Gate valves are widely used for all type of application. The gate valve is the most extensively used ON/OFF valve for great diameter, full port applications. These are particularly considered to be used in crushed coal mills and in coal-fired thermal authority plants. Gate valves are calculated for fully open or fully closed service. Gate valves can be separated into two types first is parallel and second is wedge-shaped. Gate valves are mainly designed to start or stop flow. The disk of a Gate valve is entirely removed when the valve is fully open the disk is fully drawn up into the valve Bonnet. Typical gate valves are designed to be fully opened or closed. Gate valves can be used for a vast number of fluids. A needle valve is a type of valve usually used in flow metering applications. The actuator takes the form of a nut which is rotated around the threaded stem to move it. A Gate valve can be used for a wide range of liquids and provides a tight seal when closed.