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A fuel dispenser is a machine at a filling station that is used to pump gasoline, diesel, CNG, CGH2, HCNG, LPG, LH2, ethanol fuel, biofuels like biodiesel, kerosene, or other types of fuel into vehicles. Fuel dispensers are also known as bowsers (in Australia).1, petrol pumps (in Commonwealth countries), or gas pumps (in North America).
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History
The first gasoline pump was invented and sold by Sylvanus F. Bowser in Fort Wayne, Indiana on September 5, 1885.2 This pump was not used for automobiles, as they hadn't been invented yet. It was instead used for some kerosene lamps and stoves. He later improved upon the pump by adding safety measures and also by adding a hose to directly dispense fuel into automobiles. For a while, the term bowser was used to refer to a vertical gasoline pump. Although the term is not used anymore in the United States, it still is used sometimes in Australia, New Zealand and Canada.
Design
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This section does not cite any references or sources. Please help improve this section by adding citations to reliable sources. Unverifiable material may be challenged and removed. (July 2008) |
A modern fuel dispenser is logically divided into two main parts — an electronic "head" containing an embedded computer to control the action of the pump, drive the pump's displays, and communicate to an indoor sales system, and secondly, the mechanical section containing an electric pump and valves to physically pump the fuel. In some cases the actual pump may be sealed and immersed inside the fuel tanks on a site, in which case it is known as a submersible pump. A black handle is used to warn people that the fuel dispensed is diesel. In the United States, diesel fuel pumps commonly use green hoses and green slipcovers over the nozzle, but this convention isn't necessarily universal.
Modern designs
In modern pumps, the major variations are in the number of hoses or grades they can dispense, the physical shape, and the addition of extra devices such as pay-at-pump devices and attendant "tag" readers.
In some countries, pumps are able to mix two grades of fuel together before dispensing; this is referred to as blending. Typical usages are to add oil to petrol for two-stroke motorcycles, to produce an intermediate octane rating from separate high and low octane fuels or blending of hydrogen and compressed natural gas (HCNG) for ICE.
Flow measurement
One of the most important functions for the pump is to accurately measure the amount of fuel pumped. Flow measurement is typically done by a turbine in the fuel flow. In older gas pumps, the turbine is physically coupled to reeled meters (moving wheels with numbers on the side), while newer pumps turn the turbine's movement into electrical pulses using a rotary encoder.
The metrology of gasoline
Gasoline is difficult to sell in a fair and consistent manner by volumetric units. It expands and contracts significantly as its temperature changes. A comparison of the Coefficient of thermal expansion for gasoline and water indicates that gasoline changes at about 4.5 times the rate of water.
In the United States, the National Institute of Standards and Technology (NIST) specifies the accuracy of the measurements in Handbook 44. Table 3.30 specifies the accuracy at 0.3% meaning that a ten gallon purchase could vary between 9.97 and 10.03 actual gallons at the delivery temperature of the gasoline.
The reference temperature for gasoline volume measurement is 60 degrees Fahrenheit or the slightly different 15 degrees Celsius where the metric system prevails. Ten gallons of gasoline at 60F expands to about 10.15 gallons at 85F and contracts to about 9.83 gallons at 30F. Each of the three volumes represents the same theoretical amount of energy. In one sense, ten gallons of gasoline purchased at 30F is about 3.2% more potential energy than ten gallons purchased at 85F. Most gasoline is stored in tanks underneath the filling station. Modern tanks are non-metallic and sealed to stop leaks. Some have double walls or other structures that provide inadvertent thermal insulation while pursuing the main goal of keeping gasoline out of the soil around the tank. The net result is that while the air temperature can easily vary between 30F and 85F, the gasoline in the insulated tank changes temperature much more slowly.
Temperature compensation is common at the wholesale transaction level in the United States and most other countries. At the retail consumer level, Canada has converted to automatic temperature compensation and the United States has not. Where automatic temperature compensation is used, it can add up to 0.2% of uncertainty for mechanical-based compensation and 0.1% for electronic compensation, per Handbook 44.
There are many fewer retail outlets for gasoline in the United States today then there were in 1980. Larger outlets sell gasoline rapidly, as much as 30,000 gallons in a single day, even in remote places. Most finished product gasoline is delivered in 8 to 16 thousand gallon tank trucks so two deliveries in a 24 hour period is common. The belief is that the gasoline is spends so little time in the retail sales system that its temperature at the point of sale does not vary significantly from winter to summer or by region. Canada has lower overall population densities and geographically larger gasoline distribution systems, compared to the United States. Temperature compensation at the retail level improves the fairness under those conditions.
