RUSSELL STOVER CANDIES, INC. - ABILENE, KS - Executive Summary
The Russell Stover Candies, Inc. plant, located in Abilene, Kansas, manufactures specialty candies under the Russell Stover, Whitman, and Pangburn labels. Chocolate, nuts and other ingredients are accepted at the plant and used in the manufacture of specialty candies.
The facility maintains two separate ammonia refrigeration systems which sustain a milk and nut cooler, a -10?F freezer unit, plant process water coolers and facility air conditioners. Anhydrous ammonia is used in the refrigeration systems in excess of the 112(r) threshold and is the only 112(r) listed chemical used at the facility.
The plant is located in Abilene on the south side of Interstate Highway 70, at 1993 Caramel Boulevard. The facility consists of a production building and a small wastewater treatment building south of the production building. The production building is a brick fronted, single story, metal frame structure approximately 400,000 square feet in size. The buildi
ng houses production, offices, and the Candy Store. The wastewater treatment system consists of a small cinderblock building housing the equipment for the activated sludge system including the sludge filter press and disposal container.
The facility began production in May 1995. The facility operates 24 hours a day with two production shifts and one maintenance shift. Facility operations include receiving and storage of raw materials, measurement of the various ingredients into specific batch quantities, blending of ingredients prior to hand finishing of the various chocolates, packaging, and warehousing of product prior to shipment.
The grounds are open with access to employee parking and the Candy Store along the west side from Caramel Boulevard. Area land-use is primarily agricultural, with some residential structures. Mud Creek lies approximately one mile to the east.
Ammonia Refrigeration System Description
The facility maintains a milk and nut cooler, as well as a -10?F
freezer unit. The cooler, freezer, and the plant process water coolers and air conditioners are cooled using two independent ammonia refrigeration systems.
The total charge on the plants two refrigeration systems is approximately 23,200 pounds of ammonia. Each of the systems includes a receiving tank, suction accumulator, compressors, evaporative condenser(s), and associated piping to the systems served. The systems are closed loops, and little or no ammonia is needed annually to replenish minor losses due to routine maintenance activities.
The larger of the two systems, referred to as the South System, contains approximately 16,200 pounds of ammonia and serves the milk and nut cooler as well as air cooling Niagara systems and process water cooling.
The smaller system, referred to as the North System, contains approximately 7,000 pounds of ammonia and serves the -10?F freezer.
Both refrigeration systems are visually inspected daily by the operators. Each system is provided
with emergency pressure relief valves piped to diffusers on the roof of the building. The mechanical rooms where the receivers are located are equipped with ammonia sensors which trigger an audible alarm throughout the plant. In addition to the ammonia sensors, there are either equipment electric panel lights or computer monitoring readings for temperature, pressure and/or liquid level on all pressurized elements of the systems.
The Worst-Case Release Scenario
The worst-case release scenario is calculated based on the loss of the largest, single ammonia storage vessel and associated piping used in accordance with the definition provided in the Environmental Protection Agency guidance for RMP development. As required by EPA guidance for the toxic worst-case scenario, the contents of the ammonia refrigeration process are assumed to be released instantaneously to form a liquid pool. In accordance with rule guidance, only passive control systems capable of withstanding the release ev
ent have been taken into consideration. Determination of the area of potential impact was made using RMP*Comp, modeling software developed by the EPA.
For modeling purposes, it was assumed that the largest of the two ammonia receiving tanks fails and releases 16,200 pounds of anhydrous ammonia. The receiving tank is located in a building which serves to mitigate the release. The ammonia is assumed to volatilize from the pool and dissipate to the atmosphere through building openings. Release time and weather conditions are dictated by EPA guidance. The ammonia gas is considered to pose no further risk to the public when it has dissipated to a concentration less than the toxic endpoint specified in the RMP rule. The toxic endpoint is 0.14 mg/L and the distance to the toxic endpoint is 1.7 miles (8,976 feet). The estimated number of people affected by the release is 5,067.
Alternative Release Scenario
The alternative release scenario is, by definition, a more likely release sce
nario than that considered for the worst case. Engineered controls, such as chemical detection systems and alarms, are included in the analysis. As with the worst-case release scenario, modeling is performed using RMP*Comp software provided by EPA. Release conditions, including release time and weather conditions, are dictated in the EPA Off-Site Consequence Analysis Guidance.
The type of system failure identified for the alternative release was the loss of ammonia due to a failure of the flexible hosing used to fill the ammonia receiver tank. The tank is filled from a tank truck via a fifty foot metal reinforced pressure hose. The hose is affixed to the truck and, through the nearest building door to the mechanical room where the tank is located, to the receiver fill port. Should there be a rupture of the hose, excess flow valves on the truck and receiver tank will cut off the flow of ammonia. Only the amount of ammonia in the hose will be released. The hose will release 0.6
pounds of ammonia. Calculations showing the amount of ammonia lost are included in the Appendix.
The distance to the toxic endpoint is < 0.1 miles (< 530 feet). Due to the small size of this release, no off-site receptors will be affected.
Process Hazard Analysis
A process hazard analysis (PHA) was performed on the ammonia refrigeration systems beginning with loading the receiver tanks with ammonia and ending with the ammonia returning to the receiver tank after having cycled through the entire refrigeration system. A HAZOP type of analysis was used. General questions regarding the storage and use areas as well as practices and protocols associated with the management of the ammonia systems were answered. Following the checklist, each valve, line and piece of equipment in the system was assessed. The valves and other points in the systems where ammonia could be released are identically numbered in the field and on the facility inspection forms. Compliance with code requirem
ents, considerations of potential failure, maintenance and inspection concerns and standard operating procedures were reviewed for each point in the system. The results of the PHA are summarized in a separate Process Hazard Analysis Report.
Five-Year Accident History
The facility has had one ammonia release in the past five years. An incident investigation of the release was conducted. The following information was taken from that report which was completed by the Plant Engineer.
Approximately 6,900 pounds of ammonia gas were released on March 22, 2000 from the east refrigeration system. The release was discovered the following day after it had ceased.
The four compressors associated with the refrigeration system had been shut down to allow contractors to install a new accumulator feed control system and new piping associated with the installation of a new ammonia evaporative cooling tower. The contractors purged the tower of residual ammonia. Some ammonia gas entered the
plant but was thought to be from the bleed down procedure. Only maintenance and cleaning crews were in the building as it was the scheduled shutdown period of the plant.
On March 23, one of the contractors noticed that the pressure on the low-pressure side of the system had dropped to nearly zero. It was discovered that most of the ammonia from the low-pressure side had been released. Because the system was not in operation at the time of the release, the loss of ammonia did not affect system operation and the release was not immediately noticed.
During the incident investigation, it was determined that one of the reliefs on the low-pressure side of the system lifted releasing the ammonia. Water left in the system warmed up, thus warming the ammonia. The water in the system reached approximately 85?F. This temperature corresponds to the 150 psi required to open the relief.
All 150 psi reliefs on the low side of the system were replaced prior to recharging the system wit
No injuries or fatalities occurred either on or off-site. Both the Kansas Department of Health and Environment and the National Response Center were notified by telephone of the release.