Lessons Learned from an accident involving an LNG truck

Traffic accidents involving LGN vehicles require different intervention procedures than for gasoline, diesel or even LPG powered vehicles. LNG is extremely cold when released and a leaked LNG gas cloud can freeze human tissue and kill or injure a person walking into it within seconds.

LNG burns slower than gasoline and LPG and is not ´technically´ explosive, but can cause massive destruction when ignited nevertheless.

This RETEX article describes how an emergency response team in Belgium had to learn on the spot, because they lacked a specific emergency response plan for LNG.

The article also contains a CTIF proposal for trucks being marked in accordance with ISO 17840 part 4; a new ISO standard for non traditional power system vehicles which, together with ISO and Euro NCAP, CTIF has been instrumental in creating.

The full PDF article (downloadable) also contains detailed information about LNG powered systems, how the intervention was done and what steps must be taken to ensure safety for firefighters and other first responders on the fire ground.

READ MORE: Extrication: Crumble Zones and Fortified Frame Structures

Authors: Kurt Vollmacher, Project Leader ISO & Tom Van Esbroeck, Chair of the CTIF Commission for Extrication and New Technology at CTIF kurt.vollmacher@brandweerzonecentrum.be.

This article has been produced by CTIF Belgium based on the principles of the Belgian concept of RETEX.

RETEX comes from an old French term, Le retour de l'expérience, meaning "The Return of Experience". The term has been in use in Belgium for some time, and is slowly becoming more known internationally.

RETEX is a specific way of sharing Lessons Learned through a formula of breaking down what happened, what went right, what went wrong, and what can be learned by emergency services anywhere from a particular incident.

READ MORE RETEX Lessons Learned on CTIF.org here

The accident

The accident,  involving 2 trucks, occurred on the 16th of October 2017 on highway E313 in the direction of Antwerp near Massenhoven.

After the collision involving two trucks, of which one had caught fire, the motorway was closed for all traffic for over 8 hours.

Both the cargo and the cabin of the impacting truck caught fire. The cargo of the second truck did not catch fire. One of the trucks involved was powered by LNG.

The teams arriving at the scene initially thought they were responding to a “normal” truck fire.

However, during the intervention the LNG tank (liquefied Natural Gas) was noticed. This meant that non-standard procedures had to be used.

Specialists had to be brought in who had the required knowledge and tools to manage the incident.

Also, the correct information on how to proceed in such interventions was not readily available, meaning all those involved (fire brigade, security forces, recovery service,…) were learning as they went.

The duration of the intervention had great economic impact which could have been avoided if emergency services had been well-informed/trained and the necessary specialist materials/knowledge had been readily available.

The manufacturers of both the truck and the LNG installation were contacted about this.

Also, the correct information on how to proceed in such interventions was not readily available, meaning all those involved (fire brigade, security forces, recovery service,…) were learning as they went.

The duration of the intervention had great economic impact which could have been avoided if emergency services had been well-informed/trained and the necessary specialist materials/knowledge had been readily available.

The manufacturers of both the truck and the LNG installation were contacted about this.

LNG: Liquefied Natural Gas

LNG shouldn't be confused with LPG, Liquefied Petroleum Gas.

LNG contains between about 90 and 99 % methane.

It is condensed into a liquid by cooling it to about -162 °C at atmospheric pressure.

LPG contains mainly propane and butane and turns into a liquid when kept under high pressure. This is in contrast to LNG, which becomes liquid at atmospheric pressure, but at very low temperatures.

Because of the different properties, the components and materials for both fuels differ too.

However, we have to take into account that when an LNG leak occurs, the fumes will first spread low to the ground and depending on outside temperature/ground surface temperature and air humidity, they will vaporize and become lighter than air.

The properties of LPG are also entirely different to those of LNG. As vaporized LNG has the same properties as high calorific gas, it has the same advantages and disadvantages.

Natural gas is lighter than air and therefore spreads and dissipates more quickly than LPG, which is heavier than air. LPG is more likely to explode than LNG.

Properties of LNG:

• Cooled liquefied natural gas;
• Formula CH4
• Volume of LNG 600 times smaller than its gas form;
• Doesn't contain the impurities of natural gas (especially nitrogen) so more energy;
• LNG's energy density is about 60% of that of petrol and diesel;
• Storage and transport require very well insulated storage tanks;
• Pressure: up to 16 bar;
• Clear, odourless liquid;
• Explosion limits 5% - 15%;
• LNG is lighter than water;
• At temperatures above -110 ºC LNG is lighter than air;
• LNG Density: +/- 450 kg/m3 @-160°C and 1 bar
  • As a comparison: CNG density: +/- 194 kg/m3 @ 30°C and 250 bar
• Vaporized LNG has an auto-ignition temperature of 620°C;
• Cryogenic (very cold) danger of frost bite: special PPE required;
• Be mindful of a low-hanging vapour cloud over a large area. LNG takes on the ambient temperature and mixes with air;
• The (visibility of) cloud depends on the temperature of the LNG and environmental factors such as outside air temperature and air humidity;
• Doesn't contain odorants (only odourised when made into CNG).

The Intervention

The fire service is informed about a rear-end collision. At the scene, firefighters encounter a fully developed fire inside a truck cabin.

The LNG tank is initially not noticed because of the intensity of the flames.

The fire is first tackled with high pressure, after which foam is used. An AGS is contacted and asked for advice.

They perform repeated checks for LEL (Lower Explosive Level)  concentrations.

