Here are some “official” accident facts from OSHA regarding fatal accidents involving Anhydrous Ammonia (all but 1 of the accidents involves Anhydrous NH3). These incidents can be found in OSHA’s Accident Database, but all the accident info is provided below. I have scrubbed company names from this posting, as this is meant to be a LEARNING OPPORTUNITY not a shaming event! I was surprised at the number of pressure vessel failures that had occurred since 1984! Here are the OSHA summaries:
Aut-Purger Mechanical Failure
At approximately 9:50 a.m. on October 24, 2012, Employees #1 and #2 were working as mechanical engineering technicians at a food cold storage facility. The two workers were troubleshooting an Auto-Purger, which removed non-condensable material from the refrigeration system. It was mounted on a wall inside the facility’s anhydrous ammonia compressor room. At the time of the accident, the unit was actively running and leaking liquid onto the floor. The liquid, which contained anhydrous ammonia, was corrosive. Both employees were standing near the unit. Employee #2 was refitting a cap back onto a bubbler to stop a leak. He was using a wrench to tap the cap onto the pipe section. Within minutes, the bottom pipe section of the cylinder separated from the upper section, resulting in a liquid spray that contacted the eyes, face, and body of both employees. Employees #1 and #2 sustained corneal burns. Employee #1 needed surgery as a result of this injury. Causal factors to this accident were the failure to maintain the Auto-Purger to the manufacturer’s design specifications, and a clogged drainage pipe leading to a pressure build up in the system. Additionally, the employer did not ensure that employees were using adequate eye and face protection.
Unloading Hose failure
On September 16, 2013, Employee #1 and Employee #2, were off loading a chemical (aqua ammonia 29) from a rail car. The connection failed, the hose came off, and Employee #1 was covered in product. Approximately 17,000 gallons were spilled. Employee #2 helped Employee #1 in the safety shower and then tried to stop the leak at the rail car connection. Employee #2 was exposed to the ammonia. Employee #2 wore a full face twin cartridge respirator, which was not adequate for respiratory protection. Employee #1 was airlifted to the hospital and was hospitalized for 3 days. Employee #2 was hospitalized locally for 2 days.
Oil Drain Plug
At approximately 4:45 a.m. on September 3, 2013, a coworker was approaching an ammonia display panel located in plant’s chemical room adjacent to the plant’s old engine refrigeration room, heard an audible ammonia system alarm coming from the panel. The coworker approached the ammonia display panel and saw that the display panel was reading 250 parts per million. After observing the display panel the coworker went to the old engine refrigeration room’s north door, opened it, and observed a dense vapor cloud hovering above the floor. The coworker closed the old engine refrigeration room’s door and notified the Supervisor. The Supervisor evacuated the plant and called Emergency Medical Service. As the Supervisor evacuated the plant, the coworker returned to the old engine refrigeration room with a full face respirator, ammonia gloves and a sulfur stick, and observed the oil drain plug from the High Temperature Accumulator lying on the floor in a puddle of oil. The coworker picked up the oil drain plug and screwed the drain plug back into the elbow of the accumulator’s drain and left the room. Employees #1, 2, and 3 worked as packers were working lines 5, 1 and 2. As they were being evacuated the employees started suffering health problems such as irritation in their throats, numbness around the mouth region and difficulty breathing. EMS County Paramedics treated the employees and transported them to St. Francis Hospital, where they were observed for exposure to chemicals and anxiety. The employees were released after two hours observation.
Hot Gas Defrost Human Error
On September 11, 2012, Employee #1, a temporary employee was working as a racker-blender at a Winery, was exposed to anhydrous ammonia, and died of asphyxia. Employee #1 was found in the west hallway 54 ft from the men’s restroom. Upon further investigation, a cellar supervisor was to clear iced juice in Chiller 13 by performing a “hot gas” procedure. The evaporator’s temperature is raised by opening a bypass valve that equalizes the refrigerant pressure. The cellar supervisor was distracted in conversation with a graveyard shift supervisor and inadvertently opened the dump valve. The dump valve purges excessive oil from the refrigerant system into a barrel of water. The opening of the dump valve instead of the bypass valve caused oil to discharge and liquid ammonia to release forming a gas cloud. The cellar supervisor evacuated the area but left the dump valve open. The gas cloud engulfed the area and was pushed against the building containing two hallways, a men and women’s bathroom, and a break room. The gas cloud formation was captured on a surveillance video, but dissipated within seconds. Approximately one minute before the release, Employee #1 entered the west hallway. It was calculated the refrigerant charge at the facility was 23,640 pounds of anhydrous ammonia.
