Six Steps. to Effectively Update and Revalidate PHAs. Safety

Transcription

1 Safety Six Steps to Effectively Update and Revalidate PHAs Kevin E. Smith and David K. Whittle, EQE International, Inc., an ABS Group Company Recently, many companies have started updating and revalidating their initial process hazard analyses (PHAs). This practice is necessary to help maintain an effective process safety management (PSM) program. In addition, it may be required by a government regulation (e.g., the U.S. Occupational Safety and Health Administration s (OSHA s) PSM regulation, the U.S. Environmental Protection Agency s (EPA s) risk management program (RMP) regulation, or Europe s SEVESO II requirements), a company s internal standard, an industry standard (e.g., Management of Process Hazards API RP 750 or the American Chemistry Council s Process Safety Code), or as just part of good business practices. Most PSM programs require that PHAs be Process hazard analyses must be revamped or redone from scratch every five years by law. Following the guidance given here will facilitate this effort. updated and revalidated on a regular basis. With the passing of the first 5-yr PHA cycle for companies covered by OSHA s PSM or EPA s RMP regulations, most plants have begun the PHA revalidation process. (Note: Although this article is written with references primarily to the PSM and RMP regulations, it can similarly be applied to processes covered by other regulations, industry standards, or internal company initiatives.) Many companies first revalidation attempts are taking the form of performing a new PHA (similar to the effort required to perform the initial one). This approach is often selected because of: (1) significant deficiencies in the previous PHA or its associated documentation; (2) inadequate documentation or evaluation of changes that have occurred to their processes 70 January 2001 CEP

2 since the initial PHA; (3) recent regulatory citations and interpretations; (4) new internal company standards; or (5) new regulations (e.g., EPA s RMP regulation). For other companies that have attempted simpler revalidation methods, the process of updating and revalidating previous PHAs has often left them uncertain whether the PHA revalidation actually reflects the hazards of the current process. In looking toward future PHA revalidation efforts, many companies are wondering how they can make the revalidation process simpler and more efficient, yet ensure that the analysis results reflect the hazards of the current process. This article outlines a task-oriented approach toward updating and revalidating PHAs, taking into account lessons learned by industry during the first wave of revalidations. Selecting a PHA revalidation approach The first step in any PHA revalidation plan is to gather supporting documentation for the process to be analyzed (Table 1) and determine the most appropriate approach for the revalidation. The most appropriate approach depends upon several factors, including the quality of the initial/previous PHA, the objectives of the revalidation, the number and complexity of the changes to the process since the previous PHA, the effectiveness of the management of change (MOC) program for the process, and the operating history of the process (1). Some companies have also adopted policies that dictate an approach based on elapsed calendar time since the previous PHA, or the risk associated with the process to be analyzed. Based on an evaluation of these and any other pertinent factors, it may be appropriate to either redo the PHA, or update and revalidate the previous analysis as defined by the following terms: Redo Perform a complete, new PHA using one or more recognized techniques such as hazard and operability (HAZOP) studies, whatif/checklists, or failure modes and effects analyses (FMEAs) that meet all regulatory, industry, or internal company requirements (OSHA, EPA, Seveso II, API, the American Chemistry Council, etc.) under which the process is covered. Update and revalidate Modify or supplement the previous PHA as appropriate to address changes and incidents that have occurred since the previous analysis, and confirm that the previous PHA accurately reflects the hazards of the process and that adequate controls are in place to manage them. This effort may also include upgrading the previous PHA for specific deficiencies or weaknesses that should have been addressed as part of the previous analysis. Once a revalidation approach has been selected, the next step is to define which tasks need to be performed. A redo would involve performing a PHA on the process as if it were the initial one. This effort and the associated tasks should follow established guidelines for conducting PHAs and should address the PHA issues outlined in pertinent regulations Table 1. Supporting documentation to prepare for a PHA revalidation. Process safety information Previous incident reports Management of change (MOC) and prestartup safety review (PSSR) documents Most recent PHA Written operating procedures Process safety management compliance audit results Recommendations and resolutions from previous PHA Consequence assessments, including any consequence modeling results for facility/stationary source siting or industry standards (if any) under which the process is covered. Numerous references (e.g., 2 6) are already available on hazard evaluation techniques and issues to address during an initial PHA; therefore, the tasks and