# TSB Laboratory Report LP188/2013

## Table of contents

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## 1.0 Introduction

### 1.1 Description of occurrence

#### 1.1.1

On 06 July 2013, shortly before 0100 Eastern Daylight Time, eastward Montreal, Maine & Atlantic Railway freight train No. 2, which had been parked unattended for the night at Nantes, Quebec, started to roll uncontrolled. The train travelled a distance of about 7.2 miles, reaching a speed of 65 mph. At about 0115, while approaching the centre of the town of Lac-Mégantic, Quebec, 63 tank cars carrying petroleum crude oil, UN 1267, and 1 box car derailed. As a result of the derailment, about 6 million litres of petroleum crude oil spilled. There were fires and explosions, which destroyed 40 buildings, 50 vehicles and the railway tracks at the west end of Megantic Yard. A total of 47 people were fatally injured.

#### 1.1.2

Preliminary examination of the derailment site determined that buffer box car CIBX 172032, immediately behind the locomotive consist, and the following 63 loaded tank cars derailed on the main track of a 4.25° right-hand curve in the direction of travel (eastward), covering a No. 11 turnout. The locomotive consist separated from the derailed cars and split into 2 portions, with each travelling different distances before they came to a stop. After a significant time, the front portion of the locomotive consist moved backward (westward) and collided with the second portion, both moving a short distance further (westward) and coming to a final stop together.

#### 1.1.3

The derailed buffer box car struck a stationary cut of cars on the siding track. The following 8 tank cars were scattered in separated jackknifed positions. The next 2 tank cars lay in the direction of the turnout siding, ahead of the main jackknifed pile-up of the rest of the derailed tank cars among which the fire and explosions occurred. The last 9 tank cars in the train did not derail. They were disconnected and removed back and away from the derailment and fire by the locomotive engineer and emergency responders. An aerial-view photograph of the accident site is shown in Figure 1.

### 1.2 Background

#### 1.2.1

Train MMA-002 consisted of 5 locomotives, 1 operation control car VB-1, 1 loaded buffer box car, and 72 tank cars loaded with petroleum crude oil. The train weighed 10 287 tons and was 4701 feet long. The train weight profile is shown in Figure 2.

#### 1.2.2

The train was operated by a 1-person crew. Before midnight, it came to a stop on the main track of Station Nantes with an automatic application of the air brakes. The locomotive engineer applied hand brakes on the locomotive consist and the buffer car, and then released the automatic brake, but kept the independent brake (IND) of the locomotive consist in the applied position. The engine of the lead locomotive, MMA 5017, was kept running at idle to maintain the air brake supply. The locomotive engineer left the train and went to a hotel for rest, as indicated in his schedule.

#### 1.2.3

A fire was detected on the lead locomotive sometime after the locomotive engineer left (LP181/2013). Local firefighters came and put out the fire. A local MMA engineering employee was called to attend to the fire site. The engine of the locomotive was shut down, and the train was left unattended again. Approximately 59 minutes later, the train started to move down the descending grades, and accelerated all the way until it reached the town of Lac-Mégantic, where it derailed.

#### 1.2.4

The lead locomotive, MMA 5017, was equipped with a Quantum Engineering Incorporated (QEI) locomotive event recorder (LER) version no. S45E, serial no. 0204100033. The recorded data in the “extend log” was downloaded from MMA 5017 by a MMA staff member soon after the accident and provided to the TSB.

#### 1.2.5

The train was also equipped with an end-of-train (EOT) sense and brake unit (SBU). The SBU was sent to the TSB Engineering Laboratory for examination (LP 132/2013). The records in the DataFlash were extracted and converted into Excel spreadsheets. The EOT SBU download data were provided for a comprehensive analysis of LER and SBU data together.

