Gas pump

  A Gasoline pump is a machine at a gas station that is used to put gasoline in vehicles. Gas pumps are also known as petrol pumps, fuel dispensers or (in Australian usage) petrol bowsers.

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Structure

Older gas pumps have reeled meters (moving wheels with numbers on the side), which are physically connected to a turbine in the fuel flow.

A modern gas pump consists of 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, a mechanical section containing an electric pump and valves to physically pump the fuel. Fuel flow is measured by one or more rotary encoders which generate electrical pulses. 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.

Safety, Environmental and Regulations

  Since gas pumps 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, gas pumps may be more stringently monitored by government officials, in order to detect attempts to defraud customers.

A modern gas pump will often contain control equipment for the vapor recovery system, which prevents gasoline vapor from escaping to the air.

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.

Manufacturers

Gas pumps are made by many different companies throughout the world. In earlier decades, it was common for each country to have several competing manufacturers, but much consolidation and globalisation has occurred in this industry, so that many formerly well-known names such as Satam, Schlumberger and EIN no longer exist as independent companies. Three of the largest remaining manufacturers are Tokheim, Gilbarco-Veeder Root, and Dresser Wayne.

Variations

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 blending. Typical usages are to add oil to petrol for two-stroke motorcycles, or to produce an intermediate octane rating from separate high and low octane fuels.

Communication with gas pumps

While the behaviour and design of pumps is very similar across the world, communicating with them from a point of sale or other controller varies widely, using a variety of both hardware (RS-485, RS-422, current loop, and others) and proprietary software protocols.

In western societies automation is now a standard part of service stations, and therefore this small but critical variation prevents easily changing between different brands of pump. Traditionally this gave pump manufacturers a natural tie-in for their own point-of-sale systems, since only they understood the protocols.

An effort to standardise this in the 1990s resulted in the International Forecourt Standards Forum, which has had considerable success in Europe, but has less presence elsewhere.

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