Importance

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Abstract

A leak indicating conduit for conveying fluid includes an inner tube and an outer tube, in which the inner tube is separated from the outer tube by a space maintained at a pressure having a predetermined value from the range of values less than the pressure of the conveyed fluid and the ambient pressure, and greater than the pressure of the conveyed fluid and the ambient pressure. A leak indicating device is in continuous communication with the space for indicating a change of pressure in the space from the predetermined value. The indicating device includes a chamber in which an expansible bellows is mounted in communication with the space. The expansible bellows includes a movable plate supporting an indicating element for movement between a concealed first position, thereby indicating no change of pressure from the predetermined value, and a second, visible position, thereby indicating a change of pressure. An electrical switch for operating a separate indicating or control device can be mounted adjacent the expansible bellows, so that it is operated by the bellows as the bellows moves between its first and second positions. Where the leak indicating conduit is used as an expansion joint, the ends of the inner and outer tubes are secured to the pipes by annular attachment welds. Tapered rings are welded over the attachment welds and an aperture is defined in the outer tube, under the tapered rings for detecting leaks in the attachment welds.

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First Claim