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Boiler Explosion - St. Louis Box Co. - What do you think of CSB Report

Boiler Explosion - St. Louis Box Co. - What do you think of CSB Report

(OP)

I have some problems with this report about this deadly disaster.....

Who else (with boiler experience) has comments, recommendations ?

Should all Clayton Boilers be recalled ????

http://www.csb.gov/assets/1/19/Factual_Investigati...

MJCronin
Sr. Process Engineer

RE: Boiler Explosion - St. Louis Box Co. - What do you think of CSB Report

It sounds to me like this is an issue of lack of inspection, and the repair/engineering contractor not doing due diligence. I would find it hard to pin this on Clayton when the owner neglected to make the right calls with vessel maintenance.

Rant: Why on earth would they not just eat the cost of replacing the whole bottom head at the time of the repair? Did they even get thickness readings on the rest of the vessel? I fully understand using window/inserts but that only works if the rest of the vessel has good metal to work with. They could have at least gotten a rough corrosion rate. And why did they start up that morning if they knew they had repairs that afternoon? The only thing I think Clayton should do any differently is ensure that the vessel skirt has a manway, but I don't even know if that was Clayton's call.

RE: Boiler Explosion - St. Louis Box Co. - What do you think of CSB Report

The report is only an update and by no means complete it will take several years as is typical with bureaucratic reports. I had no technical concerns with the update nor any feeling regarding recall of SCR or blame regarding Clayton. The City of St Louis is at fault become of no inspection requirements as with other Jurisdictions.

RE: Boiler Explosion - St. Louis Box Co. - What do you think of CSB Report

I would certainly like to know why the head corroded so much while the vessel walls had little corrosion. The condensate level was above this area.

RE: Boiler Explosion - St. Louis Box Co. - What do you think of CSB Report

I would speculate, as a metallurgist, that the corrosion to the SCR bottom head region was caused by oxygen cell pitting based on the level of condensate that could form during off-line conditions. The rather rough surface suggests this type of off-line corrosion pitting damage that results in general wastage to carbon steel.

RE: Boiler Explosion - St. Louis Box Co. - What do you think of CSB Report

IMO, The owner didn't address the water quality issue caused the corrosion at the vessel bottom. And, after the repair, the procedure might include a routine wall inspection of the vessel bottom, which could provide a early sign of the wall thinning problem.

RE: Boiler Explosion - St. Louis Box Co. - What do you think of CSB Report

Looks like a failure of several defense-in-depth barriers to me.

First, the owner should have followed up on their emergency repair with either increased inspections (they could have boroscoped the inside of the vessel during a yearly outage), increased water chemistry oversight (learn and better control what was driving the corrosion), and/or make a full repair of the vessel.

Second, the City of St. Louis failed to uphold it's own Mechanical Code, which did require the vessel to be inspected. While the city code is weak regarding inspections (Inspections shall be as thorough as circumstances permit? Come on...), the NBBI commissioned inspectors would have still caught enough from a cursory glance to see there were issues (such as the big hole in the vessel skirt, for starters). From there, they would have been able to follow the repair via their own permit process and been able to follow-up appropriately.

Finally, as boofi stated, I have no idea why the owner felt the need to fire the process back up after shutting it down specifically due to the observed leakage in the SCR. Any plant manager looking at the two distinct leakage areas clearly originating from the 6 inch region of original vessel bottom head should know you're in the "danger zone" already.

The original manufacturer, which I assume was not involved in the repair or decisions following the repair, very likely did not design this vessel to operate this long originally. Being that this system was installed back in the late 1960s, I'm guessing it's original design life ended around 2006 to 2008.

I agree the report is bureaucratic and "politically correct" in its tame approach to so many obvious failures.

RE: Boiler Explosion - St. Louis Box Co. - What do you think of CSB Report

DSB123

As required by NB-263, RCI-1, RULES FOR COMMISSIONED INSPECTORS (RCI-1).

Each Repair Inspector performing inspections of repairs and alterations required by the NBIC and each
Authorized Inspector performing inspections required by the ASME BPV Code shall maintain an Inspector
Diary. The purpose of the diary is to provide a record of the Authorized Inspector’s/Repair Inspector’s activity
and to support continuity of inspections.

Entries in the Inspector Diary shall:
a) Provide a clear indication of the nature and extent of the Authorized Inspector’s/Repair Inspector’s
activities and inspections made, detailing corrections and any other pertinent data that will
be useful to him and his employer. Information to be recorded shall include a description of the
item inspected, the type of observations made, and the results of the inspection.
b) Be completed daily or at each inspection visit by the Authorized Inspector/Repair Inspector.
c) Include the Authorized Inspector’s/Repair Inspector’s signature or initials, the date, and the
Inspector’s National Board Commission number.
d) Be available for reviews and investigations.
e) Meet the requirements of the Authorized Inspector’s/Inspector’s employer

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