What's the most amazing story from your piping career? 8

[McDermott1711]

Hi everyone. I would be grateful if you share your worth-hearing story from your piping career.

Nothing is more fairly distributed than common sense: no one thinks he needs more of it than he already has. Rene Descartes

 

[davefitz]

There are 2 piping events that stand out, both occurred at the same N Carolina combined cycle plant in 2003.

Case 1 is the deflection of the 20” NPS hot reheat steam bypass pipe ( dump to the surface condenser) by +- 5 ft and the deformation of the elbows and bends, caused by excessive forces of the entrained slugs of attemporator water. The cause was a combination of incorrect steam attemporator temperature control logic, incorrect placement of the downstream thermocouple, and unacceptable bypass valve design and operating characteristics. The end result was destroyed piping that needed replacement and many failed condenser tubes.

Case 2 is the failure of the dissimilar metal weld between a 14” NPS P91 HP main steam pipe ( approx 1.5” thk) and the steam turbine cast WC9 ( 2.25% Cr) stop valve , approx 4” thick. The failure was due to thermal fatigue of the butt weld after only 1 yr of service. The root cause was the EPC designer's failure to use approporiate weld geometry , and in this case the correct geometry would be to use a F91 transition piece where the variation in thickness would be at a slope less than 18 degrees. The provided butt weld did not meet ASME code geometry requirements of 30 degree max and the supplied slope was in excess of 60 degrees- very sloppy and potentially deadly.

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

 

[pmover]

some 35-miles of 34" diameter gas transmission pipeline was pigged. at the receiving end, the mainline 34" valve (wedge gate valve) was partially closed to retrieve the pig in pig trap. the pig came in and the signal to open the 34" valve was sent. however, the valve operator indicator did not indicate the valve was opened. the operators were concerned as this impact pipeline capacity. instrument techs were sent and they made several attempts to get the valve opened, which included placing the full pressure from a nitrogen bottle to the actuator get the valve opened. no luck. the actuator was a piston-cylinder type designed for pipeline operations and had a 1/2-inch rod attached to the piston and it penetrated the top of the cylinder to indicate valve position. only about 6-inches of the indicator rod was visible which caused much concern. a spare 34" valve, pipe, and fittings were readily available, so the following weekend, plans were made to replace the valve. drove to the site on Saturday to observe the work. the pipeline was isolated and excavated. the pipeline was cut and lifted out with the 34" valve. several of us stood by to look through the pipeline to see how much the valve was closed. turns out the valve was always open. the indicator rod was bound at the cylinder seal in such a way that the rod wrapped itself around the inside of the cylinder when the valve was opened. there was fine sand, dirt, and grit that penetrated the seal when the valve was partially closed that it "froze" the rod in place. needless to say, that was about 300k spent in a 34" valve, pipe, fittings, and gas loss to account for. not a good day for some folks.

 

[chicopee]

Check out on line the National Board Bulletins as these Bulletins will have articles on piping and associated components mostly associated with fired and unfired pressure vessels.

 

[KevinNZ]

 

[itsmoked]

Nice Kevin, though I hope it's just a water pipe since it seems the end points are pretty close to the channel.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[KevinNZ]

Keith

This a geothermal hot water line. The curve allows the pipe to expand. Design code B31.1. Also uses a number of pipe thickness, thinnest at the top, to pass EQ and wind loads.

The river channel has a small flood range. Channel ~18m, pipe span ~ 50m.

 

[itsmoked]

Got it. Pretty cool looking really.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[davefitz]

2 other pipeline stories taht standout are :

3. the 1985 Mohave power plant P11 hot reheat steam pipeline failure ( 30" dia, seam welded) failure that killed 6 workers and injured 10 others. The failure occurred at a section of pipe immediately outside the workers cafeteria, sending 1100 F steam blasting through the door and killing the workers during a lunch break. This accident led to the start of industry's use of routine metallurgical examinations. The accident was caused by a combinations of (a) the boiler's design prevented controlling the steam temperature at its design value of 1000F, and it operated for over 1 yr at 1100 F, accelerating the creep damage at the seam weld (b) asme 1962 design stress values for P11 were too high , so the wall thickness was not adequate and (c) multiple repair welds on the creep damaged section of seam welded pipe ( due to recurring cracks) did not account for the accelerated weld HAZ damage due to repeat weld repairs. To this date asme section I does not require operators to prevent overheat of the piping, and routine oveheats are yet common on US power plants. The fines and penalties were one cause for the corporate failure of the boiler designer, CE ( now called GE alstom).

