Pipe restraint loads

Pipe Supports Loads transmitted by piping to attached equipment and supporting elements include weight, temperature- and pressure-induced effects, vibration, wind, earthquake, shock, and thermal expansion and contraction. The design of supports and restraints is based on concurrently acting loads (if it is assumed that wind and earthquake do not act simultaneously). 

Integral pipe attachments are welded directly to the pipe and are usually of special design. They are used in high temperature services, with moderate or severe loads, and in conjunction with supports, braces, and restraints where rigidity with the pipe shell is desired. Integral attachments may be grouped into five types ears, lugs, shoes, cylindrical tmnnions, and skirts (see Fig. 8). 

Thermal-expansion and -contraction loads occur when a piping system is prevented from free thermal expansion or contraction as a result of anchors and restraints or undergoes large, rapid temperature changes or unequal temperature distribution because of an injection of cold liquid striking the wall of a pipe cariying hot gas. 

Thermal Loads Due to Restraints. These loads consist of thrusts and moments, which arise when free thermal expansion and contraction of the piping are prevented by restraints or anchors. 

The load from piping and pipe-supporting elements (including restraints and braces) shall be suitably transmitted to a pressure vessel, building, platform, support structure, foundation, or to other piping capable of bearing the load without deleterious effects. 

The local stresses as outlined herein do not apply to local stresses due to any condition of internal restraint such as thermal or discontinuity stresses. Local stresses as defined by this section are due to external mechanical loads. The mechanical loading may be the external loads caused by the thermal growth of the attached piping, but this is not a thermal stress For an outline of external loeal loads, see Categories of Loadings in Chapter 1. 

The pressurizer is supported by a cylindrical skirt welded to the pressurizer and bolted to the support structure. The skirt is designed to withstand deadweight and normal operating loads as well as the loads due to earthquakes, safety valve actuation, and Branch Line Pipe Breaks. Four keys welded to the upper shell provide additional restraint for earthquake, safety valve actuation, and Branch Line Pipe Break conditions. 

Snubbers are utilized primarily as seismic and pipe whip restraints at operating plants. Their safety function is to operate as rigid supports for restraining the motion of systems or components under dynamic load conditions such as earthquakes and severe hydraulic transients, e.g., pipe breaks. 

Equipment loads include dead weight, restrained thermal expansion and dynamic effect such as pressure transients, changes in momentum, water and steam hammer in the equipment and earthquake. They also may include the effect of the restraint of attached piping. The effect of such phenomena must be considered in the design check. 

Restraints for steam and other systems piping will be located by the Bellefonte Project Mechanical Design Sections and the Civil Engineering Branch will evaluate the design criteria for determining loads. 

Occasional loads are those loads that act on the system on an intermittent basis. Examples of occasional loads are those placed on the systan from the hydrostatic leak test, seismic loads, and other dynamic loads. Dynamic loads are those from forces acting on the system, such as forces caused by water hammer, and the energy released by a pressure relief device. Another type of occasional load is caused by the expansion of the piping system material. An example of an expansion load is the thermal expansion of pipe against a restraint due to a change in temperature. 

Loads on Supported Pipelines. Supports must be spaced frequent enough to prevent the pipeline from any sag caused by the weight of the pipe and contents. The proper spacing of supports also allow for control or restraint of thermal expansion. 

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