Vibrating thin-wall SS pipe 1

rocketscientist · Oct 22, 2021

I have a 6" schedule 5 pipe running about 92' to the top of an absorption column. It carries cooling tower water to coils running the length of the column shell. Unfortunately, it vibrates about 1/8," so much so that I couldn't get a reading with a portable ultrasonic flow meter.

Someone has made a poor attempt to prevent vibration in this long vertical pipe.

I am concerned with eventual failure of this long pipe since loss of cooling water would be an environmental disaster.

How do I go about selling this to management? I can't get a steam trap discharge relocated: the steam discharge is gradually eating a column supporting our entire raw materials pipe runs.

Any thoughts on how I can calculated the cycle time to failure.

TugboatEng · Oct 22, 2021

I would first focus on shielding the support column from the steam. A simple piece of sheet metal to deflect the flow may be all that is required.

As for vibration, an 1/8 inch over 92 feet seems trivial.

MJCronin · Oct 22, 2021

Rocket ....

Replace the Schedule 5S riser with 10S or thicker,..... the vibration you have detected will only get worse... You obviously did not have an experienced piping engineer design this part of the system. You had a group of underpaid CAD monkeys probably being led by profit hungry MBAs

The stability problem of long piping vent runs connecting to the tops of columns is nothing new .... It has been around for at least 75 years

.... and when things go south during startup ...ITS TIME TO BRING IN THE NEWLY GRADUATED ENGINEERS

You state: "Someone has made a poor attempt to prevent vibration in this long vertical pipe" ....What exactly did you mean ?

Can you be more specific ?.... can you post pictures ? How is this very long column of Sched 5S shit pipe supported vertically ???

Is the riser pipe supported from the column ?

Is there a lap-joint flanged piping connection at the top of the riser or is it "all-welded" ? ... This will be your point of failure.

Regarding your obvious steam trap problem ..... The MBA managers are smart, but do not care .... they have you to blame if something goes very wrong with the trap and someone gets hurt

Take pictures of the vertical supports if possible

.... When you have inexperienced third world piping monkeys led by the corrupt, this is what you get ....

My opinion only

MJCronin
Sr. Process Engineer

MJCronin · Oct 22, 2021

This website shows a properly supported riser-vent piping layout that will give acceptable thermal expansion stress levels.

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1634927942/tips/Supporting-of-Tower-Piping_oecian.bmp[/url]

Your 5S system will never pass such a stress evaluation, but your pipe support layout should be similar

MJCronin
Sr. Process Engineer

mk3223 · Oct 23, 2021

"Someone" has made a poor attempt to prevent vibration in this long vertical pipe.

May contact this "person" and make a group effort to add it to the O&M priority list.

Some other options for consideration, including:
- Verify the Maintenance history for the pipe failure due to the vibration
- Maintenance may add a tubing after the steam trap and point it to the drain and away from the structure column
- Involve the Inspection group and monitor the CW pipes at the critical locations
- Involve the Structural Engineer if any structural damage because of the steam discharge

hacksaw · Oct 24, 2021

92' of NPS6 Sch5, will gallop wildly in moderate winds. you'll need to secure it with ropes or leather staps like they do in Kansas and Oklahoma to prevent damage a la Tacoma Narrows Bridge Disaster....

MJCronin · Oct 24, 2021

hacksaw .....

Agreed, but I thought restraining piping systems with ropes and leather straps was only permitted in TEXAS ?

Does anyone have any pictures of this ???

MJCronin
Sr. Process Engineer

EdStainless · Oct 25, 2021

Why people believe that pipe needs less support when vertical than in horizontal has always puzzled me.
Vibration is vibration.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

LittleInch · Oct 25, 2021

question though was "How do I go about selling this to management?"

We don't know and can't advise because:
1) We don't know your management competence level or your internal procedures for raising safety or business critical issues
2) We don't know if there is anywhere on the system where that vibration results in increased stress (normally big heavy thing or a fixed point like a nozzle, elbow or other place where the pipe is retrained.
3) We don't know how highly stressed this pipe is and what sort of fatigue analysis has or hasn't been done

So it could fail tomorrow or next week or you could do the analysis and find it will take 200 years to fail.

Issue is what needs to be done to reduce the risk of failure and how much does it cost / take time to do and can it be done without a shutdown / turnaround or do you just add it to the list of things to be done in said shutdown?? We have no idea - please tell us.

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

hacksaw · Oct 25, 2021

As with stacks and other pylons, wind-induced resonance, and "galloping" can take place, with failure a given.

Management responds to the potential loss of life, and physical damage exceeding $1,000,000US.

Typically you get the structural engineers involved. Don't forget, you have to secure large cranes in high winds.

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Vibrating thin-wall SS pipe 1

rocketscientist

Chemical

TugboatEng

Marine/Ocean

MJCronin

Mechanical

MJCronin

Mechanical

mk3223

Mechanical

hacksaw

Mechanical

MJCronin

Mechanical

EdStainless

Materials

LittleInch

Petroleum

hacksaw

Mechanical

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