| 摘要 |
<p>An annular valve is constructed with an annular housing located coaxially around an axial pipe, a means to close, partly close or fully open the bore of the pipe thus stopping, partly stopping or fully opening the bore for fluid or slurry flow through the pipe and an electrical means operable to close, partly close or open the means to stop or permit flow in the pipe, The means to close, partly close or fully open the bore of the pipe may be an annular slide valve or an extrudable, packing member, which can be forced through an annular aperture into the bore to partially, or wholly, block the bore. The slide valve or extrudable, packing member is operated by an electrical means in the form of a solenoid-type of arrangement. The pipe in the housing may be a single pipe or a double, coaxial pipe, consisting of a bore and annular passage surrounding it, and the valve may be operable to close, partly close or fully open the annular passage. Means to monitor the position of the valve and hence the degree of closure are taught as are fail safe means.</p> |
