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Air compressors have been around for well over 100 years and have as many uses as there are tools that use air. One reason for their popularity is because air as a resource is safe, flexible, clean and convenient. These machines have evolved into highly reliable pieces of equipment that are almost indispensable in most of the applications they serve. Compressors can come in a wide variety of different types and sizes.

Ultimately, as with any tool, air tools and the compressors that drive them, have to save the user time and money on any given project. Most compressed air tools are more powerful and typically lighter than standard electric tools or battery powered cordless tools. They are used by virtually every industrial sector from aircraft to automobiles to dairy farming to textiles.

While there are many types of compressors, they all perform the same function, which is to increase the pressure and reduce the volume of a given gas such as air. The most common type of compressors work by filling a chamber with air and then reducing the chamber’s volume. These are called positive displacement compressors. They are the most widely available compressors and include reciprocating, rotary screw and rotary vane compressors.

Of all the positive displacement compressors, Reciprocating or Piston compressors are the most commonly available on the market and can be found in ranges from fractional to very high horsepower. These compressors are sold world wide by many mass marketers and a large variety of retail outlets.

Rotary compressors (Screw and Vane) and the centrifugal compressors are also commonly found but in more of an industrial/commercial environment. Normally they are operated at significantly higher horsepower and flow rates, which makes them more expensive buy and to operate. For more information on rotary compressors please visit www.daveycompressor.com.

The following paragraphs contain some very general information on piston compressors that will allow for a more informed decision concerning the type and size of compressor being considered.

Single Stage and Two Stage Reciprocating Pumps

Reciprocating (Piston) Compressors can be widely found in two primary configurations; Single Stage and Two Stage.

Single stage air compressors work by drawing air in and subsequently compressing the air to its final pressure in single piston stroke. Single stage air compressors can attain pressures of up to 150 PSI. Typically, a single stage pump will have a higher CFM(Cubic Feet per Minute) rating than a two stage pump because every cylinder is drawing in air and compressing it with air during every rotation.

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Two stage air compressors work in a very similar manner with the primary difference being that they compress the air in 2 steps or stages. During the first step or stage, air is drawn in and compressed to an intermediate pressure. After being compressed in the first stage, the air is piped, usually through an intercooler where the air is allowed to cool, to be compressed in the final or second stage. Two stage compressors are normally good for pressures

Researchers found toxic chemicals from recycled newspapers had contaminated food sold in many cardboard cartons.

The chemicals, known as mineral oils, come from printing inks.

Cereal firm Jordans has stopped using recycled cardboard and other firms are to ensure their recycled packaging does not contain any toxic oils.

Kellogg's and Weetabix said they were taking steps to reduce the amount of mineral oil in their packaging.

Exposure to mineral oils has been linked to inflammation of internal organs and cancer.

Government scientists in Switzerland found quantities of mineral oils between 10 and 100 times above the agreed limit in foods like pasta, rice and cereals sold in cartons made from recycled cardboard.

'Frightening' potential

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Should there be any evidence from our study - and we will carry out a risk assessment - we will take immediate action to protect the public.”

Terry Donohoe
Food Standards Agency
In one scientific paper they describe the potential for mineral oils to migrate into foodstuffs as "frightening".

However, the Swiss food safety authorities have concluded that consumers who eat a balanced and varied diet have no need to worry.

In a statement Jordans said that, as an environmentally responsible company which had previously used largely recycled packaging, it had taken the decision to abandon it reluctantly, but felt it was sensible.

The BBC investigation found other food companies were aware of the issue - but none had so far followed Jordans' lead.

More than half the cardboard used in Europe is made from recycled materials.

So-called "virgin board" from newly harvested trees is more expensive and there is not enough of it to replace recycled card completely.

The research has been led by Dr Koni Grob at the government-run food safety laboratory of the Canton of Zurich.

In one study for the German food ministry last year he and his colleagues tested a sample of 119 products bought from German supermarkets.

They found mineral oils passed easily through many of the inner bags used to keep food dry and fresh.


More than half of Europe's cardboard is made from recycled materials
The longer a product stood on the shelves, the more mineral oil it was likely to absorb.

Dr Grob told the BBC: "Roughly 30 products from these 119 were free of mineral oil.

"For the others they all exceeded the limit, and most exceeded it more than 10 times, and we calculated that in the long run they would probably exceed the limit 50 times on average and many will exceed it several hundred times."
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The agreed safe limit for mineral oil saturated hydrocarbons, derived from an expert evaluation carried out for the UN's Food and Agriculture Organization and the World Health Organisation, is a migration of 0.6mg per kilogram.

Water is purchased much the same way we purchase electricity. A meter measures the range of gallons that enters the water program, either in cubic feet or in hundreds of gallons. The meter, which isn't equipped to record the huge numbers used by most foodservice locations, will show a basic range.

The meter reader takes that range and multiplies it by a constant figure, known as the constant multiplier. For instance, if the meter shows 1200 and the multiplier is 100, we have consumed 120,000 gallons. Whenever you turn on a sink in your kitchen, the drinking water rushes out at 50 to 100 psi. This stress is a lot more than sufficient to get it from the city's pipes to the building, which only takes up to 20 psi.

The excess pressure is used to move drinking water into numerous pipes throughout the facility. his is called the upfeed system of getting water. Actually, 50 to 100 psi is strong enough to supply water to the upstairs area of a making four to six stories high. If your facility is in a taller making than that, you'll most likely require water pumps to boost the stress and flow.

Pumps could be utilized to increase drinking water stress; valves (called regulation valves) can be utilized to decrease it. Your goal is to control the drinking water coming into your facility to avoid fluctuating pressure or an uneven flow rate. And whenever there's a possibility that contaminated drinking water could backflow into the potable water program, a backflow preventor should be installed.

Backflow may occur whenever a piece of equipment, such as a commercial dishwasher, is capable of creating stress that is greater than the incoming pressure of its supply line. The segments from the typical upfeed program are:

Water meter: The device that records water consumption. It is the last point of the public drinking water utility's service. Anything on "your" side from the drinking water meter, including all pipes and maintenance, is your responsibility, not the water company's.

Service pipe: The primary supply line between the meter and the building.

Fixture branch: A pipe that carries drinking water to a single fixture. It could be vertical or horizontal and carry warm or cold drinking water.

Riser: A vertical pipe that extends 20 or a lot more feet. It can carry warm or cold water.

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Fixtures: The devices (faucets, toilets, sinks) that permit the water to be used by guests and/or employees.

Hot-water heater: The tank utilized to heat and store hot drinking water.

Pipes: The tubes which are fitted together to supply a program for water to travel via. They could be copper, brass, galvanized steel, or even plastic. Building codes determine what materials are acceptable for various uses. Copper is the most costly kind of pipe, but it's considered simple and economical to work on.

Plastic pipes are allowed only for limited, special uses. Probably the most typical type of plastic pipe is made of polyvinyl chloride (PVC). It is inexpensive, corrosion resistant, and has a long life, if you're allowed to use it.

Fittings: The joints of the pipe program. They fit onto the ends of pipes, allowing them to make turns and to connect to each other and to other appliances or fixtures. Some of their names describe their shapes, and also the most well-liked fittings include the bushing, cap, coupling, elbow, plug, and tee. Some fittings have threads (either internal or external) to become screwed into place; others are compression type.

Valves: Valves control drinking water flow, and are created of brass, copper, or cast iron. Use of the correct valve minimizes plumbing difficulties. Gate valves are used to vary drinking water flow and permit water to go in either direction. Check valves permit water to flow only one way. They're marked with an arrow indicating the direction of flow.