Dear Sirs,

I am doing the power plant piping stress analysis from past three years and using CII. Recently i have changed from my field from Power plant piping to Oil & gas. In oil & gas i need to analyse two phase flow piping system. I am new for two phase flow piping stress analysis.

When u do the two phase flow piping system stress analysis which things i need to take care and how to perform. Pl clarify?

Regards,

B.Lingarajan

You need to pay attention to trasnsient effects, particularly the potential frequency and severity of slugging. Calculating this is an art, and you will liekly have to refer the problem to a consultant who has a copy of Pipesim or Olga. Also, you need to understand the differing requirements of B31.3/B31.4/B31.8 and ISO13623, and be aware of which Code applies to each system.

Some pipelines (for instance transfer lines from gathering stations to a processing plant) fall under multiple Code jurisdictions, with the result that an analysis may need to be run twice; once under each Code, and the results for the applicable portions (only) filed in the final report.

You may also need to consider a design case that takes into account release of a lot of vapor, with the effects of isentropic expansion cooling considered in the design temperature. Many times, this requires the use of a Charpy impact tested material for your piping. Occasionally, this will require further precautions, as for instance with high pressure wellhead piping.

Consider the frequency of pigging expected in the piping; this can have an enormous impact on the corrosion life of the system. It's best to use a corrosion engineer familiar with the issues of oil & gas projects.

Consider the flow velocities expected within the system. High velocities can help to accelerate corrosion. Low velocities can create terrible slugging problems. Once again, your two-phase flow consultant will need to provide you with data.

General routing considerations:

Consider doing phase separation of the two-phase flow stream as early as possible to minimize the amount of two-phase piping. Even a partial separation will help enormously.

It is always best if two-phase flow systems slope downward toward the final destination. Even a slight incline can cause major slug formation problems.

If this is not possible, consider creating an artificial high point close to the final destination and installing a slug catcher there, so that transient forces are minimized once you get to the equipment at the final destination. This is a capital expense that will pay for itself many times over during the operating lifetime of the facility due to reduced maintenance.

sir,

thanks for the reply.
When we do the two phase flow piping stress analysis in C II what things we have ti take care? How to perform in CII?

I think every thing is the same as far CAESAR interface is concerned. The user have to ensure that correct value of the mixture density is entered in the Fuide Density Field.

CAESAR II is a "flexibility analysis program". Part of the input is the pressure and density of the fluid in the pipe, which is assumed constant for any given element for any given load case. CAESAR II is not a hydraulics program.

Check out programs like "BOSS Fluids" (Paulin Research Group) and "PipeNet" (Sunrise Systems).

Mr. Richard,

Yes, CII is not a hydralics program. Out question is about pipe stress for two flow system? How to perform two phase flow pipe stess analysis with CII?

b.lingarajan... it is apparent you do not comprehend what the program is about I suggest you do a lot of self study before going any furthrt.... and self study means just that.

Read the online manuals and the free newsletters on this web site... as well as the codes and other references...

CAESAR II doesn't know about flow - single or two phase. The required input is a (fluid) pressure and a density - CAESAR II doesn't care where you get those values.