×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Pipe vibration assessment (VDI 3842 or equivalent)

Pipe vibration assessment (VDI 3842 or equivalent)

Pipe vibration assessment (VDI 3842 or equivalent)

(OP)
Dear community members,

After having searched in several books and on the internet for a good reference, I must conclude that a good description to assess measured vibrations is difficult to find.

Suppose the goal is to perform a pipe vibration measurement and subsequent assessment. The following steps apply to my opinion:
1) measure the velocity of the pipe, resulting in a graph with velocity vs. time (time on horizontal axis)
2) perform a Fourier transform on the measurement results, resulting in a graph with velocity vs. frequency (freq. on horizontal axis)
3) assess the result from (2) using a standard as VDI 3842 or equivalent.

The question is how to perform the 3rd step. As an example I have added the result of a Fourier transform as per step (2) and an assessment graph like in VDI 3842 and comparable codes.

Figure (A): Result from step (2): Link
Figure (B): Graph like in VDI 3842 as used in step (3): Link

You may lay the VDI 3842 graph lines in figure (B) on top of figure (A), but I wonder if this is correct. My doubt is for the following reason:

case (I): suppose there is one measured frequency f1 = 10 Hz with a corresponding velocity of 0.1 mm/s. Plotting this INDIVIDUAL point in the assessment graphs (figure (B) ) shows that you are below the pink line, indicating you are somewhere below 'strong vibrations'.

case (II): suppose there are two measured frequencies f1 = 10 Hz and f2 = 20 Hz, both with a corresponding velocity of 0.1 mm/s. If you plot both points INDIVIDUALLY in figure (B), then both points are below the pink line. However, the vibration in case (II) is clearly worse than in case (I). Can you just plot both points individually or not?

case (III): suppose the most general situation of a vibration measurement with the result of a Fourier transform as in figure (B). Like in case (II), you might wonder if you can just lay the assessment lines in figure (B) over the result of the Fourier transform as in figure (A). Case (III) is just a generalization of case (II), since you have different vibrations running through each other, each with another frequency and a corresponding velocity.

Maybe the assessment graphs are generally so conservative that you can just lay the assessment graph lines over the Fourier transform results (i.e. lay Figure (A) over Figure (B)), but it is never stated if that is the case.

Anyone who has experience with performing such an assessment or who has otherwise an opinion about this interesting topic?

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources