One of the most widely observed but least recognized type of valve is the fire hydrant. Fire hydrants are connected to municipal water supply systems. They are specialized underground valves that can be opened and closed from ground level when needed in emergency situations. A valve is a product rarely noticed by the average person, yet it plays an important role in the quality of our life. Each time you turn on a water faucet, use your dishwasher, turn on a gas range, or step on the accelerator of your car, you operate a valve. Without modern valve systems, there would be no fresh pure water or automatic heat in your home. There would be no public utilities, and beyond wood and coal, almost no energy of any kind. Plastics would be unheard of, as would many inexpensive consumer products. By definition, a valve is a device that controls the flow of a fluid. Today's valves can control not only the flow, but the rate, the volume, the pressure or the direction of liquids, gases, slurries or dry materials through a pipeline, chute or similar passageway. They can turn on and turn off, regulate, modulate, or isolate. They can range in size from a fraction of an inch to as large as 30 feet in diameter and can vary in complexity from a simple brass valve available at the local hardware store to a precision-designed, highly sophisticated coolant system control valve, made of an exotic metal alloy, in a nuclear reactor. Valves can control flow of all types, from the thinnest gas to highly corrosive chemicals, superheated steam, abrasive slurries, toxic gases and radio active materials. They can handle temperatures from cryogenic region to molten metal, and pressures from high vacuum to thousands of pounds per square inch. The valve is one of the most basic and indispensable components of our modern technological society. It is essential to virtually all manufacturing processes and every energy production and supply system. Yet it is one of the oldest products known to man, with a history of thousands of years.THE HISTORY OF THE VALVE INDUSTRYNo one knows when the idea for the valve was born. Perhaps somewhere, sometime in the ancient past, man learned to regulate the flow of a river or stream by blocking it with large stones or a tree trunk. However it developed, the invention was almost as important as the wheel, for now man could regulate water flow. The early Egyptian and Greek cultures devised several types of primitive valves to divert water for public consumption or crop irrigation. It is the Romans, however, who are generally recognized as the developers of comparatively sophisticated water systems. Their plumbing was advanced enough to deliver water into individual buildings, for which they developed the plug valve, or stopcock, and there is also evidence that the Romans used check valves to prevent back flow. For centuries, throughout the Dark Ages, there were no advances in valve design. Then during the Renaissance, artist and inventor Leonardo daVinci designed canals, irrigation projects, and other large hydraulic systems, which included valves for use in these projects. Many of his technical sketches are still in existence. The modern history of the valve industry parallels the Industrial Revolution, which began in 1705 when Thomas Newcomen invented the first industrial steam engine. Because steam built up pressures that had to be contained and regulated, valves acquired a new importance. And as Newcomen's steam engine was improved upon by James Watt and other inventors, designers and manufacturers also improved the valves for these steam engines. Their interest, however, was in the whole project, and the manufacture of valves as a separate product was not undertaken on a large scale for a number of years.Brass Ball Valve