The narrowest defensible public statement
The NTSB preliminary report issued February 23, 2023 says responders began a controlled venting and burning of five derailed vinyl chloride tank cars about 4:40 p.m. on February 6 because the temperature inside one tank car was still rising, which the report says suggested polymerization that could pose an explosion hazard. The report publishes no tank temperature readings and no analysis establishing an imminent rupture or the necessity of venting, and the NTSB lists the venting and burning for review. The three detector readings it does publish, 38, 103 and 253°F above ambient, are of a wheel bearing on the 23rd car, not of any tank car.
Every clause above rests on an excerpt shown on this page. Nothing here describes anyone’s motive.
Three wayside warnings, one bearing
Measured object: Suspect wheel bearing, 23rd car. Unit: °F above ambient. These are not tank car temperatures, and the report gives no absolute temperature, ambient value, or passage time for any detector.
| Span | Mileposts | Milepost miles | Reading change | Elapsed time |
|---|---|---|---|---|
| Detector 1 to 2 | MP 79.9 to MP 69.01 | 10.89 | +65°F | Not reported |
| Detector 2 to 3 | MP 69.01 to MP 49.81 | 19.20 | +150°F | Not reported |
| Detector 1 to 3 | MP 79.9 to MP 49.81 | 30.09 | +215°F | Not reported |
Changes are differences of above ambient readings. Ambient temperature at each detector is not reported, so they are not measured changes in absolute bearing temperature.
Selecting a detector needs JavaScript. Detector 3 is shown, and every excerpt is in the source ledger below.
Detector 3 of 3
MP 49.81, 253°F above ambient at the bearing
The third HBD, at MP 49.81, recorded the suspect bearing’s temperature at 253°F above ambient.
- Threshold comparison
- above the critical threshold (greater than 200)
- What the excerpt shows
- The suspect bearing on the 23rd car read 253°F above ambient at MP 49.81, the third of three detectors the report lists.
- Change from the previous detector
- +150°F from detector 2, over 19.20 milepost miles. Elapsed time is not reported. Across all three: +215°F over 30.09 milepost miles.
- Inference limits
- Above the NS critical line quoted in the report (greater than 200). The report says this detector sent a critical audible alarm. No passage time, ambient value or absolute temperature is given. This is a bearing reading, not a tank car reading.
Between 170°F and 200°F, warm bearing (non-critical); stop and inspect
A difference between bearings on the same axle greater than or equal to 115°F (non-critical); stop and inspect
Greater than 200°F (critical); set out railcar
Sequence as reported, at the resolution reported
Items are in the report’s order and are evenly spaced; spacing is not time. Badges show how precisely each item is timed. Only the derailment and the start of venting carry clock times, and both are approximate.
- E01
Order only No clock time reported
Detector 1 passage, MP 79.9
At MP 79.9, the suspect bearing from the 23rd car had a recorded temperature of 38°F above ambient temperature.
NTSB, issued February 23, 2023, PDF p. 3 - E02
Order only No clock time reported
Detector 2 passage, MP 69.01
When train 32N passed the next HBD, at MP 69.01, the bearing’s recorded temperature was 103°F above ambient.
NTSB, issued February 23, 2023, PDF p. 3 - E03
Order only No clock time reported
Detector 3 passage under dynamic braking, MP 49.81
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.
NTSB, issued February 23, 2023, PDF p. 2 The third HBD, at MP 49.81, recorded the suspect bearing’s temperature at 253°F above ambient.
NTSB, issued February 23, 2023, PDF p. 3 - E04
Order only No clock time reported
Critical audible alarm to the crew
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.
NTSB, issued February 23, 2023, PDF p. 3 - E05
Order only No clock time reported
Engineer increases dynamic braking
The train engineer increased the dynamic brake application to further slow and stop the train.
NTSB, issued February 23, 2023, PDF p. 3 - E06
Order only No clock time reported
Automatic emergency brake; train stops
During this deceleration, an automatic emergency brake application initiated, and train 32N came to a stop.
NTSB, issued February 23, 2023, PDF p. 3 - E07
About, to the minute February 3, 2023 about 8:54 p.m. local time
Derailment of 38 railcars
The report gives this time for the derailment but does not place it against the alarm, braking or stop steps.
