Saturday, November 14, 2009

Who should be Responsible for Proper Pressure Vessel Design?

I was a bit shocked by the video message I received from CSB Chairman John Bresland late Thursday afternoon. Mr. Breisland was concerned about an increasing number of fatalities and injuries in connection catastrophic failure of pressure vessels in the USA. Appearantly in the USA the responsibility with regulating the design of pressure vessels rest with the individual states. This really chocked me!

First of all, in my view the proper design of pressure vessels is a worker safety issue – and a neighbor safety issue – and should therefore be the responsibility of OSHA and EPA, i.e. national institutions. This is the way it is here in Denmark, and to the best of my knowledge in the U.K. But at least the engineering profession in the USA have got together an defined the ASME Pressure Vessel Codes. Even the Danish national guidelines for construction and production of pressure vessels refer to the ASME codes as suitable approach for design of pressure vessels. These guidelines are issued by our equivalent of OSHA. Therefore, it was a shock to me to learn that individual states are responsible for how pressure vessels are designed in the USA.

How can one expect all these states to hire the necessary expertise to be concerned about pressure vessels? Local politicians properly assume, that pressure vessels are designed properly, and for many this is likely the case. At least all those pressure vessels, which are installed and operated by companies with activities in many states.

To me the logical thing to do with respect to pressure vessels would be for the ASME Pressure Vessel Code become a standard just like ISA SP84, which applied by chemical plants and refineries across all states. But maybe there is something, which I don't understand about the distribution of powers between the federal and state levels in the USA.

References:
1.CSB (2009): “Safety Message: Without Safeguards, Pressure Vessels Can Be Deadly”, CSB Newsroom, November 09, 2009, URL: http://www.csb.gov/newsroom/detail.aspx?nid=293 (viewed 2009-11-13).
2.At (1996): “Konstruktion og fremstilling af trykbeholdere” (Construction and production of pressure vessels), At-anvisning nr. 2.1.2.0-2, December 1996, URL: http://www.at.dk/sw5106.asp (viewed 2009-11-14) (At is the Danish equivalent of OSHA).

Sunday, October 25, 2009

Is any learning at all from process incidents really taking place?

On Thursday October 22nd, 2009 CSB News [1] reported, that the CSB was dispatching a three person team to Salt Lake City to investigate a fire at the Tesoro refinery in that city. The fire appearantly involved liquid discharge to a flare stack. The discharge resulted in a pool fire around the base of the stack. The fire resulted in no injuries to person inside or outside the refinery. The only public inconvenience was the temporary closure of an interstate highway and a commuter rail line. Equipment damage involved a trailor and other equipment close the base of the flare stack. Refinery and municipal firefigthers extinguished the fire within an hour. Currently no information is available about the quantity of liquid hydrocarbons released in the event. So why this rush to investigate a small fire, which occurred on Wednesday evening?

In their news release the CSB states, that they want to investigate similarities between the fire at the Tesoro Refinery and the March 2005 explosion and fire at BP's Texas City Refinery[2], which also involved discharge of hydrocarbon liquids to a system designed to handle only gaseous discharges. There is also similarities to the explosion and fire at Texaco's Milford Haven Refinery[3] in southwest England more than a decade ago. This event also involved discharge of hydrocarbon liquids to a system designed only to handle gaseous discharges. This event also involved a restart of the refinery after a power outage. Properly there are other similar events.

Earlier in the year CSB [4] dispatched a team to investigate a explosion and fire at another Utah refinery. This event was caused by hydrocarbon vapors escaping through vents in an atmospheric storage tank and creating a vapor cloud in the tank farm. There are striking similarities between this event, and the explosion and fire at Buncefield storage facility in the UK in December 2005 [5].

Therefore it seems reasonable to ask if any learning from accidents in the process industries is really taking place? or if most facilities has an this will not happen here attitude?

After the explosion and fire in March 2005 at BP's Texas City Refinery the reaction of many properly was: Blowdown stacks releasing to the atmosphere? We eliminated them more than 10 years ago. However, this kind of thinking is shortsighted, and eliminates an opportunity to learn from the event. The event at Texas City involved too much hydrocarbon liquids entering a gas-liquid separator, resulting in liquid entrainment in the gas stream from the separator. So learning from BP's Texas City event also involve asking do we have questions such as: Do we have any gas-liquid separators, which cannot cope with the maximum conceivable inflow? Can our flare system handle a flow equivalent to the total feed flow to one or more of our distillation towers? Only be asking though questions about inconceivable events can you learn from accidents experienced by others.

Interestingly, both the event at Texaco's Milford Haven Refinery and the event at BP's Texas City Refinery could have been prevented by a simple mass balance monitoring scheme looking at estimated tower inventory based on measured feed and product flows. Furthermore already the computer control systems of the late 70's and early 80's where sufficiently powerful to implement such monitoring schemes. So why are they rare even in the 21st century?

It furthermore seem reasonable to ask what mechanisms are in place to learn from events in other parts of the world?

References

  1. CSB News Release (2009): ”CSB to Examine Fire at Tesoro Refinery in Salt Lake City”, October 23rd, URL: http://www.csb.gov/newsroom/ (viewed 20091023).

  2. BP America (2005): ”Texas City Investigation Reports”, December 9th, URL: http://www.bp.com/genericarticle.do?categoryId=9005029&contentId=7015905 (viewed 20091025).

  3. HSE (1997): ”The explosion and fires at the Texaco Refinery, Milford Haven, 24 July 1994: A report of the investigation by the Health and Safety Executive into the explosion and fires on the Pembroke Cracking Company Plant at the Texaco Refinery, Milford Haven on 24 July 1994”, ISBN 0 7176 1413 1. See also accident summary on HSE home page http://www.hse.gov.uk/comah/sragtech/casetexaco94.htm

  4. CSB News Release (2009): ”CSB Investigative Team En Route to Utah Refinery Explosion”, January 13th, URL: http://www.csb.gov/newsroom/ (viewed 20091025).

  5. MIIB (2006): ”Buncefield Investigation Homepage”, URL: http://www.buncefieldinvestigation.gov.uk/index.htm (viewed 20091025).