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Salem Harbor tube failure
5

Salem Harbor tube failure

Salem Harbor tube failure

(OP)
anyone get any other info than what is in the newspaper?

RE: Salem Harbor tube failure

From what I could gather - either corrosion fatigue or most likely FAC in a feedwater line.

RE: Salem Harbor tube failure

I couldn't tell whether it was a boiler (or economizer) tube near where they were working or a feedwater line from the account I read.

rmw

RE: Salem Harbor tube failure

sadly, it seems like a case of being in the wrong place at the wrong time...

Another Boston paper stated that the "59-year-old boiler passed its annual inspection in April."

59 years old ??

When are boilers officailly retired, or am I so uninformed to assume that they are not "retubed forever" ??

-MJC

  

RE: Salem Harbor tube failure

There is no requirement to replace any boiler simply due to age.

RE: Salem Harbor tube failure

Sounds great.....never a requirement to replace boilers....ever..!!!

Who is going to inform the boiler steel about this ?  

I guess that the steel in boilers are immune to creep induced failure from thousands of thermal cycles.

And that those firms that offer a metalurgical evalustion of boiler parts will do a complete 100% evaluatiuon of the boilers every time...

Many bridges and buildings, who are not subject to creep induced failure do not last 60 years..

My opinion only

-MJC

  

RE: Salem Harbor tube failure

Let's see....when does a boiler need to be replaced? Well, you have safety and economics concerns, and that is about it. Environmental regs will effect the economics of deciding to spend money to install or close the doors.

Power boilers can continue to run if an owner has deep enough pockets to evaluate and replace boiler components when they need to be replaced to assure personnel safety and boiler reliability for revenue.

Great concept except all of sudden, upper management complains that we do not have enough capital to spend because bonuses are low this year. O&M budgets need to be slashed so that upper execs have more money to please wall street.

So, capital and O&M expense budgets are reduced and now the boys in the trench need to decide on what targeted evaluations/inspections and pressure part replacements need to be performed to sustain performance.

Trying to run a fleet of aged boilers requires a knowledgeable and experienced team of specialists to conduct internal boiler inspections (based on best industry practices) during scheduled outages, and when necessary to recommend replacements of major boiler pressure parts that have limited creep life. Also, maintaining water cycle water chemistry to at least EPRI Guidelines is critical in assuring long life of water-wetted boiler components.

The company I work for finally wised up and recognized that spending capital dollars makes perfect sense to continue to safely operate AND maintain aged boilers. Revenue is a large motivator for IPP's and when upper management decides to avoid replacing boiler pressure parts, cut inspection programs and personnel, suddenly boiler reliability and personnel safety are compromised, it is time to close the doors.

RE: Salem Harbor tube failure

(OP)
the major problem (as i see it) is that the older base load plants were not meant to be cycled.

they were designed to run continuously and their life had a determined number of cycles calculated into their design.

some plants have gone through estensive "life extension" programs designed to increase the life of these boilers well beyond the original 30+/- years (financial).

this included replacement of headers, tubes, deareators, and on and on.

prior to the advent of cycling these plants these considerations were relatively easy.  but with cycling you now have introduced a whole set of new design characteristics that were not originally considered.

and yes, complete boiler inspections are now a must to run safely beyond the limited calculated number of cycles.

RE: Salem Harbor tube failure

eyec;
We don't cycle any of our Coal plants because power is needed, and is a premium. We used to cycle back in the 1980-1995. Not any more, we run base load.

RE: Salem Harbor tube failure

interesting topic.

Meteng is likely correct- other reports suggest a FAC attack of a feedwater or spray water line, or an econ drain line.

Boilers are not required to be retired, but 2 trends will push in the direction of repowering old sites. First , as being done in Japan and Europe, older 33% efficient coal fired boilers + turbines are being replaced with ultrasupercritical units at 43% LHV efficiency, for a significnat reduction in normalized CO2 emmissions. Second, the corut interpretations now suggest that signiificant modifications of old boilers will imply that billon dollar scrubber retrofits will also  be required, pushing teh utility to mothball or retire or repower the site.

Also, ASME section I does not yet recognize fatigue damage for large coal fired boilers, so a 59 yr old boiler with 10,000 startups and which was never designed to manage thermal fatigue damage is probably ripe for replacement.  While there are design features that can be retrofit to improve the plants operational flexibility and manage new fatigue damage, nobody can accurately confirm the extent of fatigue damage that had occurred over the last 59 yrs.

RE: Salem Harbor tube failure

davefitz, et al

"nobody can accurately confirm the extent of fatigue damage that had occurred over the last 59 yrs"

I guess that was my point, nobody really knows the amount of cummulative creep damage that has occured, therefore nobody really knows how safe that the plant is nor do they know(exactly)how long to extend the life.

