Tag Archives: electrical

Root Cause Analysis - Incident Investigation

DC Metro shut down for entire day after fire for inspections

By Kim Smiley 

A fire in a DC Metro tunnel early on March 14, 2016 caused delays on three subway lines and significant disruption to both the morning and evening commutes.  There were no injuries, but the similarities between this incident and the deadly smoke incident on January 12, 2015 (see our previous blog on this incident) led officials to order a 24-hour shutdown of the entire Metro system for inspections and repairs.

The investigation into the Metro fire is still ongoing, but the information that is known can be used to build an initial Cause Map.  A Cause Map is built by asking “why” questions and visually laying out all the causes that contributed to an incident.  Cause Mapping an issue can identify areas where it may be useful to dig into more detail to fully understand a problem and can help develop effective solutions.

So why was there a fire in the Metro tunnel?  Investigators have not released details about the exact cause, but have stated that the fire was caused by issues with a jumper cable.  Jumper cables are used in the Metro system to bridge gaps in the third rail, essentially functioning as extension cords.  The Metro system uses gaps in the third rail to create safer entry and exit spaces for both workers and passengers because of the potential danger of contact with the electrified third rail.  The third rail carries 750 volts of electricity used to power Metro trains and could cause serious injury or even death if accidently touched.

The jumper cables also carry high voltage and fires and/or smoke can occur if one malfunctions.  Investigators have not confirmed the exact issue that lead to this fire, but insulation failures have been identified in other locations and is a possible cause of the fire. (Possible causes can be added to the Cause Map with a “?” to indicate that more evidence is needed.)

One of the things that is always important to consider when investigating an incident is the frequency of occurrence of similar issues.  The scope of the investigation and possible solutions considered will likely be different if it was the 20th time an incident has occurred rather than the first. In this case, the fire was similar to another incident in January 2015 that caused a passenger death.  Having a second incident occur so soon after the first naturally raised questions about whether there were more unidentified issues with jumper cables.  The Metro system uses approximately 600 jumper cables and all were inspected during the day-long shutdown. Twenty-six issues were identified and repaired. Three locations had damage severe enough that Metro would have immediately stopped running trains through them if the extent of the damage had been known.

The General Manger of the DC Metro system, Paul J. Wiedefeld, is relatively new to his position and has been both praised and criticized for the shutdown.  Trying to implement solutions and reduce risk is always a balancing act between costs and benefits.  Was the cost of a full-day shutdown and inspections of all jumper cables worth the benefit of knowing that the cable jumpers have all been inspected and repaired?  At the end of the day, it’s a judgement call, but I personally would be more comfortable riding the Metro with my children now.

Root Cause Analysis - Incident Investigation

Is Having a Lockout/ Tagout (LOTO) Procedure Enough?

By Staff

The number of possible types of injuries occurring when performing work on energized equipment is impossible to count.  They can range from burns, to electrical shock, to crush injuries, to cuts/lacerations, and beyond.  In an effort to help eliminate some of these injuries, the OSHA standard for Control of Hazardous Energy (29 CFR 1910.147), more commonly known as lockout/tagout (LOTO), went into effect in 1989.  The purpose of the standard is to help companies establish the practices and procedures needed to prevent injury to workers when they are performing maintenance activities to equipment requiring an energy source.  Any company in violation of the standard is subject to a fine.  It is estimated that in 2013, there were approximately $14 million in federal and state fines, and lockout/tagout was the 5th most frequently violated standard in 2015.

However, the REAL goal of the standard is to keep people safe.  So how is the standard violated?  It can happen in many ways, but this blog takes a look at one specific incident to better understand  how it can happen.  This analysis is based on a case study presented in the article “Lockout/Tagout Accident Investigation” from the August 2014 issue of Occupational Health & Safety.

In this incident, several contractors were working on a project involving a particular switchgear.  Many of these contractors had performed lockout/tagout for the switchgear box related to the projects that they were working on.  After the work began, a worker from a different contractor was asked to clean out part of the switchgear.  Unfortunately, an arc flash occurred when he reached in the switchgear, resulting in burns to his hand and a blow-out injury to his knee.  Fortunately, the employee survived, recovered, and was able to return to his normal life.

