Sampling probe for stack gas monitoring system

Claim 1

A probe for the extraction of gas samples from a high temperature, particulate laden gas stream, comprising, an elongated tube; a pair of plugs having axial bores therein, said plugs being fitted in opposite ends of said tube with said bores in alignment; a hollow, porous walled cylinder supported by said plugs concentrically within said tube, said cylinder and said tube being dimensioned to provide a clearance space between the outer wall of said cylinder and the inner wall of said tube, said cylinder forming a conduit interconnecting said plug bores; means for admitting particle laden gas to be sampled to said bore of one of said plugs; means for withdrawing gas samples from said clearance space surrounding said porous cylinder; a combination ejector-blowback valve secured to the other of said plugs externally of said tube, said ejector-blowback valve including, a body, said body having therein a cylindrical chamber, a convergent walled cavity adjacent to and communicating with said chamber and an exit bore, said body being secured to said other plug with said chamber, said cavity and said exit bore coaxially aligned with said axial bore of said other plug, a hollow cylindrical insert supported in said body chamber coaxially with and forming an extension of said axial bore of said other plug, said insert extending the length of said chamber and into said cavity, said insert being dimensioned to provide a clearance space between the outer wall of said insert and the wall of said cavity; a transverse bore in said body intersecting said exit bore; a valve stem rotatably mounted in said transverse bore, said valve stem having a transverse aperture therein which is aligned with said exit bore in one rotational position of said stem, said exit bore being closed by said stem in a second rotational position of said stem; and means for admitting fluid under pressure to said body chamber; said tube, said plugs, said porous cylinder, said body, said insert and said valve stem each being formed of temperature 40 and corrosion resistant material.