They are the support, anchor and guide.
Many piping systems have anchors and guides, especially in the risers, to permit expansion joints, bends or pipe loops to function properly. The MPDA Series and RPG Anchors and Guides are designed to eliminate or guide pipe movement and must be rigidly attached to the structure. While this is inconsistent with the.
Pipe Anchors And Guides Full Pressure Thrust
When an Expansion Joint is pressurized, internal thrust forces are created which react on the system and anchors. This force is due to internal pressure acting on the effective area of the bellows element in the expansion joint.This force created by pressure must be absorbed in the piping system by anchors to prevent the bellows element from extending. Anchors in a piping system are generally of two kinds, main anchors to absorb full pressure thrust forces generated by the expansion joint, and intermediate anchors to absorb forces generated by the expansion joint bellows spring forces.Examples of main anchors and intermediate anchors are shown in the above diagram. It should be noted that pipe guides are intended to guide the pipes in a system and not support the weight of the pipes and media conveyed through them.
For copper pipework, they should be manufactured from non-ferrous material. For steel pipework, the rollers should be manufactured from ferrous material. When the pipework is fully installed and anchored at both ends, the spacer is removed and the joint pulled up tight (see Figure 10.4.3).The remaining part of the expansion, if not accepted by the natural flexibility of the pipework will call for the use of an expansion fitting.In practice, pipework expansion and support can be classified into three areas as shown in Figure 10.4.4.The fixed or ‘anchor’ points ‘A’ provide a datum position from which expansion takes place.The sliding support points ‘B’ allow free movement for expansion of the pipework, while keeping the pipeline in alignment.The expansion device at point ‘C’ is to accommodate the expansion and contraction of the pipe.Roller supports (Figure 10.4.5 and 10.4.6) are ideal methods for supporting pipes, at the same time allowing them to move in two directions. The effect is that instead of being stressed from 0 F to +1 F units of force, the piping is stressed from -½ F to + ½ F units of force.In practical terms, the pipework is assembled cold with a spacer piece, of length equal to half the expansion, between two flanges. At working temperature and having fully expanded, the piping is stressed in the opposite direction. The pipes are left short by half of this amount, and stretched cold by pulling up bolts at a flanged joint, so that at ambient temperature, the system is stressed in one direction.When warmed through half of the total temperature rise, the piping is unstressed.
They are commonly called expansion bellows, due to the bellows construction of the expansion sleeve.Other expansion fittings can be made from the pipework itself. These fittings are placed within a line, and are designed to accommodate the expansion, without the total length of the line changing. This will cause extra stress to be added to the top pipe whose thickness has been sized to take only the stress of its working pressure.All pipe supports should be specifically designed to suit the outside diameter of the pipe concerned.The expansion fitting (‘C’ Figure 10.4.4) is one method of accommodating expansion.
An indication of the expansion of pipe that can be accommodated by these assemblies is shown in Figure 10.4.10.It can be seen from Figure 10.4.9 that the depth of the loop should be twice the width, and the width is determined from Figure 10.4.10, knowing the total amount of expansion expected from the pipes either side of the loop.These are sometimes used because they take up little room, but it is essential that the pipeline is rigidly anchored and guided in strict accordance with the manufacturers’ instructions otherwise steam pressure acting on the cross sectional area of the sleeve part of the joint tends to blow the joint apart in opposition to the forces produced by the expanding pipework (see Figure 10.4.11). This is due to the design but causes no misalignment of the flanges.If any of these arrangements are fitted with the loop vertically above the pipe then a drain point must be provided on the upstream side as depicted in Figure 10.4.8.The expansion loop can be fabricated from lengths of straight pipes and elbows welded at the joints (Figure 10.4.9). Pressure does not tend to blow the ends of the loop apart, but there is a very slight straightening out effect. It is best fitted horizontally so that the loop and the main are on the same plane. However large steam users such as power stations or establishments with large outside distribution systems still tend to use full loop type expansion devices, as space is usually available and the cost is relatively low.When space is available this type is sometimes used. When full loops are to be fitted in a confined space, care must be taken to specify that wrong-handed loops are not supplied.The full loop does not produce a force in opposition to the expanding pipework as in some other types, but with steam pressure inside the loop, there is a slight tendency to unwind, which puts an additional stress on the flanges.This design is used rarely today due to the space taken up by the pipework, and proprietary expansion bellows are now more readily available.
However, in the event of anchor failure, they behave as tie rods and contain the pressure thrust forces, preventing damage to the unit whilst reducing the possibility of further damage to piping, equipment and personnel (Figure 10.4.13 (b)).Where larger forces are expected, some form of additional mechanical reinforcement should be built into the device, such as hinged stay bars (Figure 10.4.13 (c)).There is invariably more than one way to accommodate the relative movement between two laterally displaced pipes depending upon the relative positions of bellows anchors and guides. These may have little function under normal operating conditions, as most simple bellows assemblies are able to withstand small lateral and angular movement. But it does have the same disadvantages as the sliding joint in that pressure inside tends to extend the fitting, consequently, anchors and guides must be able to withstand this force.Bellows may incorporate limit rods, which limit over-compression and over-extension of the element.
Where two or more pipes are supported on a common bracket, the spacing between the supports should be that for the smallest pipe. Pipe supports should be provided at intervals not greater than shown in Table 10.4.3, and run along those parts of buildings and structures where appropriate supports may be mounted. Steel or copper) and whether the pipe is horizontal or vertical.Some practical points worthy of consideration are as follows: Angular and lateral movement should be avoided wherever possible.Figure 10.4.13 (a), (b), and (c) give a rough indication of the effects of these movements, but, under all circumstances, it is highly recommended that expert advice is sought from the bellows’ manufacturer regarding any installation of expansion bellows.The frequency of pipe supports will vary according to the bore of the pipe the actual pipe material (i.e.
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