Of course there are "educated guesses" about replacement of superheater tubing, atemporator piping systems, places where FAC may occur etc. etc. are prudent, but to my way of thinking all of these "life extension" programs are still, fundamentally guesswork.

Because European accounting standards and environemntal laws are different than in the US, there is a tendency here to try to run older less-efficent plants virtually forever.
The European plants seem to have a plan for eventual retirement. The US accountants seem to be able to revive virtually any "zombies" boiler with a stroke of the pen

I cannot help to conclude that we will see more "Salem Harbor" type accidents in the future at older power plants....

My opinion only

-MJC

  

RE: Salem Harbor tube failure

Maybe some damage mechanisms are getting mixed up.

Creep damage in ferritic tubes occurs at metal temps above 800F, but the reports are the failed pipe was at 300-350 F. There are test procedures to estimate local creep damage.

FAC flow assisted corrosion usually can be detected by simple UT test for wall thickness. The many failures of the last 10 yrs and the many EPRI reports on this issue would suggest that a failure on an old boiler would be accompanied by the sound of many lawyers feet scrambling to get to the families.

Fatigue damage is trickier. Until the microcrack becomes visible, there is no physical test to indicate the amount of life consumed . And once the crack is visible, it is tempting to claim that a thermal stress induced crack is slef limiting, and ignore it until its lenght can predict a prompt failure due to primary stresses.

RE: Salem Harbor tube failure

(OP)
[quote]Fatigue damage is trickier. Until the microcrack becomes visible, there is no physical test to indicate the amount of life consumed .[\quote]????

I worked on a boiler where they took boat samples and had them analyzed for remaining life/fatigue/creep.  Is that not considered reliable?

RE: Salem Harbor tube failure

One thing about a boiler that old; when it was designed it was done with a slide rule and the factors of safety were a lot higher so it has a lot more metal in it.  Design one the same rating to replace it using modern tools like FEA and that thing sure won't be there in 59 years from now.

I've seen some tough old beasts out there still ticking along just fine-although inefficient as he**.  I have seen brandy new boilers split tubes and have piping let go.  So who is to say?

All in all, I think it is criminal to be operating a 59 year old unit if it hasn't had modern pollution control added and that the power industry has brought a lot of the current hype about green house gases on themselves by hanging on to some of these dinosaurs.

rmw

RE: Salem Harbor tube failure

eyec:

To be honest, I am not qualified as a modern metallurgist to say with 100% assurance that, in the general case where a field sample is taken from a 59 yr old component, that one cannot with assurance demonstrate what the fatigue life consumption is, prior to the onset of a visible micro crack.

A quick review of the some recent literature indicates that , in a lab setting , where the sample's crystal structure is known, and the sample is deliberately cycled to a known strain  value and known number of cycles, one can characterize the change in crystal microstucture vs amount of fatigue damage, using X-ray diffraction and magnetic Barkhausen emmission methods, prior to the onset of the first crack. But to proceed from that premise to determining the amount of fatigue damage consumed from a random sample sounds like a stretch at this time. Maybe in another  10 yrs.

RE: Salem Harbor tube failure

Normally, when you are dealing with boiler pressure parts the concern is low cycle, thermal fatigue and from my standpoint, this damage mechanism is understood. Thermal fatigue damage is evaluated in lower drums and steam drums by monitoring crack growth every day. In my experiences, these cracks become limited in depth based on a reduction in the stress field as you go through-thickness.

The real concern is creep/fatigue. Here, things get a little dicey because there is no clean correlation to address the effects of creep interaction with fatigue. One can only deal with periodic inspections and monitoring crack depth with the premise to change out the component at some future scheduled outage to reduce risk of failure.

Regarding critical components like piping and high temperature headers, one has to continue to monitor these items and when cracks or flaws are found to replace them to avoid risk of failure.

Age of the boiler has nothing to do with this, It is design and selection of material.

RE: Salem Harbor tube failure

Salem Harbor failure sounds like a potential corrosion fatigue of a boiler external supply tube or riser. I have seen failures like that and normally they are un detected until failure. The best detection is eather internal boroscope or digital xray looking for ID initiated pitting forming a line and eventually a crack. However if the temperature of 350F and 200PSi are correct it my not be a boiler riser.
Corrosion fatigue failures at several Utilities have become more common due to the age, number of cycles and the corrosion from multiple chemical cleanings and less then perfect water chemistry.
Anyone heard what where the failure ocurred?

