ASME STP-PT-036 pdf free download

ASME STP-PT-036 pdf free download BOLTED FLANGED CONNECTIONS IN ELEVATED TEMPERATURE SERVICE
2.2 Mechanical Effects of Temperature on Joint Behavior In early research, there were several noteworthy papers on the subject of high temperature flange leakage or temperature driven bolt load variations, such as:
• Bickford, et. al. [22] which examines the leakage of a particular reboiler flange.
• Winter, et. al. [23] which details FEA results for transient temperature effects on several piping flange sizes.
• Nau, et. al. [24] which uses FEA to examine the effect of bolt temperature lag during temperature transients.
• Singh, et. al. [25] which presents an analytic methodology to assess the radial growth of the flanges and tubesheet in a heat exchanger joint.
• Dudley [26] which outlines an analytic approach to solving the stresses and deflections of flanges due to a temperature difference between the flange ring and vessel shell.
• Sawa, et. al. [27] uses a finite cylinder heat transfer theory to examine temperature distribution in small flanges. However, in general these papers only address certain aspects of the effects of temperature and none of them developed a comprehensive method for the assessment of the distribution of temperature in the flanged joint. The determination of the component temperatures must be considered the starting point for any method aimed at assessing the effects of temperature on flange joint operation. By building on the early work of Wesstrom [28], Brown [29], [30], [31], [32], [33], [34], [35] outlined an analytical method of determining both the temperature and associated bolt load during both steady state and transient conditions. This work was summarized in a Welding Research Council (WRC) Bulletin [36]. Using the approaches outlined in the WRC bulletin, the initial operating state of a raised-face type bolted flanged joint can be determined.
2.3 Code Status The only pressure vessel design code that specifically addresses creep in the context of the design of bolted joints, other than by adjustment of the material allowable stresses in the creep range, is EN1591-1 and EN13555. However, the creep considerations are only with respect to the gasket relaxation and therefore do not appear to address operation in the flange or bolt material creep range. In addition, the methods implemented in both of the codes do not effectively describe the effects of gasket creep/relaxation on the bolted joint behavior [1], [37]. Mention of the effects of bolt load relaxation and the need to account for the effect in design and selection of assembly bolt load is made in BS 4882:1990 [7]. BS 4882 lists some relaxation data and makes reference to other sources of relaxation data. The previous edition (1973) had graphs of relaxation data for common bolting materials, but these have been removed from the current edition.
2.4 Gasket Creep Behavior Thorn’s report [39] is an early paper on the relaxation properties of asbestos sheet gasket materials. Farnam [40], Smoley, et. al. [41] and Marchand, et. al. [42] examine the relaxation characteristics of sheet gasket materials, including the effects of elevated temperature. Bazergui [43] presents the short-term (initial) relaxation of various gaskets and determines a suitable creep expression for describing the relaxation of the gaskets. Marchand, et. al. [44], Bouzid, et. al. [45], [46], [47], [48] and Nagy [49], [50] address the relationship of gasket relaxation with respect to joint interaction.
Nau [51] wrote a general paper on the operational characteristics of gaskets, in which the various mechanisms of gasket load relaxation versus time are described and a design theory presented. Kockelmann, et. al. [52] presents relaxation data for flexible graphite and metal insert graphite gaskets, the effects of temperature on relaxation are also examined. Latte, et. al. [53] and Bouzid [54] present the relaxation and leakage properties in modified PTFE gasket materials. Vignaud, et. al. [55] addresses the relaxation characteristics of spiral wound gaskets, including a comparison between two gaskets made by different manufacturers. Nassar et. al. [56] and Alkelani et. al. [57] examine the effect of creep on SBR gaskets in a simple bolted joint and propose a visco-elastic creep model to describe the relaxation behavior.