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68 Expansion joint selection HINGED LFP Gn Source: Freely adapted from EJMA Hinges in a system Hinged expansion joints can, in sets of two or three, be used for absorbing large lateral and axial movements. LFP In general, there should not be more than three angular expansion joints installed between two fix points, of LFP which a maximum of two can be gimbal expansion joints. Source: Freely adapted from EN 14917 Two-hinged system Illustrates the use of a two-hinge system to absorb the major thermal expansions in a single-plane “Z” bend. Since the pressure thrust is absorbed by the hinges on the expansion joints, only fix points are required at each end of the piping system. The thermal expansion of the offset section containing the expan- sion joints must be absorbed by the bending of the piping legs perpendic- ular to that segment, since the expansion joints are restricted to pure angular rotation by their hinges and cannot extend or compress. The amount of bending deflection imposed on each of the two long piping legs may be controlled by the effective design of guides and supports. Where one long leg is sufficiently flexible to absorb the full thermal growth of the offset leg, the other long leg may be controlled to permit longitudinal movement only. The guides shown at the ends of the long pipe system near the elbows are intended to maintain the plane of the pipe system only and must allow for the bending deflections of the long piping legs. When calculating guide clearances, consideration shall be given to the fact that the thermal expansion of the offset piping leg containing the expansion joints will be partially offset by the reduction in length resulting from the displacement of the centre pipe system. The latter effect may be ignored only where the distance between hinge pins is very large and the lateral displacement is small. www.belman.com B022016-1 – Subject to alterations and eventual misprints
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EXPANSION JOINT SELECTION 69 Expansion joint selection HINGED C PG Equipment Source: Freely adapted from EJMA Three-hinged system In this case, the entire deflection is absorbed by the expansion joints and negligible pipe bending loads will be imposed upon the fix points. Where the distance between the fix point on the left and the first hinged expansion joint C is large, a pipe guide should be installed adjacent to the expansion joint, as shown. This pipe guide will minimise bending of DIA the pipe section between expansion joint C and the left hand fix point which might otherwise result from the movement required to rotate the expansion joint. One or more additional guides (Gn) may be used to maintain the plane of the piping system and relieve the hinges of bending forces which may be created by external loads. IA Support for the piping system may be accomplished in various ways, utilising available supporting structures with greatest efficiency. It is essential that spring supports be used to permit the free movement of the piping between the expansion joints. LFP Gn LFP Source: Freely adapted from EJMA Hinge system in non 90° bend The figure illustrates the principle that there are no 90° bends. Only fix hinged expansion joint systems may points and guides are then required. also be used in other cases where B022016-1 – Subject to alterations and eventual misprints www.belman.com
