pipe vibrations- standard?

[Deemter]

Hi,

I have a question regarding pipe vibrations. Is there any standard for piping vibrations, like for example the ISO10816-3 for mechanical vibration?

What is the rule of thumb?

Best regards Deemter

 

[GregLamberson]

As you kinow there are many causes of piping vibration. To determine cyclic stresses due to vibration, a piping system needs to be analyzed using field-measured deflections. For the analysis, there is CAESAR II or AUTOPIPE, and others, those are the 2 most widely used.

For well-defined vibrating systems, such as metering pump installation or a pipe span that has been monitored for the full range of operating conditions, the safety factor built into the AWS X-curve is usually adequate.

However, in most cases, only spot measurements of vibration displacement will be available, and, in all probability, will not represent the worst situation. Vibration displacement can be affected by flow rate and many other routine process adjustments. For such cases an additional safety factor of 2.0 van be used.

One suggestion is to use desgin endurance limits based on the AWS X- curve, reduced by a factor of 2.0.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[JLSeagull]

Noise is regulated. This could be relevant if the vibration is induced by machinery or control valves.

 

[JohnBreen]

Hello Deemter,

The Eng-Tips search feature is powerful, Have a look here:

thread378-36376

Regards, John.

 

[NozzleTwister]

I couldn't get the links to work on the thread John posted.

Here is a link from the other post that has several good papers.

http://www.engdyn.com/papers/papers_table.htm

NozzleTwister
Houston, Texas

 

[JohnBreen]

Hi All,

Sorry about that, I didn't re-check the address this time and that previous thread was five years old. Y'all know how transient the Internet can be.

Thanks to NozzleTwister.

Regards, John.

 

[unclesyd]

If you will truncated the links in JohnBreen's thread link or anyone else's to the basic URL. That is XXXXX.com they will work.

 

[carthago]

I have used few years ago this book.

It is practical and straightforward.
For small bores , it ends up sometimes with extra bracing..

"Guidelines for the Avoidance of Vibration Induced Fatigue in Process Pipework"

 

[JohnBreen]

The web site for the piping vibration papers is:

http://www.engdyn.com/papers/papers_piping.htm

Regards, John.

 

[JohnBreen]

............and on that web site this may be the paper you want to be sure to read:



Vibration Troubleshooting of Existing Piping Systems
J. C. Wachel/D. R. Smith, July 1991.
When a vibration problem is reported, the vibration analyst/engineer must determine whether or not the high vibrations represent a problem. The evaluation of whether or not the high vibrations represent a problem has to be based primarily on the vibratory stresses introduced into the piping; however, the vibration levels can be high based on the psychological effect that it has on the operators. In addition, many times apparently high vibrations may not cause excessive stresses in the piping, but could cause excessive stresses to piping systems or appurtenances that are attached to the vibrating pipe.

The vibrations are obviously too high if there has been a piping fatigue failure or if the piping has extremely high vibrations. Since it requires approximately ten million cycles of stresses in excess of the endurance limit for a pipe to fail, it is desirable to correct high vibrations before failures occur, if at all possible. As a rule of thumb, excessive vibrations at 5 Hz required 20 days to reach ten million cycles, therefore, for low frequency vibrations failures may not occur for a month. If the vibrations are at 100 Hz, it would only require one day of operation at the excessive levels. This means that extreme care should be exercised in evaluating piping systems in low speed reciprocating machinery systems or any system which has low frequency vibrations.

In addition, vibrations are sensitive to engine speed and loading conditions, therefore, the vibrations that are present during the initial survey may not be the highest that will occur. The point of maximum vibration is sometimes difficult to establish in an initial survey and some safety factor is necessary to allow for these factors.

If the high vibration levels have been occurring for many months without failures, the vibrations may not be so severe that failure is imminent but may need to be reduced to increase the margin of safety.

This paper will discuss the types of problems that occur in typical piping systems and will try to direct the analyst to determine the cause of the problems and give input into possible solutions. A set of diagnostic charts has been developed to aid in the assessment of the severity of the vibrations and to help evaluate possible solutions. The following steps will help the vibration analyst/engineer diagnose and solve the problem.

You can download the entire paper as a .pdf file (2.7 mb) and read it at your leisure. Look around, there are lot of good works there.

John

 

[Deemter]

Hi

Many thanks for all tips and information!




Best regards Deemter