Out of Service Evaporator releases NH3
On May 31, 2012, Employees #1 through #6 were working when an evaporator that had been deactivated was mistakenly activated by a worker. Approximately 68.5 pounds (31 kilograms) of ammonia were released on an overhead catwalk. Employees #1 through #6 inhaled the fumes, and they were transported to a hospital. Employee #1 was not hospitalized, but Employees #2 through #6 were. The narrative did not specify whether the inadvertent release of the ammonia was caused by a coworker or one of the six employees who were injured.
Line Break gone bad
On October 31, 2006, two employees were performing maintenance on an ammonia line when the line ruptured. Employee #1 was transported to a hospital and was pronounced dead at 2:08 p.m. Employee #2 suffered chemical burns from contact to liquid ammonia and was taken to the hospital for treatment. Employee #3, a first responder, was also treated at the hospital for post event respiratory symptoms. Employees #2 and #3 were not hospitalized.
Nurse Tank Filling
At approximately 10:00 a.m. on November 4, 2003, Employee #1 was filling a nurse tank from the bulk anhydrous ammonia tank at the ammonia plant. After the nurse tank was full, Employee #1 disconnected the hoses from the nurse tank and was exposed to anhydrous ammonia. The exposure resulted in burn injuries to his face, neck, chest, and one eye, and injuries to his respiratory tract. Employee #1 drove to the fertilizer plant a few blocks away and was taken immediately to a local hospital and transferred to a regional burn center. Employee #1 died of complications due to chemical inhalation a few weeks later. There were no witnesses to the incident. A company official visited the site approximately 15 minutes after the incident and found goggles and gloves on the ground, the riser liquid and vapor valves closed, and the nurse tank vapor valve open. The company official also found the vapor hose end valve connected to the nurse tank and open, the nurse tank liquid fill valve closed and the liquid hose end valve open and lying on the ground. It appeared that Employee #1 was exposed to the ammonia remaining in the liquid hose between the riser valve and the hose end valve. The exposure appeared to have occurred either because Employee #1 did not close the hose end valve before disconnecting the hose from the nurse tank, or because the safety catch did not engage when the valve was closed, and the valve handle was bumped, causing the valve to open. There was evidence that Employee #1 applied snow to the injured areas. The required water supply had approximately one inch of ice on the surface.
Nurse Tank Catastrophic Failure
On April 30, 2003, Employee #1 and a coworker filled an anhydrous ammonia nurse tank to be transported to farm fields. After filling the nurse tank, Employee #1 was hooking the tank to a pickup truck for transport when the tank ruptured along a weld seam on the bottom front side. Liquid ammonia was released through the approximate 40-in. split. The ammonia formed a cloud and a rapidly expanding, boiling-liquid blast enveloped Employee #1. The coworker assisted Employee #1 to and into a water tank. The Employee #1 died 1.5 weeks later from chemical burns.
Line Break gone bad
At approximately 11:00 a.m. on May 12, 2001, Employee #1 was replacing a solenoid valve on a hot gas ammonia line and was exposed to anhydrous ammonia. On Monday May 14, 2001, Employee #1 was hospitalized with respiratory distress. Employee #1 was then transferred to another hospital and died on May 15, 2001. The medical examiners autopsy report indicated the probable cause of death as pneumonia and pulmonary edema as a consequence of anhydrous ammonia inhalation.
Improper repair to pressure vessel
At approximately 11:30 p.m. on May 24, 2000, Employees #1 through #12 were working in the #3 ammonia plant. Employee #7 was vacuuming desiccant from inside mole sieve vessel #109D-B, which was adjacent to vessel 109D-C. The 109D-C was one of three identical vessels at the facility that removed moisture and carbon monoxide from a synthesis gas used in the manufacture of ammonia. The 109D-C, which had been taken off line to replace its desiccant material, had been online for approximately 11 1/2 hours when the vessel exploded into flame. Employee #7 was killed instantly in the explosion. Employees #2 through #4 and #8 through 11, who were working as his attendants or were conversing with the client’s representatives, all suffered severe burns. No information on injuries was provided for Employee #5. Employee #12, a forklift driver, was thrown during the blast and suffered injuries to his neck and back. Employee #6, a crane operator for the permanent maintenance contractor, suffered from severe burns and was hospitalized for several weeks before he died. Employee #1, an ammonia operator, was standing on the catwalk above the 109D-C when it exploded. He also suffered severe burns and died several weeks later. Subsequent inspection of the vessel revealed a cracked weld. Apparently, an inadequate repair job had been made to the weld two days before the accident.
