Technical Papers. 31st Annual Meeting. International Institute of Ammonia Refrigeration. March 22 25, 2009

Transcription

1 Technical Papers 31st Annual Meeting International Institute of Ammonia Refrigeration March 22 25, Industrial Refrigeration Conference & Exhibition The Hyatt Regency Dallas, Texas

2 ACKNOWLEDGEMENT The success of the 31st Annual Meeting of the International Institute of Ammonia Refrigeration is due to the quality of the technical papers in this volume and the labor of its authors. IIAR expresses its deep appreciation to the authors, reviewers and editors for their contributions to the ammonia refrigeration industry. Board of Directors, International Institute of Ammonia Refrigeration ABOUT THIS VOLUME IIAR Technical Papers are subjected to rigorous technical peer review. The views expressed in the papers in this volume are those of the authors, not the International Institute of Ammonia Refrigeration. They are not official positions of the Institute and are not officially endorsed International Institute of Ammonia Refrigeration 1110 North Glebe Road Suite 250 Arlington, VA (voice) (fax) Industrial Refrigeration Conference & Exhibition The Hyatt Regency Dallas, Texas

3 Technical Paper #3 Designing an Inherently Safer Refrigeration System Peter Jordan MBD Risk Management Services, Inc. Langhorne, Pennsylvania Abstract After approximately 12 years of research the FAA announced a new requirement in July 2008 which is designed to make airline travel inherently safer. This requirement will mandate the use of nitrogen in airline fuel tanks to eliminate the potential for a flammable atmosphere in these tanks. At first glance it might appear that this requirement is unrelated to the ammonia refrigeration industry. But in reality the ammonia refrigeration industry has been emphasizing the use of inherently safer designs for many years. Examples include the use of secondary refrigerants and the elimination of ammonia piping manifolds in processing areas. The processes used to evaluate design options, however, have tended to be relatively informal and qualitative in nature. This technical paper will describe a formalized method that has been used to quantitatively and qualitatively evaluate different options in ammonia refrigeration systems to identify inherently safer options. The method involves adding additional questions to Process Hazard Analysis (PHA) studies to stimulate discussions on potential inherently safer designs. The method also involves the use of actual ammonia accident investigation data and published equipment and human failure rate data to evaluate various design alternatives. The end result is a suggested list of action items which are designed to make ammonia refrigeration systems inherently safer IIAR Industrial Refrigeration Conference & Exhibition, Dallas, Texas IIAR

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5 Designing an Inherently Safer Refrigeration System Introduction In days gone past it was considered acceptable to install larger and larger ammonia refrigeration systems in the United States. Numerous refrigeration systems have been installed with charges over 250,000 pounds of anhydrous ammonia. These refrigeration systems of the past may have been cost effective, efficient, and reliable but are they inherently safe? For example, have these refrigeration systems actually been designed to minimize the potential impact of ammonia releases on workers at the facility and on the surrounding environment? In some cases, the answer to this question is no. The ammonia refrigeration industry is subject to numerous government regulations throughout the world. Some of the standards and regulations a typical refrigeration 1, 2, 3, 4, 5, 6 system in the United States may be subject to are included as references. Even the most skeptical among us must admit that these standards and regulations have been valuable in encouraging facilities to design and operate safer ammonia refrigeration systems. For example, years ago most facilities were relatively unaware of the amount of ammonia losses from their refrigeration system. Now a typical facility will measure, control and minimize the ammonia losses from its refrigeration system. So it is fair to say that these standards and regulations have raised the bar for ammonia safety. In general, these standards and regulations have the following objectives in mind: Identify and assess the hazards associated with releases of potential hazardous chemicals; Design a safe facility to prevent these releases; Operate a safe facility and train facility personnel to prevent releases. Minimize the consequences of releases that occur. All of these objectives are important and interrelated. And those of us operating within the ammonia refrigeration community are constantly striving to meet these Technical Paper #3 IIAR

