AGAR Supply Company Taunton, MA - Executive Summary
This program has been developed for the ammonia refrigeration process at the AGAR Supply Company (AGAR) Taunton, Massachusetts facility to meet the requirements of the Environmental Protection Agency (EPA) Risk Management Program (RMP) 40 CFR Part 68 and the Occupational Safety and Health Administration (OSHA) Process Safety Management Program (PSM) 29 CFR 1910.119. |
AGAR operates a wholesale food supply warehouse and distribution center. The management team is dedicated to the implementation of a successful RMP/PSM program to minimize the risk of incidents to the public and AGAR employees. Every AGAR employee is trained in safe work practices and dedicated to maintaining a safe work environment.
In the event of an ammonia leak the maintenance engineers, operations manager and supervisors have been trained to shut down the system and ensure exhaust fans are operable to minimize the impact of the incident. Employees have been trained to follow the emergency evacuation plan.
The company has contracted with Refrigeration Engineering & Contracting (RECCO) Company, Inc. of Medford, Massachusetts to provide preventative maintenance and
24-hour on-call emergency response. RECCO employees are licensed refrigeration technicians trained under the OSHA standard 1910.120 Hazardous waste operations and emergency response.
The refrigeration system has been designed by Stalhman Engineers a Registered Engineer in the State of Massachusetts in compliance with all applicable standards and codes. The refrigeration system is a two stage liquid recirculation feed system. The system uses anhydrous ammonia as the refrigerant. The original charge to the system was 15,000 lbs of anhydrous ammonia. An additional 10,000 lbs will be added to the system.
The liquid recirculation system is designed to operate at an overfeed ratio of approximately 4:1 through the evaporators. Highly efficient screw compressors, evaporative condensers, ammonia pumps, and evaporators make up
the system. Energy savings technologies such as Two Stage Compression, Screw Compressor unloading, Thermosyphon oil cooling , oversized Evaporative Condensers , How Gas Defrosting, High Efficiency Motors, Oversized Piping, Air Purgers and PC based control systems have all been incorporated into the refrigeration design of the system.
Safety systems for the ammonia refrigeration system include :
- Ammonia detectors in twenty-six zones fail safe open
- Manual operation of exhaust fan system
- Dampers fail safe open
- Alarm system connected to fire department indicates ammonia and/or fire
- Operations room security access system
- Two King valves for system shut down
- Water treatment in place for condensers
- System remote monitored 24-hours day
- Spare pumps in-line in case of failure
- Automatic shut downs in case of pressure/temperature
- Relief valves and rupture discs - vent lines alarmed
The system is monitored by a 24-hour off site computer system which alerts personal if th
e system is not in normal operation mode. All ammonia detectors are tied into the local emergency response agency (Taunton Fire Department) and indicate the location and type of emergency. The Taunton Fire Department has toured the facility with RECCO to ensure that all members are familiar with the system and know how to respond in case of an emergency.
The ammonia compressor room has been designed with a ventilation system to accomplish two major criteria:
? Remove space heat given off by the refrigeration system equipment
? In case of an ammonia leak within the space remove the ammonia gas from the space at a rate to help reduce levels.
Ammonia detection in the space will initiate emergency ventilation at 35 ppm. Ammonia detection will shut down the electrical power and control power in the space at 10,000 ppm
The ventilation equipment consists of the following:
? Two operable wall louvers for outside supply air to the room
? One continuous exhaust roof fan - 2800 cfm
wo temperature/emergency exhaust fans - 14,000 cfm each
The two temperature/emergency exhaust fans are energized either manually, via a room thermostat or via the Ammonia Detection system. The wall louvers are opened based on which exhaust fan is energized.
Pressure relief valves are used on the system to prevent over-pressure scenarios. Rupture discs are installed ahead of relief valves. Rupture members have a nominal rated rupture pressure not to exceed the design pressure of the parts of the system being protected.
The worst case release scenario analysis was calculated using the EPA RMP COMP software. The greatest potential for the site of a worst case release is the ammonia receiver. Due to the potential for release during fill of the system and quantity of ammonia in a liquid form under pressure at this location. The 25,000 pound quantity in the system is to be completely release over a ten minute time period. Section 2.1 of the EPA Model Risk Management Program for Amm
onia Refrigeration was used as a basis for this worst-case scenario. The estimated distance to the toxic endpoint was calculated to be 1.5 miles. Based on Land View III software , Block Group Proration method the population within this radius is 5,632 persons.
To reduce the potential for such a release an operational procedure for filling the ammonia receiver has been developed by RECCO. Training has been provided for the contractor filling the tank. The warehouse an facility operations will be shut down during the process. RECCO will be on-site to supervise the process. There is a low potential that the tank will ever have to be refilled due to the closed loop system.
The most realistic alternate release scenario is likely to be caused by a leak in a gasket or flange. Most likely this would result in a ?" diameter orifice leading to an airborne release. The release rate calculated using the EPA RMP COMP software is 607 pounds per minute which would impact a 0.2 miles radius. B
ased on Land View III software , Block Group Proration method the population within this radius is 100 persons.
To reduce the potential for the alternate release scenario a preventative maintenance schedule has been developed by RECCO. This includes documented daily logs. All preventative maintenance involving the potential for an ammonia leak has been contracted to be conducted by RECCO.
AGAR's RMP/PSM program includes a management of change policy which states that all changes other than ordinary preventative maintenance are documented, reviewed and approved by the process hazard analysis team, RECCO and/or Stahlman as well as the operations manager and company president.
The attached diagram illustrates the consequences of worst-case and alternate scenarios as well as offsite impacts of population and environmental receptors.
PSM/RMP training is an on-going process as all new employees are provided with information regarding the program and the emergency action plan. Empl
oyees are encouraged to communicate any safety concerns to management and/or AGAR's safety committee members. All concerns are addressed and applicable preventative / corrective measures are implemented.