Extrication: Pre-Programmed Crumple Zones & Fortified Frame Constructions
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One of the most discussed topics within the CTIF Commission ‘Extrication & New Technology’ about technical assistance and ‘rescue of trapped persons’, is still the impact of ‘Pre-Programmed Crumple Zones and Fortified Frame Constructions.
Above: Video with crash impact of an old and newer car with different security systems (airbags, seat belt retractors, frame construction, …)
By: Tom Van Esbroeck & Kurt Vollmacher, CTIF Commission For Extrication & New Technology
Experienced colleagues in the fire service will every now and then tell stories of numerous interventions involving road accidents with physically trapped persons. Maybe it sounds familiar: ‘in our time we had a case every weekend!’
Today there are still plenty of accidents, but the number of accidents for which we need to intervene to rescue trapped persons has significantly dropped. In many cases the door of a vehicle can be easily opened, while the front of the car is shortened by half a meter.
It is also noticeable that, when passengers are physically trapped, it is most often a serious and complex job for the intervention team to adequately rescue the trapped victims.
Left: Impact crash on a vehicle outside of the vehicle.
Right: Impact crash inside the vehicle.
What has changed compared to the past?
During our discussions within the CTIF Commission ‘Extrication & New Technology’ about technical assistance and ‘rescue of trapped persons’, one of the most discussed topics is still the impact of ‘Pre-Programmed Crumple Zones and Fortified Frame Constructions.
Tube processed into a jamb Source Weber/ THV Level 1 A Chapter 5
Many elements we find in the modern vehicles, have been frequently applied previously as a research project in motor sports, mainly in the world of the Formula 1.
One of today's most important security systems is undoubtedly the ‘fortified frame construction’. Initially the discussion was mostly concerned with a strong frame around the passenger, offering the passenger sufficient physical space in case of impact. This was further developed into a strong cage, that can only minimally deform and that guarantees the maximum security of the passenger.
Another revolutionary technology is building ‘pre-programmed crumple zones’ into the vehicles. By using different types of steel for the frame of a monocoque, the kinetic energy that acts on the vehicle due to the impact of a road accident is absorbed and diverted throughout the construction of the car.
Parts of the car that intentionally need to deform, are made of a type of steel with a low tensile strength, while parts that need to remain intact as much as possible (such as the frame construction and the lateral fortification) are made of steel with a higher tensile strength. In other words, the designer determines which forces the construction can maximally take, when either ‘desired’, and on the other hand, ‘undesired’ deformation occurs.
Monocoque of Volvo with different tensile strengths. Source Volvo/ THV Level 1 A Chapter 7
What does this mean for us in practice?
A number of rescue techniques that are efficiently applied to older models, no longer offer the desired result when applied to newer vehicles. The opposite is also true: new techniques do not offer a solution when applied to older cars. This form of technical assistance requires a good insight from the relief workers´ perspective of what can be done and what cannot, or should not, be done.
Besides different types of steel, other types of lighter materials are also used within the construction, such as aluminium and carbon fibre, with the respective desired effect. Another technique consists of using steel tubes with a high tensile strength that are processed into the jambs of the vehicle, for instance the A and B jambs.
Dashboard lift and dashboard roll. Source Holmatro/ THV Level 1 A Chapter 5
Under the dashboard of a newer car there is a built-in steel strut with a high tensile strength. The dashboard is only assembled with a few bolts on the chassis of the vehicle. By using the steel strut as take off point for the spreader, we apply the 'direct dashboard lift’.
We place the spreader as in the figure above, the space under the spreader blocked up, and we spread the dashboard upwards without executing any other (cut) actions.
Attention: these type of fortifications may prevent you from lifting the dashboard!
Direct dashboard lift THV Level 1 A Chapter 6
Deployment of New Rescue Tools:
Besides the ‘average’ rescue equipment (scissors, spreader, ram, …) one regularly deploys ‘new’ rescue tools. Here we discuss two ‘new’ rescue tools:
Below Right Photo: Dashboard fortification.
1. Pneumatic spanner set - Spanner Technique
This technique was introduced by the late colleague corporal Mich Van Den Heuvel of the post of Wuustwezel. The advantage of this technique is being able to work autonomously, and also that there are no sparks. The pneumatic spanner set can be connected to the intermediate pressure line of a compressed-air breathing apparatus (6 to 8 bar). It can for instance be used to quickly remove the bolts of a door, a boot lid, etc.
Content of the spanner set:
- Metrical long;
- Metrical short;
- Hex key;
- Torx internal;
- Torx external.
Dashboard fortification. THV Level 1 A Chapter 6
Pneumatic spanner set. THV Level 1 A Chapter 2
2. Reciprocating saw and saw blades for hard types of steel
The use of the different types of saw blades requires some training and exercise. The material that needs to be sawn needs to be put as close as possible to the tool head in order to prevent the saw blade from folding. During the cutting one needs to always wear safety glasses and a dust mask. When sawing carbon fibre and glass, wear a P3 mask or (even better) a breathing apparatus!
Reciprocating saw. THV Level 1 A Chapter 2
Sometimes there is some critique that the reciprocating saw makes to much noise, yet a wise instructor THV has put it differently! Quote: “Nobody has died from noise, yet some have died because the rescue took too long!” We note that the paramedic perfectly can cover the ears of the victim during this work.
Deployment of reciprocating saw. THV Level 1 A Chapter 2
After the accident with the Plug-in Hybrid in Dilsen-Stokkem, the ‘CTIF Commission for Extrication & New Technology’ has started a technical investigation, together with all services involved, in order to learn lessons and translate the experience acquired into modified procedures, training and advice towards the designers.
Left Picture: The accident in Dilsen-Stokkem
Right Picture: Saw blades specifically for hard types of steel).
Source Weber/ THV Level 1 A Chapter 2
15/05/17 - 05h00 © Marco Mariotti
Tom Van Esbroeck email@example.com
Kurt Vollmacher firstname.lastname@example.org
CTIF Commission For Extrication & New Technology