Slug flow

We have a shell and tube heat exchanger to cool compressed gas at 135 barg. At tube rupture the exchanger is protected by four 10"NB bursting discs. On bursting, the scenario is that the inventory of the cooling medium (density 1038 kg/m^3), within the exchanger (approx. 2800 kg), will be forced through the bursting discs at max. gas velocity (93 m/sec), i.e. slug flow. The downstream pipework is sch 40 (9.27 mm thick) therefore the resulting loads you will appreciate will be enormous (approx. 70 tonne) and I believe unrealistic.
We would usually analyse using a time history analysis and consider loading on each bend up to the flare knock out drum.
Has anybody had similar problems? and, more to the point, any suggestions as to how to resolve the problem?

The problem of slug flow is more of stocastic in nature than deterministic. Conventional Pipe stress programms in my opinion, cannot simulate this problem ( a typical force Spectrum analysis is not possible as the time history of loading is typically unknown for a slug loading ). BOS Fluid available in FE pipe ( A Paulin research Group product ) gives you estimation of slug load . However your problem may require CFD analysis as well as some specialized software handling flow induced vibration problems.

Regards

A. Bhattacharya

Stress analyst

Bechtel Corporation

Slug flows as well as all relief flows which are multi pahase in nature are very complex events. I suggest you enlist the help of a competent chemical engineer who is familiar with the DIERS publications and methodologies.

DIERS associated loosely with the AICHE has pulled together formidable information on this subject see http://www.aiche.org/diers/

Remember if you are engaged in piping flexibility analysis you are not necessarily an expert or competent in the field of science that generates the time force data.

I agree with John, also read the these chapter's

The below will give all Piping Engineer's the detail:

and the software

"Pressure surge in pipe and duct systems" by J A Swaffield and A P Boldy

• Chapter 1 - Pressure transient mechanisms and historical development

• Chapter 5 - Pressure transient network boundary conditions

• Chapter 6 - Surge control and suppression
• Notation
• References

Waterhammer home page

http://www-interact.eng.cam.ac.uk/wh

Dr Ruth Thomas
CEE, Heriot Watt University
Riccarton, Edinburgh, EH14 4AS
Email: rct@eng.cam.ac.uk
Tel: (0131) 449 5111
Fax: (0131) 451 3327

For Shell and Tube Heat Exchanger Vibration Analysis

Kevin J. Farrell, Frederick L. Hendrix
http://www.htri-net.com/Upcoming/TrainingWeekTX2003/Course_Descriptions.htm#Vibration%20Analysis

Learn about vibration mechanisms in shell-and-tube heat exchangers, Xist methods to analyze vibration severity, and corrective measures to mitigate damage. This course is a must for anyone who evaluates the vibration potential of shell-and-tube heat exchangers.

Introduction to vibration phenomena

Flow-induced vibration in heat exchangers

Design options to mitigate vibration

Field fixes

Xist Vibration Report

Example application and case study