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Csb Recomendations On Bp Incident


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#1 rxnarang

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Posted 02 November 2006 - 08:18 AM

Houston, Texas, October 31, 2006 - On a unanimous vote of 5 to 0, the U.S. Chemical Safety Board (CSB) today issued new safety recommendations calling on the U.S. oil industry to improve safety practices for refinery pressure relief systems, eliminating the type of atmospheric vent that caused the hydrocarbon release and explosions that killed 15 workers and injured 180 at the BP Texas City refinery on March 23, 2005.

The accident occurred during the startup of the refinery's octane-boosting isomerization (ISOM) unit, when a distillation tower and attached blowdown drum were overfilled with highly flammable liquid hydrocarbons. Because the blowdown drum vented directly to the atmosphere, there was a geyser-like release of highly flammable liquid and vapor onto the grounds of the refinery, causing a series of explosions and fires that killed workers in and around nearby trailers.

The announcement followed by one day the release of new preliminary findings in the CSB's ongoing, independent federal investigation of the accident. The Board's final report is expected in March 2007.

The first recommendation calls on the American Petroleum Institute (API), a leading oil industry trade association that develops widely used safety practices, to change its Recommended Practice 521, Guide for Pressure Relieving and Depressuring Systems. The revised guidance should warn against using blowdown drums similar to those in Texas City, urge the use of inherently safer flare systems, and ensure companies plan effectively for large-scale flammable liquid releases from process equipment.

Further recommendations call on the U.S. Occupational Safety and Health Administration (OSHA) to establish a national emphasis program promoting the elimination of unsafe blowdown systems in favor of safer alternatives such as flare systems. OSHA should also emphasize the need for companies to conduct accurate relief valves studies and use appropriate equipment for containing liquid releases, the Board said. A national emphasis program results in a concerted inspection and enforcement effort around a specific safety hazard.

CSB Chairman Carolyn W. Merritt said, "Unfortunately, the weaknesses in design, equipment, programs, and safety investment that were identified in Texas City are not unique either to that refinery or to BP. Federal regulators and the industry itself should take prompt action to make sure that similar unsafe conditions do not exist elsewhere. Taken as a package, the new CSB safety recommendations we issued today will provide for effective guidance, outreach, and regulatory enforcement to reduce the risk of similar tragedies in the future."

Lead Investigator Don Holmstrom noted that the ISOM unit blowdown drum at the BP Texas City refinery had a number of safety problems. "This drum simply wasn't large enough to hold all the liquid released from the distillation tower if it flooded. Not only could the blowdown drum not hold enough liquid, but it could not assure safe dispersion of flammable vapors through the vent stack," Mr. Holmstrom said. He added that safe dispersion of flammable vapors would require a high exit velocity that could never be guaranteed when handling multiple discharges through a complex piping system.

That design weakness resulted in unsafe conditions in Texas City prior to the March 23, 2005, accident. The CSB documented eight previous releases of vapor from the same blowdown drum from 1994 to 2004. In six cases, dangerous flammable vapor clouds formed at ground level but did not ignite; in two other cases, the blowdown stack caught fire.

Prior to the 2005 accident, BP operated 17 blowdown drums for disposal of flammable materials at its five U.S. refineries. BP has since pledged to eliminate all the drums and use safer alternatives, such as flare systems. A properly designed flare system includes an adequately sized vessel for containing liquids and a stack with a flame for safely burning flammable vapors, preventing an uncontrolled fire or explosion near personnel. Flares are the most commonly used disposal system for flammable releases in refineries.

In 1992, the Texas City refinery, then owned by Amoco Corporation, was cited by OSHA for operating an unsafe blowdown drum. However, Amoco succeeded in having the citation and fine withdrawn, asserting that the drum complied with accepted industry standards embodied in API Recommended Practice 521. Today's recommendation from the CSB would strengthen that guidance document so that it would explicitly warn against such unsafe blowdown systems.

The CSB is an independent federal agency charged with investigating industrial chemical accidents. The agency's board members are appointed by the president and confirmed by the Senate. CSB investigations look into all aspects of chemical accidents, including physical causes such as equipment failure as well as inadequacies in safety management systems. The Board does not issue citations or fines but does make safety recommendations to plants, industry organizations, labor groups, and regulatory agencies such as OSHA and EPA. Please visit our website, www.CSB.gov.

For more information, contact Daniel Horowitz at (202) 441-6074 cell (Houston) or Sandy Gilmour at (202) 261-7613 / (202) 251-5496 cell.

