Monthly Archives: February 2015

Root Cause Analysis - Incident Investigation

Early Problems with Mark 14 Torpedoes

By Kim Smiley

The problems with Mark 14 torpedoes at the start of World War II are a classic example that illustrates the important of robust testing.  The Mark 14 design included brand new, carefully guarded technology and was developed during a time of economic austerity following the Great Depression.  The desire to minimize costs and to protect the new exploder design led to such a limited test program that not a single live-fire test with a production model was done prior to deploying the Mark 14.

The Mark 14 torpedo design was a step change in torpedo technology. The new Mark VI exploder was a magnetic exploder designed to detonate under a ship where there was little to no armor and where the damage would be greatest.  The new exploder was tested using specially instrumented test torpedoes, but never a standard torpedo. Not particularly shocking given the lack of testing, the torpedoes routinely failed to function as designed once deployed.

The Mark 14 torpedoes tended to run too deep and often failed to detonate near the target. One of the problems was that the live torpedoes were heavier than the test torpedoes so they behaved differently. There were also issues with the torpedo’s depth sensor.  The pressure tap for the sensor was in the rear cone section where the measured pressure was substantially less than the hydrostatic pressure when the torpedo was traveling through the water.  This meant that the depth sensor read too shallow and resulted in the torpedo running at deeper depths than its set point.  Eventually the design of the torpedo was changed to move the depth sensor tap to the mid-body of the torpedo where the readings were more accurate.

The Mark 14 design also had issues with premature explosions.  The magnetic exploder was intended to explode near a ship without actually contacting it.  It used small changes in the magnetic field to identify the location of a target. The magnetic exploder had been designed and tested at higher latitudes and it wasn’t as accurate closer to the equator where the earth’s magnetic field is slightly different.

In desperation, many crews disabled the magnetic exploder on Mark 14 torpedoes even before official orders to do so came in July 1943.  Use of the traditional contact exploder revealed yet another design flaw in the Mark 14 torpedoes.  A significant number of torpedoes failed to explode even during a direct hit on a target.  The conventional contact exploder that was initially used on the Mark 14 torpedo had been designed for earlier, slower torpedoes.  The firing pin sometimes missed the exploder cap in the faster Mark 14 design.

The early technical issues of the Mark 14 torpedoes were eventually fixed and the torpedo went on to play a major role in World War II.  Mark 14 torpedoes were used by the US Navy for nearly 40 years despite the early issues.  But there is no doubt that it would have been far more effective and less painful to identify the technical issues during testing rather than in the field during war time.  There are times when thorough testing may seem too expensive and time consuming, but having to fix a problem later is generally much more difficult.  No one wants to waste effort on unnecessary tests, but a reasonable test program that verifies performance under realistic conditions is almost always worth the investment.

To view a high level Cause Map of the early issues of the Mark 14 torpedoes, click “Download PDF”.

You can also learn more about the torpedoes by clicking here and here.

Root Cause Analysis - Incident Investigation

Deadly Train-Car Collision

By Kim Smiley

On February 3, 2015, an SUV was struck by a commuter train near Valhalla, New York.  The driver of the vehicle and 5 train passengers were killed in the accident.  The National Transportation Safety Board (NTSB) is investigating the accident to determine what went wrong.

An initial Cause Map, a visual root cause analysis, can be built to analyze and document what is known about this train-car collision.  A Cause Map visually lays out the cause-and-effect relationships that contributed to an issue and focuses on understanding all the causes, not THE root cause.  Generally, identifying more causes results in a greater number of potential solutions being considered.

So why did the train hit a vehicle?  Eyewitnesses have stated that the SUV was hit by a crossing gate as it descended.    It is not clear why the SUV didn’t stop prior to entering the railroad crossing area. The driver pulled the SUV forward onto the tracks rather than backing up and the train struck the vehicle shortly after.  Investigators don’t know why the driver stopped on the tracks, but initial reports are that all safety features, such as the crossing gate, signs and train horn, were functioning properly at the time of the accident.

Unfortunately, it’s not unusual for passengers in a vehicle struck by a train to be injured or killed, but it is less common for fatalities among the train passengers.  Investigators are working to determine what made this accident particularly dangerous for train passengers.  The NTSB plans to use information about the passengers’ injuries and a diagram of where people were sitting on the train to try to understand what happened during the collision.  Post-accident photos of the train show that significant fire damage occurred, likely fueled by the gas in the SUV.

One of the open questions is whether the electrified third rail contributed to the accident and subsequent injuries. Metro-North uses an unusual “under-running” third rail design where power is taken from the bottom of the rail.  During the collision, 400 feet of the third rail broke apart and 12 pieces pierced both the SUV and the train. This rail design uses a metal shoe that slips underneath the third rail and some think that the force of the collision may have essentially pried up the rail and threw it into the train and vehicle.

Open questions can be documented on the initial Cause Map with a question mark.  As more information becomes available, the Cause Map can quickly be updated.  Typically, Cause Maps are built in Excel and different versions can be saved as different sheets to document the investigation process.

Click on “Download PDF” above to view an initial Cause Map of this accident, built from the information in the media articles on the accident.

