Velocity boost body with wrap-around pitot tube

A pressure relief diaphragm type regulator valve includes a velocity boost body having an annular-shaped wrap-around pitot tube communicating with the vena contracta of a flowpath. The pressure at the vena contracta is communicated to the diaphragm by a small registration orifice in the boost body. The boost body defines a large relief orifice open to the annular pitot tube, but normally closed off from the diaphragm by a flapper. Under a rapid excess pressure condition, the flapper uncovers the relief orifice and large volume flow is permitted to the diaphragm.