Pipeline size reduction 1

[Bainit]

Greetings,

I stumbled upon pipeline size reduction 20" to 8" as shown below. Attached to the flange on the left is flow control valve sized 8" (the pipeline before control valve is 14"). Flow direction is from left to right, liquid is crude oil. Due to this fragment of pipeline being rebuild I wonder is there any reason to reuse shown solution over the standard ASME B16.8 BW reducers on new pipeline. I asked plant user but they don't have any idea why such solution was chosen. Pipeline is being redesigned/modified because of excessive vibration during flow under certain work condition.

Any feedback appreciated.

 

[LittleInch]

Bainit - your post would get more responses in the pipeline and piping forum.

I have to say that this is the strangest reducer I've ever seen.

They either couldn't get any reducers in time or were very short of space, but that is very odd.
The fact that someone actually drew it up is even more amazing - usually these are field bodges.

14" to 8" to 20" sounds equally odd though - what sort of flow rate do you have here?

But no, throw that thing in the scrap heap and use standard reducers. Not sure you can get 8" to 20" in one fitting so you may need two, something like 8 x 12 then 12 x 20.



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

 

[MJCronin]

My guess is that this component is a botched field attempt for mitigation of vibration and fluid instability from a poorly sized control valve.

I suggest that you first get accurate specifics about the troublesome valve and then talk with a control valve consultant. Have you considered all operating conditions ?

Next, I would ask for a quote from a competitive vendor for a brand new valve and possible silencer using the corrected operating conditions. Ask the vendor if these fluid conditions are at the limits or beyond what he could normally provide to a customer. Ask him if the conditions and his proposed valve would require a downstreaam silencer and what would this suggested silencer look like. Would it be single or multi-stage ?

Ask the vendor if he has any other suggestions, including replacing the single control valve with multiple valves.

I would also carefully examine the reducer/mess once it has been cut out of the piping system.

It would not be unusual for severe metal cavitation/erosion to occur just downstream of such control valves.

https://www.globalspec.com/referenc...valve-features-valve-features-to-reduce-noise

https://www.emerson.com/en-us/autom.../control-valves/control-valve-noise-reduction

Please keep us in the loop and tell us of your repair plans

Good luck and best regards !!

MJCronin
Sr. Process Engineer

 

[Bainit]

Thank you for your answers.

LittleInch:

Posting this in piping forum certainly would be better - I will remember for the future.

My first thought was to replace it with two ASME reducers, but then I thought: since it was drawn in detail and placed right after control valve, maybe it is important and there is something going on I don't know about.

Flow rate between is 350 and 850 m3/h - differs in time (I have access do data going year back).

MJCronin:

I've collected operating parameters of pipeline (pressure, temperature, flow rate) up to year back and asked valve vendor for reevaluation for this new data.
Those questions to vendor suggested by you are very helpful.

Inline diffuser by Fisher from your link looks very similar to drawing from my first post, so someone was clearly trying to use similar principle.

Since design process and plant fabrication are separated in my case (fabrication will be performed by different company sometime in the future) it may be difficult to examine this "reducer" for cavitation erosion, but I will try to obtain some pictures after disassembly.

 

[LittleInch]

850 m3/hr through an 8" valve eh?

That will certainly be interesting.

Pressure drop?
You might be getting cavitation in and around the valve which is causing vibrations

That diffuser versus your thing has some crucial differences, i.e. one is a closed end with multiple small holes and the other is a bit of pipe stuck through an end cap....

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