Muller-Pinehurst Dairy - Executive Summary

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1.1    SOURCE 
The Muller-Pinehurst Dairy is subject to the United Stated Environmental  
Protection Agency's (USEPA's) Risk Management Program (RMP) for  
Accidental Chemical Release regulation (40 Code of Federal Regulations  
[CFR] 68) because it has a refrigeration system that contains more than the  
threshold quantity (10,000 pounds) of anhydrous ammonia (ammonia)  
(Chemical Abstract System Number 7664-41-7).  Anhydrous ammonia is a  
gas at ambient conditions.  The anhydrous ammonia refrigeration system  
is used to control the processing and storage temperature for ice cream,  
milk, and related products.  It is a closed system that contains  
approximately 13,800 pounds (i.e., 2,600 gallons) of ammonia in various  
physical states (gas, liquid, and saturated vapor).  The largest vessel is the  
high pressure receiver that operates at approximately 150 pounds per  
square inch gauge (psig) and can contain as much as 2,840 pounds of  
liquid ammonia (at its ma 
ximum safe fill volume of 90 percent).  However,  
during typical operation, the vessel holds only about 1,300 pounds.  Most  
of the ammonia equipment is located indoors.  The condensing towers,  
make-up air units, and some piping runs are located outdoors. 
Ammonia is the oldest and most common refrigerant in general industrial  
use throughout the world.  It is a high capacity refrigerant that operates at  
reasonable pressure.  Although exposure to ammonia is irritating and  
potentially toxic in large doses, personnel exposure to more than a small  
leak is rare because ammonia operates within a closed system of vessels,  
piping, and equipment. 
The Muller-Pinehurst Dairy ammonia refrigeration system is a two-stage  
system.  The high pressure receiver supplies high-pressure (135 to  
190 psig) liquid ammonia to several units including:  the 3-barrel ice cream  
freezer, lower cooler units, Mueller vat, ante room units, glycol chiller,  
small hardening room unit #2, 
hollywood cooler units, and McDonald's  
dock air unit.  The receiver also feeds ammonia to the intercooler, which in  
turn feeds additional units including: storage area unit, large hardening  
room unit, small hardening room unit #1, new and old ice builders, and  
half-gallon air units 1 through 3.  
The Mueller vat, hardening rooms, storage area, and ante room units  
return liquid/vapor ammonia to one of three suction traps.  The suction  
traps are designed to supply liquid free suction to the booster  
compressors.  Booster compressors supply ammonia vapor at 25 psig to  
the intercooler.  Ammonia vapor from the intercooler is fed to one of five  
high stage compressors (four reciprocating compressors and one screw  
compressor).  The major discharge from the high-stage compressors (hot  
gas), at 135 to 190 psig, is vented to two condensing towers.  The  
condensed liquid is returned to the high-pressure receiver. 
A recirculator receives a liquid/vapor ammonia stream from the  
cooler units, lower cooler units, and McDonald's dock air unit.   
Liquid ammonia is recirculated to these units via a pumper drum.  High- 
pressure suction is directed to the booster compressor discharge header. 
The ammonia refrigeration system is protected by the existence of specific  
safety systems/hardware, including safety relief valves, engine room  
ventilation, and system safety interlocks.  Safety relief valves protect the  
compressor discharge, condensers, pumper drums, suction accumulators,  
and the intercooler from the hazards associated with overpressure.  Safety  
interlocks include high pressure and high temperature alarms and cutouts  
for the compressors, as well as high level floats and sensors for the system  
vessels.  The high-pressure cutouts for the compressors are set at 200 psig. 
The refrigeration system is a totally closed system.  Historically, releases of  
ammonia from industrial refrigeration systems most often occur from  
ing valves, malfunctioning pressure relief devices, or inadvertent  
releases during repair activities.  While these incidents can impact  
employees, they seldom lead to a release of a reportable quantity or  
represent an off-site impact (i.e., beyond the property line). 
Consistent with the RMP rule requirements, two specifically defined  
release scenarios (a worst-case release and an alternative release) were  
analyzed to determine the maximum distance to an endpoint where the  
ammonia concentration is 200 parts per million in air, or 0.02 percent.  This  
endpoint represents the maximum airborne concentration below which  
nearly all individuals could be exposed for up to 1 hour without  
experiencing or developing irreversible effects or symptoms that could  
impair their ability to take protective action. 
The release scenarios analyzed are based upon the guidance contained in  
the USEPA's Risk Management Program Guidance for Ammonia Refrigeration  
(the "Model Plan"), dated November 19 
98.  This guidance document used  
the SACRUNCH atmospheric dispersion model to construct "lookup"  
tables that relate the quantity and rate of ammonia released to the  
endpoint distance. 
The worst-case release is considered to be defined by the catastrophic  
rupture and complete loss of the maximum contents of the high pressure  
receiver (approximately 2,840 pounds of ammonia) over a 10-minute  
period.  Using the specified worst-case meteorology contained in the  
Model Plan, the distance to the endpoint for a worst-case release was  
estimated to be 5,060 feet or 0.96 miles. 
