High temperature steam lines in power plant piping systems are often supported by the use of pipe support stanchions welded to the steam pipe. The end of the pipe stanchion has a steel plate welded to it, which typically slides on rack steel. For vertical and guide supports, there could be considerable thermal movement in the lateral unrestrained directions, and could result in significant frictional loads. The associated frictional loads are given due consideration in piping local stress evaluations as well as in the design of pipe support structures. For some situations, it often becomes necessary to utilize a teflon-fluorogold type surface at the stanchion end plate in order to reduce the coefficient of friction and hence the frictional loads. The effectiveness of the teflon-fluorogold surface is dependent on the prevailing temperature at that surface. In situations where the stanchions on very high temperature steam lines arc relatively short, the temperature at the teflon surface of the stanchion plate could be high due to heat transfer from the steam line into the stanchion. This high temperature at the bottom surface of the stanchion plate may interfere with sliding and may eventually lead to unanticipated problems such as sticking, increase in the coefficient of friction, or unpredictable frictional behavior. In this paper, finite element analysis approach is utilized to perform heat transfer analysis and to obtain steady state temperature distribution due to decay or attenuation from the steam line surface along the stanchion. The temperature prevailing at the bottom plate surface of the stanchion is also evaluated and guidelines are provided for practical application of the results.

Piping systems are normally used to transport air, gases, steam, water, and other fluids. Piping systems in power plants, petro-chemical, and other industrial facilities that carry non-hazardous fluids like air, water, etc. with no significant pressures at moderate temperatures can be considered as non-critical. Codes such as ASME B31.1 provide suggested dead weight spans for the placement of supports. In this paper, relaxed hanger spans are computed for non-safety related piping systems taking in to consideration the maximum bending stress, maximum deflection or pipe sag, and bearing stresses due to dead weight for pipe sizes ranging from 1” to 42” diameter. For situations in which large diameter pipes are directly sitting on steel with a line contact, bearing stresses are computed using finite element analysis as well as simple formulas. A comparison of relaxed hanger spans with B31.1 suggested spans is presented. Significant benefits in lowering the cost due to reduced number of dead weight supports, and the associated savings due to reduction in materials, fabrication, and installation can be derived by using the relaxed spans. These relaxed hanger spans were utilized over the past nine years on a variety of non-safety related piping systems. Experience with more than a dozen power projects of Pulverized coal (PC), Cogen, Simple cycle, and Combined cycle types indicates that the piping systems, which used relaxed hanger spans, are operating normally and satisfactorily without any problems.