A Cause Map can be built to analyze this issue.  The first step in Cause Mapping is to determine how the incident impacted the overall goals.  For this incident, the safety goal was the most obviously impacted goal due to the injuries that the worker sustained.  The goal is always for employees to leave the workplace in the same health in which they arrived.  Additionally, the regulatory goal was impacted since the injuries were severe enough that they were classified as recordable.

The Cause Map is a visual representation of the cause-and-effect relationships that contributed to the incident.  Starting with the impacted safety goal, ‘why’ questions can be asked to identify the key factors that caused the problem.  In this case, the injuries were caused by the fact that an arc flash occurred when the worker reached into the switchgear and he was not wearing personal protective equipment.  The worker was probably not wearing PPE because he thought that the switchgear was de-energized, and this was an effect of the fact that there were locks and tags already on the switchgear.  The arc flash was a result of the fact that the circuit breaker was energized when the worker reached in to clean it.  The circuit breaker was energized because of three factors: a different contractor had put it back in service the night before, the circuit was not tested by the worker, and the worker didn’t do his own lockout procedure.  Each of these problems can be further analyzed to reveal problems with communication, adding the task at the last minute and not including every task in a job safety analysis.

For this situation, and many like it, eliminating a cause anywhere on the map could have minimized the risk of the incident occurring.  For example, had the worker taken the time to put on protective equipment or test the circuit breaker, he might not have been injured.  Similarly, had the other contractors taken the time to update their locks/tags and ensure that they had communicated that the circuit had been reenergized to all interested parties, the worker might not have been injured.  This example demonstrates that having a lockout/tagout procedure is the first step in avoiding injuries.  Ensuring that the procedure is followed in combination with other safety standards is also important to minimize the risk of injury.

Root Cause Analysis - Incident Investigation

Passengers trapped in smoke-filled metro train

By Kim Smiley

A standard commute quickly turned into a terrifying ordeal for passengers on a metro train in Washington, DC the afternoon of January 12, 2015.  Shortly after leaving a station, the train abruptly stopped and then quickly filled with thick smoke. One passenger died as a result of the incident and 84 more were treated for injuries, predominantly smoke inhalation.

This incident can be analyzed by building a Cause Map, a visual root cause analysis.  A Cause Map visually lays out the cause-and-effect relationships to show all the causes that contributed to an issue.  The first step in the Cause Mapping process is to define the problem by filling in an Outline with the basic background information as well as documenting how the issue impacts the overall goals.  For this example, the safety goal is clearly impacted by the passenger death and injuries.  A number of other goals should also be considered such as the schedule goal which was impacted by significant metro delays.  (To view an Outline and initial Cause Map for this issue, click on “Download PDF” above.)

So why were passengers injured and killed?  Passengers were trapped on the train and it filled with smoke.  It is unclear why the train wasn’t able to back up to the nearby station once the smoke formed and investigators are working to learn more.  (Open issues can be documented on the Cause Map with a question mark to indicate that more evidence is needed.)  There are also questions about the time emergency workers took to reach the train to aid in evacuation of passengers so this is another area that will require more information to fully understand. By some account, it took 40 minutes for firefighters to reach the trapped passengers.

Initial reports are that smoke was caused by an electrical arcing event, likely from the cables supporting the high voltage third rail used to power the trains. The specifics of what caused the arc are being investigated by the National Transportation Safety Board and will be released when the investigation is concluded.  What is known is that there was significant smoke caused by the arc, but no fire.  There have also been reports of water near the rails that may have been a factor in the arcing.

Eyewitness accounts of this incident are horrifying.  People had little information and didn’t know whether there was fire nearby at first.  They were told to remain on the train and await rescue, but the rescue took some time, which surely felt longer to the scared passengers.  It won’t be clear what solutions need to be implemented to prevent similar problems in the future until the investigation is complete, but I think we can agree that metro officials need to work to ensure passenger safety going forward.