Liquid gas

as liquid gas, also LPG (Liquefied petroleum gas), autogas or partially also propulsion gas mentioned, one designates frequently a mixture from propane and butane. In addition, pure propane or pure butane can concern.

Liquid gas is not to confound with liquefied natural gas (LNG) or compressed natural gas (CNG).

Table of contents


liquid gas consists connections (C m H n) with 3 or 4 carbon atoms of easily liquefyable hydrocarbon -. It can itself thereby around an individual connection or around oneMixture of several connections act.

The main parts from liquid gas are:

liquid gas is heavier in the gaseous state of aggregation than air. It becomesunder pressure transports and stored. Already under very low pressure (about 8 bar) it liquid and reduced its volume so to a 260stel. It is easily inflammable and forms explosible mixtures with air. The explosion limits lie depending upon mixing proportion between 1,5 and 11 volume. - %in air. The boiling point depends on the pressure and on the mixing proportion. It lies with ambient pressure for a propane/butane mixture between -42 °C (pure propane) and -0.5 °C (pure butane).

In the case of transportation it must have a marking after addr, with a UN-number 1965 and the Kemler number of 23.

Liquid gas has an energy content of 12,9 kWh/kg and with 20 °C a density of 0,54 g/cm ³ (propane 0.51 g/cm ³ and butane 0.58 g/cm ³)

heating and cook purposes

in areas without natural gas supply liquid gas can be used for heating purposes. In addition becomesthe liquid gas in liquid gas storage vessels stored; the tanks are filled up by tank trucks.

In smaller quantities it becomes in gas bottles or in gas cartouches, z. B. in the camping range, assigned with crickets or with the soft soldering of copper tube braze-on fitting.

For gas cricket usually gas bottles with an insulating material comeof 5 kg or 11 kg for application.

In France, south Europe and many other countries in the world cooking with liquid gas is very common; contrary to Germany, where this kind is quite unknown to cook.

In the case of adherence to of all safety regulations as well as installation and acceptance througha specialized enterprise is permitted cooking with gas bottle within the kitchen also in Germany.

Also in Austria it is to be found particularly in the rural area for heating purposes of single family houses. In addition usually larger several thousand litres seizing containers in the garden are aboveground set up, those by tank cars regularlyto be filled must.

lighter gas

the gas is often used in commercial lighters.


use in air conditioning systems as FCKW - replacement.

liquid gas fuel (autogas, LPG)

liquid gas applies also as fuel for petrol engines. Already inthe 1970er years was very common it in Italy and it until today remained. Also the entire motorbus fleet of the Viennese of transporting enterprises drives since then with liquid gas. It burns more pollution free than gasoline. The pollutant output of nitrogen oxides amounts to about 20%, CO 2 emissions decreases over15% and unburned hydrocarbons around 50%. Besides LPG exhaust gas can be converted by better chemical usability at lower temperatures in vehicle catalysts. Because of the arrears-free burn frequently fork-lift trucks are operated with liquid gas and to replace thus Diesel stackers, the soot and high quantities of nitrogen oxides emit.Liquid gas-claimant fork-lift trucks may be operated as only vehicles with combustion engine in closed areas. First LPG was with the taxis (z. B. all taxis in Istanbul), later also in the private Kfz - range, into which 1980er spreads years in Austria by favourable prices much. Due to the higher Taxation became it in Austria however again uninteresting.

