Velocity limit for Flow Induced Vibration 5

[leostar81457]

Hello All,

Can anyone share any experience or reference on what is the maximum velocity that is allowed in a piping, mostly in terms of Flow induced Vibration? I am expecting static analysis will not be affected by the increased velocity, only the dynamic needs to be considered (FIV). This is for both gas and multi-phase fluid (no slug flow as confirmed).

On one of our facility, they increased the production by increasing the velocity. Since it is already in operation with the increased velocity, we just had an assessment by visual inspection, and we measured the vibration frequency and amplitude using accelerometer and plotted the obtained frequency and RMS reading in T7-1 of EIG guidelines and it was found acceptable.

Now the problem is that they want to increase the velocity much further, and they want to know until how much further it can be increased.

I am not doing much of this FIV calculations and I am only aware of the EIG guidelines' LOF factor to assess this. If I use the LOF factor criteria to back calculate the velocity, I believe it will be very conservative.

So I was wondering if anyone has done the same calculation/assessment before; and hoping to hear some of your insight or possible references that you could share.

Thank you all.

 

[LittleInch]

Artisi,

My guess is that this is a oil & gas production facility and to get rates up or keep them up, they've lowered the operating pressure to accommodate the fall in pressure of the reservoir. Pretty common and normally once people start putting in field compression you know the field has only a few years left in it...

Of course no one then wants to invest in bigger pipes.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[shvet]

This is for both gas and multi-phase fluid (no slug flow as confirmed)

Take care with results of 2-phase modelling. All models widely used now were created far in the past based on testing of air-water in a pipe segment having long straight-runs up- and downstream of reference point.
While you are dealing mostly with fluids far from air-water and piping having no such straight-runs.

 

[GD2]

OP, Your whole assessment is based on vibration readings. So try to understand it clearly. AIV and FIV manifestations are different. AIV manifests radially whereas FIV horizontally. Frequency ranges are 500-2500 Hz for AIV and 0-100 Hz for FIV. Whereas AIV causes high cycle fatigue, FIV is a low cycle fatigue.

Location of readings are important. Small bore socket weld fittings and supports are more susceptible. Source of vibration for AIV are RO/CV/PSvs whereas FIV is caused by the turbulence kinetic energy of the flow.

Take vibration readings at susceptible locations and see what you get. One weld failure in a small bore fitting can bring down your plant.

Are you talking about flow from production wells?

GDD
Canada

 

[leostar81457]

Yes GDD and LittleInch, these pipes are part of the upstream oil and gas facility. These are condensate pipelines connecting to the main header, then goes to the Separator Vessel. I am looking to evaluate the main headers first; the Inlet header to the vessel, and outlet gas header. Currently, they reduced the operating pressure and increased the velocity.

The vibration readings were acquired on locations with longest spans, loose elbows & small bore branch connections. Most of the valves are just fully-opened gate valves; with the exception of a control valve located at the gas outlet header.

Apologies for not making myself clear. Although they want to increase the production much further, they are also looking on the limiting factors to know how much further they can increase. For example, the erosion rate is also being considered by the process team. On the piping side as of now, I can only think about the vibrations that will be the effect of the increased velocity. If all parameters are available(ex. pipe properties, piping span, fluid properties, etc.), can the limiting velocity be calculated with respect to the maximum allowed vibrations and dynamic stress? (Currently looking onto the reference shared by 1503-44)

For the FIV, I believe the failure will not be immediate and vibrations can be observed; so the line can still be rectified if FIV is present at site. (please correct me if I am wrong)

Thank you all for your replies.