Gas pump

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Dispenser with flow sight glass (yellow) and nozzle (red)

A gas pump , also gas pump is an apparatus in a filling station , to which the fuel , in some cases also an additive such as AUS 32 to the exhaust after-treatment , is filled into the vehicle to be refueled. The nozzle - colloquially known as the fuel nozzle - is connected to the fuel pump via a hose. The fuel is filled into the tank of the land, water or air vehicle via the nozzle .


The first taps on public land were often on the sidewalks in front of inns or department stores in the 1920s. They had manually operated gas pumps, also known as the "Iron Maiden". To refuel, you knocked on the shop and were served. The first models simply pumped. With the advent of the glass cylinder, the amount of petrol that was tapped was read on a scale on the outside, which then ran into the tank. With the two-glass versions, it was then possible to continue pumping while the other contents of the container drained into the tank. From the mid-1930s, there were the first petrol pumps that had counters with price displays.

Until the end of the 1970s, only columns with a mechanical calculator were used. In 1978 the first electronic price calculator for petrol pumps was developed in Germany, after which the petrol pumps with mechanical counters at the petrol stations gradually disappeared and were replaced by electronic ones. Likewise, most of the fuel dispensers, at which a maximum of two different products could be filled with two hoses, have meanwhile been replaced by so-called MPDs (abbreviation for Multiple Product Dispenser ). Up to five different fuels can be dispensed on each side of the dispenser at these dispensers. In addition, there are high-performance fuel pumps at many petrol stations that are specially designed for refueling trucks. As they have a delivery rate of up to 130 l / min (as opposed to around 35 l / min for car columns), they are equipped with nozzles that have a much larger diameter than car nozzles. On the one hand, this serves for faster delivery, on the other hand, it is more difficult to confuse them with car nozzles, since they do not fit into car filler necks. During the transition from leaded to unleaded petrol, the nozzle diameter was reduced to prevent accidental refueling with leaded petrol. The diameter of petrol dispensing pistols is 21 mm and of diesel 25 mm in the car sector. A similar system prevents confusion of fuel types in aviation.

A fuel pump also contains a display for checking the quantity and price of the fuel filled in. In addition, information on the octane number (see knock resistance ) and various safety regulations are the rule.

In the case of self-service filling stations, the fuel data (filling point number, product filled up, quantity dispensed, basic price per liter and amount to be paid) are also transmitted to one or more tills in the shop. In the early self-service filling stations, this information was still printed out on a receipt that the customer had to hand over to the cash register to pay. In southern Europe in particular, it was also common to use tokens , which the customer had to buy beforehand and put in at the pump according to the required amount of fuel. For some years now, ATM-like terminals have also been installed in fuel pumps , where you can pay for fuel directly with a credit card . Since 2018, payment by smartphone has also been possible at certain petrol stations. The mineral oil company Shell introduced this option under the name SmartPay at more than 1500 petrol stations in Germany.

Gas recirculation

Today's motor vehicle filling stations use petrol pumps and fuel nozzles with a gas recirculation system to extract the fuel that has evaporated into gas. This means that benzene vapors that are hazardous to health and the environment are largely absorbed. In Germany, due to the ordinance on limiting hydrocarbon emissions when refueling motor vehicles, since April 1, 2003, it has been a stipulation at newly built gas stations that the proper functioning of the gas recirculation system is automatically monitored (gas recirculation monitoring). In the event of a fault in the gas recirculation, the dispenser must be repaired within 72 hours, otherwise the further delivery of petrol at this dispenser is automatically prevented by technical measures.

Gas exchange is the name of the process that for every liter of liquid phase, one liter of gas phase is exchanged between the delivering tanker and the (mostly :) underground storage tank at the gas station. The vapor pressure of gasoline at 20 ° C is around 60 kPa (0.6 bar), the ratio of liquid density = 750 g / l to gas phase density = 4.5 g / l can be calculated by returning fuel vapor at each refueling step Avoid 0.6% fuel loss.

Measurement of the flow rate

Calibration of gas pumps

The flow rate inside the dispenser is measured using so-called screw or piston meters . The flow pressure generated by a suction pump (inside the dispenser) or pressure pump (outside the dispenser) moves 2–4 pistons in the piston knife or the counter-rotating micrometers that drive a common shaft. The rotation of the shaft is therefore a measure of the flow rate. Either a mechanical arithmetic unit or (in modern petrol pumps) an electronic pulse generator is flanged to this shaft, which converts the rotary movement of the shaft into pulses that can be counted by the electronics. The sight glass at the filling point enables the user to check whether only fuel (and no air) is passing through the flow meter. The tolerance permitted in commercial traffic (calibration error limit and traffic error limit) is ± 0.5% uniformly across the EU, i.e. H. with a display of 100 liters, between 99.5 and 100.5 liters must have been dispensed. The quantity of fuel dispensed at public filling stations is monitored by the calibration office. For this purpose, checks of the nature and delivery quantity (metrological check) are carried out every two years. In the case of initial verification, re-verification and re-verification after previous repairs, a full test is generally carried out, however, columns placed on the market or the measuring devices contained in them are considered to be initial verified ex works in accordance with Directive 2004/22 / EC (MID).