Line Break gone bad
At approximately 3:30 p.m. on May 24, 1998, Employee #1 was repairing a valve in an ammonia line. Employee #1 was raised to the valve location in a basket attached to a forklift. Employee #1 removed the actuator and was trying to close the valve manually when the valve became dislodged from the piping. The ammonia was released from the main system directly toward Employee #1. Employees #2 and #3, who were working in the area, tried to rescue Employee #1, who died from asphyxia. Employees #2 and #3 were taken to the Albany General Hospital in Albany, Oregon, and were released following treatment.
Forklift strikes piping
Employee #1 was working in a three-sided building approximately 100 ft from an anhydrous ammonia tank filling station. Two coworkers and Employee #2, who was driving a forklift, were off-loading a flatbed trailer when the forklift struck a section of the pipe for the filling station. The pipe blew out from its junction, releasing the contents of two 5,000 liquid gallon anhydrous ammonia tanks. Employee #1 was apparently inside the building when the ammonia plume was released and either succumbed to the ammonia gas immediately, or was blinded and could not escape from the building. He was killed. Employee #2, who worked for another company, on site, was hospitalized.
Catastrophic failure of compressor
At approximately 1:40 a.m. on December 12, 1996, Employee #1, the refrigeration manager, arrived at the plant in response to reports of problems with the Frick 2 cylinder 8 by 8 enclosed VSA refrigerator compressor, serial #HA55248. The problems had been identified and reported by a security guard working the 11:00 p.m. to 7:00 a.m. shift. Employee #1 was briefed by the security guard and then went to examine the ammonia refrigeration system equipment in the engine room of the plant. Approximately 10 minutes later, the security guard, who was in his guard shack, heard an explosion and saw a cloud rise above the main plant building. The compressor had ruptured, releasing ammonia. Employee #1 was found by the security guard in another building next to a water fountain and hand washing sink. He had been working in the small engine room and suffered extensive chemical burns. Employee #1 was killed. Subsequent investigation revealed that a section of the crankcase housing wall had blown out, discharging a mixture of refrigeration oil and ammonia. It is not known what caused the compressor to rupture.
Line Break gone bad
At approximately 10:00 a.m. on January 13, 1994, contractor employees were helping Operations purge a liquid anhydrous ammonia line with compressed air. At about 2:30 p.m. the maintenance engineer and the contractor superintendent believed they had purged most or all of the ammonia from the line. The contractor foreman and Employee #1 took the water truck to dispose of the ammonia/water solution. The maintenance engineer and the contractor superintendent discussed flushing the line with water. Neither of them was sure how to do this process, so the maintenance engineer left to confirm the procedure with the hydrostatic testing engineer. The contractor superintendent returned to his office to check on another job. The facility operator was waiting in the shipping office for the contractor foreman and Employee #1 to return. When the contractor foreman and Employee #1 returned to the field office, the contractor superintendent told them to fill the water truck 1/4 to 1/2 full of water because the host facility was considering flushing the line with water. When they returned to the dock, the operator started back to the dock from the shipping office, and the contractor foreman told Employee #1 that he was going to unroll the water hose. Employee #1 told the contractor foreman something about going to check the compressed air hose connection. At approximately 3:30 p.m. the contractor foreman, who had his back to Employee #1, heard a hissing noise that lasted 3 to 4 seconds. Employee #1 was burned by liquid and vapor ammonia in the face, neck, chest, and left leg. At 3:37 p.m. he received emergency medical treatment from intermediate EMTs on site and from paramedics (Harris County) . He suffered second degree chemical burns to about 36 percent of his body and had great difficulty breathing. At 4:22 p.m. he was taken by Life Flight to a Hospital, where he died on February 2, 1994. Since no one witnessed what happened at the time of the release- the contractor foreman had his back to Employee #1 and the operator was donning her ppe at the middle of the dock- it is uncertain exactly what caused it. Employee #1 may have disconnected the inlet hose while it was still under pressure; or he may have stepped on the inlet hose when he was stepping over the vapor and liquid ammonia lines, causing the hose to disconnect accidentally; or at the time Employee #1 was standing over the connection the inlet hose may have disconnected due to the pressure inside. The contractor foreman was wearing either a face shield or a full-face respirator. Employee #1 may have had a respirator available, but no one saw him wearing it.
