A quick opening valve plug produces a large increase in flow for a small initial change in stem travel.
Near maximum flow is reached at a relatively low percentage of maximum stem lift.
Quick opening plugs are normally utilized in two position “On-Off” applications but may be used in some linear valve applications.
This is possible because of its initial linear characteristic at a low percentage of stem travel.
The slope of this linear region is very steep which produces a higher initial gain than the linear plug but also increases the potential instability of the control valve.