RE: Salem Harbor tube failure

I've read a post on the Yahoo finance message boards that it was a water wall tube rupture on the cold side of boiler around the 16' to 20' el. The 3 men were working on a fan at 16' el.  It definitely sounds like it could be corrosion fatigue.

RE: Salem Harbor tube failure

(OP)
i am not an expert but, on most boiler designs that i am familiar with; that would put the failure down on the lower slope tubes.

with all of the dead air space, laging, and casing how this failure could have caused the damage and injuries seems puzzling to me.

i would think it had to be an external line; possible an economizer line.

RE: Salem Harbor tube failure

There are typically supply tubes 4-5inch in diameter that are external of the boiler walls. They will come off the lower mud drum and these are the ones that are most susseptale to corosion fatigue and rupture rather then leak before break. The reason is they are thick wall and can have some elevated stress level. The age (59 years) is also a clue. CorrosionnFatigue is showing up more now due to the aging boiler fleets. It is a combination of corrosion and stress.

RE: Salem Harbor tube failure

3
On Friday November 16, 2007 a Dominion Boiler Inspector(?)held three meetings for plant employees at 0930, 1000 and 1030 hours to give a slide show presentation covering the explosion that killed three men.

The job these men they where doing had nothing to do with the failure. They where "at the wrong place at the wrong time"

They where on Elevation 16 (the ground floor) and the explosion occurred directly over there heads and behind them.

Up to about two feet of ash covers the floor were they where working. All the units are off at Salem Harbor and the building is sealed while an asbestos clean up plan is made for the entire(?) building.

There was a tube failure of division wall tubes at the header (16") which was in a "dead air space". These were riser tubes, that is they supplied water to the boiler which as the tubes existed the dead air space would be exposed to products of combustion, and turned to a steam and water mixture.

The water temp. out of the economiser which supplied the header was possibly 500 to 600 degrees F and about 2000 PSI(about boiler pressure).

The header had counter bored(?) recesses in the holes where the tubes meet. A short sleeve is welded into the hole for the tube (Maybe 2" OD- not sure) the tube metal is reportedly .240" thick(when new)).

Two tube where sheared flat across just above the welded sleeve. There was evidence of other leaks cutting tubes in this area. And other tube damage "dimpled?"

I-Beams in the area about the size or bigger than the header were bent or buckled. Some tubes that did not fail  had moved 12" from original position. (before the explosion?)

The dead air space starts 19' up from the bottom of the boiler (not the floor) and slopes in 5' from the east wall to the "throat"). the boiler has dead air space running north to south on the east and west side of the unit.

This dead air space was "full of ash and asbestos". The last time it was cleaned out and entered may have been as long as 12 years ago. The "guys" at the plant are trying to remember. The Dominion "inspector" said he did not know what B&W recommends for cleaning and inspection times, and he did not know when the last time it was looked at. Dominion has owned the plant for about 3 years.

Reportedly 1 to 2 years ago this area was suspected to have a leak but the inspection was called off because when the access cover was opened and the "Ash and asbestos mixture" was seen to be in the way it was decided to put the unit online rather than delay the start up and pay for the asbestos cleanup.

Earlier this year, before the scheduled major outage which included a major turbine overhaul, (6 weeks long ?), it  is said that this boiler was operated at reduced pressure because of concern about reoccurring tube failures. Dominions "engineering department" had calculated a reduced safe operating pressure based on reduced tube thickness which was about 100 psi below normal.

Some employees believe Dominion will remove these Emails and other Emails that might be useful to investigators trying to determine the level of negligence, if any, that exist at this plant.

Unit 3 has had several serious tube failures in the last couple years,  at least 1 of which "would have killed any one who happened to be near it". According to some people at the plant.

Other units at Salem Harbor have had similar serious tube failure that "would have killed any body who happened to be near that area". This is according to plant workers.

These same workers say that the only reason that the plant is closed for asbestos cleanup and "examination" is because "people died" and the other asbestos releases from these other tube failures were just"cleaned up" without closing the whole plant to do it, and that other tube failures which "could have killed someone" where not investigated to the degree that this failure will be.

Dominion Management is alleged to have pushed operators and maintenance workers to ignore  standards that may be required in order to get units online quickly. This includes not doing hydrostatic testing after welding repairs on pressurised  parts of the boiler . Unit 3 was reported to have been put online recently without a "hydro" after a welded repair. (This if true should be able to be confirmed through interviews, log book entry's and examination of the "PI system"  (sic?)".

The ash in this boiler when mixed with water is reported to go to a PH of 2 or less. This dead air space where the failure occurred is close to the water seal, and the water used to remove the bottom ash.