documentation associated with redoing are not addressed in this article. As an alternative to a redo, it may be appropriate to update and revalidate the previous PHA (assuming that the quality of the previous analysis is sufficient, and an effective MOC program has been in place since the previous analysis). The remainder of this article discusses six tasks that should be performed if a company chooses to update and revalidate the previous PHA instead of redoing it, and how to efficiently perform these tasks to increase the overall effectiveness of the revalidation. Although not specifically addressed here, the PHA leader should also be aware of the documentation requirements necessary to satisfy regulators or other end users of the results, regardless of the PHA revalidation approach selected. Updating/revalidating steps If a company determines that updating/revalidating is the most appropriate approach for a particular PHA, then the previous analysis should be evaluated to determine what issues need to be addressed during the revalidation. The goal of the updating and revalidating process is to confirm that the PHA is consistent with and accurately reflects the hazards of the current process. This includes modifying the existing PHA as necessary to reflect the changes that have been introduced or incidents that have occurred since the previous analysis. Changes that could have occurred include, but are not limited to, modifications to: equipment configurations, process operations and procedures, chemicals used or produced, unit throughputs, staffing, location of personnel work areas, and unit surroundings (both onsite and off-site). Although seemingly straightforward, the updating/revalidation pro- CEP January

3 Safety cess has sometimes left companies uncertain whether all the changes have been reviewed, and, therefore, whether all hazards have been addressed. This uncertainty can largely be attributed to the lack of specific guidance for effectively revalidating a PHA. Many lessons have been learned as industry has struggled through the first round of revalidations. The main pitfall is the lack of a defined task list that systematically ensures that all revalidation requirements are met and all process changes are addressed. Based on specific experience helping a wide variety of industries during their first round of PHA revalidations, the following six tasks are recommended to help ensure that the PHA updating and revalidating approach is optimized and effectively represents the current hazards of the process: 1 Review all modifications made to the process since the previous PHA. To ensure that the PHA revalidation accurately reflects the hazards of the current process, it is necessary for the revalidation team to be aware of all modifications since the previous analysis. The team should be able to simply review the MOC forms or other documentation supporting each modification and incorporate it into the revised PHA. However, if there is uncertainty regarding the level of hazard evaluation performed at the time a modification was made, or there is minimal or no documentation available to support the hazard evaluation of each modification since the previous PHA, then the team may need to perform a hazard analysis of each change to ensure that all hazards have been identified. In either case, the team should consider all modifications since the previous PHA and determine if an additional analysis is necessary based on the collective changes to the process. There are several resources for identifying changes since the previous PHA, including, but not limited to MOC and prestartup safety review (PSSR) documentation, process drawings and written procedures, and the recommendation tracking system or other records of implemented recommendations from the previous PHA or previous incident investigations. Be sure to: a. Review the MOC and PSSR documentation to identify the bulk of the changes to the process, provided that the MOC program has been effective. To help gain confidence in the effectiveness of the MOC program, it is sometimes useful to also review the results and findings of any periodic PSM audits regarding the facility s MOC program; such audits are required at least every 3 yr for processes covered by OSHA s PSM and EPA s RMP regulations. b. Compare the current piping and instrumentation diagrams (P&IDs) to those used in the previous PHA (if available) to identify changes to the process. The simplest way to identify modifications is to check the revision numbers (and any corresponding explanation for the revision) on the current drawings vs. the revision numbers on the drawings used during the previous PHA. For the vast majority of revisions after the previous PHA, the documented modifications and the reason for the revisions should be included in the list of changes to be evaluated (if they are not already documented separately by MOC documentation described previously). Another method for identifying changes using the P&IDs is to visually compare each old and corresponding new drawing to identify any new equipment or lines. A similar comparison can be made between the current written operating procedures and those analyzed during the previous PHA (assuming that a hazard analysis of written procedures was performed during the previous analysis). However, because of the significant revisions that have been made to the format and style of many companies written procedures during recent years, it may sometimes be