#2 Art Montemayor

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Posted 02 November 2006 - 06:38 PM

To avoid making a long, redundant recital of what I’ve stated in the past, I’m simply going to make my comments in dark blue next to the referenced item. I can’t apologize if my common sense and engineering analysis ability makes it embarrassing and uncomfortable for certain individuals. The truth is the truth; the facts are the facts:

The first recommendation calls on the American Petroleum Institute (API), a leading oil industry trade association that develops widely used safety practices, to change its Recommended Practice 521, Guide for Pressure Relieving and Depressuring Systems. The revised guidance should warn against using blowdown drums similar to those in Texas City, urge the use of inherently safer flare systems, and ensure companies plan effectively for large-scale flammable liquid releases from process equipment.
[Flare systems are not inherently safer than well-designed blowdown drums. In actual fact, flare systems must use a blowdown drum or a similar “Knockout Drum” – which does the same thing: separates out the heavier liquids which the flare cannot burn (as in the Texas City BP incident). Flares are designed to burn gas or vapor – not liquids! The TC BP blowdown drum failed to mitigate the incident not because it is inherently unsafe. It failed to mitigate the disaster because it was TOO DAMN SMALL! If it had been big enough, it would have caught all the hydrocarbon liquids spewed out of the Isomerization Unit. A flare system designed to mitigate this case would wind up with – guess what? – a blowdown drum big enough to contain all the possible liquids spewed out of the Isomerization Unit! Duh? ].

Further recommendations call on the U.S. Occupational Safety and Health Administration (OSHA) to establish a national emphasis program promoting the elimination of unsafe blowdown systems in favor of safer alternatives such as flare systems. OSHA should also emphasize the need for companies to conduct accurate relief valves studies and use appropriate equipment for containing liquid releases, the Board said. A national emphasis program results in a concerted inspection and enforcement effort around a specific safety hazard. [We don’t need OSHA to “promote” anything; we need for OSHA to MANDATE the sizing of proper separation and containment vessels. If Congress is needed to pass laws that OSHA can enforce, then it should be stated as such. Otherwise, nothing will come out of this.]

CSB Chairman Carolyn W. Merritt said, "Unfortunately, the weaknesses in design, equipment, programs, and safety investment that were identified in Texas City are not unique either to that refinery or to BP. Federal regulators and the industry itself should take prompt action to make sure that similar unsafe conditions do not exist elsewhere. Taken as a package, the new CSB safety recommendations we issued today will provide for effective guidance, outreach, and regulatory enforcement to reduce the risk of similar tragedies in the future." [All the necessary safety guidelines and recommendations are already in API 521. Good, experienced engineers know and design for the worse case scenarios and document all relief cases according to OSHA requirements when dealing with hazardous chemicals – as in this case. Where are the required relief documentation calculations and files? Why doesn’t OSHA report the status of what they are supposed to oversee and implement? Was the blowdown drum capacity too small for the worse case scenario? Obviously it was! But where was OSHA in supervising and enforcing the proper sizing and documentation? A lot of basic, in-place, and embarrassing information and data is being kept from the general public. We, as engineers know this.]

Lead Investigator Don Holmstrom noted that the ISOM unit blowdown drum at the BP Texas City refinery had a number of safety problems. "This drum simply wasn't large enough to hold all the liquid released from the distillation tower if it flooded. Not only could the blowdown drum not hold enough liquid, but it could not assure safe dispersion of flammable vapors through the vent stack," Mr. Holmstrom said. He added that safe dispersion of flammable vapors would require a high exit velocity that could never be guaranteed when handling multiple discharges through a complex piping system.
[Gee, Don Holmstrom must be reading my threads on the Cheresources Forums. Now he’s admitting that the damn blowdown drum wasn’t big enough! So where is OSHA in all of this? OSHA is supposed to be implementing the mandate (law) that all relief devices have to be documented and justified as to size and capacity. Why are these facts not being mentioned or discussed?]

That design weakness resulted in unsafe conditions in Texas City prior to the March 23, 2005, accident. The CSB documented eight previous releases of vapor from the same blowdown drum from 1994 to 2004. In six cases, dangerous flammable vapor clouds formed at ground level but did not ignite; in two other cases, the blowdown stack caught fire. [Now we are told that the CSB already looked into EIGHT previous releases from the same blowdown drum. Didn’t anyone in the CSB check the size and capacity of the blowdown drum in regards to the worse case scenario capacity required? They had eight previous opportunities to do this simple and everyday calculation to check the ability of containing such a worse case scenario. Why wasn’t a RED FLAG raised and OSHA advised that they weren’t doing their job in enforcing proper relief case mitigation?]

