Session: CS-11-01 Recent Developments in European Codes and Standards

Paper Number: 152312

152312 - Design of Jacketed Pressure Vessels : Introduction to an Innovative Methodology Based on Formulae for Cylindrical Jackets 

Abstract: 

Pressure vessels can sometimes be required to perform thermal transfers. Heat exchangers are well documented, and design methodologies are quite common in Standards and Codes, all over the world. Another possibility to achieve this goal, and eventually to add requirements (mixing, …) is the use of jacketed vessels.

Such geometries are characterized as follows:

- It consists in a main vessel, located inside the whole equipment

- It has an annular space, generating a jacket, located on the external part of the whole equipment

- In the jacket, a coolant fluid (water, oil, …) is circulating, in order to bring or to evacuate heat

Most of the time, pressure in the jacket remains quite low, and is rarely greater than 4 Bar. This load acts as an external pressure for the main vessel and, therefore, its shell is usually thickened. It can also be reinforced by a guide coil, in charge of improving the fluid flow. If the main shapes are quite common (cylindrical shells, formed heads, …), the main originally in the geometry lies in the junction between the main vessel and its jacket.

Two main connections exist: conical type and ring type. A bibliographic review is the main international pressure vessels codes led to the conclusion that there is a very little quantity of rules to design such geometries by formulae (DBF). Therefore, finite element calculations and Design-By-Analysis (DBA) methodologies are usually required to justify the mechanical strength of a jacketed pressure vessel. However, this kind of calculations will sharply cumulate several difficulties:

- As jacketed vessels are usually appropriate to deal with heat transfers, thermal calculations (transient or steady state) may be required in order to evaluate thermal stresses due to temperature differentials (top to bottom, through wall, …)

- As the pressure in the jacket is likely to be greater than the pressure in the main vessel, its cylindrical shell and its head is subjected to an external pressure, which is likely to cause buckling. Calculation related to this failure mode should therefore be performed. Conservative assumptions may be considered but, for cases with a reduced margin, the stiffening ability of the junction and eventual guide coils would be necessary to satisfy design criteria. Such a calculation may be performed by DBA, but require a higher knowledge, and more advanced calculation tools.

- On jacketed vessels, pressure and/or thermal loads are likely to vary significantly and frequently, leading to a risk of fatigue failure. Therefore, a fatigue analysis should be performed. DBA may be employed in order to evaluate stress variations at the critical zones.

Consequently, a rigorous and accurate evaluation of the mechanical strength of a jacketed pressure vessel may be quite expensive, and existing calculation notes are often perfectible. The French Code for pressure vessels, CODAP, decided to lead studies, in order to provide new chapters dedicated to the issue of jacketed pressure vessels, and their Design-By-Formulae.

This long-term project intends to deal with four geometries:

- Vessels with U-shaped jackets (pressure vessel with jacket enclosing the lower dished end)

- Vessels with cylindrical jacket (pressure vessel with jacket at the cylindrical shell only)

- Vessels with studded jacket (pressure vessels with jacket studded by dimples or anchor pipes)

- Vessels with channels (pressure vessels jacketed with channels as coil or grating)

Paper PVP 2024 123386 was an introduction to the chapter C12.2, related to U-shaped jacketed vessels. This paper describes the rules recently published in the chapter C12.3, dealing with cylindrical jacketed vessels. It provides its technical bases, its scope (in terms of geometry, material parameters, loads considered, failure modes covered, ...), and the design criteria. It finally details the developments and evolution to come in the next versions of CODAP.

Presenting Author: Philippe Rohart Cetim

Presenting Author Biography: Mechanical Engineer with a PhD (Ecole des Mines de Douai, 2014) in the design of pressure vessels
4-year experience in the French Welding Institute, including a mission within the context of the notified body ASAP.
9-year experience in the French technical center in mechanics Cetim
Convenor of the Working Group WG59 (Creep) in the Technical Committee TC54 (Unfired Pressure Vessels, in charge of development and maintenance of EN 13445)

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