Allegedly, the acidity of the ash water mixture is common knowledge in the plant and procedure are in place to raise the pH of the water used to wash ash before it is dumped in the ocean in the harbor.

Units 1,2 and 3 use a selective non catalytic reduction system (SNCR)to reduce oxides of nitrogen (Nox). The station
does not have a permit requirement for Urea "slip". This means that Salem Harbor could spray excess urea in order to reduces nox. The effect of the excess urea, if any, that may have have collected in the ash and have an effect on the tube failures, is not reported at this time.

Salem Harbor units 1,2 and 3 run "out of compliance" in regards to oxides of sulphur or Sox permit requirements. There are conflicting reports to how this is legal but this may be a "grand-fathered" plant.

Dominion is understood  to have said publicly in newspaper articles, that  when they bought the plant that they where going to spend the money necessary to bring the plant up to modern environmental standards, so that it would not be among the "Filthy Five" worst poluters in Mass..

Salem Harbor Station is said to have between 5,000 to 8,000 outstanding work order request, while Brayton Point, another Dominion owned coal plant in Massachusetts, is said to have over 10,000. Work orders are requested by workers when a piece of equipment is not working properly.

So far dominion has not built the spray dry atomization (SDA) vessels required to remove sulphur from flue gas. Some critics believe Dominion was planning to "run the plant into the ground" and was not serious about ever bring the plant up to modern standards, this would explain the large number of outstanding work request. (Why spend money on a plant you are really planning on closing when regulators finally "get sick of you stonewalling").\

This year dominion experimented with injecting lime slurry into the furnace area of the boiler, in an area probably hotter than than 1,700 Deg f.,  in unit 3 to reduces Sox pollution from going to the atmosphere, These test were not successful.

This experimant is alleged to be based on succesfull labortory test, however succesfully reducing Sox by  injecting lime slurry into temperature zones this hot in a coal fired furnace is allegaded to be uncommon and speculated by some to have been a false attemp to buy time by showing regulators et al that Dominion was moveing forward to reduce pollution.

The sulphur in the coal, some people say, combines with water to create sulphuric acid. What difference the fact that Salem Harbor may not have been burning the lowest sulphur coal available and that they appear to have been running out of compliance with regard to sulphur oxides pollutants, and what difference this may have made if any to the increased corrosiveness of the ash  or the increased build up of sulphuric acid and its relationship to the tube failures has yet to be proven, if it exist at all.

The availability of low sulphur coal in the United States is limited in part because President Clinton prevented mining of  the worlds largest supply of low sulphur coal when through executive order(?) he created a "National Monument" on the hundreds of thousand of acres that held the low sulphur coal.

The next largest supply of low sulphur coal is in China. Salem Harbor ususually burns coal from South America in units 1,2 and 3. Unit 4  for burns Oil

Allegedly ISO New England which (operates?) the grid which Salem Harbor supplies electricity to is, according to some people understanding of newspaper articles, is under the impression that, in essence, Salem Harbor must be allowed to run because there is insufficient distribution infrastructure (electric lines) into the area around Salem Harbor.

This may be one reason Salem Harbor has been allowed to run out of compliance to its sulphur environmental permit and without a permit limit on urea that leaves that stack.

The "plume" from the stack at Salem Harbor which was sometimes visible 5-10 mile away from the plant has been attributed to excess urea "slip".

At some times Salem Harbor would reduce the urea spray for PR reasons so as not to upset "activist". This was thought to reduce the plume.
 

The Dominion Boiler Inspector(?) said Dominion owns other boiler with similar design and that as of Friday, november 16, 2007,( 10 days? after the explosion), they are still online(not an exact quote).

In newspaper articles and on TV news, some IBEW Union representatives and the Salem Fire Department have publicly said that this is a very safe plant.(not an exact quote)

The president of Dominion spoke at the Plant Friday, 11/16/07 at 1:00 pm at the North Stores warehouse. He did not address the outstanding work order problem but he did say that for Dominion Safety was the #1 priority. (not an exact quote). Nor did he say how this accident might effect Dominions plans to open new nuclear plants.

He did not talk about bonuses paid to himself or plant managers either nor did he say if he received bonuses paid for meeting online percentage goals.

Some workers believe that "corruption" will allow for criminal responsibility, if any, to be covered up.

According to news paper articles( see Boston Herald, web sight FYI1301.com and others) FBI and Massachusetts State Police have arrested or  investigated some Massachusetts Dept of Public Safety Boiler Inspectors in the the last 10 years for corruption.

The District Attorney, OSHA and Massachusetts Department of Public Safety and others are investigating this accident.

Posting this with the hope that nobody else dies in our plants.

