Enzyme Bio-Systems Ltd. - Executive Summary |
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1.0 SOURCE AND PROCESS DESCRIPTION 1.1 SOURCE Enzyme Bio-Systems Ltd. (EB) operates a food-grade enzyme production facility located in Beloit, Wisconsin that is subject to the United States Environmental Protection Agency's (USEPA's) Risk Management Program (RMP) for Accidental Chemical Release (40 Code of Federal Regulations [CFR] 68). EB is subject to RMP as it has an anhydrous ammonia system that contains greater than the threshold quantity (10,000 pounds) of ammonia (Chemical Abstract System [CAS] Number 7664-41-7). The ammonia system is used for pH control within the enzyme production process. The system consists primarily of a storage vessel and delivery piping. The storage vessel, at 80% full, can contain 42,320 pounds of ammonia. 1.2 PROCESS DESCRIPTION The ammonia storage system consists of a single storage vessel located outdoors on the south side of the plant. The ammonia is received from tank trucks which fill the vessel to a maximum of 80% of its total volume. The 80% limit is an established and enforced site operating requirement. Within the vessel, the ammonia is a liquid at approximately 120-150 psig. Ammonia in a gaseous state is transported from the storage tank, through distribution piping to the enzyme process. The ammonia is mixed with air at the process vessel and directed into the enzyme process to control the pH and provide nitrogen for the growth of the micro-organisms. There are multiple safety devices protecting the ammonia system. The storage vessel is designed to the specifications of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code. The vessel is protected from overpressure by four safety relief valves that prevent hazardous pressure levels from existing within the vessel. All connections to the vessel are protected from excess flow by internal valves that will close if the design flow is exceeded. 2.0 POTENTIAL RELEASE SCENARIOS Consistent with the RMP rule requirements, the two E PA mandated release scenarios (a worst-case and alternative-case release) were analyzed for the ammonia system to determine the maximum distance to which the EPA defined release could have off-site consequences. For ammonia, Appendix A of the RMP rule defines this distance as the point at which the ammonia can reach an instantaneous concentration of 200 parts per million in air or 0.02 percent. This airborne concentration has been published by the American Industrial Hygiene Association as the maximum airborne concentration below which nearly all individuals can be exposed for up to one hour without experiencing or developing serious health effects. 2.1 WORST-CASE RELEASE The worst-case release as required by the RMP rule is defined as a catastrophic rupture and complete loss of the maximum contents of the ammonia storage vessel (approximately 42,300 pounds of ammonia) over a 10-minute period. Using the specified worst-case meteorology contained in the Model Plan, it has been deter mined that a worst-case release would have off-site consequences. Although the worst-case consequence analysis is required by the RMP, it should be considered a highly unlikely event. Design, construction, and operation of the storage vessel is such that catastrophic failure is implausible. The tank was designed and constructed in strict accordance with the ASME Boiler and Pressure Vessel Code (Section VIII), and was certified and stamped by the National Board of Pressure Vessel Inspectors (National Board). Third party and state mandated inspections of the vessel's condition occur at least annually by a National Board certified inspector. In addition, the vessel is inspected monthly by a plant facility mechanic, trained in the operation of the system. There are two theoretical causes for a catastrophic loss of containment of the ammonia storage vessel: (1) the internal pressure were to increase uncontrollably and rupture the vessel from the inside or (2) rupture of the vessel wal l due to inadvertent contact and damage from the outside. Regarding the internal pressure theory, the vessel is operated well below the design pressure (i.e., maximum allowable working pressure) of 250 psig and because of the safety factors built into the ASME Code, a fourfold pressure excursion, to approximately 1,000 psig, would have to occur before catastrophic vessel failure. However, such pressures could not be generated internally. The only external cause of high pressure would be flame impingement or surface radiation from a fire adjacent to the vessel. However, even if this were to occur, the vessel is equipped with four safety relief valves (SRVs) set to relieve internal pressure at 250 psig. A high-pressure excursion would not occur as long as any one of the four SRVs functioned. Actuation of the SRVs would result in an ammonia release similar to that described in Section 2.2 for the alternative-release scenario. The SRVs are on a five-year replacement schedule to ensur e that they will function properly when required. Further, rupture of the vessel from the outside as a result of inadvertent contact (e.g., vehicular) is unlikely since facility access is controlled and the unit is provided with substantial barrier protection to preclude this occurrence. In addition, the worst-case release scenario is implausible for the following additional reasons: * The worst-case weather conditions which were used for this scenario are uncommon; * Typically, the vessel contains much less than the maximum intended inventory resulting in a TEP less than the worst-case. * Industry standards were followed for the manufacture and quality control of the vessel; * Ammonia is not corrosive in this service, the vessels are relatively new, and the vessel is well-painted to protect against exterior corrosion; * Safety relief valves limit operating pressures in the vessel; * The facility has a preventive maintenance program in place to maintain the ongoing integrity of the vessel; * The facility has a training program designed to ensure that the system is operated by qualified personnel; * Main ammonia shut-off valves exist, and are prominently labeled, to allow personnel to stop the flow of ammonia quickly in an emergency. 