#### 1.2.6

The TSB investigation team also obtained a copy of the standard report of the public crossing at Mile 117.11, Moosehead Subdivision, that indicated the activation of the crossing signal and protection. The time record was calibrated by an independent crossing company. This record was used as a reference in the synchronization and calibration of the downloaded LER time records. The comprehensive analysis of the downloaded LER records, SBU data and the standard report of the public crossing at Mile 117.11 was conducted and a number of significant events of interest were identified to assist the investigation (LP136/2013).

### 1.3 Engineering services requested

#### 1.3.1

The preliminary investigation found that the train experienced a number of events, including unattended parking, fire, engine shutdown, runaway, derailment, and explosion. There were several broken knuckles, including those between the second and third locomotives, indicating that the locomotive consist had separated and rejoined. The derailed cars were scattered in several small, jackknifed groups as well as in a main pile-up. The final positions of the derailed cars and the LER data analysis suggested that the point of derailment (POD) was likely located around the west end switch on the 4.25° right hand curve. The excessive centrifugal force due to the high speed (65 mph at the derailment) may have caused or contributed to the derailment.

#### 1.3.2

A laboratory project was opened for calculation of the lateral force and the rollover speed at the POD curve. The preliminary calculation indicated that the derailment speed was lower than the rollover speed due to the pure centrifugal force on the curve for the derailed tank cars. A further simulation was conducted to obtain the longitudinal in-train force at the derailment moment and the corresponding transformed lateral force. The combination of the centrifugal force and the transformed lateral force of the in-train buff force could cause the derailment if the couplers and the tank car were in jackknifed position.

#### 1.3.3

Subsequently, the investigation team obtained the latest track geometry car test records in form of brush charts dated 21 August, 2012 which showed some significant geometry irregularities near the switch. These track geometry defects might generate significant dynamic forces and contribute to the derailment. However, the digital data of the track geometry record charts was not available and the track geometry state on the day of occurrence was not known as the track was destroyed in the accident. It is not possible to determine the exact effect of the track geometry condition and the resulting dynamic force quantitatively.

#### 1.3.4

The TÜV Rheinland Mobility Inc. Rail Sciences Division (TRRSI) was contracted to conduct a VAMPIRE vehicle/track dynamic simulation to evaluate the effect of the track geometry. A generalized tank car model developed by TRRSI was used. As the track and derailed cars were destroyed, it was not possible to obtain the actual wheel and rail profiles of the first derailed car at the POD. Standard AAR wheel and rail profiles were used in the simulation.

#### 1.3.5

This LP report describes the calculation of the centrifugal force on the curve caused by the high speed, the simulated in-train force at the derailment moment, the available track geometry records and VAMPIRE simulated dynamic response. The analysis of the combination of the centrifugal force, the dynamic forces generated by the track geometry and the in-train force helps to identify and explain the most likely derailment scenario and the contributions of the factors.

## 2.0 Centrifugal force and roll over speed at POD curve

### 2.1 Equilibrium speed and superelevation

#### 2.1.1

Curved tracks are normally elevated by an amount (superelevation) depending on curvature to provide a lateral force balance at a given speed. The superelevation is the height, in inches, that the outer (high) rail of a curve is elevated above the inner (low) rail. It is intended to balance the effect of centrifugal force.

#### 2.1.2

The weight of the vehicle, acting downward vertically from the vehicle’s center of gravity (CG), is added to centrifugal force to create a resultant force as shown in Figure 3:

• A resultant force $F$ that passes through the track centerline indicates balanced elevation and the weight of the vehicle will be distributed equally between the high and low rails.
• A resultant that passes to the inside of track centerline indicates over-balanced elevation.
• A resultant that passes to the outside of the track centerline indicates under-balanced elevation.

