Session: DA-01-05 Design and Analysis of Heat Exchangers and Components

Paper Number: 123508

123508 - Case Study: Lip Seal Heat Exchanger Retrofit 

A high steam pressure tube side heat exchanger with channel integral to a U-tube bundle was upgraded from low chrome to austenitic materials, while the shellside material remained ferritic.  Due to concerns with thermal differential expansion between the austenitic tube sheet and the ferritic shell side flange, an Omega-type lip seal design was incorporated, replacing the traditional flat lip seal design.

The finite element method was used in a transient fatigue analysis of the lip seal loop and internal fillet welds.  Historic plant operating data was used to define idealized plant startup, shutdown, and transient  temperatures, which were utilized in the model.  Due to conditions of low/no flow through one side of the exchanger during some upsets and the absence of shellside outlet temperatures, a heat balance was utilized to predict terminal temperatures while film coefficients were scaled based on flow data. 

The internal fillet welds connecting the lip seal halves to the flange and tubesheet pair were found to be limiting.  Due to the requirement to reuse the existing ferritic shells, incremental improvements were made to the design cycle life of the lip seal welds by incorporating groove welds in combination with the fillet welds.  Further the effects of initial bolt stress were considered to determine the optimum lip seal weld life.

Presenting Author: Louis Pasnik Becht

Presenting Author Biography: Mr. Pasnik has over 20 years of experience as a thermal and mechanical engineer with a specific emphasis on heat exchangers, furnaces, and combustion equipment. His experience includes thirteen years as a practical plant-based “boots-on-the-ground” heat transfer engineer for an Owner / Operator supporting multiple plants. He has experience in technically assuring heat transfer equipment configuration and design on large and small capital projects both as an EPC and as an Owner/Operator. Mr. Pasnik currently serves as the co-chair of API 660.

Authors:

Louis Pasnik Becht
Forrest Gu Becht
Trevor Seipp Becht