6 2009 IIAR Industrial Refrigeration Conference & Exhibition, Dallas, Texas objectives. Recent examples include initiatives within IIAR to study the risks associated with sight glasses and with stress corrosion cracking. I would argue, however, that the most important of these four objectives is to ensure that the facility is designed with safety as a top priority. If a facility is designed with safety in mind, you can minimize the potential hazards, simplify the operator training and preventive maintenance requirements which are required to maintain a safe facility, and ideally never have to implement your emergency action plan to minimize the consequences of an actual ammonia release. The goal is to make an equal or greater emphasis on prevention rather than mitigation by taking a step back to examine the system with a fresh perspective to determine if it can be made safer. After all, the best way to control a potential risk is to eliminate it entirely. The question is how to go about this task in a structured manner. Step 1: Identifying Potential Release Points In order to make a refrigeration system inherently safer, we should step back and ask a very basic question: Where is ammonia being released from ammonia refrigeration systems? In order to answer this question, three sources of information were consulted: EPA RM Program database Accident information available on the internet Failure rate data EPA RM Program Database The U.S. Chemical Safety and Hazard Investigation Board (CSB) has been studying the EPA Risk Management Program (RM Program) database to assess the impact of ammonia releases. CSB estimates that 60,000 facilities in the United States are using ammonia, and that 16,000 of those facilities use ammonia in a refrigeration system. 4 IIAR 2009 Technical Paper #3

7 Designing an Inherently Safer Refrigeration System Table 1 summarizes ammonia release information contained in the RM Program database for incidents that were reported between 1994 and The information provided in the table breaks down the releases by release source. This data is taken from over 600 incidents involving ammonia refrigeration systems. Note that multiple release sources can be reported for the same incident so the number of releases exceeds the number of incidents. Note that valves and piping account for over 50% of the reported ammonia releases from ammonia refrigeration systems over this ten year period. The specific causes of the valve and piping releases was not available. Accident Information Available on the Internet In June 2005, I started collecting and analyzing ammonia accident data using publicly available internet information. Most of the incidents were reported on the Incident News Reports updated on a daily basis by the CSB on their website ( gov/index.cfm?folder=circ&page=index). Other incidents were identified by setting up a Google Alert for Ammonia. The information collected from the internet between June 2005 and December 2008 broken down by release source is summarized in Table 2. This data is taken from approximately 200 incidents involving ammonia refrigeration systems. The information is imperfect at best because of the vagaries of the various sources of information. But it can be used to spot trends in release sources and to confirm the information in the EPA s RM Program database. The resource source trends identified in the RM Program database (Table 1) are virtually identical to the trends found on the internet (Table 2). In both cases, valves and piping account for almost 50% of the reported ammonia releases from ammonia refrigeration systems. It should be pointed out that approximately half of the releases listed in Table 2 under the valves category were releases from pressure relief valves Technical Paper #3 IIAR

8 2009 IIAR Industrial Refrigeration Conference & Exhibition, Dallas, Texas and the other half were from manual valves or automated valves. A release from a pressure relief valve is not a valve failure; the relief valve is simply doing its job, and the problem is located elsewhere in the system. No such distinction was available for the valve releases reported in Table 1. Failure Rate Data Failure rate data can be used to determine the anticipated likelihood/frequency of a particular release. Table 3 contains a summary of such data provided by the State of New Jersey Department of Environmental Protection. 8 This data covers a fairly broad range of equipment used to handle or store hazardous materials. When applying this data it is important to note that the failure rate is applicable for each component in the system. For example, if you have only one gauge glass in your system this data would predict one small leak from that gauge glass every 8 years. But if you have 8 gauge glasses in your system this data would predict eight small leaks (one from each gauge glass) over that same 8 year period. Earlier in the paper the following question was posed: Where is ammonia being released from ammonia refrigeration systems? The historical accident data and the failure rate data all point in the same direction. Approximately half of the releases appear to be occurring from the valves and piping installed in the system. It would therefore logically follow that the biggest impact that a facility can make in reducing the frequency or impact of ammonia releases is to minimize the number of valves and piping in the system, i.e., get rid of valves and piping if you can. If the valves and piping cannot be eliminated they should be located to minimize the impact of ammonia releases on workers and on the surrounding environment. 6 IIAR 2009 Technical Paper #3

9 Designing an Inherently Safer Refrigeration System Formal IST Reviews In the United States, facilities that operate ammonia refrigeration systems are required to identify and assess the hazards associated with potential ammonia releases regardless of the size of their system. If the facility is covered by the PSM standard and the Risk Management Program regulation, this assessment is typically conducted using the What-If/Checklist technique. 9 If the facility is subject to the General Duty Clauses, the IIAR provides checklists in the Ammonia Refrigeration Management (ARM) program to conduct the assessment. 10 When properly applied, the What-If/Checklist technique and the ARM checklists are excellent at identifying and potentially correcting the potential hazards in existing ammonia refrigeration systems. What these techniques don t necessarily do is force facilities to step back and take a fresh look at the facility to determine how the basic equipment design can be modified to eliminate or greatly reduce potential risks. With some simple changes these techniques can become much more effective in identifying action items which can make the systems inherently safer. Currently, there are requirements in two states, New Jersey and portions of California, which require facilities to formally analyze their systems to determine if they are inherently safe. In New Jersey, this requirement was adopted on May 5, 2008, when the New Jersey Department of Environmental Protection added amendments to the Toxic Catastrophe Prevention Act (TCPA) program rules. 11 All refrigeration systems operating in New Jersey which contain more than 5,200 pounds of anhydrous ammonia are subject to the TCPA program rules and are now required to conduct a formal inherently safer technology (IST) review of their system. The primary objective of the IST review is to identify available IST alternatives or combinations of alternatives that minimize or eliminate the potential for a chemical release. Technical Paper #3 IIAR

