7 replies to this topic

[sanchit_11]

Dear All,

 

I have recently noted that maximum velocity criteria for sizing of gas line is quite different as per NORSOK and API 14 E standards.

 

As per API 14 E maximum velocity in gas line shall not exceed 60 ft/s in order to avoid noise. However as per NORSOK P-001 the maximum velocity in gas line shall not be more than 60 m/s.

 

Further API has also mentioned that 60 ft/s should not be interpreted as absolute criteria and higher velocities are acceptable when pipe routing, valve choice, and placement are done to minimize noise level.

 

my querries are as follows:

 

1. Which standard API or NORSOK shall be considered for sizing gas lines.

 

2. Why API & NORSOK are following different standards.

 

3. If I want to go for velocities higher then 60 ft/s as per API 14 E, then how to calculate noise level at particular velocity.

 

regards

 

Sanchit

[Shivshankar]

Sanchit,

 

Similar thread was discussed below.

 

http://www.cheresour...g-calculations/

[sanchit_11]

Dear Shivshankar,

Thanks for providing me link to such a nice discussion.

 

But please accept apologies from my side for not framing my question properly

.

Actually I was looking for gas velocities criteria for topside piping and not for long distance sales pipe lines.

 

regards

sanchit

[Shivshankar]

Sanchit,

 

Use search Tab above and you will find more information discussed.Also you can download free excel sheet made by Ajay for line sizing criterion.

 

http://www.cheresour...rent-standards/

 

Hope this helps.

Edited by Shivshankar, 12 November 2013 - 02:53 AM.

[Art Montemayor]

Sanchit:

 

First – and foremost: do not design your pipes in accordance with Norsok’s figures that are defined as “Maximum Gas Velocities”.  Bear in mind carefully that this has no mention of the recommended DESIGN velocity.  It simply states that the velocity shall not exceed the given value.  The design velocity to be incorporated in designing the size of the pipe is totally another value.  The values that Norsok gives as maximum are notoriously too high – especially with regards to liquid flow.

 

I have always used Norsok standards in conservative design.  However, I have a serious issue with regards to the way they have written the fluid velocity standards.  A lot of engineers have interpreted them as stating that operating with a liquid containing sand and flowing at 5 m/s (15 ft/sec) is OK.  Of course IT IS NOT OK.  In my design, the velocity will NEVER get to 5 m/s.  That is why I have always stuck with API design velocity recommendations and not Norsok’s – especially in offshore installations.

[sanchit_11]

I have an existing 20" 160 schedule topside piping system (Single Phase Gas) which was designed for handling around 6.3 MMSCMD gas at high operating pressure range of 30-108 kg/cm2g and temperature of 43 deg C in accordance with API 14 E guideline with velocity consideration of 60 ft/s.

 

At present operating pressure of the system is 30 kg/cm2g and velocity in topside piping is near to 60ft/s.

 

Now client want to operate the system at 12 kg/cm2g without doing any changes in piping for handling 4 MMSCMD of gas

 

My queries are

 

* Will i be able to operate the system at new reduced pressure of 12 kg/cm2g, as velocity at this condition is around 96 ft/s ?

* What will be noise level and how to calculate that in decibels for existing piping system at new pressures of 12 kg/cm2g ?

* Further client also want some design standard to certify the same.

 

regards

Sanchit

[Erwin APRIANDI]

Hi Sanchit,

 

With the situation that you have mentioned above, I think you better calculate what is the real velocity limits that can create noise problem (the noise limit will be govern the type of operation, whether it is emergency or continous, emergency case may allow noise level up to 110DB, while continous case will only allow up to 85DB may be different for each project).

 

Since you also have to realize that either in API RP 14E or Norsok P-001 said that the velocity limit mentioned is not ultimate criteria. And in Norsok P-001, 60 m/s is the maximum but if the velocity to get the noise limit criteria is even less we have to use whichever is lower.

Edited by Erwin A. CEng MIChemE, 29 November 2013 - 01:50 AM.

[ankur2061]

Sanchit,

 

Refer the links below for noise value calculations.

 

http://www.peutz.de/pdf/Pipe_noise.pdf

 

http://www.iceweb.co...trol Manual.pdf

 

Hope this helps.

 

Regards,

Ankur