RE: Salem Harbor tube failure

(OP)
thank you for this post.  aside from local news media info you mention, i also detect a more personal and informed depth to your post.

sad to say that many of the issue you point out are almost common place.

my prayers go out to the families and friends of this tragedy.

RE: Salem Harbor tube failure

Powerplantfailure,

Thank you very much for your post....

I am also very sorry for the famlies that have lost breadwinners and loved ones....

I pray that the legal system in Massachusetts will make things whole again for these families...as best they can

-MJC

  

RE: Salem Harbor tube failure

A good write-up on the failure.  But, I'm still not clear on the cause.  Was the riser tube failure described as corrosion fatigue or was it flow accelerated corrosion?  Also, it sounds like the dead air space was pressurized by the tube failure and resulted in an "explosion" which could have caused the buckling of the I-beams and bulging of the tube panels.  Is this correct?

RE: Salem Harbor tube failure

From the write-up above it was neither, to me it appears to be external corrosion attack on one or more terminal tubes coming off the the lower supply header. The external corrosion was attributed to wet boiler ash (during off-line conditions) that accumulated in the dead air space.

RE: Salem Harbor tube failure

Thanks Dave.

RE: Salem Harbor tube failure

Could be external corrosion, could be a small leak had washed and cut away the tubes prior to failure.  Could also have been a slag fall- such a large slag fall had killed 21 operators at a boiler in China 10 yrs ago, tubes ahd failed in a similar boiler section. Let the boiler CSI team make their report- we'll hear about it later.

RE: Salem Harbor tube failure

to all..

Another recent article on this deadly accident:

"Anatomy of a Boiler Failure—A Different Perspective"

http://coalpowermag.com/ops_and_maintenance/147.html

(Please note that the author provides refractory inspection services)

-MJC

   

RE: Salem Harbor tube failure

To all,

Information from the Commonwealth of Massachusetts; Department of Safety Report on this accident:

http://www.mass.gov/Eeops/docs/dps/inf/salem_harbor_boiler_3_failure_nov2007_redacted.pdf

The report is contained in a large .pdf with an extensive collection of pictures.

IMHO, It is important to note that we seem to have a "perfect storm" for similar boiler accidents in the future as we have:

1) Many other 40-60 year old boilers designed by B&W (the USA GM of boilers) still in operation, at or beyond thier rated capacities and performing in a cyclic service that they were never designed for

2) A US accounting system that is configured to keep these "Zombies" in operation until people die....

3) A reactive, punishing state regulatory agency that only becomes functional after an accident, only seems to have a limited understanding of boiler operations and can only shut things down and punish individuals.

Please tell me or prove me wrong here....Why cant a very similar accident occur in another state with another of these ancient boilers..??

Comments ?

-MJC

   

RE: Salem Harbor tube failure

Well, on the one hand any poorly maintained 50 year old unit doing cyclilng service is probably a ticking time bomb, but on the other, this reminds me of the current mortgage crisis-featured daily are the 4-6% of the mortgages that are in trouble and nothing is ever said about the 94-98% that aren't.  There are hundreds of these old units, (adding in the FW's, CE's, etc that were also built during that time) that didn't (or haven't yet) explode(d).

I suspect that there are some serious inspections being conducted by the other 399 of these old B&W units (as well as the other makes that I mentioned) that were built.  The insurance carriers are seeing to that.

And, I have seen furnace bottom slope explosions in boilers that weren't even old enough to be termed teenagers yet, so I don't think the problem is isolated to just these old boat anchors.  Poor maintenance will get you every time.

rmw

RE: Salem Harbor tube failure


This all makes for very interesting reading. Unfortunately, nowhere did I see anything mentioned about the boiler supports. Some would say that the North American  "bang and clang" method of setting and monitoring hanger loads may have had some impact here.

Significant effort is taken during the design phase to properly spec the load of each hanger so that headers are accurately balanced in an effort to prevent undue stresses (which can lead to tube failure - exacerbated by creep). Alas, when it comes time for construction, the extent of QA in this critical application is the use of the "Magic Hammer": If the rod "pings" when struck by this high-tech instrument, all is fine. If it "pongs", the nut must be driven further down the rod, against the bearing plate. This same "complex and highly controlled technique" (hah!) applies a year or so later when it's decided that it might be time to determine if the loads have migrated.

Come now: Is this "Mechanical Voo-doo" really how we want to entrust the safety of our people and the availability of our plants? Following this I wouldn't be surprised if somebody proposes checking rad levels in vaults by measuring the viscosity of a 'possum's spit after being inside for two turns of a purple egg timer sad

Ciao,

HevïGuy
www.heviitech.com

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