difficult to identify changes using this comparison, even when the content of the procedures has not changed significantly. Still, in the future, this comparison should become another useful tool to help identify changes to a process that may not have been reviewed by a company s MOC protocol. c. Review records of implemented recommendations from the previous PHA and previous incident reports (if any), and compare these items to MOCs. If the MOC program is working effectively, the vast majority of implemented recommendations will have a corresponding MOC document. If there is no associated MOC form, then the implemented recommendation should be treated as a change to the process and included in the revalidation analysis. The reviews described above in sections (b) and (c) can be useful in auditing the effectiveness of the MOC program. In fact, in some cases, these reviews may have been performed as part of the periodic PSM audit (e.g., every 3 yr) of the MOC program. However, these tasks are not necessarily required as part of the periodic MOC audit; even if they were performed, the auditors typically only select a few samples to do this review, and these samples may not have been from the process being revalidated (i.e., for facilities with multiple processes). Therefore, having the PHA revalidation leader and any other appropriate plant personnel (e.g., the PSM coordinator) perform or confirm these reviews before convening the full PHA revalidation team will lead to a higher degree of confidence that the revalidation has considered all changes to a specific process since the previous PHA. If many modifications that do not have corresponding MOC or PSSR documentation are detected through these or other reviews (e.g., a crosscheck of work orders, purchasing records, or project files to MOCs; interviews with operating personnel asking about undocumented changes), 72 January 2001 CEP

4 then this may be an indication that the MOC process has not been implemented effectively. This, in turn, may lead to reconsidering whether updating and revalidating the PHA is the appropriate approach; redoing it may be a better alternative. Once all of the changes to the process have been identified, the PHA analyst should categorize them according to the estimated amount of time it would take for the revalidation team to review each change, so that an approximate required meeting time can be established. There are no standard rules for categorizing changes in this manner. However, one method is to group the changes into four categories for estimating review time: small (5 min or less), medium (15 min), large (30 60 min), and very large (greater than 60 min). When grouping changes, any that will take longer than 60 min should be reviewed in more detail to get a more accurate time estimate. Table 2 gives typical examples of changes that may fit into each of these categories. The time estimates noted above assume that the PHA revalidation leader or one or more experienced personnel from the process or plant who are familiar with the modifications have reviewed them against the process (and any associated documentation) prior to the revalidation meetings, so that they can attempt to understand and explain to the full revalidation team the rationale for each change. If the previous PHA tables (e.g., HAZOP, what-if, checklists) are to be updated, then the revalidation leader should also flag appropriate deviations/questions in the table that may require updating based on this preliminary assessment of each modification. This preparation work will greatly help accelerate the pace of the revalidation meetings and allow the leader to methodically guide the team through this task. 2 Review previous incidents. Another task that must be performed by the PHA revalidation team is to review all of the incident reports written since the previous PHA for the process being revalidated. The revalidation must address any previous incident that had a likely potential to result in catastrophic consequences (consequences affecting employees, the public, or the environment). Assuming a review of previous incidents was also performed as part of the previous PHA, the revalidation team typically only needs to review those that have occurred since the previous analysis. In New CCPS Book on PHA Revalidation AIChE s Center for Chemical Process Safety (CCPS) has recognized the need for concise, common-sense guidance on the conduct of PHA revalidations. A recent addition to its Concept Book series, Revalidating Process Hazards Analyses, describes approaches for the resource-effective revalidation of PHAs. These approaches have been derived from the experience of many companies in the chemical and hydrocarbon processing industries. This new book, written by Walt Frank and David Whittle of EQE International, includes flowcharts, checklists, and worksheets that provide invaluable assistance to persons involved in the revalidation process. Revalidating Process Hazards Analyses, 108 pp., $59, 2000, can be ordered online at or by calling (Fax: ). addition, when reviewing previous incidents, it is helpful to include documented near misses (any incident that challenged the system safeguards, regardless of actual consequences). The purpose of this review is twofold: to determine whether there is a trend that suggests a hazard discussed during the previous PHA has a greater risk than perceived then; or to identify a hazard previously not recognized. In either case, some