Valves are products that are rarely noticed, yet they play a vital role in our daily life. Each time you turn on a water faucet or a gas range, or use your water heater, you operate a valve. Valves help preserve our quality of life by controlling flow of all types. They are essential to our homes and to virtually all manufacturing processes, as well as every industrial plant and system. There are a large variety of valves and valve configurations for a wide variety of purposes and conditions: different uses (on/off, control), different fluids (liquid or gas; combustible, toxic or corrosive), different materials (metal or nonmetal) and different pressure and temperature conditions(low, medium or high pressure applications and low-, room- or high-temperature applications).