Influence of Shape of Pressure Vessel Shell on Bolt Working Load and Tightness

Abstract

The area of flange joints with gasket includes many types of pressure vessels, which are mainly defined by the purpose of use and specific load conditions. These differences in definitions caused the existence of many types of pressure vessels with different shell shapes. Calculations of basic shapes are defined by standards. However, in some fields of engineering practice, these shapes are atypical. The article discusses the issue of circular sealed flange joints with a nonstandard shape of the pressure chamber shells. The aim of this article is to describe influence of shape of pressure vessel shell on bolt working load and the final tightness of the sealed joint using FEM.

Influence of Symmetry of Tightened Parts on the Force in a Bolted Joint

“…In the area of the circular joints of pressure vessels, it turned out that the asymmetry of the connected envelope also has a significant influence on the magnitude of the operating force in the bolt. A detailed description of this issue is given in [6].…”

“…The size of the force increase in the bolt ∆F S (see Figure 3) from the operational force is not dependent only on the stiffnesses C S and C F . Previous research in the field of flanges (especially circular) joints has shown that the behavior of the load force in the bolt is also influenced by the position of the point of the operational force, see [7] (p. 161) and [6]. This location may be subject to change during operation, especially in the case of joints where significant deformations occur due to the operating load (e.g., the flange joints of thin-walled vessels).…”

“…Attention was also given to new methods of calculations as reported by Y. Tian [5]. Previous research on the effect of the asymmetry of a multi-bolted connection on the asymmetry of the connected pressure vessel shell has also provided an important basis for solving the problem, see [6]. A key source of information is the book by F. Pospisil [7], which is still one of the most detailed summaries of knowledge about bolted connections based on experiments and practical experience.…”

Unsymmetrically Distributed Bolt Axial Forces between Symmetrically Spaced Bolts of Clamping Sleeve

“…In none of the articles mentioned above are the uniformity of axial forces and therefore also the uniformity of stresses and pressures of the clamping sleeve addressed. Very often, the tightening procedure for flanged sealing surfaces is solved [10,11], where, of course, the uniformity of the axial force in the bolts has an influence on the uniformity of the pressure acting on the seal, which is needed for the correct functioning of the seal. It is at this point that the similarity between this flanged sealant joints and a clamping joint becomes apparent, where the pressure acting on the tapered surfaces and cylindrical surfaces to transfer the load is essential to the correct function of the joint.…”