Selecting and Purchasing Weld Overlayed Piping
Internally weld overlayed piping offers several advantages over solid alloy piping in many corrosive applications. The advantages include: cost effective vs solid alloy, obtain a fabricated product (e.g. piping spool) versus buying individual alloy components and fabricating and delivery of fabricated spools in a matter of weeks versus months for solid alloy components. Another key advantage is often clients will determine that corrosion or erosion of piping has occurred in a refinery or gas plant and have obtained replacement weld overlayed piping within one month from the weld overlay specialist.
Piping weld overlay specialists can include overlaying all piping components: pipe, fittings, flanges and valves. A significant factor in weld overlaying is the thickness of the base material. If the base material is too thin the heat of welding may distort the dimensions of the pipe, fitting, etc, and lead to improper fit up or alignment with other components. A rule of thumb is that components should be schedule 80 or higher. Also weld overlay of individual components should ensure internal diameters must match for fit up.
The usual alloys applied to carbon steel or alloy steel piping are types 300 series and 400 series stainless steels and nickel alloys: 825, 625, C-22 and C-276. For erosion applications chromium carbide may be applied. As indicated earlier several weld overlay specialists offer complete piping spool fabrication, a key advantage.