Main anchors by definition are installed where directional changes take place, at the end of a line or between expansion joints of different size. They have to carry the full pressure thrust, the spring forces, and the frictional forces due to alignment guides and supports, and in some cases, the weight of piping, fittings and contents. The design of such anchors is therefore, beyond the scope of the design engineer, unless full details of the entire structure are provided. In these cases, anchors may be furnished as an integral part of the expansion joint. An intermediate anchor divides a pipe system into an individual expanding section, and is only responsible for the forces imposed upon it by this section, i.e. it includes only for the spring forces, friction of guides and possibly the wind load and weight etc., as it effects each section of pipe. Intermediate anchors may be built into expansion unit assemblies by arrangement with the manufacturer and may lead to economies by the elimination of flanges or other fittings. Directional anchors or guides are designed to absorb loading in one direction whilst permitting motion in another. It may constitute either a main or an intermediate anchor, depending upon the application. Clearly, such guides are required to have a minimum of friction in order to reduce the loading elsewhere, and ensure its proper functioning as a guide.
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