection made to illustrate theorder of the numbers which may be expected. In practice, it is usual to use a computer toundertake what is otherwise a laborious and time consuming exercise.