Root Cause Analysis - Incident Investigation

TransAsia Plane Crashes into River in Taiwan

By Kim Smiley

On February 4, 2015, there were 53 passengers onboard TransAsia Airways Flight 235 when the plane crashed into the Keelung River shortly after taking off from the Taipei Shonshan Airport.  There were 15 survivors from this dramatic crash where the plane hit a bridge and taxi cab prior to turning upside down before hitting the river. (The crash was caught on video by dash cameras from a vehicle on the bridge and can be seen here.)

Investigators are still working to determine exactly what happened, but some early findings have been released.  The plane involved in this crash was a turboprop with two engines.  This model of plane can fly safely with only one engine, but both engines had issues immediately prior to the crash so the pilots were unable to control the plane.

Data from the flight recorder shows that the right engine idled 37 seconds after takeoff.  No details about what caused the problem with the right engine have been made available.  The initial investigation findings are that the left engine was likely manually shut down by the pilots.  It’s not clear why the functioning engine would have been intentionally shut down. Early speculation is that it was a mistake and that the pilots were attempting to restart the idled right engine when they hit the switch for the operating left engine.

The investigation into the crash is ongoing and the final report isn’t expected to be released for about a year, but based on the initial findings, a few solutions to help reduce the likelihood of future crashes have already been implemented.  TransAsia has grounded most of its turboprop aircraft pending additional pilot instruction and requalification because it is believed that pilot action may well have contributed to the deadly accident.  More than 100 domestic flights have been canceled as a result.  Additionally, Taiwan’s Civil Aeronautic Administration has announced that the carrier will be banned from adding new international routes for 12 months.  A previous crash in July 2014 had already tarnished TransAsia’s reputation and this latest disaster will certainly be scrutinized by the authorities.

An initial Cause Map, a visual root cause analysis, can be built to analyze the information that is available on this crash and to document where there are still open questions.  To view a Cause Map and Outline of this incident, click on “Download PDF” above.

Uncategorized

Working Conditions Raise Concerns at Fukushima Daiichi

By ThinkReliability Staff

The nearly 7,000 workers toiling to decommission the reactors at Fukushima Daiichi after they were destroyed by the earthquake and tsunami on March 11, 2011 face a daunting task (described in our previous blog). Recent events have led to questions about the working conditions and safety of these workers.

On January 16, 2015, the local labor bureau instructed the utility that owns the plants to reduce industrial accidents. (The site experienced 23 accidents in fiscal year 2013 and 55 so far this fiscal year.) Three days later, on January 19, a worker fell into a water storage tank and was taken to the hospital. He died the next day, as did a worker at Fukushima Daini when his head got caught in machinery. (Fukushima Daini is nearby and was less impacted by the 2011 event. It is now being used as a staging site for the decommissioning work at Fukushima Daiichi.)

Although looking at all industrial accidents will provide the most effective solutions, often digging into just one in greater detail will provide a starting point for site improvements. In this case, we will look at the January 19 fall at Fukushima Daiichi to identify some of the challenges facing the site that may be leading to worker injuries and fatalities.

A Cause Map, or visual form of root cause analysis, is begun by determining the organizational impacts as a result of an incident. In this case the worker fall impacted the safety goal due to the death of the worker. The environmental goal was not impacted. (Although the radiation levels at the site still require extensive personal protective equipment, the incident was not radiation-related.) Workers on site have noted difficult working conditions, which are thought to be at least partially responsible for the rise in incidents, as are the huge number of workers at the site (itself an impact to the labor/time goal). Lastly, local organizations have raised regulatory concerns due to the high number of incidents at the site.

An analysis of the issues begins with one impacted goal. In this case, the worker death resulted from a fall into a ten-meter empty tank. The worker was apparently not found immediately (though specific timeline details and whether or not that impacted the worker’s outcome have not been released) because it appears he was working alone, likely due to the massive manpower needs at the site. Additionally, the face masks worn by all workers (due to the high radiation levels still present) limit visibility.

The worker was checking for leaks at the top of the tank, which is being used to store water used to cool the reactors at the site. There is a general concern about lack of knowledge of workers (many of whom have been hired recently with little or no experience doing the types of tasks they are now performing), though again, it’s unclear whether this was applicable in this case. Of more concern is the ineffective safety equipment – apparently the worker did not securely fasten his safety harness.

The reasons for this, and the worker falling in the first place, are likely due to worker fatigue or lack of concentration. Workers at the site face difficult conditions doing difficult work all day (or night) long, and have to travel far afterwards, as the surrounding area is still evacuated. Reports of mental health issues and fatigue in these workers has led to the opening of a new site providing meals and rest for these workers.

These factors are likely contributing to the increase in accidents, as is the number of workers at the site, which doubled from December 2013 to December 2014. Local organizations are still calling for action to reduce these actions. “It’s not just the number of accidents that has been on the rise. It’s the serious cases, including deaths and serious injuries that have risen, so we asked Tokyo Electric to improve the situation,” says Katsuyoshi Ito, a local labor standards inspector.

In addition to improving working conditions, the site is implementing improved worker training – and looking at discharging wastewater instead of storing it, which would reduce the pieces of equipment required to be monitored and maintained. Improvements must be made, because decades of work remains before work at the site will be completed.

Click here to sign up for our FREE webinar “Root Cause Analysis Case Study: Fukushima Daiichi” at 2:00 pm EDT on March 12 to learn more about how the earthquake and tsunami on March 11, 2011 impacted the plant.