Abstract: The present invention is directed to catalytic compositions and to curable compositions containing them. Catalytic compositions of the present invention typically comprise: (i) a reactive compound comprising at least one group selected from acid-functional groups and/or groups that may be converted to acid-functional groups; (ii) a metal compound; and (iii) a compound different from (i) and (ii) that catalyzes an addition reaction between an ethylenically unsaturated compound and a thiol. Curable compositions according to the present invention comprise: (a) a polyene, (b) a polythiol, and (c) the afore mentioned catalytic composition.

Abstract: A welding system for performing a welding process on a pipe in a confined space includes a motor housing, a weld head assembly and an insertion tube that extends between the motor housing and the weld head assembly with the weld head assembly remote from the motor housing. The motor housing is supported on a platform for rotational and translational movement of the weld head assembly and houses a motor for positioning the weld head assembly relative to the pipe. The weld head assembly includes a clamp assembly for attaching the weld head assembly to the pipe and a weld tool assembly mounted adjacent the clamp assembly for welding the pipe. An arc length gear and a travel gear adjust the distance between a torch assembly and the pipe and adjust the location of the torch assembly around the pipe when the weld head assembly is attached to the pipe.