On February 3, 2023, about 8:54 p.m. local time, eastbound Norfolk Southern Railway (NS) general merchandise freight train 32N derailed 38 railcars
NTSB, issued February 23, 2023, PDF p. 1 - E08
Order only No clock time reported
Crew sees fire and smoke; notifies dispatcher
After the train stopped, the crew observed fire and smoke and notified the Cleveland East dispatcher of a possible derailment.
NTSB, issued February 23, 2023, PDF p. 3 - E09
Date only February 5, 2023
Fire mitigated; one tank car's internal temperature reported still rising
On February 5, responders mitigated the fire, but five derailed DOT-105 specification tank cars
NTSB, issued February 23, 2023, PDF p. 3 carrying 115,580 gallons of vinyl chloride continued to concern authorities because the temperature inside one tank car was still rising.
NTSB, issued February 23, 2023, PDF p. 3 Evidence gap
No tank temperature readings are published
Internal tank temperature value: Not reported. No reading, rate, pressure, car number or measurement time stands between the February 5 concern and the February 6 venting in this record.
- E10
Not dated No clock time reported
Venting scheduled; evacuation zone expanded; ditches dug
Who scheduled it, and when the decision was made, are not reported.
Responders scheduled a controlled venting of the five vinyl chloride tank cars to release and burn the vinyl chloride, expanded the evacuation zone to a 1-mile by 2- mile area, and dug ditches to contain released vinyl chloride liquid while it vaporized and burned.
NTSB, issued February 23, 2023, PDF p. 3 - E11
About, to the minute February 6, 2023 about 4:40 p.m.
Controlled venting and burning begins
The controlled venting began about 4:40 p.m. on February 6 and continued for several hours.
NTSB, issued February 23, 2023, PDF p. 3 - E12
Date only February 23, 2023
NTSB preliminary report issued (evidence cutoff)
Issued: February 23, 2023 Preliminary Report RRD23MR005
NTSB, issued February 23, 2023, PDF p. 1 This information is preliminary and subject to change.
NTSB, issued February 23, 2023, PDF p. 1
Observation, interpretation, and what is missing
Reported observation
What the report says was seen or recorded
Three hot bearing detectors recorded the same suspect wheel bearing, on the 23rd car, at 38, 103 and 253°F above ambient, in that passage order.
At MP 79.9, the suspect bearing from the 23rd car had a recorded temperature of 38°F above ambient temperature.
NTSB, issued February 23, 2023, PDF p. 3 When train 32N passed the next HBD, at MP 69.01, the bearing’s recorded temperature was 103°F above ambient.
NTSB, issued February 23, 2023, PDF p. 3 The third HBD, at MP 49.81, recorded the suspect bearing’s temperature at 253°F above ambient.
NTSB, issued February 23, 2023, PDF p. 3 The report quotes NS alarm thresholds of 170 to 200 (warm, stop and inspect), a same axle difference of 115 or more, and greater than 200 (critical, set out railcar).
NS has established the following HBD alarm thresholds (above ambient temperature) and criteria for bearings:
NTSB, issued February 23, 2023, PDF p. 3 Between 170°F and 200°F, warm bearing (non-critical); stop and inspect
NTSB, issued February 23, 2023, PDF p. 3 A difference between bearings on the same axle greater than or equal to 115°F (non-critical); stop and inspect
NTSB, issued February 23, 2023, PDF p. 3 Greater than 200°F (critical); set out railcar
NTSB, issued February 23, 2023, PDF p. 3 The third detector sent a critical audible alarm; the train then slowed and stopped under an automatic emergency brake application.
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.
NTSB, issued February 23, 2023, PDF p. 3 During this deceleration, an automatic emergency brake application initiated, and train 32N came to a stop.
NTSB, issued February 23, 2023, PDF p. 3 On February 5 the temperature inside one of five derailed vinyl chloride tank cars was reported as still rising. No value, rate, time, car number or measurement method is given.
On February 5, responders mitigated the fire, but five derailed DOT-105 specification tank cars
NTSB, issued February 23, 2023, PDF p. 3 carrying 115,580 gallons of vinyl chloride continued to concern authorities because the temperature inside one tank car was still rising.
NTSB, issued February 23, 2023, PDF p. 3 Responders scheduled the controlled venting, expanded the evacuation zone and dug ditches; venting began about 4:40 p.m. on February 6 and continued for several hours.