Today liquid gas is as fuel in some European neighboring countries (as, NL, GB, PL, IT, F…) established. In Germany it has an increasing meaning. (Conditions 2005) liquid gas (LPG/autogas) and natural gas (CNG/LNG) become momentary the use inEqual 2009 low taxed, starting from 2010 a tax preference applies for motor vehicles concerning the calorific value to at the end of until 2020 possibly only to natural gas vehicles (CNG). With liquid gas (autogas/LPG) an extension of the fiscal privilege is expected in the context of the European Union harmonization. In Austria there is a tax reduction starting from 2006/2007 onlyfor natural gas fuel. In Switzerland ground connection and liquid gas are to become tax-privileged starting from 2007.

vehicle re-equipment

a re-equipment of the passenger cars on liquid gas (LPG) is relatively uncomplicated. Nearly each vehicle with petrol engine can for approximately 1500 to 3500 euro (depending upon number of cylinders and tooreaching exhaust standard) to be converted; (at present still) engines with gasoline direct injection are excluded. The unloaded weight of a LPG plant amounts to about 40 kg. The tank finds its place either in the spare wheel well (34 to 85 litres, which spare wheel then replaced by a breakdown spray) or in the trunk (60 to200 litres). Also lower floor panel tanks are possible. The range amounts to depending upon consumption 350 km to 1000 km. With the change the gasoline tank remains, so that the vehicle can be operated alternatively with gasoline or liquid gas (bivalent drive). Switching between gasoline and liquid gas enterprise can take place automatically or manually while driving. With the installation thus also a substantial range increase is connected, if also still according to gasoline one carries. Opposite gasoline a volumetric increased consumption must be set from 5 to 20% for LPG depending upon selected system (see below),since liquid gas exhibits a smaller density. To the comparison: Premium fuel with 95 Oktan has a density of approx. 0,76 g/cm ³, liquid gas depending upon mixing proportion between 0,51 and 0,56 g/cm ³.


with autogas claimant Kfz are started either on gasoline and afterwards automatically upGas operation changed over, in order to go around possible warming up problems, or it run directly on autogas. Between venturi plants, sequenziellen plants as well as LPI plants are differentiated.

The first two installation types have together that the liquid gas the engine over an evaporator and a pressure control valve, in the tank under pressure, gaseouslyone supplies. The evaporator must be heated for the compensation of the evaporative cold („cooling spray effect “) with cooling water. Therefore with many autogas plants of these types only with a certain coolant temperature to gas one switches (approx. 30°C). It is to be noted that even the cooling water one at the beginning of still cold engine toHeat to be used can, since butane becomes liquid with -0,5 °C and propane with -42 °C.

Since 2004 also LPI plants are offered. These systems promote liquid gas by means of a fuel pump under pressure in a ring circuit, of where it by metering valves in liquid form into thatAnsaugtrakt is squirted. By the evaporative cold it comes to a cooling effect of the intake air, which can amount to depending upon load 5 to 15 K. Thus it comes to a slight increase in output (see turbo engine/intercooler).

The autogas burn takes place with smaller pollutant emissions and increased quiet running. The latterOktan is to be due to the high anti-knock quality from 105 to 115.

To the topic security writes the General German Automobile Association: „There are no references from practice that with these vehicles a increased safety risk exists, also not from those countries, where relatively many autogas cars are certified. Crash andFire tests show that autogas cars are not more dangerous than comparable gasoline vehicles. “Autogas tanks are equipped with tubing outline valves. If the tank from the mounting plate should be torn and torn off lines with a Crash, then the appropriate connections are sealed immediately. All tanks are equipped with fuses, so that in the case of fireGas controlled to escape and burn down can, in order to avoid a spontaneous bursting of the steel tank by large heat.

venturi technology

the venturi technology is the oldest and most inexpensive solution. Here a negative pressure-steered metering valve in the intakes is installed and proportioned gas negative pressure-steered. By the narrowingthe sucking in cross section is to be counted on an easy power loss and a higher increased consumption. This technology is suitable up to the exhaust standard E2 without loss of a tax schedule.

Teilsequenzielle plants

Teilsequenzielle plants use a more precise electronically steered metering valve, which the gas by means of a star shaped gas distributorinto the intakes of the cylinders leads. A cross-section contraction and thus a power loss do not take place. These plants have frequently their own programmable characteristic diagram giver for the gas operation. Therefore also older automobiles and passenger car up to the pollutant standard euro 3 can be equipped with this system.

