7 replies to this topic

[shin29]

Dear All 

Greetings !!

 

I  am working on Hydraulics of a long Pipeline . I assumed the Diameter and calculate the pressure drop . I Have following doubts though which I  need kind explanation .

 

1. My total pressure drop through Pipeline is 78 (98 to 20 ) Bar . This pipelines has spur lines Taking -Off the natural Gas intermediately, in turn changing the hydraulics  . When i do calculations section-wise there are some sections where pressure-drop is less than 40% of the inlet pressure of that section . 

 

•   I refereed to Crane Tech paper -410 . And it states that For Pressure drop more than 40% , calculation should be made by Isothermal equations (Panhandle- in my case .
• In Crane there is a Height correction factor mentioned. some time when the pipeline is descending it give negative (-) Pressure drop that means increasing pressure , Is it practically possible in case of Natural gas (pressure around 45-50 barg) . 
• There is a Height correction factor in " Handbook of Natural Gas Transmission and Processing" by  Saeid Mukhatab which is not in agreement with The Height correction factor mention in Crane , Latter one seems to be more correct and reliable though.

I seek guidance whether I need to use in-compressible flow equation for the section where pressure drop is less than 40% than the inlet pressure  .

 

2. Is their some clear-cut criteria to use these equations , Pan-A, Pan -B , AGA and others . How do we judge and justify using one over other 

 

3. I am not getting any material regarding  Pipe Efficiency factor and its value .

 

Your kind help is appreciated 

Regards,

 

Sahil

[breizh]

Shin 29 ,

Probably good to read !

 

Breizh

[ankur2061]

Sahil,

 

1. No you cannot use incompressible flow for natural gas pipeline applications

 

2. a. AGA equation is a generalized equation for fully turbulent isothermal gas pipeline flow and derived from basic equations for mass and momentum flow for compressible fluids

b. The Weymouth equation for compressible gas flow gives results quite similar to AGA equation for fully turbulent isothermal gas flow

 

c. Panhandle A equation is recommended for use with large diameter pipelines (>=250 mm) and long distanbces. Pipeline efficiency factor of 0.92 is recommended with Panhandle A equation. Calaculated flow values are reasonable with Panhandle A if the Reynolds number is between 5 & 11 million

d. Panhandle B equation is recommended for use with large diameter pipelines (>=250 mm) and long distanbces. When using Panhandle B the pipeline efficiency factor recommended values are between 0.88-0.94. Panhandle B covers a wider range of Reynolds number between 4 to 40 million.

 

A prominent middle-east gas transmission and distribution company specifies usage of Panhandle B equation for sales gas pipeline hydraulic calculations.

 

A single-phase gas pipeline software based on all the above mentioneed equations can be found in the store section of "Cheresources" at the following link:

 

http://www.cheresour...-pipeline-flow/

 

Hope this information helps.

 

Regards,

Ankur.

Edited by ankur2061, 29 April 2014 - 01:30 AM.

[Ajay S. Satpute]

Sahil,

 

Can you share your calculations?

 

Regards.

 

Ajay S. Satpute

[breizh]

^{Hi ,}

^{Additional resources to support your work .}

 

^Breizh

[shin29]

Dear Ankur ,

 

Will You kindly elaborate Your  Point 1.  And also  the interpretation of Crane Tech Paper regarding use of Incompressible flow equation for Pressure drop less than 40% if inlet pressure. 

 

Could you help me regarding my point about pipeline efficiency factor. For a new pipeline with internal anti-friction coating how much value of Pipeline efficiency factor is recommended and on what basis

 

Regards,

Sahil

Edited by Art Montemayor, 04 May 2014 - 09:08 AM.

[ankur2061]

Sahil,

 

The Crane Paper 410M assertion of using incompressible flow method for pressure drop less than 40% of inlet pressure in my opinion should be used for short distance piping and not for long distance pipelines. 

 

Pipeline efficiency factors as recommended in the "Pipeline Rules of Thumb Handbook" are as follows:

 

1. E = 1 for new pipe with no bends, fittings, or pipe diameter changes

2. E = 0.95 for very good operating conditions, typically through first 12-28 months

3. E = 0.92 for average operating conditions

4. E =0.85 for unfavorable operating conditions

 

Hope this helps.

 

Regards,

Ankur

Edited by ankur2061, 03 May 2014 - 09:32 AM.

[shin29]

Thanks Everybody