10 2009 IIAR Industrial Refrigeration Conference & Exhibition, Dallas, Texas A formal IST review is conducted using many of the same procedures used to conduct a What-If/Checklist analysis. Specifically the following steps can be used to conduct a formal IST review: 1. Assemble a small team with knowledge of engineering, safety, operations and maintenance. The same team used to conduct a What-If/Checklist study can be used to conduct an IST review. 2. Divide up the equipment in the refrigeration system into subsystems to make the review more manageable and to focus the review team. 3. Ask a list of questions for each subsystem. The questions are typically based on the sample questions contained in the Center for Chemical Process Safety s IST guidelines. 12 Appendix A contains a sample list of questions. The questions are designed to force the team to focus on the following points: a. Can the amount of ammonia in the refrigeration system be reduced? b. Can we substitute less hazardous materials? c. Can ammonia be used in less hazardous process conditions? d. Can changes be made to the equipment or processes to minimize the potential for equipment failure and human error? 4. Document the inherently safe features which already exist in the system. These features are typically categorized as inherent, passive, active or procedural safety features. Appendix B contains a table which defines these categories. 5. Identify action items that can improve the inherent safety of the facility. 6. Assess the feasibilities of the action items. Note that the last step of the process is to determine the feasibilities of the action items. In New Jersey feasible means capable of being accomplished in a successful manner taking into account environmental, public health and safety, legal, technological, and economic factors. 11 In practice, this has been accomplished by identifying the potential advantages and disadvantages of each action item which has been identified. The potential advantages are typically evaluated quantitatively by estimating the reduced severity of ammonia releases by conducting dispersion modeling and/or by estimating the reduced frequency of potential ammonia releases 8 IIAR 2009 Technical Paper #3

11 Designing an Inherently Safer Refrigeration System using failure rate data. The potential disadvantages are evaluated by identifying other risks which may be introduced if the action item is implemented and by estimating the potential costs necessary to implement the action item. In many cases, facilities have chosen not to implement IST action items because doing so is not economically justified. To date, I have conducted formal IST reviews at ten facilities. Initially I felt the formal IST review was an unnecessary burden on my clients. But I quickly came to realize that when applied correctly, it can be a powerful tool for suggesting improvements to the facility that may not have been identified during What-If/Checklist analyses. Methods to Incorporate IST Results into a Facility Design Most facilities that operate ammonia refrigeration systems will not want to conduct a formal IST review. A formal IST review takes two or three days to conduct and will typically involve costs to hire an outside consultant to lead and document the review. Also, there is no regulatory requirement outside of New Jersey or California which requires facilities to conduct formal IST reviews. I would encourage facilities, however, to ask the questions in Appendix A (or equivalent questions) at some point in the life of their process. The perfect opportunity to ask these questions would be during the design of a new facility and/or during a major re-design of an existing system. It is at this point that the IST review would be most cost effective. Alternatively, the questions could be added as an additional subsystem during a traditional What-If/Checklist review. Even if you choose not to implement this technique you can benefit from the results of the formal IST reviews which have already been conducted. Table 4 contains a list of some common IST action items which have been identified during past IST reviews. Facilities can survey this list to determine which of these items can be practically implemented at their facility. Technical Paper #3 IIAR