#### 2.1.3

The equilibrium speed on a curve is the speed at which the resultant of the weight and the centrifugal force is perpendicular to the plane of the track. The relationship is

$hb = 0.0007 ⁢ D V2$

where
${h}_{\text{b}}$ is balance superelevation, inches
$D$ is degree of curvature (100-foot chord)
$V$ is train speed, mph

#### 2.1.4

The MMA requires that the maximum allowable operating speed for each curve must not produce an underbalance in excess of 1 ½ inches unless authorized by the System Office of Engineering. The maximum speed will be computed using the following formula:

$Vmax = ( ha + u ) / ( 0.0007 ⁢ D )$

where
${V}_{\text{max}}$ is maximum allowable operating speed, mph
${h}_{\text{a}}$ is actual elevation of the outer rail, inches
$u$ is underbalance, inches
$D$ is degree of curvature

#### 2.1.5

The average superelevation in the 4.25° curve located from Mile 0.05 to Mile 0.28 was about 1 ½ inches, corresponding to a balanced speed of 22 mph. Typically, for freight trains negotiating this degree of curvature with the superelevation that existed, train speed should not exceed 32 mph (assuming a maximum of 1 ½ inches of underbalance).

### 2.2 Lateral forces on curve

#### 2.2.1

A rail vehicle travelling on a curved track at a speed generates a centrifugal force, as shown in Figure 3. The centrifugal force ${F}_{\text{cg}}$ can be calculated as:

$Fcg = (W/g) * V2 / R$
$R = 5730 / D$

where
$W$ is the gravity force or weight, in lbs
$g$ is the gravity acceleration or gravitational constant, 32.16 ft/s/s
$V$ is the speed at curve, feet/sec
$R$ is the radius of curve, in feet
$D$ is the degrees of curve

#### 2.2.2

The centrifugal force ${F}_{\text{cg}}$ acts at the center of gravity of the vehicle in the lateral outward direction and transmits to the wheel/rail interface. The elevation $h$ on the curve transforms a portion of the vehicle weight into a lateral inward force ${L}_{\text{e}}$.

$Le = W * tan(α1) = W * h / B$

where
${\alpha }_{1}$ is the elevation angle, rad
$h$ is the superelevation, inches
$B$ is the track width between rail centers, approximately 59 inches.

#### 2.2.3

The net lateral force on the entire car ${L}_{\text{c}}$ is the balance of the centrifugal force and the lateral portion of weight due to elevation.

$Lc = Fcg - Le$

#### 2.2.4

The vertical forces on the outer rail ${V}_{\text{out}}$ and the inner rail ${V}_{\text{in}}$ are respectively

$Vout = W / 2 + Fcg * H / B$
$Vin = W / 2 − Fcg * H / B$

where $H$ is the height of center of gravity of vehicle above rail top, in inches

#### 2.2.5

The lateral force of the entire vehicle on the outer rail is

$Lout = Lc - Vin * f$

where $f$ is coefficient of friction between wheel tread and rail top

#### 2.2.6

The lateral forces of a truck side, a wheel on the outer rail and an axle are approximately,

truck side ${L}_{\text{ts}}={L}_{\text{out}}/2$

wheel ${L}_{\text{w}}={L}_{\text{out}}/4$

axle ${L}_{\text{ax}}={L}_{\text{c}}/4$

### 2.2 Rollover speeds at POD curve

#### 2.3.1

Vehicles may roll over outward on curves at high speeds because of excessive centrifugal force, as shown in Figure 3. The critical condition occurs when the compound force $F$ resulting from the centrifugal force ${F}_{\text{cg}}$ and the gravity force $W$ points to the high (outer) rail so the low (inner) wheel will be lifted from the low rail. Under the critical condition, the following equation exists:

$tan(α) = tan(α1 + α2) = Fcg / W$
$α1 = tan-1 (h/B)$
$α2 = tan-1 (B/2/H)$

where
$h$ is the elevation on curve, in inches
$B$ is the track width between rail centers, inches
$H$ is the height of center of gravity of vehicle above rail top, in inches

#### 2.3.2

The critical rollover speed ${V}_{\text{r}}$ can be calculated as