Williams Mobile Bay Gas Plant - Executive Summary
Executive Summary |
Company: Williams Energy Services
Facility: Mobile Bay
1. The accidental release prevention and emergency response policies at the stationary source.
Mobile Bay is a natural gas processing plant. We handle natural gas and natural gas liquids (which contain methane ethane, propane and other like materials). The EPA considers these materials hazardous (flammable). Because they are flammable it is necessary to handle them with certain safety precautions. Mobile Bay has a strong commitment to employee safety, protecting the environment, and community advancement. This commitment is demonstrated by the resources invested in accident prevention, such as extensive employee training and a standard practice to incorporate safety in the design, installation, operation, and maintenance of our facility. Additional safety precautions include safety systems such as alarms, shutdowns, and overpressure relief valves. These safety precautions provide protection for our e
mployees' health and welfare and provide safeguards for the public and environment. It is our policy to comply with all applicable local, state and federal laws and regulations.
In addition to implementing EPA's Risk Management Program to protect the public and the environment, the Mobile Bay Plant has implemented the 14 elements of OSHA's Process Safety Management (PSM) program to insure facility and process safety.
Mobile Bay Emergency Response Plan includes procedures for notifying local, state and federal agencies, as well as adjacent business. Local officials including our LEPC have reviewed our emergency response plan. The Mobile Bay employees receive training over these procedures.
2. The stationary source and regulated substances handled.
The primary function of the Mobile Bay facility is the recovery of natural gas liquids from natural gas. The natural gas is delivered to Mobile Bay via pipeline. Liquids are extracted from the gas by the use of a cryogenic process. The
processed gas is shipped via pipeline to end-users. The recovered liquids are sent via pipeline to a fractionation facility where the individual components of the mixture are separated and sold to various users.
The regulated substances at the Mobile Bay Plant are flammable mixtures of natural gas and natural gas liquids.
The maximum intended inventory for the Mobile Bay Plant is approximately 1,800,000 pounds.
3. The worst-case release scenario (s) and the alternative release scenario (s).
The flammable worst case scenario for Mobile Bay is the release of 109,000 gallons from the slug catcher. This release results in 410,000 pounds of a flammable mixture of natural gas liquids. Administrative and engineering controls include level switches which alarm and stop the inlet flow into the slug catcher. Relief valve has also been installed to protect the slug catcher. The TNT Equivalency Method with 10% conversion was use to calculate the worst-case releas
e scenario with a vapor cloud explosion. The endpoint of a 1 psi overpressure was 0.58 mile radius from the slug catcher. The flammable worst case scenario two for Mobile Bay was the release of the entire contents of the Mobile Bay Condensate Storage Tank when the tank is at 100% capacity would result in the release of 174,061 pounds of a flammable mixture of natural gas liquids. Mobile Bay administrative and engineering controls have a level switch high set at 83% capacity for the condensate storage tank. The TNT Equivalency Method with 10% conversion was used to calculate the worst-case release scenario where the entire content of the tank is released with
a vapor cloud explosion. The endpoint of a 1 psi overpressure was 0.44 mile radius from the tank.
A seal failure in one of the four product booster pumps. The discharge duration reflects the approximate time needed for the operator to manually isolate or block-in that piece of equipment. Based on the calculations, there would be about 2,432 pounds of natural gas liquid discharge at a rate of 187 pounds/minute. The maximum distance for the alternate release scenario is 376 feet or 0.07 mile radius. With this scenario being the most likely, this release could reach beyond facility boundary with the correct conditions.
4. The general accident prevention program.
The following is a summary of the accident prevention program in place at the plant. Because processes at the Mobile Bay plant that are regulated by the Environmental Protection Agency's (EPA's) risk management program (RMP) regulation are also subject to the Occupational Safety and Health Administr
ation's (OSHA's) process safety management (PSM) standard, this summary addresses each of the 14 OSHA PSM elements and describes the management system in place to implement the accident prevention program.