2.2 ALTERNATIVE-CASE RELEASE The alternative scenario, an unlikely, but somewhat more realistic scenario as compared to the unrealistic, mandated, worst-case scenario presented in Section 2.1, is defined as a release of ammonia through a 1/4-inch effective diameter hole in the vessel or a pipe, releasing 100 pounds of ammonia per minute for up to 60 minutes. This release is representative of a small pipe or vessel leak. It would also be representative of a flange leak. Because the storage vessel and some piping are located outdoors, passive (building) mitigation was not used to reduce the release rate or the distance to the endpoint. Using the specified meteorology contained in the Model Plan, the distance to the en dpoint for the alternative release scenario would have greatly reduced offsite consequences. The alternative-release scenario is unlikely for the following reasons: * Much of the piping is located in enclosed areas that could help to contain such a release, and the outside piping is elevated to promote dispersion; * The excess flow valves would close with any surge or high flow caused by a leak; * Industrial standards were followed for the manufacture and quality control of the ammonia lines and equipment; * Ammonia is not corrosive in this service; * The ammonia delivery pipe is well-separated from potential contact with plant traffic; * The facility has a preventive maintenance program in place to maintain the ongoing integrity of the system; * The facility has a training program designed to ensure that the system is operated by qualified personnel; and * The facility has emergency response procedures that enable trained personnel to respond quickly to isolate any potentia l small releases by closing valves and shutting down the system. 3.0 PREVENTION PROGRAM The facility has carefully considered the potential for accidental releases of ammonia, such as the occurrence of the worst-case and alternative-release scenarios described in Section 2.0. To help minimize the probability and severity of an ammonia release, a prevention program that satisfies the Occupational Safety and Health Administration, Process Safety Management of Highly Hazardous Chemicals standard (29 CFR 1910.119) has been implemented. The key components of the prevention program are summarized below: * The development, documentation, and operator availability of critical process safety information regarding the hazards of ammonia, the design basis of the system, and the equipment. This information is used to fully understand and safely operate the ammonia system. * The development of an employee participation program, which includes employees from all levels of the organization and from all areas within the plant (i.e., production and maintenance). This program also assumes that employees that utilize the ammonia system and are most knowledgeable about it are best able to easily, effectively, and regularly recommend changes or improvements that enhance safety. * The performance of a formal process hazard analysis (PHA) using the HAZOP technique. A team with expertise in engineering, operations, maintenance, and safety evaluated the existing ammonia system in depth and developed recommendations to improve the safety and operability of the system. The PHA addressed: (1) process hazards,(2) previous incidents,(3) engineering and administrative controls applicable to the hazards,(4) the consequence of control failure,(5) facility siting,(6) human factors, and(7) a qualitative evaluation of possible safety and health effects of control system failures. The PHA resulted in multiple procedural and/or hardware recommendations to improve the safety and operation of the system. These recommendations have been implemented. The PHA will be updated and revalidated every five years. * Written operating procedures (OPs) were reviewed and updated in 1998 and 1999 to provide the basis for proper and safe operation of the ammonia system. The OPs include procedures for normal operation, startup, shutdown, emergency operation, and emergency shutdown. They also describe safe operating limits for temperature and pressure, the consequences of operating outside these safe operating limits, and a description of safety systems and how they operate. * Ammonia system operators receive refresher training at least every 3 years. The training content is based upon the process safety information and operating procedures. The training program ensures that the operators understand the nature and causes of problems arising from system operations and serves to increase awareness with respect to the hazards particular to ammonia. * Formal authorization systems ( i.e., management of change procedure, pre-startup safety review) are in place to ensure that system changes or expansions are as safe as the original design and that an independent recheck, prior to start-up, confirms that the changes are consistent with the engineering design and safety requirements. * Events that might (or did) cause an accidental or unexpected release of ammonia are subjected to a formal investigation. The objective of the investigation is to correct deficiencies in such a way as to prevent recurrence. * Contractors that are hired to work on, or adjacent to, the ammonia system are "pre-qualified" based upon their knowledge of ammonia and its hazards, understanding of applicable codes and standards, and their demonstrated ability to work safely. * Prior to the performance of any hot work (i.e., spark or flame producing operations such as welding, cutting, brazing, and grinding), management must approve the work by executing a written hot work authorization pe rmit to verify that appropriate precautions to prevent fire have been implemented. * Periodic walk-throughs occur to find unusual or increasing vibration, incipient leaks, or other indications of potential upsets or failures that could lead to a release. * Replacement of the pressure relief valves in 1999 and every 5 years thereafter. * Numerous safety systems including pressure relief valves, excess flow valves, and ammonia vessel level indicators and vaporizer safety interlocks are used in the system. * Periodic inspections are performed for major equipment, including heat exchangers, pressure regulators, and piping. * Proper design including adherence to recognized safety codes, such as the American National Standards Institute (ANSI) standard, Storage and Handling of Anhydrous Ammonia (K61.1). * Adherence to fire codes and preparation for fires, storms, or events that could impact the ammonia system. * Planning with the local fire department to ensure a rapid response to pot ential incidents involving the system or external events, such as tornadoes. * Prevention program compliance audits performed every 3 years to verify that the elements are being properly implemented. Any deficiency found in an audit is corrected. 4.0 ACCIDENT HISTORY There have been no accidental releases of ammonia at the facility in the last 5 years that have resulted in on-site death, injury, or significant property damage or off-site death, injury, evacuation, sheltering-in-place, property damage, or environmental damage. 5.0 EMERGENCY ACTION PROGRAM The facility has implemented a detailed written Emergency Action Plan (EAP). The EAP is intended to address all emergencies at the facility in addition to incidents related to a minor release of ammonia. The EAP includes awareness and response training for employees, coordination with the local fire department, and evacuation of the facility. The plan details what personal protective equipment and spill response equipment is available; identifies specific individuals, their 24-hour telephone numbers, and their responsibilities; identifies procedures for emergency medical care; and refers to other pertinent elements of the management system (i.e., standard operating procedures). |