Reposted from LBN as per recommendation from forum hosts:
Source: National Transportation Safety Board
https://www.ntsb.gov/investigations/Documents/RRD23MR005%20East%20Palestine%20OH%20Prelim.pdf
Issued: February 23, 2023
"On February 3, 2023, about 8:54 p.m. local time, eastbound Norfolk Southern Railway (NS) general merchandise freight train 32N derailed 38 railcars on main track 1 of the NS Fort Wayne Line of the Keystone Division in East Palestine, Ohio. The derailed equipment included 11 tank cars carrying hazardous materials that subsequently ignited
Train 32N was traveling about 47 mph at the time of the derailment, which was less than the maximum authorized timetable speed of 50 mph.
Train 32N was operating with a dynamic brake application as the train passed a wayside defect detector on the east side of Palestine, Ohio, at milepost (MP) 49.81.
The wayside defect detector, or hot bearing detector (HBD), transmitted a critical audible alarm message instructing the crew to slow and stop the train to inspect a hot axle. The train engineer increased the dynamic brake application to further slow and stop the train.
During this deceleration, an automatic emergency brake application initiated, and train 32N came to a stop.
On the Fort Wayne Line of the Keystone Division, NS has equipped their rail network with HBD systems to assess the temperature conditions of wheel bearings while en route. The function of the HBD is to detect overheated bearings and provide audible real-time warnings to train crews. Train 32N passed three HBD systems on its trip before the derailment. At MP 79.9, the suspect bearing from the 23rd car had a recorded temperature of 38F above ambient temperature. When train 32N passed the next HBD, at MP 69.01, the bearing's recorded temperature was 103F above
ambient.
The third HBD, at MP 49.81, recorded the suspect bearing's temperature at 253F above ambient.
NS has established the following HBD alarm thresholds (above ambient temperature) and criteria for bearings:
Between 170F and 200F, warm bearing (non-critical); stop and inspect
A difference between bearings on the same axle greater than or equal to 115F (non-critical); stop and inspect
Greater than 200F (critical); set out railcar"
Read more:
https://www.ntsb.gov/investigations/Documents/RRD23MR005%20East%20Palestine%20OH%20Prelim.pdf
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Key points & takeaways in the NTSB preliminary report:
1) The train was operating within allowable speed limits (paragraph 1 above)
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2) The train was operating in dynamic braking mode (paragraph 2 above).
Dynamic braking is an additional braking system over & above the airbrakes and involves the use of the electric traction motors on a diesel-electric locomotive to slow the train.
In many cases dynamic braking alone will just about hold back what tonnage a locomotive can pull, with conventional airbrakes being "blended-in" at lower speeds to bring the train to a complete stop.
Furthermore, the NTSB Chair has issued a statement indicating that the use of conventional airbrakes was not the root cause of the derailment:
(Per my prior post at:
https://www.democraticunderground.com/10143035850 )
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3) The rail car that initiated the derailment had an overheated wheel bearing (paragraphs 3 & 4 above)
A device that can play a role in preventing derailments is the wayside hot-box detector. It uses infrared sensors to detect bearings, axles or other components of a rail car that are overheating, then uses radio signals to flag rail crews of any overheated components.
Train 32N passed three HBD systems on its trip before the derailment, and these hotbox detectors appeared to be working.
At Mile 79.9, the suspect bearing from the 23rd car had a recorded temperature of 38F above ambient temperature.
At Mile 69.01, the bearing's recorded temperature was 103F above ambient.
At Mile 49.81, the HBD recorded the suspect bearing's temperature at 253F above ambient.
Between 170F and 200F above ambient temperature the rules state for the crew to stop and inspect the train and greater than 200F the crew must uncouple the defective railcar from the rest of the train.
As per the operating rules, the bearing temperature threshold that would invoke stopping the train and remedial action by the crew was not reached until Mile 49.81 - right at the east side of Palestine, Ohio
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4) The report also indicates that the partners in the investigation include:
The FRA,
Norfolk Southern Railway,
Trinity Industries Leasing Company,
and GATX Corporation among others.
In most cases, the companies that own the railcars are the ones responsible for railcar safety inspections. Norfolk Southern does not own the railcars but owns the locomotives & right of way.
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Summary:
The root cause of the derailment was not brakes, but an overheated bearing on one of the railcars owned by a third party.
The wayside sensors appeared to be working correctly and the crew following the operating rules
The NTSB investigation is still ongoing and will be up to them to determine whether the 3rd-party railcar owners, &/or Norfolk Southern & other parties bear - or share - in the responsibility.
It will also be up to them & the FRA to determine if required, and recommend & enforce, any changes to the operating rules such as lowering the temperature threshold (recorded by the hotbox detectors) at which to stop a train