Mobile Bay plant encourages employees to participate in all facets of process safety management and accident prevention. Examples of employee participation range from tailoring, compiling, and updating plant operating procedures and participating in process hazard analysis (PHA) of new or modified processes. Employees have access to all vital information pertaining to plant operations. In addition, the plant has institutes various ways to get employees involved. One such was is the formation of the safety committee. This committee focuses on safety issue related to the plant. The committee is made up of employees from various areas of the plant, including operations, maintenance, and management.
Process Safety Information
Mobile Bay plant keeps a
variety of technical documents that are used to help maintain safe operation of the process. These documents address chemical properties and associated hazards, limits for key process parameters and specific chemical inventories, and equipment design basis/configuration information.
Chemical-specific information, including exposure hazards and emergency response/ exposure treatment considerations, is provided in material safety data sheets (MSDSs). This information is supplemented by documents that specifically address known corrosion concerns and any known hazards associated with the inadvertent mixing of chemicals.
The plant also maintains numerous technical documents that provide information about the design and construction of process equipment. This information includes materials of construction, design pressure and temperature ratings, and electrical rating of equipment. This information, in combination with written procedures and trained personnel, provides a basis for
establishing inspection and maintenance activities, as well as for evaluating proposed process and facility changes to ensure that safety features in the process are not compromised.
Process Hazard Analysis (PHA)
Mobile Bay plant has a comprehensive program to help ensure that hazards associated with the various processes are identified and controlled. Within this program, each process is systematically examined to identify hazards and ensure that adequate controls are in place to manage these hazards.
The facility primarily uses the What-if/Checklist method for identifying hazards. Secondarily, the hazard analysis and operability (HAZOP) analysis technique may also be used. The analyses are conducted using a team of employees who have operating and maintenance experience as well as engineering expertise. This team identifies and evaluates hazards of the process as well as accident prevention and mitigation measures, and the team makes suggestions for additional prevention and/
or mitigation measures when they believe such measures are necessary.
Mobile Bay plant maintains written operating procedures that address various modes of process operations, such as (1) unit startup, (2) normal operations, (3) temporary operations, (4) emergency shutdown, (5) normal shutdown, and (6) initial startup of a new process. These procedures can be used as a reference by experienced operators and provide a basis for consistent training of new operators. These procedures are periodically reviewed and annually certified as current and accurate. The procedures are kept current and accurate by revising them as necessary to reflect changes made through the management of change process.
To complement the written procedures for process operations, Mobile Bay utilizes task progressing experience as a means for operator growth and advancement. New employees receive basic training in gas plant operations if they are not already familiar wit
h such operations. After successfully completing this training, a new operator is paired with a senior operator to learn process-specific duties and tasks. After operators demonstrate (e.g., through tests, skills demonstration) having adequate knowledge to perform the duties and tasks in a safe manner on their own, they can work independently. In addition, all operators periodically receive refresher training on the operating procedures to ensure that their skills and knowledge are maintained at an acceptable level. This refresher training is conducted at least every 3 years. All of this training is documented for each operator, including the means used to verify that the operator understood the training.
Mobile Bay plant uses contractors to supplement its workforce during periods of increased maintenance or construction activities. Because some contractors work on or near process equipment, contractor orientation is provided to contractors so they can (1) perform
their work in a safe manner, (2) have the appropriate knowledge and skills, (3) be aware of the hazards in the workplace, (4) understand what they should do in the event of an emergency, (5) understand and follow site safety rules, and (6) inform plant personnel of any hazards that they find during their work.
Pre-startup Safety Reviews (PSSRs)
Mobile Bay plant conducts a PSSR for any new facility or facility modification that requires a change in the process safety information. The purpose of the PSSR is to ensure that safety features, procedures, personnel, and equipment are appropriately prepared for startup prior to placing the equipment into service. This review provides one additional check to make sure construction is in accordance with the design specifications and that all supporting systems are operationally ready. The PSSR review team uses checklists to verify all aspects of readiness. A PSSR involves field verification of the construction and serves a quality assur
ance function by requiring verification that accident prevention program requirements are properly implemented.
