LPG systems, layout and security


One of the most known indicator that gives us an immediate idea about the safety level provided by a vehicle is the number of stars rated during the Euro NCAP test.

The stars are rated to the shock tests passed and to the presence of security – related contents.
Thanks to the tightening up both of the tests and the calculation method, today we have on our vehicles an infinitive of electronic devices, which guarantee us a security, at low speed, certainly better than few years ago.

So far so good, but what happens, always regarding the security, when for instance we want a car with a LPG system?

The solution adopted almost universally is that to assemble the LPG tank, called “ciambellone” (big doughnut), in place of the spare wheel.
It is formed by two steel shells welded, which normally are 2/2.5mm thick, with the valve unit on the top.

This position to the security it’s definitely wrong!
Indeed in case of a “significant” rear impact the valve group, although structurally solid, can deform and break allowing the leaking of LPG very gaseous and flammable with possible dramatic consequences.

The same gasoline cars once mounted the tank in that position considering they all were rear-wheel drive while today, with the front-wheel drive, the tank is in a safer position, under the rear seat.

The current type-approval legislation requires a rear impact test with a trolley of mass 1,100 kg, which crash into the rear at 35-38 Km/h; unfortunately the Euro NCAP doesn’t provide this kind of impact for the LPG versions.
This test is very easy to pass even with the tank in the back because the energy is low, but what happens if a van or a truck hit us?

So this is the point, even ethic, in the case we can do better than the current legislation, which to choose? The ‘good engineering’ or lower costs and investments and consequently lower prices to customers?
To what extent is it right to “invest” both for the company and for the customer in improving solutions?

For instance, several years ago, my team and I developed a project for a LPG tank to put in the place of the gasoline; while for the gasoline there was a little tank of 10l, in the shelter of the rear suspensions, and so protected in case of strong impact.

At that time if was considered too expensive, you can see the tank in picture after the test pressure at 100 bar, the little bumps are due to the test pressure.
Tank 1 Tank 2

Certainly I understand the market workers position, who declare that everyone would always want more and better but only if it is… for free!

But we won’t give up … and the challenge of the engineers of the full-liner builders continues to make “democratic”, that means affordable by all pockets, new solutions for improving the product.

As well as I hope the actions of the Governments and various agencies go on to improve more and more the cars security and the LPG ones in particular, considering the growing number of sales and transformations in recent years.

Translated by Federica Izzo

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