Oil Draining gone bad
Employees #1 and #2 were draining refrigerant oil from anhydrous ammonia refrigeration system oil traps in fruit cold storage warehouses. They were working approximately 24 feet above floor level on a mobile scissor lift personnel platform using hand tools including a wrench, a flashlight, and a bucket. The cause of the unexpected ammonia release is unknown. Employees #1 and #2 suffered thermal and chemical burns over large areas of their bodies and of their respiratory tracts. Employees #1 and #2 died.
Line Break gone bad (no LOTO)
At approximately 9:30 p.m. on June 30, 1993, Employee #1 was cleaning up the cut floor at the facility. Facility maintenance employees were removing a valve from the refrigerant line in the ceiling and had not locked or tagged out the main valves on the roof. The valve on the cut floor was removed and taken to the maintenance shop for alteration. The foreman gave workers their evening assignments, then went to the roof and turned on the main ammonia valve(s), sending ammonia through the lines and onto the cut floor. Employee #1 was overcome and died of ammonia irritation and pulmonary complications. Employees #2 through #9, who attempted to rescue Employee #1, were sent to the hospital for throat, eye, and skin irritation, treated, and released.
Ammonia Explosion
At approximately 3:30 p.m. on or about July 10, 1991, Employees #1 and #2 were standing atop an 80,000-gallon capacity tank that contained about 35,000 gallons of “ammonia liquor”. When Employee #3, using a torch, began to cut off the elbow from the seal pot they were replacing, sparks flew inside the tank through an unblinded flange and caused an explosion. Employee #1 was thrown 288 feet and died of his injuries; Employee #2 was thrown 157 feet and died of his injuries. Employee #3 sustained burns on his left arm and was sent to the hospital. Employee #4, who was in a building adjacent to the tank, was blown off his feet by the explosion and was sent to the hospital for treatment of general pain. Employee #5 was in the cab of a crane next to the tank and was sent to the hospital for ringing in his ears and general discomfort.
Catastrophic failure of pressure vessel when steam was used to heat up congealed oil
On December 26, 1989, Employee #1 was attempting to replace a leaking oil valve on a minus 30-degree freezer when a tank inside the freezer exploded. The company uses anhydrous ammonia to manufacture ice cream. The liquid ice cream mixture (at 50 degrees) is added to the tank. When the liquid ammonia changes to a gas, the liquid ice cream mixture becomes solid. As the ammonia gas pressure builds up inside the tank, it is sucked out in a suction line and directed through the system. This freezer was down for seven days and the oil inside the tank had congealed. Normal weekly maintenance requires the removal of used oil through the oil valve. Employee #1 closed all valve lines and used steam to loosen the thick oil. The steam caused pressure to build up inside the tank and with no relief valve, the tank exploded. When the tank exploded, Employee #1 was killed. Employee #2 was approximately 10 feet away and was hospitalized with burns to his eyes. Employee #3 was in an adjacent room and was injured when he inhaled the ammonia vapors.
Catastrophic failure of compressor oil separator
An oil separator on a two-stage ammonia refrigeration system became over pressurized and exploded, killing Employee #1. While looking for Employee #1 after the accident, Employee #2 fell into a drain. Ammonia that had been uncovered as a result of the explosion had flowed into the drain. Employee #2 was hospitalized.
Adding heat to NH3 compressed gas cylinder to speed up “charge”
At approxmately 3:15 pm on may 9, 1986, employees at a juice company, started to charge the number 1 line carbo-cooler, using a cylinder containing 150 pounds of anhydrous ammonia at 129 psi (room temperature). Employee #1, in an effort to speed the charging process, was adding water at 132 degrees to the ammonia cylinder (to raise the internal pressure). Employee #2 was working on 2 magnetic switches located near the sight glass on the carbo-cooler. Employee #3 was operating the #1 line filler, approximately 25 feet from the ammonia cylinder. Employee #4 was painting in aisle #3, approximately 45 feet from the cylinder. At approximately 3:30 pm the cylinder ruptured, producing a white cloud of ammonia gas. Employee #1, who was approximately 5 feet from the cylinder, was burned in the eyes and body and admitted to the hospital. Employee #2 was also admitted to the hospital. Employees #3 and #4 were both treated had released at the hospital. All employees reentered the plant at 5 pm. The anhydrous ammonia cylinder had a 21 inch long split in it, approximately 3 1/2 inches wide at the widest spot. On sunday, may 18, 1986, employee #1 died at loyola university burn center, chicago, illinois.
Catastrophic failure of Pressure Vessel
A pressure vessel in an ammonia refrigerator system ruptured under pressure of 170 psi. The explosion caused extensive physical damage and released dense clouds of ammonia gas. Employees #1 through 4 died of acute ammonia inhalation.