PRECISION VALVE CORP. - YONKERS PLANT - Executive Summary |
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A) Accidental Release Prevention and Emergency Response Policies Precision Valve Corporation (PVC) believes that all accidents can be prevented, and is committed to providing employees with resources, training, and support consistent with that goal. PVC is a responsible member of the Yonkers community, and recognizes that incident-free facility operation protects not only the safety of PVC employees but, additionally, contributes to the safety and welfare of the community. PVC has a single process hazard falling under the scope of the EPA RMP Rule; i.e., the storage of flammable liquefied petroleum gases (LPG). Industry experience with such materials has shown that they can be handled safely when proper attention is given to maintaining the equipment that contains them. Accordingly, PVC places a high value on, and devotes considerable effort to, maintaining the mechanical integrity of vessels, piping, and the affiliated equipment in the LPG system. It is PVC's policy that clear , accurate, and up-to-date procedures are required for all operations, and that personnel be adequately trained on these procedures before they assume their job responsibilities. Such procedures and training lessen the potential for upsets that might lead to releases. Nevertheless, PVC believes in planning for the unlikely. Written procedures have been prepared outlining employee actions in the event of emergencies, including those potentially involving LPG. Since flammability is the principal concern with LPG, PVC has coordinated its contingency plans with the Yonkers Fire Department. Generally, it is PVC's policy to rely upon these trained professionals to respond to an LPG incident, should one occur. B) The PVC facility is located at 700 Nepperhan Avenue. The portion of the facility handling the LPG is located on the south side of the main building, between Nepperhan Avenue and the Saw Mill River. Two tanks are provided for storage of the LPG. The larger tank contains a maximum of 43,000 lbs of LPG; the smaller contains approximately 2000 lbs. The storage tanks are periodically refilled from tank trucks. The LPG is used as propellant in devices used to spray paints and other liquids. Two (2) ounces of the LPG are charged into each device in a loading facility adjacent to, but outside of, the main building. Small diameter pipelines carry the LPG from the storage tanks to the loading facility. With the exception of the loading equipment itself, all other equipment handling LPG is located outdoors. Forced ventilation is provided for the loading facility and flammable gas detectors are provided within the loading facility to detect leaks should they occur. For perspective, it should be noted that the storage tanks are similar in size, configuration, and operation to propane storage tanks that might be used, for example, for fuel storage at a school, hospital, or other large public building. C) Discussion of the Worst Case Scenario (WCS) The RMP Ru le requires the evaluation of a "worst case" release scenario to determine the most severe offsite consequences that could conceivably result from a release of hazardous materials (LPG, in this case). The Rule defines the scenario and the modeling conditions to be used. For a tank of flammable materials, such as LPG, the scenario requires the assumption that the total contents of the largest tank is instantaneously released, leading to a vapor cloud explosion. An explosion overpressure of 1 psi defines the limits of the potential effect zone. At PVC, the largest LPG tank contains less than 43,000 lbs of liquid, and the potential effect zone extends out 0.3 miles from the tank, in all directions. It is estimated that the residential population within this zone is approximately 2200 people. One day care center and one school have been identified within the zone. There are also a number of industrial and commercial facilities within this zone. Industry experience has shown that cat astrophic failures of vessels, such as postulated by the WCS, are extremely rare events. The LPG storage tanks are robust vessels, designed and manufactured in accordance with applicable industry standards. Pressure relief valves are provided to ensure that high internal pressures (rare events in, and of, themselves) would not rupture the vessels. Additionally, the area around the LPG tanks is barricaded to protect the tanks from vehicle impact. As EPA has acknowledged, worst case scenarios, as they are defined, are anticipated to be very rare events. Furthermore, the 1 psi effect pressure has been conservatively selected. C) Discussion of the Alternative Release Scenario (ARS) The RMP Rule also requires that PVC conduct at least one Alternative Release Scenario. The ARS is defined as an event that is more likely to happen than the WCS, and its results are intended for use in emergency response planning. The ARS also provides an opportunity to place the results of the WCS in perspective. Three ARS have been analyzed for PVC, and are discussed below: 1. BLEVE of the larger storage tank. Boiling Liquid Expanding Vapor Explosions (BLEVEs) can result when a vessel, containing a material such as LPG, is exposed to an external fire. The fire raises the temperature, and pressure, of the contained liquid; at the same time, the vessel grows weaker as the wall temperature increases. Given the proper set of circumstances, even vessels protected by relief valves can fail explosively. When the vessel contains a flammable liquid, a fireball typically results from the vessel failure. This fireball emits considerable heat that can be felt at great