Viskase Corporation - Executive Summary
VISKASE CORPORATION, 2221 EAST STATE HWY 198, OSCEOLA, ARKANSAS 72370 |
FACILITY DESCRIPTION, REGULATED SUBSTANCE, ACCIDENTAL RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES:
Viskase Corporation is a manufacturing facility that produces cellulose food casings for the meat packing industry. Viskase utilizes the regulated chemical carbon disulfide in the cellulose food casing process. Viskase's commitment to providing a safe, healthy work environment for employees as well as providing a safe, healthy environment for the surrounding community is supported by Viskase's installation of the latest technology in process controls, active mitigation, passive mitigation, and monitoring detection systems.
Viskase's policy in the event of an uncontrolled accidental release of carbon disulfide is to respond to the release with trained emergency personnel (Emergency Response Brigade). Local emergency agencies will be contacted for assistance as well as necessary contractors needed to respo
nd, clean up and restore facility functions to normal. Viskase adheres to all applicable Federal, State and local safety and environmental regulations for the prevention of releases of this chemical.
A worst-case scenario analysis was conducted for the carbon disulfide process at Viskase utilizing requirements contained in EPA guidelines. EPA has defined a worst-case release as, "a release of the largest quantity of a regulated substance from a vessel or process line failure that results in the greatest distance to a specified endpoint." The release is assumed to occur instantaneously. Administrative controls that limit the quantity of a substance in a vessel or pipe can be considered when determining the worst-case scenario. The possible causes of the release or the probability that such a release might occur is not considered in the worst-case scenario analysis; the release is simply assumed to take place.
For toxic liquids, such as carbon disulfide, th
e total quantity in a vessel is assumed to spill onto a flat, non-absorbing surface. Only passive mitigation systems may be taken into account for the worst-case consequence analysis. The total quantity spilled is assumed to spread instantaneously to a depth of 0.39-inch (1 centimeter) in an undiked area or the spill will cover a diked area instantaneously. The release rate to air is estimated as the rate of evaporation from the liquid pool.
The toxic endpoint for carbon disulfide is 0.16 mg/L. This airborne concentration has been published by the American Industrial Hygiene Association (AIHA) and is the maximum airborne concentration below which is believed that nearly all individuals can be exposed for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual's ability to take protective action.
Meteorological conditions for the worst-case scenario are defined by EPA Guidance as atmospheric stabil
ity class F (stable atmosphere), wind speed of 1.5 meters per second (3.4 miles per hour), and ambient air temperature of 25 degrees C. Topography for the worst-case scenario is either rural or urban.
WORST-CASE SCENARIO FOR CARBON DISULFIDE - TOXIC SUBSTANCE
The analysis conducted by Viskase Corporation identified the worst-case carbon disulfide release as the carbon disulfide railcar splitting open while spotted on site. Due to the conditions required by EPA, it is assumed that the entire contents of the railcar will release instantaneously. Containment walls or "splash walls" are located around the railcar, with the exception at the ends of the railcar, that direct any release or spill into the containment that is located directly under the railcar. The ends of the railcar are protected by splash baffles.
In determining the total amount released for the worst-case scenario, it is assumed that the entire contents of the railcar (168,480 pounds), taking into account administra
tive controls, is released. It is also assumed that 50% of the total volume released flows into the containment vault filled with water directly parallel to the railcar (to the west) by wave action. 45% is assumed to be contained by the catch basins and the containment wall, and 5% is assumed to overflow onto the ground surrounding the railcar. Therefore, the amount that is released from the railcar after passive mitigation considerations is 2,564 pounds. A spill of carbon disulfide from the railcar would: 1) flow into the three catch basins underneath the railcar, 2) flow into the containment vault filled with water adjacent to the railcar, 3) flow into the containment wall which would then direct the flow into the containment vault, and 4) overflow from the containment area onto the ground around the railcar. The surface area of the three catch basins and the surface area of the overflow were used to calculate the evaporation rate and the duration of the release. The entire co
ntents of the catch basins drain into a containment vault filled with water in less than 10 minutes, therefore the distance to the toxic endpoint of the release is based upon the evaporation rate (QR) and duration of the release from the overflow.
A wind speed of 1.5 meters per second and an atmospheric stability class of F was used in calculating the worst-case scenario per Risk Management Guidance, and the topography of the area surrounding the property is rural.
Using these parameters it was determined (using EPA Offsite Consequence Analysis Guidance tables) that with a toxic endpoint of 0.16 mg/L, rural conditions, an evaporation rate of 103.60 lb./min and duration of 24.75 minutes, the distance to the toxic endpoint is 2.1 miles.
This worst-case scenario does not take into account Viskase's active mitigation measures that are in place for the carbon disulfide system, and or materials of construction of the railcar, that would make a release of this type improbable. The railc
ar unloading location is equipped with a deluge system that is triggered manually or by heat sensors that will protect against vapor ignition. In addition, Viskase's operating procedures require constant monitoring of the railcar during unloading activities.
ALTERNATIVE RELEASE SCENARIO:
EPA requires that an alternative scenario be analyzed for each regulated toxic chemical present above the threshold quantities. The release scenario must include consideration of the following:
1. Transfer hose releases due to splits or sudden uncoupling;
2. Process piping releases from failures at flanges, joints, welds, valves and
valve seals, and drains or bleeds;
3. Process vessel or pump releases due to cracks, seal failure, drain bleed, or
4. Vessel overfilling and spill, or overpressurization and venting through
relief valves or rupture disks; and
5. Shipping container mishandling and breakage or puncturing leading to a spill.
Alternative release scenarios, as re
quired by EPA guidance, should be those that lead to concentrations above the toxic endpoint beyond the facilities fence line, unless no such scenario exists. In identifying alternative scenarios, active mitigation systems are allowed to be considered, such as interlocks, shutdown systems, pressure relief devices, flares, emergency isolation systems, and fire water and deluge systems, as well as passive mitigation systems.