level of reassessment may be appropriate. The incident reports should be gathered and preliminarily reviewed by the revalidation leader to estimate the time needed to review each report with the full team, so that an approximate meeting time can be set. For incident reports without recommendations or with those represented by MOCs, allowing approximately 10 Table 2. Examples of modification categories for estimating PHA revalidation meeting time. Category Modification Small Change the set point on a pressure controller. (5 min or less) Replace a carbon steel coupling with a stainless steel coupling. Change the sampling frequency on a product tank from once per shift to once per day. Install an additional block valve on the drain line from a heat exchanger. Medium Replace an existing gas-fired reboiler with a shell/tube heat exchanger. (15 min) Install a new fixed firewater nozzle on the west side of the process. Replace a rupture disk with a relief valve on a vessel. Install a 2-in. temporary hydrogen line from the hydrogen header to a reactor. Large Install a new storage tank in the tank farm. (30 60 min) Tie-in an atmospheric vent line from a reactor to an existing line to a thermal oxidizer. Remove a nitrogen regulator from a unit s nitrogen supply header. Install a new bypass line around the dehydration and scrubbing system from a reactor. Very large Install an additional process train that includes a line with a pump and two columns (> 60 min) (approximately three HAZOP nodes requiring 3 h). Add a new scrubber tower and associated caustic circulation system (approximately two HAZOP nodes requiring 2 h). CEP January

5 Safety min per report are usually sufficient for team review. For reports with recommendations not covered by MOCs, allow 10 min plus the time to review each implemented recommendation, which can be estimated using the same method for MOCs in Table 2. 3 Review the status/ resolution of previous PHA recommendations. This task is not specifically required in the OSHA and EPA regulations. However, one advantage of so doing is that the review is a way of confirming that each modification that was a result of a PHA recommendation (e.g., to add a new alarm or interlock) was identified during the review of changes previously discussed in Step 1. In addition, if the product of the PHA revalidation effort is an evergreen PHA report (similar to a report from an initial PHA), then this task will be necessary to produce current PHA tables (HAZOP, what-if, checklists, etc.). Regardless of whether or not this is required as part of your documentation choice, the revalidation meetings provide an excellent forum for addressing unresolved recommendations from the previous PHA, which the OSHA and EPA regulations require to be resolved in a timely manner. In fact, many companies are using this review to have the team reassess the need for unresolved PHA recommendations that were not related to process safety or may not be required to meet a company s current risk threshold. In addition, this forum can be used to evaluate the resolutions to closed recommendations to ensure that the PHA revalidation team agrees with the rationale for not implementing the recommendations or the actions taken to resolve them. The first step in preparing for a review of the previous PHA recommendations is to determine if the revalidation team is only going to review unresolved recommendations or if it is going to review all of them. Once this decision has been made, the time for this task can be estimated by assuming that each recommendation will take approximately 5 10 min for review. (This estimate can often be reduced if the leader and the person in charge of tracking the resolution of PHA recommendations review the previous recommendations prior to the revalidation meetings, so that they understand and can explain the status/resolution of each recommendation to the full team.) 4 Update the human factors or facility/stationary source siting analysis. Depending on how these issues were addressed in the previous PHA, the PHA revalidation team should upgrade/update the previous human factors or facility/stationary source siting evaluation or perform a new one, focusing on how process modifications (including changes to the surroundings) may have affected these issues. To help address these two topics in a systematic and thorough manner, many companies often use specific checklists (7, 8) to supplement the primary hazard evaluation technique Does your MOC protocol address changes to staffing? (HAZOP, what-if, etc.) used in the PHA. Human factors checklists often include topics such as: Labeling; Accessibility and availability of controls and equipment; Feedback/displays of controls; Personnel workload/stress; Training; Procedures; and Housekeeping. Siting checklists often include issues such as: Unit layout and spacing between equipment; Location of large inventories; Location and construction of the control room and the motor control center; Location of any likely sources of ignition; Location of engineering, lab, administration, and other buildings; also of the facility relative to on-site and off-site neighbors; Location of firewater mains and backup; Location and adequacy of drains, spill basins, dikes, and sewers; Location of emergency stations (showers, respirators, personal protective equipment); Electrical classification; and Contingency planning. For companies covered by EPA s RMP regulation, it is also prudent for the revalidation