Model valves

In this arrangement of stop valve, which was patented in 1904 by Mr. S. Z. de Ferranti, the size of the valve and the perimeter of leakage are reduced by the use of a valve of considerably less area than that of the piping, the requisite flow being obtained without excessive frictional losses by leading the fluid into the valve by a gradually contracting vein, and then after it has passed the valve the excessive velocity energy is reconverted into pressure energy by the use of a corresponding but longer expanding orifice.

This valve, patented in 1903 by Mr. J. Hopkinson and improved in 1906, was designed to lessen the strains both on the valve and seat, whilst ensuring steam tightness. With this type of valve it is claimed that scoring action on the faces of both valve and seat, when opening or closing, is avoided. The controlling valve also prevents the flow of steam while the main valve is being opened or closed.