Multi-turn valves – what are the common types?

The Diaphragm Valve effects closure by means of a flexible diaphragm attached to a compressor. When the compressor is lowered by the valve stem onto a weir, the diaphragm seals and cuts off flow. The diaphragm valve handles corrosive, erosive, and dirty services. It is an easily maintained valve. The Globe Valve effects closure by a plug with a flat or convex bottom lowered onto a matching horizontal seat located in the center of the valve. Raising the plug opens the valve to let flow through. The globe valve is used for on-off service and handles clean service throttling applications. The Needle Valve is a volume control valve that restricts flow in small lines. The fluid going through the valve turns 90 ° and passes through an orifice that is the seat for a rod with a cone shaped tip. The size of the orifice is changed by positioning the cone in relation to the seat. The Gate Valve is a general service valve used primarily for on-off, non-throttling service. The valve is closed by a flat face, vertical disk or gate that slides down through the valve to block the flow. The Pinch Valve finds wide application in slurries or liquids with large amounts of suspended solids. It seals by means of one or more flexible elements, such as a rubber tube, that can be pinched to shut off...