Here is the difference between butterfly valve and gate valve:
The Gate Valve:
This valve functions very similar to a gate, a simple open/close movement, with the disc perpendicular to the direction of the flow. Available in Wedge, Knife, Parallel Slides and Pipeline slab designs, they serve a myriad of purposes. Discharge is usually complete with no residues left standing in the pipeline.
Uses and Functionality:
It is often used to either fully open up the pipe structure to enable free flow or completely cut off the flow when fully closed. It can function well across different temperatures and pressures; however, is susceptible to seepage under very high pressures, unless lined with special seat inserts to ensure a snug seal.
Applications:
Gate valves are extensively used in large-scale systems that require uninterrupted bi-directional flow of liquids and gases, or uni-directional discharges at specific time intervals.
Operation Modes:
Manually operated using round handles.Operations can be automated using electric actuators or pneumatic handles.
Construction Materials:
Metal (steel) with special seat material if required.
The Butterfly Valve:
Uses and Functionality:
Butterfly valves find use only in low pressure and low temperature flow systems. Lightweight and short face-to-face dimension, they can be used both for isolation and regulating the flow of material using their characteristic quarter turn rotating action.
Applications:
Widely used for regulating large volumes of liquid and gaseous material.Disc designs are not advisable for hazardous, hydrocarbon or other inflammable substances.
Operation Modes:
Valves can be operated using manual levers or energized hydraulic or pneumatic actuators.
Construction Materials:
Metal with metal or soft seats with polymer or elastomeric seals.Select styles have alternate metal and graphite layers sheets in the seal.
Valves are usually constructed using a range of metals that support specific thermal and corrosion resistant properties that make them ideal for select industrial uses. Common construction materials usually are copper, bronze, graphite, tungsten, aluminum, brass, different types of stainless steel or fortified iron, as well as special alloys such as stellite, monel, colmonoy, hastelloy C, nickel with iron or bronze with aluminum or silicone.