By Ronald L. Allen, MS, PE, CSP Senior Consulting Engineer, Fauske & Associates, LLC
Generally speaking, there are negative connotations associated with the phrase “Steering with Your Rearview Mirror” and its close cousin, “Hindsight is 20-20”. Despite the fact that no one likes to be second-guessed, huge opportunities are missed if lessons are not constructively learned from experience – including the experience of others.
Readers of this blog need no introduction to the value of incident investigation. In many cases, investigation reports or case studies represent the inverse and are often complements to safety standards. Safety standards utilize inductive reasoning to provide instruction and requirements needed to reduce risk. Investigations and case studies provide detail about breakdowns that allowed incidents to occur. Through deductive reasoning (i.e., identification of contributing and root causes), these reports often close the loop by reinforcing the need to adhere to the inductive-reasoning safety standards that were previously mentioned.
Because of the widespread use of dust collectors (a.k.a., air-material separators) across many industries, users of such equipment can benefit from the learnings produced by investigation of incidents at other facilities. Combustible dust fires and dust explosions involving collectors are at the top of the list for dust hazard incidents according to FM Global. Hence, Fauske & Associates, (FAI) plans to provide a series of articles dealing with dust collection systems beginning with this summary of the Chemical Safety Board’s (CSB) recently-published, case study detailing the background and causes of an October 2012 fire and explosion at a US Ink manufacturing facility (unit of Sun Chemical Corporation).
The incident occurred at US Ink’s East Rutherford, NJ’s facility and involved a recently-commissioned dust collector. The incident that resulted in burns to seven workers – including third degree burns to three workers – along with property damage and significant downtime. The new dust collector was installed as a part of a larger process modification and had only been in service for only two days when the incident occurred. The collection dust hopper and dust fines chute were filled with approximately 322 pounds of dust fines following the incident. The US Ink manufacturing process that associated with the incident employed both combustible dusts and flammable liquids (hybrid mixture).
The case study provides extensive background about the incident. It identifies actions taken by US Ink and its contractors that mitigated the severity of the incident along with discussions about contributing and root causes and recommendations.
On the favorable side of the equation, functioning fire and explosion suppression and isolation systems reduced the severity of the incident.
Key lessons from the incident that could assist any firm utilizing dust collection systems are summarized below. Readers are encouraged to review the rich detail provided in the complex case study for additional information. While some of the circumstances associated with the incident were unusual (e.g., retirement of lead engineer prior to commissioning the dust collecting equipment), those circumstances may not be unique or isolated.
A. Safety management concerns brought up in the CSB report:
B. Safety management concerns inferred in the CSB report
- Inadequate Project Oversight and Misrepresentation of Management of Change (MOC) Exemption: The CSB rejected US Ink’s argument that a process hazard analysis (PHA) was not necessary because the new dust (dry) collector was a replacement in kind for the former dust (wet) collector.
- Inadequate Management of Organization Change and Contractor Oversight: US Ink claimed to rely upon the expertise of the manufacturers of the dust collection system and on their contractors for smooth operation of the system without providing adequate oversight for the dust collection project. The study also observed that US Ink had failed to adequately engage its engineer staff to support the design, installation, and commissioning of the dust collection system.
- Ineffective Hazard Communication and Emergency Response Planning: Shortcomings referenced in the case study included:
- Failure to adhere to activate the facility evacuation plan in a timely fashion.
- Inadequate fire hazard and emergency training.
- Ineffective automatic fire alarm system associated with sprinkler system. NFPA requires audible and visible fire emergency notification.
- Audible alarm for sensing a pressure rise in the dust collector did not function properly
- Inadequate shutdown procedures
- Ineffective Employee Training on Dust Collection Mechanism:
- The 15-minute meeting following the start-up of the dust collector for supervisors and one of the day-shift operators was deemed as “inadequate” by the CSB.
- Absence of a fire or explosion incident prevention program
- No mechanism for operators to determine changes in the collector's performance. One worker reported that he relied on instinct.
- Failure to Communicate Lessons Learned from Previous Incident: The CSB observed that US Ink had not applied “lessons learned” from a similar fire incident that occurred in 2008 at the same facility. No injuries were associated with the earlier incident.
C. Additional design concerns, including:
- Hazard Assessment Not Conducted: Testing of materials for explosible properties was not performed. The company relied on values obtained from material suppliers – these values are questionable unless provided in an actual laboratory test report. Values gleaned from an SDS form is not sufficient.
- No Prestart Up Safety Review:
- Testing of equipment prior to start-up was not suitable (e.g., no measurement of system pressures were taken at commissioning of the dust collection system as required by NFPA 91 and NFPA 654).
- Equipment not inspected.
- Personal Protective Equipment: the CSB report states that US Ink employees were not wearing FRC (fire resistant clothing). One of the workers who sustained third degree burns was wearing a short-sleeve T-shirt. A hazard assessment conducted prior to start-up would have identified the requirement to wear FRC because of the risk of flash fires or explosions.
- Equipment Maintenance: the CSB reports that US Ink had knowledge that the system for collecting dust was operating improperly (defective interlock) during the weekend that preceded the incident but did not take effective action to investigate or remedy the situation.
- Procedures: Safe operating temperature parameters were not established.
- The dust pickup points in the dust collection system pulled excessive quantities of dust and condensable vapors into the ductwork, which operated at low conveying velocities. This accumulation in the ductwork was the fuel for the primary deflagration that initiated the incident chain of events.
- There was no automatic temperature control for mix tanks
- Installation of vacuum hoses for housekeeping purposes that were powered by the system for collecting dust without consideration of how those vacuum lines could affect the performance of the dust collection system.
- Lack of system controlling parameters for operators to monitor performance and detect system degradation
- The system for collecting dust not designed to prevent, contain, or extinguish fires:
- US Ink employee testimonies revealed that rubberized flexible hoses used for housekeeping were the first parts of the system to fail when the duct fire started.
- Flexible hose lengths exceeding recommended best practice of being “as short as possible” (usually not more than 3 feet) added resistance to branch lines.
Back to the value of investigations and “steering with your review mirror” . . . knowledge by itself does not produce improvement. Or, in the words of famed educator and author Henrietta Mears, “It is difficult to steer a parked car, so get moving”. Readers desiring assistance in applying the lessons described in this article or other combustible dust controls are encouraged to contact Fauske & Associates, LLC Risk Management Director Amy Theis, at firstname.lastname@example.org, 630-887-5211.