A gas detection sensor proves more effective and works faster than a multi gas meter.

AN LNG leak is confirmed.

While awaiting further action and the arrival of an AGS, firefighters set up a water supply and the area is zoned off.

Situation after extinguishing

• Extremely deformed truck, the LNG tank has partly come loose from the chassis;
• It is only attached to the chassis with one strap and with a plate at the back;
• The mounting at the back is inaccessible;
• The manual valves of the LNG tank are inaccessible;
• The pressure relief valve is inaccessible;
• The connector of the primary pressure relief line is showing icing;
• An LNG leak is detected (already gaseous).
• There is no indication of the fuel level of the LNG tank (can only be seen on the truck's dashboard)
• The truck + detached LNG tank can't be towed safely in this state.
• The operational stage is announced to get more resources in.

• As mentioned earlier the LVO contacts the Adviser Hazardous Substances (AGS) relatively quickly to gain additional information and advice.
• In the AGS (Advisers Hazardous Substances) network, information is shared nationally and internationally via a WhatsApp group.
• This was very much the case in this intervention.
• They come to the conclusion that in this case the fire services/AGS don't have enough technical expertise regarding the installation.
• External expertise (manufacturer) is needed to safely manage this accident.
• This external expertise will have to come to the scene.
• The LNG tank is shielded from sunlight with a screen.
• This is to prevent the LNG tank heating up and venting gas from the primary pressure relief valve (16 bar).

Advice from LNG expert and mutual agreement with all parties (LVO/AGS) please note: this is not a standard response but a jointly agreed response based on the situation observed!

• As the truck and the LNG tank couldn't be towed safely, it is jointly agreed that the tank should be detached from the chassis.
• The current pressure in the tank (16 bar) should be lowered before it can be disconnected and dismounted safely.
• In addition, the manual red “intake” valve should be closed.

• An area needs to be cleared to allow access to the valves, to connect a cryogenic hose and vent the gas at a safe distance. This cryogenic hose has to be brought to the scene (under police escort).

• The cryogenic hose needs to be connected to the vent connector of the tank in order to release the pressure using the grey manual vent valve.
• Cold-resistant gloves should be worn due to possible exposure to the extreme low temperatures of LNG when disconnecting.
• Dismounting the tank is only justified after the above measures have been taken.
• After dismounting the tank, pressure can be further released in a safe place.

Pressure release and dismounting the tank:

Releasing the pressure and dismounting the tank proves difficult because of poor access to the valves/vent connector and the back mounting plate.

After disconnecting the LNG tank, pressure was further released in a more suitable place.

After towing, the road was re-opened.

Recommendations:

Recognition of drive system(s)

Upon arrival, the type of drive system was not immediately visible from a distance. This was partly due to the raging fire.

The marking on the tank was added by the supplier of the tank itself.

It had a reference to the UN Number 1972, meaning:

METHANE, REFRIGERATED LIQUID OR NATURAL GAS, REFRIGERATED LIQUID, with high methane content.

However, the marking was too small to allow detection from a distance (and during a raging fire).

However, the marking was still intact after the fire had fully developed, which is interesting because this is often used as an argument not to provide markings.

This incident proves the contrary; the markings do survive intense fire.

    Markings

    All trucks should bemarked in accordance with ISO 17840 part 4; a new ISO standard for non traditional power system vehicles which CTIF has been instrumental in creating, together with ISO and Euro NCAP.

    Pictograms should be fire-resistant and reflective.

• Markings on the truck: the drive system(s):

• Front of truck cabin;
• Back of truck cabin;
• Both sides of truck cabin

PLEASE DOWNLOAD THE FULL, NON ABBREVIATED ARTICLE for more recommendations on CTIF proposed ISO standards for non traditional powered vehicles.

Note: ISO 17840-4 is info specifically intended for first and second responders

This mustn't be confused with EN 16942.

About RETEX or Return of Experiences:

RETEX comes from an old French term, Le retour de l'expérience, meaning:  "The Return of Experience".

The term RETEX has been in use on Belgium for some time, and is slowly becoming more known internationally.

RETEX is a specific way of sharing Lessons Learned through a formula of breaking down what happened, what went right, what went wrong, and what emergency services anywhere can learn from a particular incident.

RETEX is typically shared as a written document with photos, diagrams and drawings as illustrations, but could also include videos, or be in the form of an educational style video.

CLICK HERE to read recent RETEX articles.

No matter how old or new vehicles are, no matter how new the technology is, accidents will happen. The key task of any emergency responder is to help the public as best they can when things go wrong. But the responder equally wants to return home safe and sound after such intervention.

Because technology is rapidly evolving, it isn't easy to keep up to date with all the evolutions and innovations.  They can make interventions very different and complex, both for volunteers and professional firefighters.

Emergency services aren't consistently consulted or informed when new technology is introduced. As a result, emergency services may not be able to respond appropriately. When they don't, incidents get a lot of negative attention through social media nowadays.

Therefor it is important for all the information that currently exists and may be overwhelming, to be structured and standardised into concrete tools each emergency responder can use.  It goes without saying that close collaboration between all stakeholders such as manufacturers, consumers and government, is needed to achieve this.

International contact and exchange of knowledge can help to ensure incidents are investigated thoroughly and lead to ‘lessons learned’ or ‘return of experience’.

Integrated training and constant practice regarding emergency response can ensure public safety in incidents involving new forms of technology.