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Power plant explosion in CT
3

Power plant explosion in CT

Power plant explosion in CT

(OP)
A sad accident, details still coming out. There may be more casualties.

Only few miles from me, but I have no other insight.
 

Rafiq Bulsara
http://www.srengineersct.com

RE: Power plant explosion in CT

Good grief!!  On Sunday no less?

How do you get an explosion that big in a gas power plant?
Did they charge the whole system with an un-ignited fuel air mix?


Sounds like it:

Quote:

"They were doing the firing of the engines this morning and so something went wrong and it blew up and flames came shooting up almost as tall as that stack," she told the station.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Power plant explosion in CT

(OP)
Local TV news reports it was a natural gas explosion. There was some kind of a test scheduled and something went wrong.

There were 50-100 people around the 'scene' and many were flung 30-50 feet away....

 

Rafiq Bulsara
http://www.srengineersct.com

RE: Power plant explosion in CT

Thanks Rafiq. A bad day for the workers there. I hope the investigators can establish the root cause so others can learn.
  

----------------------------------
  
If we learn from our mistakes I'm getting a great education!
 

RE: Power plant explosion in CT

Time for guessing.

Generally these types of disasters are caused by a chain of events, not just one, or they would be far more common.

Perhaps screwing with the DCS ran the entire engine and stack assembly full of air/fuel then they skipped the purge cycle?

Keith Cress
kcress - http://www.flaminsystems.com

RE: Power plant explosion in CT

"Construction workers had to move 1.6 million yards of earth and rock to claw out a 137-acre site for the plant on land owned by Middletown trash czar Phil Armetta. He's a former partner in the project who withdrew after he was convicted in a federal crackdown the trash industry."

Can you say "Sopranos"?


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln  
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies  

RE: Power plant explosion in CT

Whoa!!!!

This one hits way too close to me.  I try to reveal as little about my personal self on these sites, but I have a very strong connection to just such a site in the Middletown area, although those don't look like the type of stacks I would recognize nor is the quoted unit MW size quite right for my situation.  But the rest is.  A lot of the 'buzz words' that the reporters used are part of my daily lexicon.  

I can't get the video to run, but I can see the stills, and some of it looks familiar.

None the less, the thought remains that this is a potential at any site I visit and could have been me instead of those poor lads.

Way too close for comfort.

rmw

RE: Power plant explosion in CT

My understanding (from on line)is that it was a gas explosion during gas blow the unit wasn't running.  Often actual gas volume and pressure is needed to clean the gas line.  It is normally vented to atmosphere but i could see where a combination of vent stack too low and weather conditions could cause a build up of gas.  Or perhaps it was just a comnno or garden gas leak.

RE: Power plant explosion in CT

In fact there are a rather large number of such events during commissioning tests, usually involving only electrical accidents, but nothing is reported in the media unless there is a loss of life.

In my time I have seen a 31 MVA transformer blow up, one person killed in a 60kV indoor substation, two hydroelectric accidents, one of which flooded a station up to tailwater level, an excitation transformer destroyed by wrong connected secondary cables, an electrician burned in a 415V panel, a grounding switch closed in on a live 154kV line, and numerous near-misses.

And that was all before we had computers and software dependent control systems...

regards, rasevskii

RE: Power plant explosion in CT

Wait for the investigation guys. I can remember how angry I was at the erroneous speculation, and the idiot reporters who encouraged it, after the huge explosion at my former plant. At the time it amazed me how many people were experts on power plants but had never actually been in one.
  

----------------------------------
  
If we learn from our mistakes I'm getting a great education!
 

RE: Power plant explosion in CT

(OP)
amptramp:

The event you posted is a different one from the one in the OP. Different State, day and company.

Rafiq Bulsara
http://www.srengineersct.com

RE: Power plant explosion in CT

rbulsara

I apologize for the lack of clarity. The link to the "story" I posted was related to the CSB link posted immediately above it. I was providing background information for the CSB article.   

RE: Power plant explosion in CT

And both of amptramp's links are about the type of explosion that happen at the plant in CT.

RE: Power plant explosion in CT

(OP)
I see the erring similarities! Although not much details have come out of the CT incident.

But you cannot make codes against stupidity.

I am flabbergasted to read this in amptramps' link:

Quote:

CSB investigations supervisor Donald Holmstrom said his team made the recommendations to the board during the course of the ConAgra investigation after discovering gaps in the fuel gas codes. "Purging flammable gases into building interiors is a recipe for disaster. At ConAgra, we determined the accident would not have happened had the gas been vented safely outdoors through a hose or pipe." Mr. Holmstrom noted that since the June 2009 accident, ConAgra has instituted strict policies on purging, requiring it be done to safe outdoor locations.

NO SH&%!

I hope purging flammable gas in building interiors is not as common as it is stated above.

