The valve plate is the material, usually flat or nearly so, that makes up the valve assembly. It needs to be durable and strong, and in many cases also resistant to heat, pressure and corrosion. There are valves that are automatically activated by changes in pressure within the setup of a machine. Other valves are manually operated through a lever, pedal or handle. In either case, the valve plate needs to be tough, non-corroding and resilient, because of its frequent exposure to varying pressures and temperatures. Some valves, like those in boilers and hot water systems, have to continually withstand temperatures well exceeding the boiling point of water.
A valve is simply a device that adjusts the flow of a fluid or gas. It works by opening, closing, or partially blocking the passageway where it is located. Most valves are used as pipe fittings; as such, they are a basic element in plumbing construction. Very easily recognizable are the plumbing valves in homes, which are used as taps for hot and cold water. Other familiar forms of valves are those found in cookers as gas control valves, and those in washing machines and dishwashers.
Less known to ordinary people are valves called open valves. In hydraulic setups, open valves guide the flow of fluids or gases from a place of higher pressure to one of lower pressure. In the context of transportation, commerce and industry, valves are an indispensable part of oil and gas apparatuses, and in machines or instruments used in mining, manufacturing, power generation, sewerage, and water reticulation. There are valves used in pneumatic, hydraulic, motor and manual setups. Given their various uses, valves also come in very varied sizes, from as small as 0.1 mm to a sizable 60 cm. There are even valves as big as 16.5 feet (5 meters) in diameter.
Depending on its intended use, a valve plate is made from materials such as cast iron, spheroidal graphite iron, spring steel, stainless steel and carbon steel. Special preparation for these materials such as proper grounding and fine finishing are also often required, so that they can be matched perfectly to other component pieces. This also ensures that micro-leaks in the valve plate assembly are avoided.
There are stringent specifications for the manufacture of valve plates. These must be followed to ensure the structural integrity of the mechanism that the valve plates will be part of. A compressor valve assembly, for example, is a basic and integral component of industrial machinery. The functionality, safety and reliability of a machine depends on the strength and dependability of its component parts, including every valve plate that goes into its assembly.