8 replies to this topic

[go-fish]

Hi

Please can anyone advise on some good references with a number of examples on evaluating overpressure scenarios and approach to calculate the corresponding relieving rate.

Thanks

[Art Montemayor]

Go-fish:

Through the years, I’ve gone through many scenarios. Some of them are listed in the attached document that I’ve extracted from one of my Excel workbooks.

As you can see, some of the more difficult-to-identify scenarios are based solely on personal, field experience and, as a result, it can’t be expected for a student to know or understand these. All pressure relief applications should be considered as unique and a generalized list of scenarios should not be the only criteria applied to a specific application. The same logic applies to the appropriate relieving rate to be applied.

The listing I supply as an example should be considered as just a starting point and not as a finalized and complete listing.

As a student, it is my opinion that you are best prepared to approach this type of problem by simply making sure that you have studied and understood the entire process that you are dealing with and subsequently sit down and start writing down possible scenarios based on what you know about the process, how it is operated, and what sources of energy are around your application that could affect it with a pressure increase / decrease. Note that I categorize “pressure” as a mechanical engineer would: internal pressure and external pressure.

Attached Files

•  Typical Pressure Relief Scenarios.doc   32KB   162 downloads

[go-fish]

Thanks Art

Actually I am not a student but have less experience in relief system design. I posted my query in this forum because I would consider myself as a student in this area. I understand basic scenarios like pool fire and blocked outlet but have difficulty in understanding case 4 and case 12. Also, when to consider simultaneous occurance of scenarios which would otherwise be considered as double jeopardy. Also, do we consider failure of emergency isolation valves (Safety instrumented system) as an overpressure scenario. eg. if sphere is filled with liquid propane (no pumping out at same time as filling) and an external fire occurs. Do I need to consider combined vapour relieving rates both from vaporization and incoming liquid flow rate or can I consider that the emergency valves in the inlet will isolate the sphere on detection of fire and the only relief will be due to fire case.

Please can you also provide some reference (books, literature etc) which go step by step with illustrative examples, something like the Crane Fluid Flow handbook.

Edited by go-fish, 29 March 2012 - 02:07 PM.

[breizh]

These papers may help you .

Breizh

[Shivshankar]

Gofish,

Also this papers will help you out,

1) Rigorously Size Relief Valves for supercritical fluids by Ryan Ouderkirk.
2) Easily Size Relief Devices and piping for two phase flow by Joseph. C .Leung
3) Properly size Pressure Relief Valves for two pahse flow by Ron Darby, Freeman E. Self, Victor
H. Edwards.
4) Using Ideal gas specific heat ratio for Relief Valve Sizing by Aubry shackelford.

Regards
Shivshankar

[sheiko]

Go-fish,
Click on the link below to see some references:
http://www.linkedin....6141&_mSplash=1

Edited by sheiko, 30 March 2012 - 05:38 PM.

[go-fish]

Thanks all, as always this forum has been very useful.

I think I should first read the following:

- Wong, W., "Protect Plants Against Overpressure",CHE, June 2001
- Shackelford, A., "Using the ideal gas specific heat ratio for relief-valve sizing", CHE, November 2003.
- Rahimi Mofrad, S., "Relief rate calculation for control valve failure", HP, January 2008
- Rahimi Mofrad, S., "What you should know about liquid thermal expansion", HP, November 2008
- Rahimi Mofrad, S., "Rethink your overpressure systems", HP, Avril 2009
- Rahimi Mofrad, S., "Designing the correct pressure-relieving system", HP, November 2010
- Kim, R. and al., “Proper relief-valve sizing requires equation mastery,” HP, January 2011
* Wong, W., "Size Relief Valves More Accurately", CHE, June 1992
* Wong, W., "Control the DP on the PRV Inlet Line", CHE,September 2001
* Darby, R., "Size Safety-Relief Valves for Any Conditions", CHE, September 2005

I understand most of these articles are from CHE and HP. I do not have subscriptions to these magazines. Is there a way I can access these articles?

[kkala]

Since these are a lot of articles, a practical way to get them is to visit a technical library and order photocopies of the pages. Cost is expected to be quite low, if the library has the relevant magazines containing the articles. The latter is quite probable, seeing that the articles needed are not very old.

If the library does not have the article, it can get it from another library at some cost.

Note 1: Recommended practices (e.g. API) and some standards are not permitted to be copied, so these have to be studied in the library. It does not concern our case, though.

Note 2: Rear articles of the past can be ordered in big libraries. I remember my order of an article of 1930s about cement kilns to the Library of British Museum (1972). Such big libraries seem to have almost all available articles, but the cost to get any of them was rather high.

[sheiko]

The articles from Rahimi Mofrad can be downloaded for free on his website: www.chemwork.com

Edited by sheiko, 31 March 2012 - 07:21 AM.