team to be aware of the worst-case and alternative-case release scenarios selected for consequence modeling, and ensure that any modifications to the process have not affected these scenarios or the assumed safeguards, such as operator response time to a release. Using a checklist to help evaluate or update human factors and siting issues usually requires approximately 2 4 h, depending on the complexity of the process and the extent of the modifications made since the previous PHA. Based on industry experience in performing recent PHA revalidations, it has become evident that changes affecting human factors or siting issues, for example, facility surroundings, personnel, and procedural changes, are often overlooked by companies MOC programs. In this regard, under their MOC guidelines, many firms have not reviewed staff reductions or relocations, or the placement of tem January 2001 CEP

6 porary trailers/buildings for unit turnaround or maintenance. However, these changes could adversely affect the risk of specific scenarios assessed by the previous PHA team (because the consequences of failure of the controls could be more severe given these changes). Thus, these types of changes should be analyzed in the same manner as an equipment change. To help teams brainstorm and identify such process modifications that may have been overlooked by a company s MOC program, PHA revalidation leaders should always ask team members (after Steps 1 through 4 are completed) whether they are aware of any other changes that have not been discussed/reviewed during the revalidation meeting. To aid in this, Table 3 presents a checklist of questions related to facility or process modifications that could be reviewed with the team. An abbreviated form of the table appears here; the full table is at Many of the questions in Table 3 are based on the actual experience of teams identifying overlooked changes (as well as suggesting related recommendations) that were not identified during Tasks 1 through 4. Using such a checklist to guide these discussions also helps to increase confidence that the team has reviewed all known modifications. 5 Address hazards associated with nonroutine operating modes. The hazards involved during startup, shutdown, maintenance, sampling, etc. in a process unit should be evaluated to help identify procedural or equipment deficiencies that could contribute to human errors. Because, historically, many accidents do not occur during normal operation, but, rather, during nonroutine operation, a PHA must evaluate the hazards of a process during normal, as well as nonroutine operation. Since many initial PHAs either did not address or did a poor job of specifically addressing hazards during nonroutine Table 3. Abbreviated checklist for modifications to a process potentially overlooked by the MOC program. Facility Modifications Have buildings, trailers, etc., been constructed or relocated since the previous PHA such that they could be affected by a release? Have staffing levels changed since the previous PHA such that capabilities to quickly respond to emergency situations have diminished? Have traffic patterns (e.g., new rail spur, new chemical truck routing) changed since the previous PHA (e.g., could the process be affected by a new release source, can emergency responders reach the process easily, and are external impacts more likely)? Are there new ignition sources near this process? Are new utilities being used to prepare equipment for maintenance? Has the area electrical classification changed such that some equipment is not properly rated for its service? Have facility modifications made alarms difficult to see or hear? Have facility modifications increased the number of locations that should have personal protective equipment (PPE) available? Modifications to the Process Was a MOC system implemented before or in conjunction with the completion of the previous PHA? Have all PHA issues (e.g.., facility siting, human factors) been addressed for equipment added to the process? Have equipment relief valves been changed from atmospheric discharge to a closed system (or vice-versa)? Are new hazards present due to new operating modes? Have the hazards associated with equipment that has been returned to service since the previous PHA been evaluated? operation, PHA revalidation teams may need to augment the previous PHA by performing this task. One highly effective method of doing this is by performing a detailed hazard analysis (using the HAZOP analysis or what-if technique) of selected written operating procedures for the process (8, 9). Because members of the PHA team are usually familiar with the process and are aware of its highhazard areas, it is usually prudent to let the team select which written procedures to analyze in detail. An alternative, but less rigorous, way is to include these modes as guidewords in the hazard analysis of each process section (deviation during startup, shutdown, etc.). However, this method is usually more productively used during a redo of a PHA after a team has discussed all of the relevant deviations or upsets associated with each process section during normal operation. If the team only plans to primarily address process modifications, then it should also consider the hazards associated with nonroutine operating modes as each modification is reviewed. Regardless of the method selected, the time for this task needs to be estimated. Again, there are no standard rules for this estimate, but, for a detailed hazard review of selected written procedures, time can be estimated based on the number, length, and complexity of the procedures; as a rough estimate, assume approximately 1 h for every procedural steps. Times for the less-rigorous guideword approach for nonroutine operation should already be accounted for in the estimate for Step 1. 6 Ensure that the PHA meets the requirements of any existing or new regulations, industry standards, or internal company requirements. The revalidation team should evaluate any existing or new regulations or standards regarding PHAs for the CEP January