12 2009 IIAR Industrial Refrigeration Conference & Exhibition, Dallas, Texas Most good refrigeration engineers and contactors regularly incorporate the items listed in Table 4 in their design projects. But the IST process can allow you to think outside the box. For example: 1. Do you really need a pressure receiver? I have seen several ammonia refrigeration systems where the high pressure receiver was completely eliminated through the use of liquid drainers on the evaporative condenser drain lines. 2. Among the most serious leaks that could occur in a compressor room are leaks from the thermosyphon oil cooling system. Why not replace the ammonia thermosyphon compressor oil coolers with glycol-chilled compressor oil coolers? 3. Is hot gas the best option to defrost low-temperature freezer units? I was recently surprised at the relatively low difference in energy costs when comparing evaporators equipped with traditional hot gas defrost systems with evaporators equipped with electric defrost systems. 4. Should stainless steel equipment and piping be used in place of carbon steel equipment and piping in highly corrosive environments? A previous IIAR paper did an excellent job identifying highly corrosive environments Is it time to consider installing a hard piped ammonia pump-out system? A previous IIAR paper described the benefits and applications of ammonia pump-out systems. 14 Thinking outside of the box has risks since it may involve using unfamiliar technology. It is important that knowledgeable designers are used when trying things outside of the tried and tested. Conclusions Two of the biggest issues in the ammonia refrigeration industry are (1) how to design a safe system using limited resources and (2) how to reduce the number of accidents that occur in our industry. This technical paper is designed to address both of these issues. It attempts to present a practical approach for evaluating various design alternatives with the ultimate goal of producing an inherently safer system. 10 IIAR 2009 Technical Paper #3

13 Designing an Inherently Safer Refrigeration System References 1. Occupational Safety and Health Administration (OSHA), 29 CFR , Process Safety Management of Highly Hazardous Chemicals, Explosives and Blasting Agents. 2. Occupational Safety and Health Administration (OSHA), 29 CFR , Employee Emergency Plans and Fire Prevention Plans, paragraph (a). 3. Occupational Safety and Health Administration (OSHA), 29 CFR , Hazardous Waste Operations and Emergency Response. 4. US Environmental Protection Agency, 40 CFR part 68, Chemical Accident Prevention Previsions. 5. Section 112(r) of the Clean Air Act Amendments of 1990 (CAA 112(r)), The General Duty Clause. 6. Section 5(a)(1) of the Occupational Safety and Health Act (29 U.S.C. 654(a)(1)), The General Duty Clause. 7. Susan Casper, Manuel R. Gomez, and E. Allen Smith, The CSB Incident Screening Database: Description, Summary Statistics and Uses, Journal of Hazardous Materials Volume 159, Issue 1, 15 November 2008, Pages , Presented at the 2006 Annual Symposium of the Mary Kay O Connor Process Safety Center. 8. State of New Jersey Department of Environmental Protection and Energy, Bureau of Release Prevention, Source Data for Risk Assessment in Compliance with N.J.A.C. 7:31-1 et seq., The Toxic Catastrophe Prevention Action (TCPA) Program, Acute Toxicity Concentration Data, Likelihood/Frequency Data, April 5, Technical Paper #3 IIAR

14 2009 IIAR Industrial Refrigeration Conference & Exhibition, Dallas, Texas 9. International Institute of Ammonia Refrigeration, Process Safety Management Guidelines for Ammonia Refrigeration, 2nd Edition. 10. International Institute of Ammonia Refrigeration, The Ammonia Refrigeration Management Program (ARM). 11. State of New Jersey Department of Environmental Protection, N.J.A.C. 7:31-1.5, 3.3, 3.4, 3, 6, 4.2, 4.9, 4.11, 4.12, and 11.4, Toxic Catastrophe Prevention Action Program, Inherently Safer Technology Review. 12. Center for Chemical Process Safety of the American Institute of Chemical Engineers, Inherently Safer Chemical Processes A Life Cycle Approach, Ronald A. Cole and Godan Nambudiripad, Mechanical Integrity for Ammonia Refrigerating System Piping and Pressure Vessels, Presented at the 26th Annual Meeting of the International Institute of Ammonia Refrigeration, March, Kris Hinds and Peter Jordan, The Joy of Ammonia Pump-Out Systems, Presented at the 28th Annual Meeting of the International Institute of Ammonia Refrigeration, March, IIAR 2009 Technical Paper #3

15 Designing an Inherently Safer Refrigeration System Table 1. RM Program Database: Ammnoia Release Sources RELEASE SOURCE NUMBER OF RELEASES % OF TOTAL RELEASES Valve % Piping % Other Release Source % Process Vessel % Pump % Storage Vessel % Joint % Transfer Hose % Total % Table 2. Ammonia Release Sources: Public Information RELEASE SOURCE NUMBER OF RELEASES % OF TOTAL RELEASES Other Release Source % Valve % Piping % Process Vessel % Compressor or Pump 6 3.1% Storage Vessel 4 2.1% Transfer Hose 2 1.0% Joint 1 0.5% Total % Technical Paper #3 IIAR

