Book - School of Science and Technology

258 Piping design for indirect heating systemsOff setBellowsPin jointsReduced lengthwhen deflectedTie barsCentre tubesPin jointsFlanged endsFigure 9.16 Restrained bellows and their application (Engineering Appliances)installation whereby the loop or offset is shortened to take up a proportion (often half) ofthe anticipated expansion in service. By this expedient, the force on the anchor points isreduced pro-rata.When applying natural flexibility cold draw should not be used to reduce the offset asthis is difficult to monitor on site and it actually increases the anchor forces due to theincreased rigidity of shorter offset pipes.Offsets and loopsThe Guide Section B16 presents a collection of data which enable the dimensions of offsetsand rectangular loops to be evaluated and the thrust upon anchors determined. Thefollowing five salient points, not in order of merit, require greater emphasis:. Contrary to previous usage, it is the distance between any guides, as distinct fromanchors, in the pipework which is the critical dimension.AnchorGuideIGuideAnchorWLTFigure 9.17 Leading dimensions for analysis of an expansion loop