Temperature compensation

Since the implementation of the European MID directive, fuel pumps with temperature compensation have also been permitted in Germany. During the refueling process, these adjust the displayed delivery quantity according to the calculated expansion at an assumed ambient temperature of 15 ° C. In temperate latitudes, the ground temperature is rarely above 15 ° C all year round, so that i. d. Usually a higher than the actual delivery amount is displayed and billed. The correction factor for carburetor fuels is about one per thousand per Kelvin, from which it follows that z. B. with a delivery of 100 liters of 9 ° C cold fuel 100.6 liters would be charged. Temperature-compensated dispensers can be recognized by the fact that the unit for the dispensed quantity on the display board and invoice is not "liter" or "l", but "liter at 15 ° C". For the operator, temperature-compensated dispensers have the advantage that the delivery to the customer takes place under the same conditions as the delivery (this is always temperature-compensated), which reduces the otherwise inevitable "loss". For the customer, temperature-compensated fuel dispensers have the disadvantage that they do not underestimate the amount of fuel drawn compared to a conventional dispenser that measures the actual delivery temperature.

Nozzle automatic

The automatic nozzle system (ZVA) automatically ends the refueling process when the tank is full, and it works as follows:

The fuel flow creates a vacuum in the narrow gap on the valve seat ( Venturi effect ). Air is sucked in to compensate for the negative pressure through the sensor line, which leads via the membrane and the tilt ball safety release to the sensor nozzle. As long as the sensor nozzle remains free, the nozzle valve can work. If fuel covers the sensor nozzle at the end of the pipe, the air supply is interrupted. A negative pressure builds up immediately, the membrane is sucked up and the shut-off mechanism is triggered. Because the valve closes against the direction of flow, the counterpressure alleviates the shutdown shock and there is no high pressure peak. The automatic switch-off is also activated when the sensor line is closed by the ball of the safety release. This always happens when the nozzle is directed upwards; For example, if it does not point correctly downwards when filling, if it slips out of the filler neck, or if the switch lever is accidentally actuated when removing it from the dispenser.

Water protection and explosion protection

Historical fire notice

The filling area around the pumps is designed to protect against spilled water-polluting substances that seep into the ground, e.g. B. by precast concrete parts with special permanently elastic grouting. At the edge of the surface there are raised edges so that no spilled fuel can flow out of this surface. This filling area is drained via separators , even if the area is covered. The fuel pumps themselves are set up in such a way that they cannot be easily damaged by shunting vehicles (collision protection), e.g. B. by raised approach boards or circumferential guard rails. In order to avoid dangerous electrostatic discharges (arcing), the dispensing valve is earthed via the dispensing hose; The road surface of the refueling area must also be electrically conductive to a certain extent in the case of highly flammable products (petrol) in order to enable equipotential bonding between the fuel dispenser and the vehicle. In the case of aircraft refueling, a conductive connection to the fuel pump is first established before the actual refueling process by connecting a grounding cable attached to the fuel pump to the ground connection of the aircraft. In Germany, these requirements were defined in the Technical Rules for Flammable Liquids - TRbF 40 - Petrol Stations or TRbF 30 - Filling Points, Emptying Points and Airfield Refueling Stations until the end of 2012, and were defined by TRBS 3151 - Avoidance of fire, explosion and pressure hazards at filling stations and filling systems for filling of land vehicles replaced, which the relevant requirements for the storage and filling of mineral oil and liquefied petroleum gas ( LPG summarized) and natural gas.

Web links

Commons : Gas Pump  - Collection of images, videos and audio files
Wiktionary: gas pump  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. Joachim Kleinmanns: Super, full! A brief cultural history of the gas station. Jonas Verlag, Marburg 2002, p. 43.
  2. Bernd Polster: Super or Normal. Gas stations - story of a modern myth. DuMont, Cologne 1996, p. 44
  3. en: Bob Hoover # Hoover Nozzle and Hoover Ring Hoover Nozzle and Hoover Ring, accessed September 9, 2015.
  4. ^ Manfred Bremmer: Mobile payment at the Shell petrol station. Computerwoche, March 29, 2018, accessed on September 23, 2018 .
  5. Safety data sheets ( Memento from June 30, 2011 in the Internet Archive )