Although the worst-case consequence analysis is required by the RMP, it  
should be considered a highly unlikely event.  Design, construction, and  
operation of the high pressure receiver is such that catastrophic failure is  
extremely remote.  The receiver was designed and constructed in strict  
accordance with the American Society of Mechanical Engineers (ASME)  
Boiler and Pressure Vessel C 
ode (Section VIII), and was certified and  
stamped by the National Board of Pressure Vessel Inspectors (National  
Board).  Third party and state mandated inspections of the vessel's  
condition occurs annually by a boiler and machinery insurance inspector  
who has been certified by the National Board.  In addition, the vessel is  
inspected daily by a plant facility mechanic, trained in the operation of the  
There are only two plausible causes for a catastrophic loss of containment  
of the high pressure receiver:  (1) the internal pressure were to increase  
uncontrollably and rupture the vessel from the inside or (2) rupture of the  
vessel wall due to inadvertent contact and damage from the outside. 
The vessel is operated well below the design pressure (i.e., maximum  
allowable working pressure) of 250 psig and because of the safety factors  
built into the ASME Code, a fourfold pressure excursion, to approximately  
1,000 psig, would have to occur before catastrophic vessel fail 
ure.  Such  
pressures could not be generated internally.  The only logical external  
cause of high pressure would be flame impingement or surface radiation  
from a high challenge fire adjacent to the vessel.  If this were to occur, the  
vessel is equipped with a safety relief valve (SRV) set to relieve internal  
pressure at 250 psig.  A high pressure excursion would not occur as long  
as the SRV continued to function.  Actuation of the SRV would result in an  
ammonia release similar to that described in Section 2.2 for the alternative- 
release scenario.  The SRVs are on a five-year replacement schedule, in  
compliance with the International Institute of Ammonia Refrigeration  
(IIAR) guidance contained in IIAR Bulletin Number 109, Minimum Safety  
Criteria for a Safety Ammonia Refrigeration System, to ensure that they will  
function properly when required. 
Further, rupture of the vessel from the outside as a result of inadvertent  
contact (e.g., vehicular) is unlikely since the unit is  
provided with  
substantial barrier protection to preclude this occurrence. 
In addition, the worst-case release scenario is unlikely for the following  
additional reasons: 
? The worst-case weather conditions which were used for this scenario  
are uncommon; 
? Only rarely, if ever, are the contents of the system intentionally  
pumped back to the receiver.  Typically, the receiver contains only  
1,300 pounds; 
? Industry standards were followed for the manufacture and quality  
control of these receivers; 
? Ammonia is not corrosive in this service and the vessels are relatively  
? Safety relief valves limit operating pressures in the receiver; 
? The facility has a preventive maintenance program in place to maintain  
the ongoing integrity of the vessels; 
? The facility has a training program designed to ensure that the system  
is operated by qualified personnel; 
? The facility has emergency response procedures which enable trained  
personnel to respond quickly to isolate a 
ny potential releases; 
? Main ammonia shut-off valves exist, and are prominently labeled, to  
allow personnel to stop the flow of ammonia quickly in an emergency; 
? Inadvertent vehicular contact with the vessel is unlikely since the unit  
is located indoors and provided with substantial barrier protection to  
preclude this occurrence. 
The alternative, or "more likely," scenario is considered to be defined by a  
release of ammonia through a 1/4-inch effective diameter hole in a high  
side (i.e., 150 psig) pipe or vessel, releasing 100 pounds of ammonia per  
minute for up to 60 minutes.  This release is representative of a small pipe  
or vessel leak.  It would also be representative of a flange leak or pump  
seal failure.  Because some piping is located outdoors, passive (building)  
mitigation  was not used to reduce the release rate or the distance to the  
endpoint.  Active mitigation  was considered, because it is believed that  
emergency responders cou 
ld identify and stop the leak in less than 60  
minutes.  However, the application of active mitigation does not change  
the TEP distance obtained from the Model Plan. 
Using the specified meteorology contained in the Model Plan, the distance  
to the endpoint for the "more likely" release scenario was estimated to be  
1,020 feet or 0.2 miles. 
The alternative release scenario is unlikely for the following reasons: 
? Many of the high pressure liquid lines are located in enclosed areas  
that could help to contain such a release, and the outside piping is  
elevated to promote dispersion; 
? Industrial standards were followed for the manufacture and quality  
control of these lines; 
? Ammonia is not corrosive in this service; 
? Most of the lines are elevated or in service tunnels to minimize  
potential damage from fork lifts; 
? The receiver is fitted with a manually operated valve (i.e., King valve)  
which can be closed to reduce the flow of liquid in an emergency; 
? The facility has 
a preventive maintenance program in place to maintain  
the ongoing integrity of the system; 
? The facility has a training program designed to ensure that the system  
is operated by qualified personnel; and 
? The facility has emergency response procedures which enable trained  
personnel to respond quickly to isolate any potential releases by  
closing valves in the liquid lines. 
