Session: DA-02-01 Design & Analysis of Piping and Components - 1

Paper Number: 105205

105205 - Cryogenic Aluminum to Stainless Steel Pipe Transition Joint Qualification 

Many cryogenic applications use aluminum pressure vessels which need to be connected to stainless steel piping. These connections can be made using aluminum and stainless steel flange pairs, but aluminum to stainless steel pipe transition joints provide a number of advantages. Transition joints not only provide a leak tight connection which can eliminate fugitive emissions, they can also be designed to accommodate the thermal contraction or expansion differences at the junction. Aluminum to stainless steel transition joints have been built using different technologies, including:

1.       Friction welding

2.       Explosion welding

3.       Nonwelded, diffusion-bonded (heat shrinkage/hot pressing assembly)

This paper focuses on explosion-welded transition joints, although some of the concepts discussed may also apply to other technologies. Explosion-welded aluminum to stainless steel transition joints for cryogenic applications typically require additional intermediate material. In these applications, a circular section is cut from a welded plate and machined to match the pipe sizes at the joint ends. Intermediate materials between the aluminum and stainless steel joint ends may be weaker in strength and limit the load carrying capacity of the joint. If needed, flange reinforcing can also be added to increase the axial load carrying capacity of the transition joint.

ASME Pressure Vessel and Piping codes do not provide specific design guidelines or qualification requirements for these joints. ASME Code Case 2493 was released to address many questions related to the explosion welding of dissimilar metal plates and provides qualification requirements, but these are limited to the qualification of the explosion-welded parent plate and not the final transition joint design. This paper shall highlight Air Products’ approach to addressing specific concerns regarding the qualification and production testing of explosion-welded plates for cryogenic applications.  It shall also cover aspects of the design, qualification, and rating of the cryogenic transition joints made from explosion-welded parent plates.

ASME B31.3 Section 304.7 Pressure Design of Other Components addresses the pressure design of unlisted components in 304.7.2. This section lists four acceptable methods for substantiating the pressure design of unlisted components:

(a)    Extensive, successful service experience

(b)    Experimental stress analysis

(c)     Proof test

(d)    Detailed stress analysis

This paper will concentrate on the methods in (c) proof test and (d) detailed stress analysis, i.e., Finite Element Analysis (FEA). A combination of these can be used to ensure a safe and effective design for both pressure and additional loads imposed on the joint.

Presenting Author: Ali Ok Air Products and Chemicals

Presenting Author Biography: Mr. Ok is Senior Principal Mechanical Design Engineer for LNG Technology and Products group. He is responsible for developing and leading the mechanical component design and implementation associated with the manufacturing of LNG Coil Wound Heat Exchangers. He has a B.S. in Mechanical Engineering from Istanbul Technical University and M.S in Aerospace Engineering and Engineering Mechanics from University of Texas at Austin. He has more than 15 years of industrial experience, the last 3 of which have been with the Air Products LNG Team. He also has wide-ranging industry experience in offshore platform evaluation, refinery fitness for service assessments, cryogenic helium vessel design, and LNG CWHE design. He is a licensed professional engineer in Texas.

Authors:

Ali Ok Air Products and Chemicals
John A. Dally Air Products and Chemicals
Stephen C. Tentarelli Air Products and Chemicals