Meteorological conditions for the alternative release scenario are defined by EPA Guidance as atmospheric stability class D, wind speed of 3.0 meters per second, and ambient air temperature of 25 degrees C and 50 percent humidity. Topography for the alternative release scenario is either rural or urban.
ALTERNATIVE RELEASE SCENARIO FOR CARBON DISULFIDE - TOXIC SUBSTANCE
The alternative release scenario identified for the carbon disulfide process would be a release due to a leak or break at a flange on the pump side of the piping. This scenario was chosen becaus
e a release of this type is the only alternative scenario identified that would lead to concentrations above the toxic endpoint beyond the facilities fence line.
If a break or release at the flange at this location occurred, the amount being pumped from the pump plus the amount from the piping from the pump to the holding tanks would represent the total quantity that could be released. The holding tanks are located below the level of the piping, therefore preventing the carbon disulfide contained in the holding tanks from flowing back into the piping. The amount of piping, which is one-half inch (1 1/2") Schedule 40 stainless steel, from the holding tanks to the break or site of the release is approximately 741 feet. The carbon disulfide (CS2) process pump is equipped with CS2 sensors, which detect CS2 in the exhaust gas at the pump. When this sensor is triggered, an audible alarm is sounded. Viskase carbon disulfide operators can manually stop the pump from the control panel; a
nd if operators fail to manually shut the pump off, the pump automatically stops operating after five (5) minutes even during normal operations. Therefore, in the event of a leak or break at the flange in the piping at the beginning of the pump cycle, the pump would continue to operate for five (5) minutes. Therefore, the total amount of CS2 that would be released is the amount released from the pump operating for five (5) minutes and the amount released from the piping from the holding tanks to the break. A release of carbon disulfide at the pump area would flow into the diked area around the pump which is equipped with a drain that directs flow into the containment water pit where the two storage tanks are located. Approximately 95% of the total release would flow into the containment basin underneath the railcar unloading area due to the grade and flow pattern of the diked surface area on which the release would occur.
Meteorological conditions for the alternative release scen
ario is atmospheric stability class D, wind speed of 3.0 meters per second, and ambient air temperature of 25 degrees C and 50 percent humidity. Topography for the alternative release scenario is rural.
Using these parameters it was determined (using EPA Offsite Consequence Analysis Guidance tables) that with a carbon disulfide release of 119.90 pounds, and vapor release rate to air of 7.74 lbs/min, the estimated distance to the toxic endpoint of 0.16 mg/L is 0.09 miles or 475.2 feet. This distance does not reach any public receptors.
Although this scenario could occur, preventative maintenance, scheduled inspections of the equipment in the carbon disulfide process and monitoring by Viskase operator's help to identify and reduce the risk of leaks or releases due to failures of this type.
ACCIDENT RELEASE PREVENTION PROGRAM:
Viskase complies with the Process Safety Management rule of OSHA standard 29 CFR 1910.119 for the prevention of hazardous chemical releases. The Process
Safety Management Plan is a comprehensive program with fourteen elements, including process hazard analysis, employee training, operating procedures, mechanical integrity, pre-safety startup, contractor safety, emergency planning and response, compliance auditing, and employee participation. The Process Safety Management Program ensures that the process and the equipment in the process is designed, constructed, and maintained according to industry codes and standards and that the process is operated according to good engineering practices. The mechanical integrity element of the program includes scheduled inspections and tests of equipment and of monitoring devices in the process to detect any deficiencies or defects in equipment. Preventative maintenance and replacement policies of parts and equipment ensures that deficiencies are addressed and corrected before they could potentially contribute to a release incident. All elements of the Process Safety Management Program help to
ensure an uncontrolled release of carbon disulfide is prevented.
FIVE YEAR ACCIDENT HISTORY:
No accidental releases of carbon disulfide have occurred at Viskase in the past five years that has resulted in deaths, injuries, or significant property damage on site, or known offsite deaths, injuries, evacuations, sheltering in place, property damage, or environmental damage.
EMERGENCY RESPONSE PROGRAM:
Viskase has developed an emergency response plan (in accordance with 29 CFR 1910.38 and 29 CFR 1910.120) that includes provisions to respond to chemical emergencies on site with trained Viskase personnel and provisions to evacuate non-responding employees from the facility in the event of an uncontrolled accidental release of a hazardous chemical. The emergency response team is trained to respond to chemical emergencies involving spills, fire, confined space rescue, etc. at the facility. It is also Viskase's policy to contact the local emergency planning committee, and the local fire
department in the event of a hazardous chemical release. Viskase has coordinated with the local emergency planning committee on its emergency response plan, and in the unlikely event of an uncontrolled release, the local authorities will be notified by Viskase and a joint decision will be made on whether local areas will be evacuated. The local authorities will notify any affected neighbors or surrounding properties if an evacuation is necessary.
PLANNED CHANGES TO IMPROVE SAFETY:
Viskase is committed to continuous efforts to improve the safe operation of the carbon disulfide process by implementing preventative maintenance programs, inspection programs, and employee training in the safe operation of the equipment and the system. The carbon disulfide process is designed in accordance with good engineering practices. Periodic auditing of the Process Safety Management Prevention Program ensures that any system changes or modifications are evaluated and necessary safety precautions a
nd or safety improvements are made before the process is placed into operation.