Axial flow throttling valve

A self-contained valve assembly for controlling the flow of gaseous fluid in a pipeline to maintain uniform downstream pressure with varying downstream load, comprising a housing having a main fluid passage therethrough, cage means and a resilient boot member in said main passage for controlling the flow of fluid therethrough, a chamber formed in the housing around at least a portion of said boot means, upstream passage means wholly contained in said housing connecting said chamber with said main passage at a point upstream of said cage, a variable restriction in said upstream passage means to control the rate of entry of upstream control fluid into said chamber, downstream passage means wholly contained in said housing connecting said chamber with said fluid passage at a point downstream of said cage, diaphragm controlled pilot valve means mounted on said housing having a control valve projecting into said downstream passage means to control the flow of control fluid out of said chamber through said downstream passage means, and means on said pilot valve means to facilitate a fluid connection between the diaphragm of said valve means and said pipeline downstream of said valve.