Responders scheduled a controlled venting of the five vinyl chloride tank cars to release and burn the vinyl chloride, expanded the evacuation zone to a 1-mile by 2- mile area, and dug ditches to contain released vinyl chloride liquid while it vaporized and burned.
NTSB, issued February 23, 2023, PDF p. 3 The controlled venting began about 4:40 p.m. on February 6 and continued for several hours.
NTSB, issued February 23, 2023, PDF p. 3
Preliminary interpretation
What the report says it may mean
The report reads the rising tank temperature as suggesting polymerization, which could pose an explosion hazard. This is a stated possibility, not a confirmed reaction.
This increase in temperature suggested that the vinyl chloride was undergoing a polymerization reaction, which could pose an explosion hazard.
NTSB, issued February 23, 2023, PDF p. 3 Video showed what appeared to be a wheel bearing in the final stage of overheat failure; the bearing and wheelset are still to be examined.
Surveillance video from a local residence showed what appeared to be a wheel bearing in the final stage of overheat failure moments before the derailment.
NTSB, issued February 23, 2023, PDF p. 4 The wheel bearing and affected wheelset have been collected as evidence and will be examined by the NTSB.
NTSB, issued February 23, 2023, PDF p. 4
Not yet established
What the report does not show
Any internal tank temperature value, trend over time, or rate of rise. The report gives only the word rising.
carrying 115,580 gallons of vinyl chloride continued to concern authorities because the temperature inside one tank car was still rising.
NTSB, issued February 23, 2023, PDF p. 3 Proof of an actual polymerization reaction. The report says the rise suggested one.
This increase in temperature suggested that the vinyl chloride was undergoing a polymerization reaction, which could pose an explosion hazard.
NTSB, issued February 23, 2023, PDF p. 3 An imminent tank rupture, or its timing. The report says only that the reaction could pose an explosion hazard.
This increase in temperature suggested that the vinyl chloride was undergoing a polymerization reaction, which could pose an explosion hazard.
NTSB, issued February 23, 2023, PDF p. 3 The necessity of venting and burning, or which alternatives were weighed. The NTSB lists the venting and burning as a subject of future review.
a review of the accident response, including the venting and burning of the vinyl chloride
NTSB, issued February 23, 2023, PDF p. 4 Absolute bearing temperatures, ambient temperatures, and detector passage times. Readings are reported only as degrees above ambient, in passage order.
At MP 79.9, the suspect bearing from the 23rd car had a recorded temperature of 38°F above ambient temperature.
NTSB, issued February 23, 2023, PDF p. 3 Final findings of any kind. The report is preliminary and subject to change.
This information is preliminary and subject to change.
NTSB, issued February 23, 2023, PDF p. 1
Do these records alone establish the case for venting?
An imminent, polymerization driven tank rupture. The report says the rise suggested polymerization that could pose an explosion hazard, and gives no readings, rate, pressure or time to failure.
The necessity of venting and burning. No decision maker, decision time or alternatives are reported, and the NTSB lists the venting and burning for future review.
a review of the accident response, including the venting and burning of the vinyl chloride
That authorities were concerned about a possible polymerization hazard on February 5, and that controlled venting began about 4:40 p.m. on February 6.
Unanswered questions in this record
- Ambient temperature at each detector Not reported. Readings are relative; absolute bearing temperatures cannot be computed.
- Absolute bearing temperature at each detector Not reported. Only above ambient values are reported.
- Clock time of each detector passage Not reported. Detector readings can be ordered, not timed.
- Elapsed time between detectors Not reported. A rate of heating per minute cannot be derived.
- Train speed at each detector Not reported. Only the 47 mph speed at derailment is reported.
- Reading for the other bearing on the same axle Not reported. The same axle difference criterion cannot be checked.
- Whether detectors 1 and 2 sent any crew message Not reported. The report describes a message only for detector 3.
- Internal tank temperature values Not reported. The report says rising but gives no number.
- When and how tank temperature was measured Not reported. A trend cannot be assessed without timed readings and a method.
- Which tank car was rising Not reported. The report names five cars and says one was rising.
- Tank pressure and relief device status Not reported. Not reported; relevant to any rupture assessment.