Vollsequenzielle plants

Vollsequenzielle plants (at present state of the art) have their own metering valve for each cylinders. These modern plants have frequently no more their own autonomous characteristic diagram computer, but convert the injecting characteristic diagram for gasoline, put down in on board computer, to equivalent masses of gas. Therefore is the re-equipment and programming more simply, require however a sequenzielle or gruppensequenzielle fuel injection. Modern vehicles have already since center of the 90's this technology. The introduction of the pollutant standards euro 3 and euro 4 with EOBD (euro on board diagnosis) made then the sequenzielle fuel injection compellingly necessary.The exhaust standard euro 4 is problem-free reached and/or. undercut (at least the Umrüster - which does not apply always) states. In any case one is an exhaust confirmation over at present valid (and/or. to require the vehicle appropriate) exhaust standard, there otherwise an acceptance (TÜV) in Germany not (and/or. onlyvery heavily,) to keep thus expensive is. Likewise a certificate over the correct installation as well as the leak test are in accordance with VDTÜV 750, etc. to require. (This is necessary and with abroad inserted plants often missing also with the aforementioned systems.)

LPI plants

LPI is the abbreviation for liquid Propane Injection and is called translates liquid propane injection, i.e. Liquid gas injection. Sequenzielle gas injection in liquid form probably places the newest (so-called 5.) Generation of the autogas systems. The large advantage of injecting in liquid form is the refreshing effect of theevaporating autogas (interior cooling) in the combustion chamber, here a better rate of admission in the individual cylinders and thus a higher engine performance result. Thus a power loss hardly is in relation to the gasoline enterprise and/or. not at all noticeably. Although this technology was already presented at the beginning of the 90's, to have problems inDetail however up to the today's day a further spreading of this technology prevents.


in some European countries (the Netherlands, Belgium, Italy, Poland, France, etc.) as well as Turkey exists a surface covering gas station net.

In Germany it gave in April 2006 approx. 1363 [1] autogas gas stations. ThoseTendency is strong rising, so that autogas is common clearly further as the natural gas drive (number of CNG gas stations approx. 683 [1]). As Tankanschlüsse regionally differently two different standards became generally accepted: ACME (approx. 86% of the gas stations) and Dish (approx. 11%). By suitable (screwing) adapters this can Problem to be easily gone around.

The prices for autogas are to l in Germany with 0,50 to € 0.70 for each, abroad about 0,30 to 0.60 € for each l. With the price comparison with gasoline it must be however still considered that litre consumption with liquid gas enterprise around approximately 20% rises, since liquid gas in the comparison to the gasoline has a substantially smaller density and thus a smaller calorific value per litre. Therefore can be proceeded with the comparison of the fuel costs between gasoline/super and liquid gas roughly from a halving of the fuel costs. Petrol engines know the fuel costs with autogas operation for instancean appropriate Diesel reach or also undercut.

Autogas gas stations for firm fleets can be furnished starting from approximately € 5,000 and be supplied with approximately 40 to 45 cent for each l. A calibrated gasoline pump including data communication for p.o.s. systems costs about 15,000 to 20.000 €.