7 Safety process and determine what additional information needs to be added to the previous PHA to make it compliant, and the tasks required to obtain that information. Currently, the new regulation most likely to affect U.S. companies is EPA s RMP regulation. The requirements of the RMP regulation differ from those of the earlier OSHA PSM regulation in that the RMP regulation requires that the PHA consider whether hazards in the process can have off-site effects to the public or the environment. To update a previous PHA that was performed solely to meet the requirements of the PSM regulation so that it also complies with the RMP regulation, the team needs to discuss every scenario identified in the previous PHA that involves a release of hazardous process material to determine and document whether that scenario could have off-site effects. Then, in light of these effects, the team should assess the need for additional safeguards to reduce the risk. To expedite this RMP update task, the analyst should review the previous PHA tables to identify and flag all release scenarios. After the scenarios have been identified, the meeting time for this task can be estimated based on the number of release scenarios, assuming approximately 1 3 min for each. Another common example of when updating/upgrading the previous PHA may be required is when new internal company standards require the PHA team to risk-rank (i.e., assign a likelihood, severity, and risk rank category) hazardous scenarios identified in the PHA. Many firms use a company-specific risk matrix to help their management prioritize and allocate resources more effectively when addressing PHA recommendations. New standards, such as those for safety instrumented systems (IEC 61508) (10), have accelerated the trend toward using risk matrices. The meeting time required to assign a risk ranking to any new PHA recommendation is usually minimal. However, if a company s PHA protocol requires assigning a likelihood and severity to every accident scenario identified in a PHA, regardless of whether a recommendation was suggested by the PHA team, then substantially more time will be required, depending upon the size of the PHA project and the number of accident scenarios identified. As a rough estimate, assume 1 2 min per scenario to be risk ranked. Resource requirements When deciding whether to redo or update/revalidate, companies should compare the resources (preparation Does your MOC protocol address the location of temporary trailers/buildings? time, meeting time, documentation time, overall costs, etc.) required for each. Although many PHA leaders have developed good rules of thumb for estimating the time and corresponding resources required for redoing a PHA (similar to those for an initial PHA), analogous rules of thumb have not been well developed for PHA updating and revalidating. Nevertheless, using the task-oriented approach and the corresponding meeting time estimates outlined here, companies can begin to refine their estimates of the time and resources necessary for this approach and compare it with redoing the PHA. The preparation time by the PHA leader (and possibly other personnel) for updating and revalidating a PHA can take substantially longer than the preparation time necessary for redoing a PHA. However, this investment (preliminary review and understanding of the previous PHA report, all modifications, incidents, previous recommendations, etc.) will significantly reduce the meeting time when the full PHA revalidation team convenes. As the estimated time for updating/revalidating the PHA approaches or exceeds that for redoing the PHA, companies usually choose to redo the PHA to gain a higher level of confidence that the analysis will be consistent with the current process. However, when the estimated time for updating/revalidating is significantly less than redoing it, companies typically select this quicker approach. Although updating/revalidating may not always be an option where the previous PHA quality is inadequate or an effective MOC program has not been consistently applied, by following the six steps described in this article, companies can help to ensure that the results from this quicker approach reflect the hazards of and are consistent with the current process. Simplifying future revalidations The underlying intent for PHA revalidations is to update the PHA so that it represents the current hazards of the process, and the engineering and administrative controls used to manage them. To satisfy this intent, the effectiveness and the extent of the ongoing hazard reviews of changes to the process, represented by MOC documentation, is obviously one of the main driving factors affecting the efficiency of the revalidation. However, due to the lack of regulatory 76 January 2001 CEP

