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Letter from the Chevron refinery manager in Richmond explaining the company's decision to pick the chromium alloy called 9 chromium over another type of stainless steel material.
Nigel Hearne Chevron Richmond Refinery Manager Chevron Products Company 841 Chevron Way Richmond, CA 94801 Tel 510 242 4400 Fax 510 242 3515 Nigel.Hearne@chevron.com November 19, 2012 Mr. Bill Lindsay Richmond City Manager 450 Civic Center Plaza Richmond, CA 94804 Dear Mr. Bill Lindsay, We are writing with respect to the letter from the U.S. Chemical Safety and Hazard Investigation Board (“CSB”) to you, dated November 17, 2012. In the aftermath of the August 6, 2012 fire at the Richmond Refinery, Chevron U.S.A. Inc. recognizes that numerous parties are interested in not only the factors that gave rise to the incident, but also the steps that we are taking to prevent a recurrence. For these reasons, we have been open and transparent with respect to our incident investigation and our plans to repair damaged piping and other process equipment in the No. 4 Crude Unit. We initially met daily (now weekly) with interested governmental agencies to discuss the proposed work. During these discussions in early October, we first communicated our plans to replace all carbon steel piping in high temperature sulfidation (“HTS”) service within the fire-damaged area with a 9 chromium alloy (“9Cr”). As an initial matter, we agree with Richard Mitchell that the City of Richmond’s scope of review of the repair work is limited to the ministerial issuance of permits pursuant to Title 24 of the California Code of Regulations, which includes the Building, Fire, Mechanical, and Electrical Codes. Permits for process equipment, including for process piping in hydrocarbon service, are reviewed by the Fire Marshal for adherence to the National Fire Protection Association’s Flammables and Combustible Liquids Code (NFPA 30) to ensure that the selected equipment is approved for use in the proposed service under applicable industry standards. We understand, additionally, that in this instance the City has an interest in a transparent explanation of the factors underlying Chevron’s decisions on material selection. We are confident we have made the right decision, considering all the technical factors, in selecting 9Cr as the material of repair for this service. We appreciate the CSB’s acknowledgement of our excellent cooperation and our willingness to meet to further explain the technical basis for our decision to utilize 9Cr. We would hope that such a meeting could occur early this week so as to avoid any delays in the project that might November 19, 2012 Page 2 force the layoff of the men and women performing the work, especially given the upcoming holidays. In the interim, we wanted to provide some preliminary information with respect to our selection of 9Cr. As the entity responsible for assuring the safe operation of the Richmond Refinery, Chevron strives to continually improve its performance and considers inherently safer systems when appropriate. As part of these efforts, we take material selection decisions very seriously. Selecting materials for process units is a complex process that necessitates consideration of multiple factors, including operating conditions (particularly temperature), operating history, process chemistry, velocities and other flow conditions, local unit conditions, potential unusual operating conditions, and turnaround considerations. In making these decisions, Chevron and its technical experts consider all possible damage mechanisms and the ability to monitor the equipment against those damage mechanisms. A focus in material selection on only a single damage mechanism may inadvertently shift the risk to another potential failure mode. There also often is not a clear cut answer because each material has its own unique advantages and disadvantages. For the purposes of the repair project, Chevron recognizes that both 9Cr and 300-series stainless steel would be an appropriate material for the service.1 Our analysis, however, indicates that 9Cr provides the greater reliability and predictability. As observed by the CSB, its “letter focuses principally on the issue of preventing sulfidation- related corrosion failures and does not examine other factors or potential failure modes that could influence pipe selection” (emphasis added). Chevron, however, considered these other factors and failure modes when selecting 9Cr over 300-series stainless steel. Of greatest concern to Chevron was the susceptibility of stainless steel to stress corrosion cracking (“SCC”) from chlorides and polythionic acids. SCC, which can lead to leaks and piping failures, can be difficult to detect and less predictable. We therefore viewed the benefits of 300-series stainless in providing somewhat increased sulfidation protection as outweighed by the cost of introducing additional risks. The CSB acknowledges in its letter that it does not have information regarding the cost of 9Cr versus 300-series stainless steel with respect to the repair project. Nonetheless, we want to emphasize that material cost did not drive our decision. In fact, on an installed basis, 9Cr piping is more expensive than 300-series stainless steel because the 9Cr piping has to be post-weld heat treated. We selected 9Cr because we believed in this instance, after taking into account technical issues and potential community sensitivities about carbon steel, that 9Cr was the appropriate material. In closing, it is important to avoid the false notion that “alloying up” is always the answer. A reasoned, technical basis must underpin the decision to ensure that one is not simply trading one 1 We also would note that carbon steel is used throughout the industry and continues to be suitable for service with an appropriate inspection program. As we have previously indicated and in light of the potential for low silicon carbon steel components, we are inspecting every carbon steel component exposed to HTS corrosion conditions. November 19, 2012 Page 3 corrosion risk for another that, like SCC, may be even harder to detect. The material selection decision then must be supported with a robust inspection program to monitor for any corrosion and other potential damage. We look forward to discussing these issues with you in more detail. If you have any questions in the interim, please contact me. Sincerely, Nigel Hearne Cc: Hon.Rafael Moure-Eraso, Ph.D., U. S.Chemical Safety Board Mr. Mike Smith, United Steelworkers Local 5 Mr. Kim Nibarger, United Steelworkers International Union Ms. Ellen Widess, CalOSHA Mr. Jack Broadbent, Bay Area Air Quality Management District Hon. Jared Blumenfeld, U. S. Environmental Protection Agency
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