  

Rafiq Bulsara
http://www.srengineersct.com

RE: Power plant explosion in CT

I am with Scotty on this one.  Way too many speculations by people who can barely spell power plant.  We do know that a terrible event has happened, but I tend to wait until those who "speak the language" give the official report.  I've just seen too much garbage (rubbish) put out by media journalists.

rmw

RE: Power plant explosion in CT

Agreed.....but at least we are not the media!

Alan

RE: Power plant explosion in CT

Well, I rather disagree.  I'm not with Scotty on this.

  Discussing things like this disaster is how we learn.  Saying "don't talk about it until some investigator/tion is done" is NOT helpful and is a poor way to learn anything.

  Likely we would never discuss it a year after the fact.  How do the investigators do this?  They start speculating, (educated guessing), the moment they know anything.  Then they fastidiously try to keep an open mind.  They don't go take pictures and then stare at them until The Cause jumps out at them.

I'd never even heard of purging as being a problem until yesterday.  It could be it wasn't the actual problem, I don't care.  If it isn't I'll learn something else!

Sometimes people who say don't, "discuss or speculate", have been caught in discussing and speculating who's at fault  and are leery of preliminary discussions.   I don't blame them a bit and can understand their reticence.

Blame is not what I'm interested in, I'm interested in science and technology and learning about possible work place hazards.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Power plant explosion in CT

Well stated, Keith. I also agree with racobb's statement, but in the literal sense. Hopefully we here are better qualified to discuss such things than the average reporter.

Alan
"The engineer's first problem in any design situation is to discover what the problem really is." Unk.

RE: Power plant explosion in CT

For several reasons, I am with both Scotty AND Smoked. Waiting for a (hopefully) qualified view on what happened is good and what we usually do.

But I have been through several investigations where the 'qualified view' is anything but 'qualified'. In most cases, there was an insurance company steering the investigation and in one case, the Union had the final say.

I actually once could prove that a rather big fire in an electrical room in a power plant didn't start at all as the insurance company and the VBCC* said it started. Most of that investigation involved own searches (many photographs taken) and also discussing with people that were no experts in the particular field of technology, but had made observations that added details to the pcture.

That is, as I see it, Smoked's view.

I also fully agree with Scotty that speculations in the tabloids very seldom add any value to an ongoing investigation and that we, qualified or not, usually are in no better position to speculate than their journalists. Simply because we very seldom have the facts.

This unnecessary and sad accident verifies again that no security standards or rules can replace education, craftmanship, insight and experience.


*Very Big Consultant Company

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: Power plant explosion in CT

Hi Keith,

My intent wasn't to stifle intelligent discussion, especially as a few folks here are in the general area of this plant and will likely pick up some information, but PLEASE don't put much faith in anything you read or hear in the media.

I mentioned an accident where I used to work. That accident killed three of our friends, colleagues and critically injured a fourth. In the hours after the accident the media interviewed some brainless moron who stated that it was a gas cyclinder explosion, presumably because that was all he could think of which might go bang, and straight after that the stupid reporter authoritavely blathered some complete crap about the explosion having taken place inside the turbine hall. The plant didn't have a turbine hall, and it was a big transformer which blew up. Anyone who didn't know the plant would have listened to this report and taken it at face value. I threw something - the remote control, I think - at the TV in rage and walked out.

Don't trust the opinion of anyone in the media to be anything other than convincing lies. Look at the photographs, listen to the people qualified to comment, and judge for yourselves.

/rant
  

----------------------------------
  
If we learn from our mistakes I'm getting a great education!
 

RE: Power plant explosion in CT

ScottyUK, sometimes not only reporters, but even qualified people can talk nonsense. I remember a case from first years of my career as commissioning engineer. It was in middle of 80's, when I worked as commissioning engineer in specialized commissioning company. We made rehabilitation of 110 kV switchyard of power plant. As part of the work we energized power plant auxiliary services transformer - 110/6,3kV, 16 MVA. Transformer was not new, so we did only maintenance tests on it, as well as change of relay protections. Transformer was put in operation around 11 p.m. and we went home. In the morning at 6,30 we met with a colleague in a company bus on the way back to the plant and he told me that in the night transformer exploded  with no one protection operated ! I was really surprised, as I personally did setting and testing of all relays and everything was OK. We came to the plant, ran in control room and asked operators from daily shift what happened with the transformer. They said "Nothing, they energized it during the night shift and it is on-load now". I came to the control board, saw ammeter showing about 50% of full load and still didn't know whom to believe.
What have been the actual situation? After we left the plant around 1 p.m. operator from night shift looked on remote temperature indicator and found that it shows 105 degree Celsius. Overtemperature protection have to trip, so he went down to the transformer and found local indicator showing about 60 degree (it was in January, very cold like it is now!). So he decided to call National Dispatching Center and report them that discrepancy. They say that probably it is an instrumental mistake, but to be on safe side ordered him to check hourly what is the situation. After that dispatcher in NDC phoned home (3 a.m. !) the CEO of our holding company and told him that transformer we commissioned is overheating and nothing operates. CEO immediately phoned General Manager of our company and told him that transformer exploded and protections didn't trip. Our GM phoned my colleague and ... you know the rest. I have to add that after 2-3 checks during the night operators understood that it is really instrumental mistake and forgot to say to colleagues from daily shift about the case. Of course something have been written in the logbook, but who wants to read about the solved problems of previous shift!
Most funny point in that stupid chain was that it was not our fault. We were external contractors and did our job perfectly. Remote temperature indication was obligation of Control Instruments Team of the power plant. These guys simply replaced the indicator without going in troubles to calibrate it together with the sensor!