8 Literature Cited 1. Whittle, D. K., and D. K. Crumpler, How to Effectively Revalidate PHAs, Hydrocarb. Proc., 75 (10), pp (Oct. 1996). 2. Guidelines for Hazard Evaluation Procedures, 2nd ed. with Worked Examples, Center for Chemical Process Safety, AIChE, New York (1992). 3. Process Safety Management of Highly Hazardous Chemicals, U.S. Occupational Safety and Health Administration, 29 CFR , Federal Register, 57 (36) (Feb. 24, 1992). 4. Accidental Release Prevention Requirements, U.S. Environmental Protection Agency, 40 CFR Part 68, Federal Register, 61 (120) (June 20, 1996). 5. Management of Process Hazards, American Petroleum Institute Recommended Practice 750, 1st ed., API, Washington, DC (1990). 6. Responsible Care A Resource Guide for the Process Safety Code of Management Practices, Chemical Manufacturers Association (CMA), Washington, DC (Oct. 1990). 7. Hunter, B. L., and S. J. Wallace, Optimize Facility Siting Evaluations, Hydrocarb. Proc., 73 (5), pp (May 1994). 8. Lorenzo, D. K., et al., Consider Human Errors in Process Hazard Analyses, Chem. Eng. Progress, 90 (5), pp (May 1994). 9. Williams, T. R., and W. G. Bridges, Create Effective Safety Procedures and Operating Manuals, Chem. Eng. Progress, 93 (12), pp (Dec. 1997). 10. Summers, A. E., et al., Safeguard Safety Instrumented Systems, Chem. Eng. Progress, 95 (11), pp , (Nov. 1999). guidance and the cultural change that is frequently required when implementing their MOC programs, many companies have struggled (and, in some cases, are still struggling) with the development, implementation, and documentation of a formal and effective MOC program. As a result, many firms have had to redo their initial PHAs rather than update and revalidate them. To improve the efficiency of future PHA revalidations, a task-oriented approach to MOC (similar to the method described above for PHA revalidations) should be adopted. The following three tasks, if incorporated into an MOC program, should help to enhance the effectiveness of the MOC program in identifying and managing hazards associated with changes as they occur: 1. Identify and document all hazards associated with the modification that could adversely affect employees (as well as the public or the environment, when required). 2. Evaluate and document the modification with respect to human factors and facility/stationary source siting issues. 3. Evaluate and document the hazards associated with nonroutine operating modes involved with the modification. To sum up PHAs must be revalidated periodically for the life of a process to maintain an effective PSM program. Because of different starting points and company-specific goals, the actual approach may vary between processes or from one revalidation to the next (for the same process). However, the ultimate goal of most companies is to make the revalidation as simple and cost-effective as possible, while still effectively addressing the process hazards. Following the taskoriented approach outlined in this article should help to ensure that process hazards are adequately controlled while increasing the efficiency of the revalidation. Although the effort required to update and revalidate a previous PHA may be significant, by enhancing their MOC programs and corresponding documentation using the suggestions described above, companies can ultimately reduce the effort required for future PHA revalidations. CEP K. E. SMITH is a process safety engineer for EQE International, Inc., an ABS Group Company (formerly, JBF Associates, Inc.), Knoxville, TN ((865) ; Fax: (865) ; ksmith@eqe.com; Web site: He has participated in numerous PHAs and PHA revalidations for the chemical, pulp and paper, pharmaceutical, and refining industries using the HAZOP, what if, and checklist methodologies. In addition, he assists clients with OSHA PSM, as well as EPA RMP activities. Previously, Smith was with Kimberly Clark Corp., where he worked in research and development, designing and developing pilot-plant processes, supervising construction of pilot processes, and participating in process startups. He has a BS in chemical engineering from the University of Tennessee - Knoxville, and is a member of AIChE. D. K. WHITTLE is manager of process hazard analysis services at EQE International, Inc., an ABS Group Company, Knoxville, TN ((865) ; Fax: (865) ; dwhittle@eqe.com). During his 18 years in industry, he has been involved in a broad range of process safety and risk management activities for domestic and international clients, including companies in the petroleum, petrochemical, pharmaceutical, pulp and paper, and other allied industries. He has extensive experience in leading and revalidating PHAs, and auditing, developing, and implementing and PSM programs. He is also the instructor for courses in hazard evaluation techniques, as well as PHA revalidation. Whittle received a chemical engineering degree from Vanderbilt University, and is a member of AIChE. AIChE Course on PHA Revalidation Studies Coauthor David Whittle is an expert on PHAs and revalidations, and is the instructor for AIChE s Course #295, Updating and Revalidating Process Hazard Analysis for OSHA PSM-Covered Processes. The course is for those who want to learn how to select an effective and efficient PHA revalidation approach, as well as those who are responsible for leading, documenting, or participating in PHA revalidation analyses. The course is ideally suited for PSM/PSA coordinators, process safety engineers, PHA leaders, and plant management. For more information, see or call (800) CEP January