Acoustic Induced Vibration - LOF 0.5 to 1.0

Dear Experts,
As per Energy Institute guideline, for AIV, module T2.7.1, "It is at the discontinuities with an LOF equal to one where corrective actions are required ".

However, Table 3.1 says to follow T-09 in-case of LOF is in-between 0.5 to 1. But as per my understanding, this table is generic one and specific corrective action (for LOF 0.5 to 1)is required if vibrations are due to transient mechanisms i.e. flow, pulsation etc.. (Refer Note-1 of table 3.1).

My query is, "SHOULD WE PERFORM ANY CORRECTIVE ACTION in AIV analysis, if LOF is in-between 0.5 to 1."?

Hi Ankit,

The difference between the LOF>=1 and LOF>=0.5 is the word "should" and "shall".

For LOF>=1:

The main line shall be redesigned , resupported or
a detailed analysis of the main line shall be
conducted , and vibration monitoring of the main
line shall be undertaken (Note 1)

Corrective actions shall be examined and applied
as necessary

Small bore connections on the main line shall be
assessed .

A visual survey shall be undertaken to check for
poor construction and/or geometry and/or support
for the main line and/or potential vibration
transmission to neighbouring pipework.

For LOF>=0.5:

The main line should be redesigned , resupported
or a detailed analysis of the main line should be
conducted , or vibration monitoring of the main line
should be undertaken (Note 1)

Corrective actions should be examined and
applied as necessary

Small bore connections on the main line shall be
assessed.

A visual survey shall be undertaken to check for
poor construction and/or geometry and/or support
for the main line and/or potential vibration
transmission to neighbouring pipework.


I'm not sure how to deal with this also, but in my previous experience our company interpreted as "shall" is mandatory and "should" is not mandatory. It's like they interpreted it more on commercial terms. The company "shall" implement the required actions if LOF=>1 but the client if he wish to implement the LOF=>0.5 and <1 it will be at his own expense.

Not sure also if this is the proper way to do it. I think it's better you direct the question to the committee who developed this standard (something like the ASME B31.3 interpretation) so you will have an official answer.

But if you want a robust design and the design change is not so costly and will not impact any project schedule then better use LOF>=0.5 and <1 criteria for your design (such as using full encirclement repad locally at the point where LOF>=0.5). But if it has a major impact to the cost and schedule align with your project management team the way forward.

Please correct me fellows if I have made a wrong statement. I know this is a sensitive issue but I want to know also how others deal with this in their company practice.

Many thanks in advance for your opinion.

Cheers!!!

You can download also this article in google.

"Acoustically induced vibration: a review of industry best practice"

The conclusion part of the article is related to this topic.

Cheers!!!

The equations are statistically driven. If you have an LOF > 1, you are statistically significant to have a failure due to fatigue. If you have an LOF between 0.5 and 1.0, the rate of failure is more ambiguous, but less so as it approaches 1.0.

Each end user will have a risk vs installation cost they wish to maintain, and requires an earnest discussion with project management what they seek to see.

Dear Borzki,
Thanks for your detailed explanation..
I will further look into article mentioned...

Thanks...

You're welcome. As Michael pointed out, the evaluation using EIG is more related to risk assessment. Maybe insurance related?....Just guessing.

Any other opinion is greatly appreciated.

Cheers!!