16 2009 IIAR Industrial Refrigeration Conference & Exhibition, Dallas, Texas Table 3. Failure Rate Data RUPTURE (50 to 100%) LARGE LEAK (5 to 20%) SMALL LEAK (0.5 to 2%) COMPONENT (Years) (Years) (Years) Gauge glass Flexible hose 1, Relief valve 6, Ball valve 10,000 2, Drain valve 10,000 1, Heat exchanger 50,000 2, Pipe (<2", 100 feet) 65,000 15,000 4,000 Pump mechanical seal 70,000 3, Pipe (2" 6", 100 feet) 130,000 40,000 12,000 Pressure vessel 160,000 8, IIAR 2009 Technical Paper #3

17 Designing an Inherently Safer Refrigeration System Table 4. Common IST Action Items TYPICAL IST ACTION ITEM Use secondary refrigerants in place of ammonia Replace high risk equipment Interlock ammonia detectors with shutdown devices Provide enclosures for and/or relocate ammonia refrigeration equipment EXAMPLES Consider using a secondary refrigerant, such as propylene glycol, in place of ammonia in the area unit coolers. Consider replacing the low temperature portion of the ammonia refrigeration system with a carbon dioxide/ammonia cascade refrigeration system or a Dowtherm system. Consider replacing shell & tube condensers with plate & frame condensers. Consider eliminating the use of pump-out vessels (transfer vessels). Consider interlocking solenoid valves and/or pumps with the ammonia detectors so that the solenoid valves will close automatically and/or the pump will stop automatically if ammonia is detected. Consider installing curbs or dikes to contain ammonia releases. Consider relocating ammonia vessels inside containment areas such as compressor rooms and/or constructing buildings around these vessels. Consider relocating ammonia equipment and/or piping out of occupied areas. Technical Paper #3 IIAR

18 2009 IIAR Industrial Refrigeration Conference & Exhibition, Dallas, Texas Table 4. Common IST Action Items (continued) TYPICAL IST ACTION ITEM EXAMPLES Install a water diffusion tank Consider installing a water diffusion tank which would contain the ammonia released from pressure relief valves if a relief valve were to open. Eliminate common sources of ammonia leaks Considering the use of water diffusion tank should be done with great care and consideration of the added mechanical integrity issues associated with safety relief valve and relief header inspection and maintenance, replacement of all relief valves discharging to the diffusion tank to accommodate the added back pressure, and local regulations which may prevent any discharge of water and ammonia into the municipal drainage system. For these reasons, IIAR has recommended other means to minimize atmospheric releases (see below). Consider replacing the ammonia pumps in the system with seal-less pumps. Consider installing an EPCS to minimize atmospheric release of safety relief valves. (vs. water diffusion tank) Consider removing and/or replacing sight glasses. Install devices designed to minimize the potential for thermal or hydraulic shock Consider physically disconnecting un-used equipment which has been decommissioned. Consider installing soft start valves in the hot gas feed lines to low temperature freezer units. Consider installing CK-5 valves (or equivalent) in the suction lines from low temperature freezer units. 16 IIAR 2009 Technical Paper #3

19 Designing an Inherently Safer Refrigeration System Appendix A. Sample IST Review Questions Worksheet System: 1. Ammonia Refrigeration System Subsystem: 1. Sample IST Review Questions IST Potential Already Action Question POTENTIAL REDUCTION IN THE AMOUNT OF Opportunities Present CAT Items AMMONIA MATERIAL HANDLED ON-SITE 1. Can some equipment be removed because it is redundant, excess capacity, or unused? 2. Can the size of vessels, storage tanks and/or containers be reduced? 3. Can other types of equipment or unit operations be installed to reduce ammonia inventory? (e.g., plate & frame vs. shell and tube exchanger) 4. Can piping lengths be reduced to minimize ammonia inventory, for example by relocating piping or process equipment? 5. Can piping diameters be reduced to minimize inventory? 6. Is it possible to feed ammonia as a gas instead of as a liquid to reduce ammonia inventory? SUBSTITUTE LESS HAZARDOUS MATERIALS 7. Is it possible to reduce ammonia usage by using an alternative process, for example through the use of a secondary refrigerant? USE THE AMMONIA IN THE LEAST HAZARDOUS PROCESS CONDITIONS OR FORM 8. Can the process be operated under less severe conditions, for example by lowering the system head pressure? Technical Paper #3 IIAR

