PHA, MOC and Incident Investigation in Partnership: A Catalyst for Process Safety Excellence

Transcription

1 PHA, MOC and Incident Investigation in Partnership: A Catalyst for Process Safety Excellence John Paul Gathright INVISTA S.à r.l East 37 th St. N. Wichita, KS, U.S.A. Paul.gathright@invista.com Rainer Hoff, Ph.D., P.Eng. Gateway Consulting Group, Inc Transit Road, Suite 100 East Amherst, NY, U.S.A. rhoff@gatewaygroup.com

2 Introduction The PHA-MOC-II Triad Examples Analysis Conclusions

3 (U.S.) Process safety management regulations have 14 key elements: c) Employee participation d) (management of) Process safety information e) Process hazard analysis f) Operating procedures g) Training h) (management of) Contractors i) Pre-start safety review j) Mechanical integrity k) Hot work permits l) Management of change m) Incident investigation n) Emergency planning and response o) Compliance audits p) Trade secrets initial compliance (1992) typically used a division of labor approach causing fragmentation

4 This research focuses on the inter-relationships between: c) Employee participation d) (management of) Process safety information e) Process hazard analysis f) Operating procedures g) Training h) (management of contractors i) Pre-start safety review j) Mechanical integrity k) Hot work permits l) Management of change m) Incident investigation n) Emergency planning and response o) Compliance audits p) Trade secrets

5 This is the baseline risk document

6 Selecting PHA Scenarios: Identify all scenarios where process energy can create a consequence of interest Consequences of interest : community effects, environmental releases, equipment damage, injuries and fatalities, product quality impacts, regulatory compliance, reputation impacts, and, Others Caution! Lower threshold for becoming a consequence of interest generates far too many (inconsequential) follow-ups and mitigations

7 Selecting PHA Nodes Usually depicted on piping and instrumentation diagrams Include: Equipment Piping Instrumentation Control system elements Process safety scenarios must identify individual nodes No aggregate nodes: e.g. entire P&ID

8 Essential MOC elements: Technical basis for change Impact on health and safety Modifications to operating procedures considered Time period of the change Authorization Informing of affected persons Relevant persons trained Process safety information updated Procedures updated If a proposed change affects any PHA nodes, then the MOC triggers a PHA update

9 Essential incident investigation elements: Timely reporting and investigation Investigation by knowledgeable individuals Assessment of contributing factors Recommendations Corrective action implementation Communication to relevant persons Common II triggering event is a demand on a safety system

10 Was the triggering event considered in the PHA? Case 1: Scenario considered in PHA Frequency consistent with PHA No PHA remediation needed Case 2: Scenario considered in PHA Frequency inconsistent with PHA PHA should be revised Case 3: Scenario not considered in the PHA Scenario should be added to the PHA

11 System initially purged with N2 gas Process fluid introduced into tank T1 V1 and V2 are initially closed Due to adiabatic compression concerns, the procedure is to open V1 first, then V2 When attempted in the plant, after an MOC, V2 opened first, and then the line ruptured This was considered in the PHA, so no action taken on PHA T1 High Pressure Gas V2 N 2 purge V1 T2 Atmospheric Pressure

12 Procedure specifies: Open V1 and bleed Run for a few seconds, then open V2 Close bleed V1 Block Valve V3 Bleed V2 Block Valve Drain In practice: Operator closed bleed prior to opening V2 This deadheaded the pump The pipe between V1 and V2 immediately ruptured PHA considered this pump deadheading error, but only once every 10 years In reality it happened every few months

13 Procedure specifies: Open V1 and bleed Run for a few seconds, then open V2 Close bleed Fluid subject to detonation V1 Block Valve V3 Bleed V2 Block Valve Drain In practice: As before PHA did not consider that the fluid could detonate: Because the volume was low, self-detonation was ruled out as a possible consequence of interest

14 Typically, the 3 PSM processes are independent efforts Independent Efforts Model PHA MOC II

15 Example A: MOC led to II Example B: II informs, modifies PHA And here are the other possibilities Document-Centric Model informs PHA modifies triggers MOC II

16 A more nuanced view would focus on the fundamental objects, underlying the documents: Assets (LOC) Events (PHA) Scenarios This is a more logical basis for an electronic implementation PHA Scenario Asset-Centric Model can fail due to... (LOC) Event triggers II Asset MOC

17 Many incidents are avoidable, if the already existing knowledge were more accessible Recommend a two-step process: Recognize the interdependence of PHA, MOC and II Work towards integrating the management of these relationships, leveraging the capabilities of electronic information management systems

18 Thank You