Higher energy prices have raised awareness of this issue for consumers. At the same time, alternative fuel applications are now reaching the retail market and accurate comparisons between them in normal usage are needed. Eventually the basis for retail sales will change from volume units in liters or gallons to energy units such as the BTU, joule, therm or kWh so that electricity, liquids, liquefied gases and compressed gases can all be sold and taxed uniformly.
Communications components
The technology for communicating with gas pumps from a point of sale or other controller varies widely, involving a variety of hardware (RS-485, RS-422, current loop, and others) and proprietary software protocols. Traditionally these variations gave pump manufacturers a natural tie-in for their own point-of-sale systems, since only they understood the protocols. 3
An effort to standardize this in the 1990s resulted in the International Forecourt Standards Forum, which has had considerable success in Europe, but has less presence elsewhere. ("Forecourt" refers to the land area on which the fuel dispensers are located.)
Autocut in fuel dispenser
Most modern pumps have an auto cut-off feature that stops the flow of fuel once the tank is full. This is done by having a second tube, the sensing tube, that runs from just inside the mouth of the nozzle up to a Venturi pump in the pump handle. While the tank is being filled, air displaced from the tank is drawn up this tube. Once the fuel level reaches the mouth of the sensing tube, air is no longer drawn up the sensing line. A mechanical valve in the pump handle detects this change of pressure and closes, preventing the flow of fuel. 4
Other components
A modern fuel pump will often contain control equipment for the vapor recovery system, which prevents gasoline vapor from escaping to the air.
Manufacturers
Fuel dispensers are made by many different companies throughout the world. In earlier decades, it was common for each country to have several competing manufacturers, but consolidation and globalization has occurred in this industry, so that many formerly well-known names such as Satam and EIN no longer exist as independent companies.
Some of the largest remaining manufacturers are Tokheim5, Gilbarco Veeder-Root6, Dresser Wayne7 (of Dresser Industries), and Tatsuno Corporation 8.
Variations
Early designs
 Petrol pump in Vienna, Austria. |
 Display of various antique gas pumps at Deutsches Museum in Munich, Germany. |
 Antique diesel pump located at Roscheider Hof, Open Air Museum, Konz, Germany. |
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 Old Soviet Union gas pumps. |
 Antique "Mobilgas" pumps, manufactured by Tokheim, located in Wilton, Connecticut, USA. |
 Two types of Shell gas pumps at Soulsby Service Station in Mount Olive, Illinois, USA. |
Regulations
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This section does not cite any references or sources. Please help improve this section by adding citations to reliable sources. Unverifiable material may be challenged and removed. (July 2008) |
Since fuel dispensers are the focal point of distributing fuel to the general public, and fuel is a hazardous substance, they are subject to stringent requirements regarding safety, accuracy and security. The exact details differ between countries and can depend to some extent on politics.
For example in countries fighting corruption, such as Mexico 9, gas pumps may be more stringently monitored by government officials, in order to detect attempts to defraud customers.
Typically, individual pumps must be certified for operation after installation by a government weights and measures inspector, who tests that the pump displays the same amount that it dispenses.
See also
- Cascade storage system
- Point of sale electronic system connected to fuel dispensers for processing sale transactions
References
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This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (July 2008) |
- ^ Mark Gwynn (October 2005). "When people become words". Ozwords (Australian National Dictionary Centre). http://www.anu.edu.au/andc/pubs/ozwords/pdfs/ozwords_oct05.pdf. "But one doesn’t have to be an Australian to enter the Australian lexicon — take bowser ‘petrol pump’ (in Australia), which is named after a company established by U.S. inventor and entrepreneur S.F. Bowser (d. 1938).".
- ^ http://www.wired.com/science/discoveries/news/2008/09/dayintech_0905
- ^ http://www.ifsf.org/Software/IFSF%20Management%20Intro%20-%20V3.01.pdf IFSF Management Intro, sec 1.1 Background history
- ^ http://www.pa.msu.edu/sciencet/ask_st/122591.html
- ^ Tokheim corporate website
- ^ Gilbarco Veeder-Root corporate website
- ^ Dresser-Wayne corporate website
- ^ Tatsuno corporate website
- ^ Not Quite Measuring Up at Mexico's Gas Pumps - Los Angeles Times
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Wikimedia Commons has media related to: Petrol pumps |
External links
Hosed at the Pumps: an Ottawa Citizen investigation in to Canadian fuel pump accuracy, with a searchable database on inspection records. By journalists Glen McGregor, Jessey Bird, Doug Schmidt, and Barb Pacholik.
Wikipedia content modification information:
- This page was last modified on 12 December 2008, at 18:38.
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