distances. The RMP Rule defines the potential effect zone for the BLEVE as that area within which unprotected individuals would be expected to receive 2nd degree burns. For the larger LPG vessel, the effect zone extends out to a distance of approximately 0.25 miles from the tank. It is estimated that the residenti al population within this zone is approximately 1500 people. One school have been identified within the zone, and there are a number of industrial and commercial facilities within this zone. It should be noted that a significant fraction of the potentially exposed people would either be indoors, or shielded from the fireball by structures or other obstacles. Persons so protected from the fireball would have a greatly reduced chance of injury. Additionally, BLEVEs are relatively rare events, and BLEVEs that injure a large number of persons are even more rare. It takes time to heat the vessel to the point of failure, and this interval typically allows for the evacuation of many endangered personnel. Further, the fire services have become more aware of the BLEVE hazard, and have learned proper techniques for cooling fire-exposed vessels to prevent BLEVEs. Indeed, while BLEVEs in fixed facilities do occur from time-to-time, the more frequent BLEVE scenario involves a transportation accident where vessels, such as railcars, are involved in remote locations where fire-fighting efforts may be less effective. 2. Relief valve opens at design capacity. The second ARS involves a discharge from one of the storage tank relief valves, with a flow rate equal to the design capacity of the valve. This 1360 lb/min release is assumed to continue for 20 minutes until response personnel can don the necessary protective equipment, and stop the release. This scenario was modeled as a vapor cloud explosion, and the potential effect zone (to the 1 psi overpressure) was determined to be 0.15 miles. It is estimated that the residential population within this zone is approximately 550 people. There are no schools or day care centers within the zone. However, there are a number of industrial and commercial facilities within this zone. Credible release scenarios involving relief valves would likely result in lower release rates. The design capacity of the relief valve is based up on the most severe challenge; i.e., an external fire engulfing the vessel. There are no other scenarios identified which would result in a comparable heat input to the vessel; lower heat inputs would result in lower release rates. An actual fire exposure would most likely ignite the LPG discharging from the relief valve, preventing the gas accumulation necessary for a vapor cloud explosion. Relief valves are provided in manifolded pairs. Should one valve fail, and discharge prematurely, it can be valved out of service for repairs, with the spare valved into service to take its place. 3. Failure of liquid line from storage tank. The third ARS involves the failure of the liquid pipeline leading from the LPG tank. It is estimated that the leak rate would be a maximum of 340 lbs/minute. The liquid outlet line is protected by an excess flow valve that automatically closes should the flow rate through the valve exceed this figure. It is estimated that 20 minutes would be required for response personnel to don the necessary protective equipment, and stop the leak. Therefore, the total leak amount is estimated to be 6800 pounds. This scenario was modeled as a vapor cloud explosion, and the potential effect zone (to the 1 psi overpressure) was determined to be 0.1 miles. It is estimated that the residential population within this zone is approximately 280 people. There are no schools or day care centers within the zone. However, there are a number of industrial and commercial facilities within this zone. In all likelihood, the release rate from the liquid transfer line, should a leak occur, would be less than that postulated here. The line is well supported, LPG is a non-corrosive service, and the line is protected against external impact. Other scenarios (such as failure of the unloading hose running from the LPG supplier truck to the PVC piping system) were considered, and modeled, but the results of the offsite consequence assessments for these scenario s were no more severe than those described above. D) Accident Prevention Program PVC is covered by the OSHA PSM Standard, which requires a prevention program equivalent to that required under the RMP Rule. There is a considerable body of knowledge available in the industry relative to the safe handling of LPG materials. PVC adheres to applicable industry consensus standards. As mentioned previously, considerable emphasis is placed on mechanical integrity issues. E) Five-year Accident History PVC has never experienced an accident involving LPG that had significant offsite or onsite consequences, as defined under the five-year accident history requirements of the RMP Rule. F) Emergency Response Program PVC has a written Emergency Action Plan (EAP) addressing matters such as LPG releases or fires. PVC personnel are not intended to take action to mitigate a release or other emergency involving LPG. The EAP requires the notification of the fire department, and other local auth orities, as warranted. PVC personnel would evacuate the facility as conditions dictated. PVC management would provide liaison with the local authorities, as required. G) Planned Changes to Improve Safety. At the current time, PVC has no specific plans for substantive procedural or engineering modifications to further enhance the safety of the LPG system. Future improvement opportunities will be evaluated on a case-by-case basis, as they are proposed by facility personnel. |