- Proof of an actual polymerization reaction Not reported. The report says the rise suggested it.
- Analysis of rupture imminence Not reported. Not reported.
- Who made the venting decision Not reported. The report says responders scheduled it, without naming them.
- When the decision was made Not reported. Only the start of venting is timed.
- Alternatives considered to venting and burning Not reported. Necessity cannot be judged without them.
The first record to request
The time stamped internal temperature log for the tank car reported as still rising, from February 5 through the start of venting on February 6.
It should carry the car number, each reading with its clock time, the sensor or method and its location, and who recorded it.
It is the only measured input the report cites for the polymerization concern, yet the report publishes none of its values. It would show whether the rise was sustained and how fast, before any judgment about imminence or necessity.
Complete source ledger
Every excerpt used on this page, verbatim from the packet’s copy of the NTSB preliminary report, issued February 23, 2023. Page numbers are PDF pages of the original report.
| Entry | Page | Exact excerpt | Value |
|---|---|---|---|
| E01 | 3 | At MP 79.9, the suspect bearing from the 23rd car had a recorded temperature of 38°F above ambient temperature. | 38°F above ambient at MP 79.9 (bearing) |
| E02 | 3 | When train 32N passed the next HBD, at MP 69.01, the bearing’s recorded temperature was 103°F above ambient. | 103°F above ambient at MP 69.01 (bearing) |
| E03 | 2 | 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. | No measured value |
| E03 | 3 | The third HBD, at MP 49.81, recorded the suspect bearing’s temperature at 253°F above ambient. | 253°F above ambient at MP 49.81 (bearing) |
| E04 | 3 | 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. | No measured value |
| E05 | 3 | The train engineer increased the dynamic brake application to further slow and stop the train. | No measured value |
| E06 | 3 | During this deceleration, an automatic emergency brake application initiated, and train 32N came to a stop. | No measured value |
| E07 | 1 | On February 3, 2023, about 8:54 p.m. local time, eastbound Norfolk Southern Railway (NS) general merchandise freight train 32N derailed 38 railcars | No measured value |
| E08 | 3 | After the train stopped, the crew observed fire and smoke and notified the Cleveland East dispatcher of a possible derailment. | No measured value |
| E09 | 3 | On February 5, responders mitigated the fire, but five derailed DOT-105 specification tank cars | No measured value |
| E09 | 3 | carrying 115,580 gallons of vinyl chloride continued to concern authorities because the temperature inside one tank car was still rising. | No measured value |
| E10 | 3 | Responders scheduled a controlled venting of the five vinyl chloride tank cars to release and burn the vinyl chloride, expanded the evacuation zone to a 1-mile by 2- mile area, and dug ditches to contain released vinyl chloride liquid while it vaporized and burned. | No measured value |
| E11 | 3 | The controlled venting began about 4:40 p.m. on February 6 and continued for several hours. | No measured value |
| E12 | 1 | Issued: February 23, 2023 Preliminary Report RRD23MR005 | No measured value |
| E12 | 1 | This information is preliminary and subject to change. | No measured value |
| Context | 3 | NS has established the following HBD alarm thresholds (above ambient temperature) and criteria for bearings: | No measured value |
| Context | 3 | Between 170°F and 200°F, warm bearing (non-critical); stop and inspect | No measured value |
| Context | 3 | A difference between bearings on the same axle greater than or equal to 115°F (non-critical); stop and inspect | No measured value |
| Context | 3 | Greater than 200°F (critical); set out railcar | No measured value |
| Context | 3 | This increase in temperature suggested that the vinyl chloride was undergoing a polymerization reaction, which could pose an explosion hazard. | No measured value |
| Context | 2 | When exposed to heat, vinyl chloride can undergo a rapid polymerization reaction, an exothermic chemical process that can pose an explosion hazard. | No measured value |
| Context | 4 | Surveillance video from a local residence showed what appeared to be a wheel bearing in the final stage of overheat failure moments before the derailment. | No measured value |
| Context | 4 | The wheel bearing and affected wheelset have been collected as evidence and will be examined by the NTSB. | No measured value |
| Context | 4 | a review of the accident response, including the venting and burning of the vinyl chloride | No measured value |
| Context | 4 | The NTSB’s investigation is ongoing. | No measured value |