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1 1 Subcommittee On Pressure Relief Systems CRE Meeting Spring 2011 Meeting Clark Shepard.

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Presentation on theme: "1 1 Subcommittee On Pressure Relief Systems CRE Meeting Spring 2011 Meeting Clark Shepard."— Presentation transcript:

1 1 1 Subcommittee On Pressure Relief Systems CRE Meeting Spring 2011 Meeting Clark Shepard

2 2 1 Standard/RPTitleCurrent Edition Date Notes or Comments Expected Publication Date Std 520 Part 1Sizing, Selection, and Installation of Pressure- relieving Devices in Refineries Part I—Sizing and Selection 8th Edition, December 2008 Work items beginning in Spring th Edition 2013 RP 520 Part 2Sizing, Selection, and Installation of Pressure- relieving Devices in Refineries Part II—Installation 5th Edition, August 2003 Reaffirmed 1Q11 Waiting on 6 th Edition Reballot 6th Edition Waiting for committee and API guidance Std 521 (ISO 23251) Pressure-relieving and Depressuring Systems 5th Edition, January 2007 Reviewed Issues with DIS Ballot Through ISO 6th Edition November 2012 (FDIS) Std 526Flanged Steel Pressure Relief Valves 6th Edition, May 2009 None7th Edition 2Q14 Std 527Seat Tightness of Pressure Relief Valves 3rd Edition, July 1991 Re-affirmed July Std 2000 (ISO 28300) Venting Atmospheric and Low- Pressure Storage Tanks Nonrefrigerated and Refrigerated 6th Edition, November 2009 (API adopt back); ISO release 2008 DIS June 2011December 2012

3 3 Std 521 (ISO 23251) Currently greater than 400 comments submitted on 521 Ballot (closing June 15) Session planned for July 2011 to work on comments Chemical Safety Board submitted response concerning revisions made to address 2007 CSB recommendations Five comments provided; response framed during meeting Task group formed to develop API response (John Burgess - Lead) Plan to draft response for Fall 2011 meeting Comment highlights: 1. “unaccepted risk” – point to API 752 and 4. Urging use of flare - inherently safer alternative – Provide comment when flare is not always inherently safer. API Environmental working on industry response to EPA regarding flare Paul Eichemer attended meeting as liaison for API Environmental; +EPA continues to formalize position and is looking at minimum heating value Providing Table 11 clarification in next edition of API 521

4 4 API RP 520 Part 2 Inlet Pressure - Proposals for Path Forward 1.Revise API 520 Part 2 (6 th Edition) Ballot to incorporate all changes except those related to Inlet pressure drop and other sections addressing PRV chattering reverting back to the 5 th edition wording. –Update guidance addressing PRV chattering in RP 520 Part 2 when there is stronger technical support for the revisions. 2.Agree to text reviewed at Fall 2010 meeting allowing 5% with safety margin (2%) and engineering analysis requirements when exceeding 5%. –Update guidance addressing PRV chattering in RP 520 Part 2 when there is stronger technical support for the revisions. (note 1) 3.Ballot after completing 1 and work on adding design guidance for liquid filled systems to reduce chattering potential. 4.Ballot after completing 2 and work on adding design guidance for liquid filled systems to reduce chattering potential. Note 1 - Consider working with DIERS on engineering model (stability) Note 2 - Work with API on path forward for Re-Balloting in light of OSHA involvement.

5 5 API 526/527 and – Continue to work document revisions for preparation of ballot 527 – Need to correct publishing mistakes made to the 2007 reaffirmed version

6 6 1.Improved Pressure Relieving Systems Modeling - Industry has been modeling pressure relief and flare systems using commercial software to better estimate pressure relieving rates and flare system hydraulics. 2.API 521 and 2000 have been adopted as ISO documents increasing global review and application 3.API 521 is always undergoing continuous improvement. The last version included improved guidance on 1) hierarchy of mitigation based on inherent safety, 2) expansion to address fire types and details of methodology, 3) introduction of low probability contingencies, 4) expanded flare limits, 5) addition of toxic limits for atmospheric releases and 6) added cautions around CBDs. 4.API 2000 content revisions include improved basis for tank vent sizing and added cautions open vent discharge Changes to Pressure Relieving Systems Over Last 5 Years

7 7 Back-Up

8 8 PERF PRV Stability Project Project winding down with equations developed to model lift of PRV Contracted phases complete with final report expected after meeting Meeting scheduled for Thursday to determine if additional work should progress, how to use the tool and what is the tools limitations Results for valves tested at 50 psig and 250 psig appear to indicate model reasonably predicts chattering based on test data; Needs additional work to determine unknown variables Some limitations including: –Requires variables for each valve; two of which can only be determined through testing –Not sure if models can be extrapolated above 250 psig set pressure –Need to understand effect of larger vessels/system (increased capacitance)

9 9 API 520 (Part 2) – 3% Status and Ballot API SCPRS approved ballot for 6th Edition with comments OSHA sent letter with regard to inlet pressure drop revisions in 520 ballot (April 2010) Met with OSHA to review letter and API’s path forward (Sept 2010) API SCPRS task group agreed to revisions to inlet pressure drop (5% with safety factor) –With goal to include a performance basis for exceeding 5% OSHA’s Jim Lay, attended API Fall 2010 committee meeting. During API Fall 2010 meeting agreed to develop survey for data collection that would support inlet pressure drop to 5% is lower risk (Not supported by all members) –API Law placed hold on 5% inlet pressure drop survey Reaffirmed current API 520 Part 2 version to meet API/ANSI standards document review cycle to reset review process for additional 5 years (January 2011) API task group recommended a ballot (without revisions to inlet pressure drop; using 5th edition wording) OSHA continues to inquire on status with regard to API 520 Part 2 - Inlet Pressure Drop (April 2011) Subcommittee looking at Lift Criteria/Cycling analysis to allow greater then 5% inlet pressure drop PERF Stability project (goal to provide guidance with regard to PRV stability) reviewing results of funded phases to determine path forward. API completing literature search on incidents.


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