Repair of flange sealing surface damage
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When installing flanges, damage to the sealing surfaces is a common issue; especially, damage to the sealing surfaces of vessel heads and tube sheets poses significant problems, such as dents from impacts, scratches, and corrosion-induced pits. We often use metal repair agents for repairs, but they have issues such as long curing times and low resistance to temperature and pressure. I appeal to all the experts! If there are any better methods or tools, please share them!
It is best to perform machining after patch welding, but operational feasibility must be taken into account. If the flange has already been installed on the equipment or pipeline, manual repair is the only option; this involves filling in the concave areas and smoothing out the convex areas. When installing gaskets, sealant can be applied to the sealing surfaces (although some standards prohibit such application).
Before welding the flange, apply a protective cover to it, similar to the one used on new valves, to prevent scratches. It is not recommended to use a curing agent for repairs; generally, if the scratch is minor and the pressure applied is not high, no action is needed. In more severe cases, welding followed by polishing is advisable
Everything depends on the quality of the installation process. Focusing on technical operations is better than focusing on post-damage handling. For reference.
Online machining can be used to repair the sealing surface; either RF or RJ is acceptable.
Generally speaking, through-thickness defects basically do not require repair, unless the hole is particularly large; however, the protruding parts need to be removed. Grinding is not recommended as it will damage the overall flatness of the flange sealing surface. If conditions permit, perform patch welding—or machine processing.
I remember there is a type of end milling that, after welding repairs, can be used to machine a sealing surface on the equipment flange.
Online repair welding and online machining can be used to solve this issue.
I ran into this before; I tried grinding it by hand, but it wasn’t possible. Liquid sealant was used later. The pressure itself isn’t high either.
On-site patch welding and machining of the sealing surfaces are carried out.