Pipeline pig with collapsible spider legs for e.g. deep sub-sea pigging lock aided by divers

摘要

The collars (10a,10b) are constructed for radial expansion. Collars are pivoted for radial expansion, to a greater diameter than fixed collars (9), one of which forms a leading (direction B) protrusion of the pig. Collar expansion is automatic. Expanding collars are held on spiders which trailing the direction of advance (B), expanded radially at an angle. Spiders are polyurethane braces carrying attached flexible material sealing discs (26). Anchoring systems (33a, b) hold the expanded position. These are flexible, and are especially chains. They may be telescopic- or linked rods. The expanding collars are plate-like when deployed. The fixed collar (9) is an annular shell. Guide rollers (8a, b) follow the collars, expanding radially. Their arms are spring-loaded outwardly. Two units make up the pig, of which the leading unit (2) has expanding collar(s). Each unit has at least two sets of support and guide rollers (8a, b). There are also fixed collars (11) on the units. The second unit serving for guidance, can be moved axially with respect to the first.