comparison liquid gas(LPG) and natural gas (CNG) for motor vehicles

  • Physically
    • LPG is liquid stored with approximately 5 to 10 bar pressure (approx. 400 gFuel per litre of tank volume).
    • CNG is stored gaseously at approximately 200 bar (approx. 160 g fuel per litre of tank volume) and of a high pressure automatic controller to 7 bar reduces.
  • Tank technology
    • LPG permits recess tanks without trunk loss. Cylinder tanks are available with volumes to over 100 l, recess tanks become everafter hollow size to 85 l offered. The net tank volume amounts to 80% of the gross volume. This is necessary for safety reasons (expansion in the hot vehicle). The test pressure of these service stations (TÜV) is at 40 bar with usual operating pressures from 8 to 12 bar.
    • CNG requires accommodated cylinder tanks in the trunkor with series vehicles lower floor panel arranged tanks, in order to have no trunk loss, which over 300 bar test pressure must withstand. The bursting pressure of natural gas bottles amounts to 600 bar.
  • Spreading
    • LPG: The European-wide higher spreading at gasoline pumps has (in particular in the countries France, Poland, Spain, Benelux, Italy and England).Germany is here European Union far quasi tail light, however there are also here still more LPG gas stations than natural gas gas stations. In Germany there are 6,203 vehicles (conditions according to data of the force travel federal office: January 2004). This number shows itself however only a fraction of the actually existing vehicles, there itwith most LPG-able vehicles around reequipped non oem - vehicles acts, which in most cases geschlüsselt in the registration papers with that original key and therefore in the statistics not when bivalent LPG vehicles are recognized. There are LPG gas stations at present in Germany 1239 (conditions March 2006 [1]).
    • CNG: In Germany primarily offensively one applies at present, although the number of the gas stations is still very small compared with LPG. (approx. 30,000 vehicles in Germany, Switzerland, Austria, Italy, Argentina at present.) CNG gas stations are there in Germany 676 (conditions March 2006 [1]).
  • Distribution
    • of LPG is usually transported and loaded like gasoline and Diesel fuels on the road to the gas station so the traffic. However the Tankstellenbetreiber is not compellingly bound to a regional gas servicer.
    • CNG however consists of natural gas and finds its way to the consumer over pipelines.Gas stations receive the natural gas from the net of the local gas supply enterprises, the dressing to CNG effected locally. Rural CNG gas stations without connection to a natural gas net is only heavy and/or. to supply expensively.
  • Practical consequences
    • LPG is somewhat more expensive as fuel than CNG (December 2005 [1]), the changes are however higher with the lower pressure and the world-wide higher spreading clearly more cheaply and attainable ranges generally. If a petrol engine on gas operation is re-tooled, then frequently LPG offers itself from costing and space reasons.
    • CNG is somewhat cheaper as fuel thanLPG (December 2005 [1]) (rule of thumb: 1 kg natural gas = 1.4 l super = 1.65 l LPG), requires however heavier tanks and permits only small ranges from usually 240 to 300 km depending upon consumption. If a vehicle is ex factory equipped with lower floor panel tanks, then are also with CNG ranges of over 400 km with a tank filling attainable. Frequently new acquisition and re-equipment of the local gas supply enterprise are promoted.

Result: Depending upon gas station availability, motor vehicle type, use profile and prospective service life must be individually measured, which technology is appropriate. As rule of thumb can be held:

  • New vehicle and/or.City traffic: LPG or CNG (range of mono valences and bivalent vehicles in the natural gas enterprise up to 300 km without renewed refuelling)
  • used car and/or. Long-distance employment: LPG

safety regulations

liquid gas storage vessel plants monitoring-needy plants are examined after the working reliability regulation and must therefore before start-up by a certified supervisory bodyand will have in certain periods to be recurring examined. Also the regulations of the working reliability regulation regarding the explosion prevention are to be considered.

Special measures are necessary with work under Erdgleiche (cellar among other things), since liquid gas is heavier than air and can than „lake “collect itself. Also soil openings (duct covers,Hatches, cellar outlets) are to be included into the safety consideration.

The transport of liquid gas is regulated by the addr regulations.

Particularly the garage orders are often different, so that one must absolutely pay attention when bringing in to the signs. Even within Austria the regulations are not uniformly, there them into thoseAuthority of the Lands of the Federal Republic fall.


  • Sven Geitmann: Renewable energies and alternative fuels. Hydrogeit publishing house, 2. Aufl., January. 2005, ISBN 3937863052
  • technical rules liquid gas: TRF 1996; Publisher: DVGW/DVFG; 1. Edition 1996, ISBN of 3-87793-039-5

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