20 2009 IIAR Industrial Refrigeration Conference & Exhibition, Dallas, Texas IST Potential Already Action Question 9. Can the system be re-designed to minimize the Opportunities Present CAT Items potential for contaminants such as air, water or oil accumulation? DESIGN EQUIPMENT AND PROCESSES TO MINIMIZE THE POTENTIAL FOR EQUIPMENT FAILURE AND HUMAN ERROR 10. Is the equipment s pressure rating sufficient? 11. Can equipment be relocated to minimize the damage, for example from fork lifts? 12. Can the area be modified to minimize the accumulation of ammonia vapors? 13. Can dikes, containment walls, or other passive features be installed to contain any releases which might occur? 14. Have the number of sight glasses installed in the equipment been minimized? 15. Has the equipment been designed to minimize the potential for thermal or hydraulic shock, vibration, liquid carry-over or freezing? 16. Has the equipment been designed to minimize the potential for trapped liquid? 17. Can other types of equipment or unit operations be installed to reduce the potential for ammonia releases? (e.g., canned pumps, CK-5 valves, soft-start valves, spring-loaded valves) 18. Can different construction materials be used which would minimize the potential for corrosion? 19. Can any by-pass or other multi-use lines be eliminated to minimize system complexity? 20. Can equipment be modified to minimize the potential for ammonia releases during line opening procedures? 18 IIAR 2009 Technical Paper #3

21 Designing an Inherently Safer Refrigeration System IST Potential Already Action Question 21. Does the system contain sufficient controls, safety Opportunities Present CAT Items interlocks, and emergency shutdown systems? 22. Are there sufficient procedural safeguards in place, for example SOPs, administrative checks and emergency response procedures? 23. Is sufficient personnel available to be able to monitor the system and respond to system upsets? LOCATION, SITING AND TRANSPORTATION ISSUES 24. Can process units be located to reduce or eliminate adverse impacts from other adjacent hazardous installations? 25. Can process units be located to eliminate or minimize off-site impact? 26. Can process units be located to eliminate or minimize impact to employees on-site? 27. Can process units be located to eliminate or minimize impact on other process or plant facilities? 28. Can the equipment be modified to eliminate or minimize security risks? 29. Can the plant site be modified to minimize the need for transportation of hazardous materials and to use safer transport methods and routes? Technical Paper #3 IIAR

22 2009 IIAR Industrial Refrigeration Conference & Exhibition, Dallas, Texas Appendix B. IST Categories CATEGORY DESCRIPTION Inherent Eliminates the hazard by using non-hazardous materials or conditions Passive Minimizes the hazard by process or design features Active Minimizes the hazard using controls, safety interlocks, and emergency shutdown systems Procedural Minimizes the hazard using operating procedures, administrative checks and emergency response 20 IIAR 2009 Technical Paper #3

23 Designing an Inherently Safer Refrigeration System Appendix C. Water Diffusion Tanks As noted in the technical paper one of the typical IST action items is to consider installing a water diffusion tank which would contain the ammonia released from pressure relief valves if a relief valve were to open. It must be noted that in all IST reviews conducted to date by the author it was decided NOT to install a water diffusion tank because (1) there would have been only a minimal reduction in risk based on dispersion calculations, (2) because other IST action items were implemented to reduce risk on the system, and (3) because of the significant capital investment and business interruption costs that would have been incurred with no offsetting reduction in costs (i.e. it was not considered economically feasible). The position that IIAR has taken recognizes that water diffusion tanks do not provide a complete and practical remedy to the problem of ammonia releases. IIAR has recommended the installation of Emergency Pressure Control Systems (EPCS systems) in lieu of water diffusion tanks. EPCS systems, in conjunction with a welldesigned safety relief valve manifold system with appropriate atmospheric discharge, are a practical alternative to water dispersion tanks. They are also an engineered and automatic remedy that requires less administrative oversight and should, therefore, be a more attractive solution to the concerns of the authorities. Eliminating or dramatically reducing the accidental release of ammonia vapor is in the best interest of the facility, the surrounding neighborhood and the emergency response providers. Where authorities having jurisdiction have mandated water diffusion tanks, the following recommendations should be addressed: Adequate and practical disposal methods should be available to the facility operator for the safe and authorized disposal of the aqueous ammonia solution that would result from an ammonia release. The water diffusion system should be included in the facilities mechanical inspection program. Technical Paper #3 IIAR

24 2009 IIAR Industrial Refrigeration Conference & Exhibition, Dallas, Texas Notes: 22 IIAR 2009 Technical Paper #3