Well, after we calm down we found the story quite funny, but these 30 minutes we traveled in the morning to the plant were very, very long!

------------------------
It may be like this in theory and practice, but in real life it is completely different.
The favourite sentence of my army sergeant
 

RE: Power plant explosion in CT

Tangent: I suppose that the temperature transducers were Ni100 and that the new instrument was for Pt100. Had exactly that several years ago. The VBCC (again) checked the 6 kV grid and found lots of problems - unbalanced, phase shifts, around 20 percent harmonics.

I found that they had measured phase-gnd and also that the transducers were Ni100 and not Pt100. The interesting thing is that the VBCC saw no problem with 20 % voltage distortion. Neither with severe phase shift and voltage unbalance.  BTW: VBCC reported directly to the production manager - not to electrical department.

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: Power plant explosion in CT

My post agreeing with Scotty was in reference to the media reports.  While the true cause is still conjecture, we who 'speak the language' can engage in a discussion of such conjecture without actually thinking it is more than what it is.  To Scotty's point, who knows what "expert" at the plant gave the meida the buzz words that they did use in that report.  The blackened surfaces on that one HRSG and the blown out building panels probably say a louder message to us than the words in a news account by suzie que reporterette.

rmw

RE: Power plant explosion in CT

Well, I'm heading over to Slashdot to  discuss this. Where we formulate our conclusions without even having to read TFA. winky smile  

RE: Power plant explosion in CT

To be scientific ... like my brother says, again, you are talking of technicalities!

And unfortunately, many, many times he says so, it is well brought.  

RE: Power plant explosion in CT

First- My condolences to the family and friends of the deceased and injured.

A former co-worker who is an experienced startup engineer was working on commissioning this plant. (Our company was not involved.) Here's some information from a personal conversation he had with a friend in my office. (It's second hand information; may be inaccurate.)

Gas line blows were in progress, scheduled for Sunday morning when minimal personnel were on site. Lines were vented outside to a safe area. The first blow using pipeline gas was done  without problems, the line secured and the coupon target removed for inspection. (That's the tattletale metal target at end of line that collects evidence of any dirt or debris in the pipe.) The construction workers were told to standby and not start the next blow until the startup engineer returned. He inspected the coupon in the office and went into the control room.  Then the explosion occurred.  He regained consciousness lying outside the building uninjured but covered with debris.  

He thinks the crew may have started the second blow without checking the valve line up and speculates that valves leading to pipes in the building may have been opened.

There's probably some memory loss from his concussion and I'm sure he is still very distraught at the deaths that occurred.

Another reminder to pay attention to our designs and our instructions to others on how to implement them.
 

RE: Power plant explosion in CT

Is there normally anything out at the ends of the pipes that route the blow outside?  Like blowers to help disperse the gas or are they just pipes/hoses that end?

Keith Cress
kcress - http://www.flaminsystems.com

RE: Power plant explosion in CT

what is purge cycle ? i cant find anything...

RE: Power plant explosion in CT

That is when you get rid of air (or oxygen) in a system before you put explosive prone gas into it.  

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: Power plant explosion in CT

For Keith,

No, normally the gas just vents to atmosphere.

Even during normal operation of a gas turbine, when the unit trips, or shuts down, the length of pipe between the main gas shut off valve and combustor is just vented to atmosphere with a motor operated vent valve.  The vent pipe is normally quite high but the exact height depends on various factors

RE: Power plant explosion in CT

The main purpose of gas blows is cleaning the gas piping after initial assembly is complete.  It is common to use the pipeline gas as a cleaning medium although compressed air might be used until the final purge.  

Temporary piping is added to the ends of the pipes to route the discharge outside and up to a safe elevation.  Hoses have too much pressure drop and may not handle the mechanical forces.  The discharge piping and temporary supports should be designed to allow the maximum flow with minimal pressure drop and no pipe movement as the gas slams into bends.   High velocity is needed to properly clean the pipe and any restriction slows the flow. It's like an  impulse test on a transformer.  You want a fast, steep wave front.  