The facility has carefully considered the potential for accidental releases of  
ammonia, such as the occurrence of the worst-case and alternative-release  
scenarios described in Section 2.0.  To help minimize the probability and  
severity of an ammonia release, a prevention program that satisfies the  
Occupational Safety and Health Administration, Process Safety Management  
of Highly Hazardous Chemicals standard (29 CFR 1910.119) has been  
implemented.  The key components of the prevention program are  
summarized below: 
? The development, documentation, and operator availability of c 
process safety information regarding the hazards of ammonia, the  
design basis of the system, and the equipment.  This information is  
used to fully understand and safely operate the ammonia refrigeration  
? The development of an employee participation program, which  
includes employees from all levels of the organization and from all  
areas within the plant (i.e., production and maintenance).  This  
program also assumes that employees that utilize the ammonia system  
and are most knowledgeable about it are best able to easily, effectively,  
and regularly recommend changes or improvements which enhance  
? The performance of a formal process hazard analysis (PHA) in 1998,  
using the "What if/checklist" technique.  A team with expertise in  
engineering, operations, maintenance, and safety evaluated the  
existing refrigeration system in depth and developed  
recommendations to improve the safety and operability of the system.   
The PHA addressed:  (1) process ha 
zards, (2) previous incidents,  
(3) engineering and administrative controls applicable to the hazards,  
(4) the consequence of control failure, (5) facility siting, (6) human  
factors, and (7) a qualitative evaluation of possible safety and health  
effects of control system failures.  The PHA will be updated and  
revalidated every five years. 
? Written operating procedures (OPs) were prepared in 1997 and 1998 to  
provide the basis for proper and safe operation of the ammonia  
refrigeration system.  The OPs include procedures for normal  
operation, startup, shutdown, emergency operation, and emergency  
shutdown.  They also describe safe operating limits for temperature  
and pressure, the consequences of operating outside these safe  
operating limits, and a description of safety systems and how they  
? Refrigeration system operators receive refresher training at least every  
3 years.  The training content is based upon the process safety  
information and operating procedures 
.  The training program ensures  
that the operators understand the nature and causes of problems  
arising from system operations and serves to increase awareness with  
respect to the hazards particular to ammonia and the refrigeration  
? Formal authorization systems (i.e., management of change procedure,  
pre-startup safety review) are in place to ensure that system changes or  
expansions are as safe as the original design and that an independent  
recheck, prior to start-up, confirms that the changes are consistent with  
the engineering design and safety requirements.   
? Events that might (or did) cause an accidental or unexpected release of  
ammonia are subjected to a formal investigation.  The objective of the  
investigation is to correct deficiencies in such a way as to prevent  
? Contractors that are hired to work on, or adjacent to, the refrigeration  
system are "pre-qualified" based upon their knowledge of ammonia  
refrigeration, understanding of appli 
cable codes and standards, and  
their demonstrated ability to work safely.   
? Prior to the performance of any hot work (i.e., spark or flame  
producing operations such as welding, cutting, brazing, and grinding),  
management must approve the work by executing a written hot work  
authorization permit to verify that appropriate precautions to prevent  
fire have been implemented. 
? Periodic walk-throughs occur to find unusual or increasing vibration,  
incipient leaks, or other indications of potential upsets or failures that  
could lead to a release. 
? Replacement of all pressure relief valves in 1999 and every 5 years  
? Numerous safety systems including pressure relief valves and  
ammonia vessel level controls and safety interlocks are used in the  
refrigeration system. 
? Periodic inspections are performed for major powered equipment,  
including compressors, large fans, bearings, couplings, shaft seals, and  
mountings, etc., for vibration or incipient mechanical f 
? Proper design including adherence to recognized safety codes. 
? Adherence to fire codes and preparation for fires, storms, or events  
which could impact the ammonia system. 
? Planning with the local fire department to ensure a rapid response to  
potential incidents involving the system or external events, such as  
storms or tornadoes. 
? Prevention program compliance audits performed every 3 years to  
verify that the elements are being properly implemented.  Any  
deficiency found in an audit is corrected. 
There have been no accidental releases of ammonia at the facility in the  
last 5 years (since June 1994) that have resulted in on-site death, injury, or  
significant property damage or off-site death, injury, evacuation,  
sheltering in place, property damage, or environmental damage. 
The facility has implemented a detailed written Emergency Action Plan  
(EAP).  The EAP is intended to address all emergencies at the fa 
cility in  
addition to incidents related to a minor release of ammonia. 
The EAP includes awareness and response training for employees,  
coordination with the local fire department, and evacuation of the facility.   
The plan details what personal protective equipment and spill response  
equipment is available; identifies specific individuals, their 24-hour  
telephone numbers, and their responsibilities; identifies procedures for  
emergency medical care; and refers to other pertinent elements of the  
management system (i.e., standard operating procedures). 
    Passive mitigation means equipment, devices, and technologies that function without  
human, mechanical, or other energy input.  Examples include enclosures (e.g.,  
buildings) for compressed gases and secondary containment dikes for liquids. 
    Active mitigation means equipment, devices, or technologies that require human,  
mechanical, or other energy input to function.  Active mitigation for compressed  
gases, like ammonia, may incl 
ude automatic shut-off valves, rapid transfer systems,  
and scrubbers. 
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