5 replies to this topic

[ankur2061]

Karteek,

 

NORSOK standards are basically tailored for the needs of offshore platforms where space is a premium. Wherever space is a premium the idea is to reduce the footprint of any item whether equipment or piping. Obviously if you are reducing pipe sizes for a given flow due to space being a premium you will tend to have higher pipe velocities. NORSOK does not provide the derivation of the equations which you have mentioned in your post and I think that it is not necessary to go into the background of these equations if you know that these equations are being followed by companies who follow NORSOK standards.

 

Having said that, a lot of veteran engineers who have been involved in piping design and sizing feel comfortable with the values that they have been using since long in their careers and do not wish to deviate from their concept of limiting velocities for a given service for a pipe. Even operating company standards have no uniformity in the limiting or maximum allowable velocities advocated by them.  

 

On a personal note, I would never recommend a velocity of more than 120 ft/s (36 m/s) for any gas pipe. Too me, higher velocities than this put you in a zone of uncertainty and you are never quite sure of the reaction forces acting on the pipe which can lead to mechanical issues such as pipe support integrity and excessive vibrations. But again this is a personal choice of restricting the velocity to 120 ft/s based on personal experience and certainly not binding to those who have a different experience.

 

Maybe others who have a different opinion can share their views on the subject matter.

 

Regards,

Ankur.

[Ajay S. Satpute]

_{Dear Karteek,}

 

_{Please refer below link and the attached file.}

_{http://engedu.ca/wp-...lae-Rev.-11.pdf}

 

_Regards.

 

_Ajay

Attached Files

•  SPE_Paper_Erosional_Rates_Velocities1.pdf   276.02KB   159 downloads

[Shivshankar]

Karteek,

 

The basic source equation is ,

                  

                   

Where,

• is the shear stress at the wall (N/m2)
• is the Fanning friction factor of the pipe
• is the fluid velocity in the pipe (m/s)
• is the density of the fluid (kg/m3)

http://www.standard..../P-CR-001r1.pdf (older Version)

http://www.thermoped...om/content/789/

http://en.wikipedia....friction_factor

 

If you want more information, you can contact www.standard.no . I am not sure if they will answer you but you can try.

Edited by Shivshankar, 23 April 2013 - 02:15 AM.

[Padmakar Katre]

Hi,

Just one concern, evaluate possibility of liquid carryover if any as it will lead to erosional issues. There is an inverse relation of vapor velocity with operating pressure. It's not just the velocity but you need to be careful for DeltaP/unit length limit. Higher Delta P due to large equivivalent length will force you to cut down on velocity although estimated velocity is within the allowable norms.

 

Small addition to the best explainations given by other memebers. Hope it helps you.