4. A 1989 trip to the TVA coal plant Bull Run ( 700 MWe supercritical) was to try to convince them to replace the failing P22 HP main steam pipe with the newly approved alloy SA335P91.The 150 ft long pipe was exhibiting cracking at the elbow butt welds and there was excessive piping interference with bumpers and supports. A discussion with plant operators revealed the root cause of the problem: an earlier plant shutdown to inspect the steam turbine included adding static pins to the pipings spring hangars so the turbine casing could be opened up. They forgot to remove the pins prior to the plant restart, so the piping creep releived its excessive stresses as it heated up from 65 F ambient to 1005 F final steam temperature, and the pipe thus grew an extraa 12" in length.

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

 

[mbelly84]

dave, congratulations. those were 4 really great stories.

 

[DekDee]

Welding a live methanol tie-in many years ago with water pouring into the bellhole faster than it could be removed.
Water was up to the neck and the pumps just managed to keep the water 3-4 inches below the weld.
All 6 x welds passed X-ray but the "amazing" part of this was the owner of a major pipeline company was passing me electrodes in the trench from under an umbrella - on a Sunday afternoon !

 

[itsmoked]

DekDee; Phenomenal!

Keith Cress
kcress -

http://www.flaminsystems.com

 

[NovaStark]

One I can distinctly remember:

Rupture on a 304H stainless steel line at around 1200 degF and 600 psi ruptured along a seam weld. The rupture was fish-mouthed and about 5 feet long and 2 feet wide. Lead to loss of gas at through that opening which lead to an entire reverse flow scenario. Basically all of the high alloyed components melted through. Cause was due to improper weld geometry creating microcracks which over time resulted in the failure.


@davefitz - do you happen to have an actual failure report for that ? All I can seem to find are online news articles about it which don't fully encapsulate the technical aspect of the failire.

 

[davefitz]

Novastark,

I think the offical reports may be under court seal , considering the mulit billion dollar settlements. I obtained unofficial reports from asme code inspectors from the site and also from a former mohave operations supervisor who now works at a nearby combined cycle plant. There are other stories associated with the faillure: the entire boiler ( 300 ft tall) needed to be wrapped in plastic to prevent asbestos from blowing away into the nearby city, inspectors needed to shave off beards to allow use of fitted respirators, etc.

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

 

[blacksmith37]

A 8" line was laid from IN to AL , x-60, 0.219 wall. Built in several sections each one individually hydro tested -all good. Connected the sections and started filling with liquid product . Product did not come out in AL when it should have ; search found a problem . When it was dug up there were 2 squarish holes in the pipe that matched backhoe teeth. One of the contractors had needed to do a little work replacing broken clay field tiles he was responsible for on a farm. Because it had nothing to do with the pipeline , he did not contact the pipeline company.

 

[davefitz]

novastark,
you might obtain technical info on the Mohave failure analysis by directly contacting the CE metallurgists who worked at CE in 1985. I think they may be J.H., currently at applied thermal coatings and I.P. at structural integrity associates.There is likely notes and meeting minutes from the ASME materials properties committee meetings following th failure.

Another pipeline failure of note is the Bellingham washington 1999 failure of a 100 miles long UG gasoline pipeline failure, with several fatalities. The 2 interesting aspects of this failure were (a)the impact load of a sudden stoppage of gasoline ( water hammer) in a 100 mile long pipeline due to a fail-closed signal to a stop valve and the upgrade / conversion of the control system from analog to DCS- the switching to a backup DCS server led to the fail closed signal that failed the pipe. To limit financial exposure to huge settlements the failure was nominally blamed on a penniless backhoe operator.

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick