TRAPPED AMMONIA CAUSED AN INCIDENT DURING MAINTENANCE

 On January 7, 2023, at approximately 4:55 p.m., about one pound of anhydrous ammonia was released at the a Meats facility in Iowa.
At the time of the incident, the employee was working on an out-of-service ammonia compressor used in the refrigeration system. The compressor had been previously isolated from the system, and the ammonia was understood to have been removed entirely.
When removing the bolts on the flange connecting the outlet piping to the compressor, a burst of ammonia vapor was released directly into the employee’s chest and face. The employee was not wearing respiratory protection because the ammonia compressor was understood to be empty. The injured employee was taken to a hospital for treatment of the ammonia exposure injuries he suffered.
The company's investigation found that the company’s ammonia removal procedure allowed some ammonia to remain trapped between the compressor’s discharge check valve (a valve that only allows for single-direction flow) and an isolation valve. Another valve needed to be opened to remove ammonia from the isolated piping. It was determined that this valve had remained closed because the procedure did not include this valve.

Based on the company's investigation, the CSB determined that the probable cause of the anhydrous ammonia release was disconnecting the outlet piping from the ammonia compressor while some ammonia remained within the equipment. The company’s ammonia removal procedure contributed to the incident because following it did not effectively remove the ammonia from the compressor.

Source:CSB.gov

ICE DAMAGES EQUIPMENT DUE TO ANAMALOUS EXPANSION - ANOTHER INCIDENT

Water exhibits "anomalous behavior" because it expands when cooled from 4°C to 0°C, unlike most substances which contract when cooled. 

On December 24, 2022, at approximately 10:55 a.m., an accidental release of approximately 1,400 pounds of light straight-run gasoline (flammable hydrocarbon) occurred within a hydrotreating unit at a refinery. The release formed a vapor cloud that ignited, resulting in an explosion and fire. One operator was seriously injured due to thermal burns. The company estimated $40 million in property damage. 

From June 17, 2022, until the day of the incident, a steam turbine-driven pump and the surrounding equipment associated with the unit were a temporary dead-leg (a section of piping with no flow). During this period, the pump was locked out for maintenance by closing the inlet and outlet valves to isolate the equipment and piping from the process flow. As a result, the process fluid (hydrocarbon and water) within this equipment was stagnant for 190 days before the incident.

The chemical release occurred during a partial shutdown of the plant due to the severe cold weather. The ambient temperature dropped below freezing between December 21–24, 2022, freezing the water within the isolated pump’s piping (the dead-leg). On December 24, 2022, the daytime temperature increased, and the ice began to melt. At 10:40 a.m., flammable hydrocarbons escaped from the flange of an ice-damaged valve. This release quickly created a flammable vapor cloud, which drifted toward a fired heater (furnace), where it most likely ignited. Simultaneously, two operators, wearing their everyday flame-
resistant coveralls, were performing emergency response tasks in the fired heater area and were engulfed in the colorless and odorless portion of the vapor cloud. The two operators were injured when the vapor cloud exploded.

Probable Cause
Based on the company's investigation, the CSB determined that the probable cause of the incident was the release of flammable hydrocarbons through the flange of an ice-damaged valve. A nearby fired heater most likely ignited the flammable hydrocarbon vapor cloud.
Contributing to the incident was the company's dead-leg identification and management program, which did not identify and protect the temporary dead-leg created during maintenance activities. As a result, the water in this piping froze and expanded during cold weather.
Also contributing to the severity of the incident was the company's emergency response procedure, which allowed the operators to respond to the flammable vapor cloud to “eliminate any source of ignition if it can be done safely.” Under these circumstances, the operators relied (in part) on their senses to determine when and where it was safe to perform emergency response tasks near imperceptible portions of the vapor cloud. The company could have reduced the severity of the event by establishing clear policies and training its operators to respond to the flammable vapor release without putting themselves in harm’s way.

 Source: CSB.gov

ANOTHER INCIDENT DUE TO MOVING EQUIPMENT IN PLANTS

 On December 19, 2022, at approximately 11:10 a.m., an accidental release of anhydrous ammonia occurred at a facility in Massachusetts. Exposure to the toxic ammonia vapor fatally injured one contract worker and seriously injured another contract worker. In addition, the release caused about $4 million in property damage.
The company had hired a contractor to install an electrical (ceiling-mounted) heater to replace an existing leaking steam heater that provided comfort heating inside the facility’s ammonia refrigeration room. The work plan included using a scissor lift to access the installation area. At the time of the incident, two contract workers were on the scissor lift to install the electric heater. While the scissor lift was in an elevated position, the lift was moved forward and then upward, impacting an ammonia refrigeration valve.                                                                                                                                                                       After the scissor lift impacted the piping, a leak formed at the partially severed ½-inch threaded piping connection to the larger ammonia system piping. The anhydrous ammonia was released as a vapor and engulfed the workers. Contractor 1, who was directly in front of the damaged piping, was unable to escape and was fatally injured by the release. Contractor 2, who was further away from the point of release, jumped over the lift’s guardrail to escape from the area.
Two employees heard the sound of the release and saw the ammonia vapor cloud through a door window. One of these employees grabbed a two-way radio and instructed maintenance to initiate an evacuation of the building. Alarms in the ammonia machine room and throughout the building were activated, alerting all employees to evacuate from the building. Evacuating employees found Contractor 2 outside the building. After checking on Contractor 2, one of the employees called emergency responders. Emergency responders recovered Contractor 1’s body from the scissor lift and transported Contractor 2 to a nearby hospital to treat his serious injuries.
Approximately 22,000 pounds of ammonia was released during the incident.

Source:CSB.gov

DESIGN YOUR SAFETY DEVICES DISCHARGE CORRECTLY!

 On January 15, 2022, at 4:51 a.m., 201 pounds of hot methylene diphenyl diisocyanate (MDI) were accidentally released, seriously injuring two workers at a facility in Louisiana.
The company's investigation of this event concluded that the accidental release occurred when a rupture disc activated prematurely. The design activation pressure was 30 pounds per square inch (psi), and process data indicated that this emergency pressure-relief system activated at about 13 psi.

The equipment protected by this rupture disc was typically operated under vacuum conditions. At the time of the incident, however, the equipment was operating at an elevated pressure due to a problem that had developed within the system used to create and maintain the low-pressure (vacuum) conditions. Although the operating pressure was elevated, it was within safe operating limits.
When the rupture disc activated, a 400-degree Fahrenheit mixture of liquid and vapor MDI discharged into 8-inch piping that was vertically orientated downward and ended about eight inches above the concrete floor. At the time of the incident, non-essential workers were not restricted from the area near the rupture disc discharge piping because the system was operating within the safe operating limits.                               
When the high-velocity, two-phase mixture exited the discharge piping, it hit the solid floor, spraying two contract maintenance workers installing a pump near the rupture disc’s discharge piping. The two maintenance workers were hospitalized with thermal burns from exposure to the hot fluid.                                                                                                                                                                  Although Rubicon’s process hazard analysis had identified personnel exposure to hot MDI as a potential consequence of activating the rupture disc, the company had not mitigated the potential hazard of personnel working near the rupture disc discharge piping.

Source:CSB.gov

"IGNITION SOURCES ARE FREE"

 On October 6, 2021, an accidental release of crude oil and produced water occurred during vacuum truck loading operations at  a facility. An unknown amount of flammable vapors from the released fluids ignited, resulting in a flash fire that seriously injured the vacuum truck driver.
An emulsion layer periodically developed at the oil and water interface within the heater treater at the facility and grew thicker over time. The presence of the emulsion layer impaired the heater treater’s efficiency. To address this problem, the company periodically removed the emulsion layer by transferring fluids from the heater treater to a vacuum truck.
The company's investigation identified the sequence of events as follows:
1. The contractor vacuum truck driver discussed the planned work with an operator, and the operator approved the truck driver to start the loading operation;
2. The vacuum truck driver connected a three-inch hose between the truck and the heater treater;
3. The driver opened valves on each end (the truck inlet valve and the process valve);
4. After these valves were opened, produced water and crude oil flowed from the pressurized heater treater into the vacuum truck (the truck’s vacuum pump was not operating);
5. When the vacuum truck driver detected crude oil, he closed the process valve on the heater treater to stop additional fluid from entering the hose; and
6. The vacuum truck driver disconnected the hose from the heater treater, and the contents flowed out of the truck and into the atmosphere through the open hose. The released fluid contained flammable hydrocarbon vapor that ignited, creating a flash fire that seriously injured the driver.
The company’s investigation concluded that the fired heater treater components may have been the ignition source. The heater treater burner was inadvertently left online during the vacuum truck loading operation. The company's investigation team did not eliminate static electricity as the potential ignition source because the hose components were non-conductive, and the truck was not electrically bonded or grounded.
The company's investigation identified additional causal factors, including:
A. The procedures, training, and administrative controls did not effectively control the hazards associated with draining an emulsion layer from its heater treaters;
B. No safety or hazard analysis was performed to identify or control potential hazards before performing this work;
C. There was no pre-determined location to electrically ground or bond the vacuum truck; and
D. Using system process pressure from the vessel to transfer the fluid to the vacuum truck rather than using the truck’s vacuum pump to pull the fluid into the truck contributed to the incident.

Siurce:CSB.gov

BEWARE OF MOVING EQUIPMENT IN PLANTS......

On June 14, 2021, at approximately 6:50 a.m., an accidental release of mineral oil occurred at a facility  that led to the permanent closure of the facility
Leading up to the incident, a contractor was hired to replace insulation on its heating oil piping system. To reach a portion of this piping, the contractor used a scissor lift.
As the contractor began raising the scissor lift near the work location, the top guardrail of the lift impacted a section of a ½-inch piping assembly that included a valve. This threaded piping was connected to a four-inch pipe containing mineral oil, which was part of a hot oil system that provided heating for other process equipment.
After the guardrail impacted the piping, a leak formed at the ½-inch threaded connection to the four-inch piping. The hot mineral oil, which was over 500 degrees Fahrenheit, was released as an aerosol. The mineral oil formed a white cloud and created the electrostatic conditions that most likely ignited the mineral oil.

Upon seeing the white cloud, workers responded to the release. The workers tried to contain the spill by placing absorbent barriers around mineral oil on the floor. Additionally, the workers shut off the oil heating system. The workers also lowered the pressure of the hot oil system, but the leak could not be remotely isolated from a safe location. As a result, the mineral oil ignited, and the fire grew and destroyed the facility.
The CSB estimated that less than 100 pounds of mineral oil was released between the start of the release and the time of ignition.
Probable Cause
Based on the company's investigation, the CSB determined that the probable cause of the mineral oil release was piping damage that resulted from force applied by the scissor lift. The flammable mineral oil was most likely ignited by static electricity. The hot oil system did not allow for the remote isolation of the damaged piping. Had they been able to stop the flow of mineral oil through remote isolation from a safe location, the incident could have been less severe.

Source:CSB.gov