A silencer/muffler is placed on the outlet to reduce the exhaust noise, mounting that can be a problem.

The process is a little more complicated than it sounds.  Complications also mean there are more places to go wrong.

I may have some of the details/reasoning wrong. I've usually left the site when gas blows are in progress.
 

RE: Power plant explosion in CT

Thanks GT and rc for the info.  Most interesting all this!

I ignorantly always thought that you just plumbed everything up and turned on the 'main' gas valve.  The burner controls  go thru their purge cycle venting the combustion chamber and stack, then open the controlled gas valves for a start attempt.  Maybe the first few start attempts fail because of air in the lines not supporting combustion.  Eventually the the gas shows up and ignition occurs and you're off to the races.

It seems like the purges here are for 'pipe cleaning'.

I can also envision that in a large pipe, say 6" or bigger, that during the start attempts as you run out blocks of air and some gas that eventually you might have an explosive mixture in the plumbing near the burner.  Could the burner flame backfire into the gas line?  Is this a different reason to purge?

Keith Cress
kcress - http://www.flaminsystems.com

RE: Power plant explosion in CT

Pipe cleaning by blowing gas is a one time only (normally) event during first commissioning.  

After the unit is commissioned and in operation there is a different type of purge each time the unit is started.

When the GT is not operating (standstill) the length of pipe between the trip valve (last valve before combustor) and the main shutoff valve is vented by a block and bleed system.  

During startup there is a purge about 800-1500 RPM depending on the GT type.  This is achieved by using the SFC to turn the generator as a motor.  After a predermined time (I believe 5 HRSG air changes required by NFPA - about 5 minutes) the sequence continues and the vent valve is closed and the main valve opened.  Gas is sent to the trip valve immediately prior to the combustor and when that valve opens the ignition system is turned on.  This is normally a propane system with spark plug.  Once this ignition system has started there is a perdetermined allowed time for main flame (about 10 secs).  If the flame detectors do not detect flame within this time, the unit trips automatically and the whole cycle must be reinitiated.

During shut down the gas shut off valve is closed, the trip valve is closed and the vent valve vents the air in the pipe between the shut off valve and the trip valve to atmosphere

For those GTs in simple cycle (no HRSG) there is no purge required as long as the stack is immediately after the GT exhaust (no long duct section).

RE: Power plant explosion in CT

To address your question about combustible mixtures between combustor and main valve, this is normally taken care of by check valves and by the normal venting that occurs when a GT coasts down and the block and bleed system.

I did have a strange experience once though when some water injection check valves were installed backwards and gas filled up the top 20% of a 500,000 gallon water tank.  I was told that one of the reasons there wasn't an explosion was that the top of the tank was 100% gas.

RE: Power plant explosion in CT

An experienced startup engineer corrected me: gas purge is only used on outdoor systems where a gas leak is not as dangerous.  

Our procedure on any indoor piping is to clean with high pressure air (1000 psi), reassemble piping, leak test under pressure, purge with nitrogen, then displace nitrogen with gas just prior to first firing of the equipment.  

RE: Power plant explosion in CT

GTstartup,

So, how did you get the gas out of the tank.  I think some of the hairiest moments I have ever spent were after a boiler flame-out when the fuel didn't trip immediately filling the entire boiler, back passes and all with gas.  Not a problem at that point.  Pure gas isn't explosive.  

BUT, you ultimately have to purge it and when the purge starts and the air begins to displace and mix with the gas, when (if) it goes stoichiometric, kaboom.  Not always, but potentially always.

Those were moments when certain body parts puckered the worst.

rmw

RE: Power plant explosion in CT

And, that last post wasn't intended to take the thread off topic, but to amplify on the problem of gas/air mixtures especially in the presence of any potential ignition source, even if it is nothing more than static electricity.

rmw

RE: Power plant explosion in CT

RMW,  we opened the tank vent and filled the tank with water.  Stand back and fingers crossed.     

RE: Power plant explosion in CT

Those who are familiar with my former site will remember the cranked shaped of the stacks - roughly two 135[°] bends. On one occasion an ex-colleague 'did something'* with the control logic and nearly straightened out the stack after detonating a fuel-air mix somewhere in the expansion duct to the HRSG. The vibration probes on the other side of plant picked up the event. A bit of damage to the front end tubes, but at least it wasn't the full HRSG which went bang.

*Something the top brass didn't need to know about. wink
  

----------------------------------
  
If we learn from our mistakes I'm getting a great education!
 

RE: Power plant explosion in CT

Thanks for the update Rafiq.
  

----------------------------------
  
If we learn from our mistakes I'm getting a great education!
 

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