Prior to the 2005 accident, BP operated 17 blowdown drums for disposal of flammable materials at its five U.S. refineries. BP has since pledged to eliminate all the drums and use safer alternatives, such as flare systems. A properly designed flare system includes an adequately sized vessel for containing liquids and a stack with a flame for safely burning flammable vapors, preventing an uncontrolled fire or explosion near personnel. Flares are the most commonly used disposal system for flammable releases in refineries. [Now there is mention of what I’ve been stating: a flare system requires a properly designed knockout drum – or otherwise called a blowdown drum. If the flare knockout drum were the same size as the BP blowdown drum, a disaster would still be a probability. This proves my point that a blowdown drum, of itself, is not a “danger”. Had the blowdown drum been sized big enough, it would have contained the spewed liquid and mitigated the disaster. A flare is simply not enough to deter a similar incident. A big-enough knockout drum upstream of the flare is required.]

In 1992, the Texas City refinery, then owned by Amoco Corporation, was cited by OSHA for operating an unsafe blowdown drum. However, Amoco succeeded in having the citation and fine withdrawn, asserting that the drum complied with accepted industry standards embodied in API Recommended Practice 521. Today's recommendation from the CSB would strengthen that guidance document so that it would explicitly warn against such unsafe blowdown systems. [I don’t believe any serious and knowledgeable engineer is going to believe this statement that the CSB recommendation “……would strengthen the guidance document” and “explicitly warn”. We already know how to avoid such worse case scenarios: first we identify them, next we identify the capacity required to mitigate the scenario, and then we size the proper equipment to carry out the mitigation. It’s that simple and that direct. We also document all sizing and calculations as well as identification of all scenarios studied - to have them ready and up-to-date when OSHA makes an inspection of the facilities.]

#3 jom

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Posted 02 November 2006 - 10:20 PM



The CSB documented eight previous releases of vapor from the same blowdown drum from 1994 to 2004. In six cases, dangerous flammable vapor clouds formed at ground level but did not ignite; in two other cases, the blowdown stack caught fire. [Now we are told that the CSB already looked into EIGHT previous releases from the same blowdown drum

I read the CSB statement to mean they found these eight releases during their investigation into the March 2005 accident, rather than when they occurred.

John.



#4 gvdlans

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Posted 03 November 2006 - 01:13 PM

A flare would probably have resulted in a rain of burning liquids - not in a vapor cloud explosion, so that's a case of "out of the frying pan into the fire".

Anyway, I don't think I would have sized the relief system for a case where the tower would be completely filled with liquid. The high level protection on the column should have prevented this overfilling (together with the operating procedures). When assessing the Safety Integrity Level of the high level protection, I would not have considered the possibility that there would be manned trailers located next to the vent stack. When this would have been taken into account, you would end up with a SIL3 or even SIL4 (meaning redesign of the system...).

In reality, they did hardly have a high level protection on the column. Together with the relief system that was not sized for this case and the location of the manned trailers, it was a matter of time for a disaster to happen.

I wonder why it takes two years for the CSB to come with a final report...

#5 jom

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Posted 04 November 2006 - 04:47 AM

QUOTE (gvdlans @ Nov 3 2006, 01:13 PM) <{POST_SNAPBACK}>
I wonder why it takes two years for the CSB to come with a final report...


The final report will influence industry for decades. Let them take as long as they need to produce the best possible report. This is far better than reporting to a deadline.

John.


#6 pleckner

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Posted 04 November 2006 - 07:55 PM

Responding to whether this should have been a relieving scenario:

As API RP521 suggests, a 10-30 minute response time is a reasonable time period to wait for operator response. I have, in the past, looked at just this type of scenario. If I could fill the vessel (even a tower) within the time period, then yes, I would have designed my relief system for it. Of course, the big word is "IF" it filled within the time period. If it could not, then I probably wouldn't have considered it either....but not any more!! Time and time again we are shown how bad operator judgement can be or the type of "honest" mistakes that can be made.

#7 jom

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Posted 07 December 2006 - 06:09 AM

Art's thesis that a flare system must be designed to cater for the worst case flow, just as a knock out drum must be, is illustrated by the accident at Texaco refinery, Milford Haven, UK (1994):-

"The explosion was caused by flammable hydrocarbon liquid being continuously pumped into a process vessel that, due to a valve malfunction, had its outlet closed. The only means of escape for this hydrocarbon once the vessel was full was through the pressure relief system and then to the flare line. The flare system was not designed to cope with this excursion from normal operation and due to liquid breakthrough at the FCCU flare knock out drum, a failure occurred in the outlet pipe.

A total of 20 tonnes of a mixture of hydrocarbon liquid and vapour was released, which found a source of ignition about 110 m from the flare drum and subsequently exploded"

More:-

http://www.hse.gov.u...asetexaco94.htm

John.





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