Monel Sheathing Large Diameter Pipes

The fabrication and installation of Monel sheet shall be done as per approved company specification. The sheets will be pre-rolled in cold condition to suit the outside diameter of the steel pipe, fitted on to the pipe and clamped tightly against the pipe before welding. The total area covered by the Monel jacket shall be divided into two sections of Monel plate of approximately equal length. Each section shall have been at the ends of jacket and in middle and in between sections all outer welds will be Monel to Monel.

Welding Procedure
For Butt-welding of Monel to Monel, a removable copper strip shall be used jigged and clamped to maintain alignment and prevent bucking.

All Monel to Carbon steel welds shall be preheated up to 90 C. No post-weld heat treatment will be done. The Monel sheet after fitting to the pipe shall be tack welded at both top and bottom and on the overlap seam prior to welding. After each weld run, the welds will be cleaned by hand brush. To prevent the damage to the Monel cladding by weld spatter, the Monel surface adjacent to the welds will be coated with a temporary lime wash. Care shall be taken to keep lime wash out of the joint preparation. WPQ shall be carried out in accordance with ASME section IX & DNV and shall be submitted for company approval.