Mobile Bay plant have practices and procedures in place to maintain pressure vessels, piping systems, relief and vent systems, controls, pumps and compressors, and emergency shutdown systems in a safe operating condition. The basic aspects of this program include: (1) conducting training, (2) developing written procedures, (3) performing inspections and tests, (4) correcting identified deficiencies, and (5) applying quality assurance measures. In combination, these activities form a system that maintains the mechanical integrity of the process.
Safe Work Practices
Mobile Bay plant has instituted a number of programs to ensure a safe work environment. Examples of these include (1) control of the entry/presence/exit of support personnel, (2) a lockout/tagout procedure to ensure isolation of energy sources for equipment undergoing maintenance, (3)
proper protective equipment is utilized while working on certain pieces of equipment, (4) a permit and procedure to control spark-producing activities (i.e., hot work), and (5) a permit and procedure to ensure that adequate precautions are in place before entry into a confined space. These procedures (and others), along with training of affected personnel, form a system to help ensure that operations and maintenance activities are performed safely.
Management of Change
Mobile Bay plant has a comprehensive system to manage changes to all covered processes. The system requires that changes to items such as process equipment, chemicals, technology, procedures, and other facility changes be properly reviewed and authorized before being implemented. Changes are reviewed to (1) ensure that adequate controls are in place to manage any new hazards and (2) verify that existing controls have not been compromised by the change. Affected chemical hazard information, process operating limi
ts, procedures, and equipment information are updated to incorporate these changes. In addition, operating and maintenance personnel are provided any necessary training on the change.
Mobile Bay plant investigates all incidents within 48 hours that resulted in, or reasonably could have resulted in, a fire/explosion, gas release, major property damage, or personal injury. The goal of each investigation is to determine the facts and develop corrective actions to prevent a recurrence of the incident or a similar incident. The investigation team documents its findings, develops recommendations to prevent a recurrence, and forwards these results to management for review. The final resolution of each finding or recommendation is documented and made known to all employees.
Compliance audits are conducted to ensure procedures and practices are followed. Compliance audits are conducted at least every 3 years.
5. The five-year accident hi
Mobile Bay is a newly construct facility with no accidental releases, injuries or damages.
6. The emergency response program.
Mobile Bay Plant maintains a written emergency response program that pertains to any uncontrolled or emergency condition at the process plant which requires immediate action to provide for the safety of the general public and of individuals at the emergency site, and/or to prevent or control damage to facilities on the site or in the vicinity.
The Mobile Bay Plant emergency response plan includes specific plant personnel responsibilities and procedures during an emergency. The plan also contains emergency contact numbers to local officials. This facility will conduct periodic emergency drills that involve the LEPC and emergency response organizations. The emergency response plan will be review annually with employees unless changes have occurred, which will be communicated immediately.
The Mobile Bay Plant conducted a meeting with the Local Eme
rgency Planning Committee (LEPC), Mobile Fire-Rescue Department, Mobile County EMS, Southflight Aeromedical Services, and Transco (receptor) at the facility. This coordination meeting consisted of a review of our emergency operating procedures as well as a table-top exercise to discuss sequences of events during an emergency and the rolls of responding agencies.
7. Planned changes in improving safety.
Mobile Bay Plant has plans on implementing a thorough preventative maintenance program on the stabilizer reboiler tubes to aid in identifying a tube leak. In addition, the operators will be required to inspect the stabilizer reboiler for hot spots and improper flame patterns during normal rounds.
Install a high temperature switch to cooler outlets to prevent overheating the compressor, scrubbers and associated piping in the event we lose stabilizer compressor inter-cooler and/or after-cooler.
Mobile Bay will continue to implement system changes that may be required to increase over
all plant safety.