Stephens Gas Plant - Executive Summary
ONEOK FIELD SERVICES COMPANY |
Stephens Gas Plant
THE RISK MANAGEMENT PLAN (RMPlan)
Introduction and Policies
ONEOK Field Services Company (ONEOK) is committed to being associated with unmatched environmental performance as measured by our employees, customers, regulators, and the public. Our management philosophy goals are achieved by the personal commitments of our employees and contractors, and by open communication with our employees, customers, neighbors, and with regulators. The accidental release prevention and emergency response programs we have at our facilities are part of the high standards for which we strive. Our high standards are achieved by operating in compliance with all required environmental permits and regulations, by operating and maintaining our assets in such a manner that any unpermitted release will be unintentional and acknowledged as unacceptable, by remedying any shortcomings found during regular audits of our fac
ilities, and by reporting promptly to regulators any shortcomings found during the course of our audits as required by law.
The Stephens Gas Plant is one of many facilities operated by ONEOK. At the facility, we receive wellhead gas from wells via pipeline. We separate the liquid hydrocarbons out by employing a 25,000,000 cubic feet per day cryogenic/turbo-expander/demethanizer process. The demethanized residue gas is either sold to customers as low pressure gas or recompressed for sale to customers as high pressure gas. There is a product surge tank with a maximum capacity of 7,943 gallons which contains demethanized product. This demethanized product is the only flammable substance at the facility in an amount greater than threshold quantity that is regulated under the Risk Management Program (RMP). There are no RMP-covered toxic substances present at the plant in amounts greater than threshold quantity. The facility is classified as Program Level 3 under the regulation. T
he purpose of this Risk Management Plan (RMPlan) is to provide information about our operations at the facility, our programs to prevent accidental chemical releases, our emergency response plans in case an accidental release should occur, our 5-year accident history, and our planned changes to improve safety at the facility.
Worst Case and Alternative Release Scenarios
As specified by the U. S. Environmental Protection Agency (EPA) RMP Regulations, our worst case release scenario for flammables would be the loss of all of the flammable mixture in our largest vessel causing a vapor cloud explosion. In the case of the Stephens Gas Plant, this would involve our 7,943-gallon product surge tank. Such a scenario is highly unlikely, however, using the EPA Offsite Consequence Analysis (OCA) methods, the distance that the resulting vapor cloud explosion could cause an overpressure of 1 psi would be approximately 0.3 miles (approximately 1,600 feet). An overpressure of 1 psi is EPAs thr
eshold for measurable impacts. Although we have numerous controls to prevent such releases (high level alarms, emergency shutdown, etc.) and to manage their consequences, no credit for any controls or mitigation measures was taken into account when evaluating this scenario.
The alternative release scenario characterized as a more likely scenario that would involve offsite consequences is calculated to reach approximately 0.2 miles (approximately 1,050 feet) from the release point. This distance calculation is also based on the EPA OCA methods, which are known to overpredict the impact of any potential release from such a scenario. We have selected the alternative release scenario based on a release from our demethanizer tower due to the relief valve sticking open. We have several mitigation measures in place to greatly reduce the chance that such an event could ever occur. These measures include the following: 1) We conduct regular visual inspections of all equipment at our fa
cility; 2) We keep the operating pressure of the vessel (less than 200 psig) at well below the set pressure of the relief valve (400 psig); 3) We continuously monitor the pressure in the tower 24 hours per day; 4) We have a manual emergency shutdown system to shutdown all product movement in case the pressure in the tower gets too high. The presence of these mitigation measures serves to either prevent this scenario from occurring or minimize its impact if it does occur.
We have discussed these potential hydrocarbon releases with our employees and with local emergency response officials in Stephens County, thereby further reducing the possibility of any impact on the public.
The Stephens Gas Plant has been operating under the strict guidelines of the Occupational Safety and Health Administration (OSHA) Process Safety Management (PSM) Program since 1992. Our ongoing analysis of the potential hazards of our process, detailed training of our employees, and con
stant emphasis on safety have helped us avoid any serious accidents over the last 5 years. Part of this program has also involved identifying and taking steps to avoid potential accidental chemical releases. A few examples of the additional prevention features implemented at this facility include:
7 We installed a flare system that will burn off any hydrocarbon vapor when high pressure is encountered within the plant.
7 We provided manual emergency shutdown (ESD) buttons (which are tested semiannually) at several locations within the facility in order to shutdown the entire facility during emergency situations. The ESD system will also isolate the facility from the incoming feed pipeline and outgoing product pipeline.
7 We installed gas detectors in the compressor room in order to detect flammable hydrocarbon vapors and alarm the control room.
7 We provided dual seals on the booster pumps.
7 We provided high pressure and low-flow shutdown switches on our product pipelin
e as well as high pressure shutdown on the demethanizer that will vent hydrocarbon vapors to the flare prior to any release to atmosphere through the relief valve.
7 We provided fire extinguishers throughout the facility for extinguishing incipient fires. These fire extinguishers are inspected annually by third party inspectors and monthly by plant employees.
These safeguards as well as the vigilance of our trained employees have helped us operate safely at this facility for many years.
Five Year Accident History
No incident having resulting in onsite or offsite impacts from a hydrocarbon release has occurred at the Stephens Gas Plant within the last five years. Although we take pride in that record, we also place daily emphasis on our prevention and safety programs to ensure this record continues.
Emergency Response Program
We will continue to conduct emergency response preparedness activities and coordinate any emergency response actions necessary for the Stephens G
as Plant with the Velma Fire Department. Also involved in emergency response for the facility would be the Velma Police Department, the Stephens County Sheriff, Duncan Regional Hospital, the Velma Ambulance Service, and the Oklahoma Department of Public Safety. The Stephens Gas Plant Operator is responsible for coordinating all emergency actions. A specific Emergency Response Plan for the facility is in place and that plan has been coordinated with local officials, along with evacuation procedures, regular drilling, and training. Our Emergency Response Program provides the essential planning and training for effectively protecting workers, the public, and the environment during emergency situations.
Planned Changes to Improve Safety
Diligent compliance with our RMP Prevention Program forms the framework on which we will continue to improve the level of safety at the Stephens Gas Plant. Some of the key components of the safety improvements we expect to achieve are as follows:
7 The Management of Change provisions ensures that we consider the potential safety and health impacts of any change we make to process chemicals, technology, equipment or procedures.
7 The Process Hazard Analysis (PHA) provisions serve as a tool to ensure continual evaluation of potential hazards, thereby leading to continual improvements in our safety standards.
7 The Mechanical Integrity provisions ensure that process equipment and instrumentation are designed, constructed, installed and maintained to minimize the risk of hazardous releases, thereby serving as an integral part of our safety program.
7 Internal and third party compliance audits will ensure we maintain and increase our level of safety protection.
7 An ongoing dialogue with the Stephens County Emergency Management Director or his designate will ensure a constant state of readiness to respond to any potential emergencies, as well as a means to implement improvements as the need develops. In this way, we shall bolste
r our strong commitment to the safety of our workers and the community.
We encourage all interested citizens or community organizations to contact the Stephens County Emergency Management Director for the latest information on emergency response for the county. We plan to diligently integrate our response capabilities and personnel with those of the county on an ongoing basis.