1. Buttering Welding, See also the information regarding buttering in the fabrication handbook. This with reference to Norsok M-101, rev.5 item 6.8
Max acceptable buttering is t/2 or max 20mm for the joint (weld)
Buttering welding may be done without, with ceramic backing or with use of permanent backing.
Important:
Use of permanent backing shall be approved by KST for each joint (Weld) and shall be shown on fabrication drawing.
This welding will increase more stresses and shrinking and is not acceptable.
Use buttering layer, prepare a new “groove” within the tolerances for the groove and weld it like an ordinary weld joint.
Eddie Flatås

2. Use of WPS and reporting in MIPS This with reference to Norsok M-101, rev.5 item 6.8
For ordinary grooves with tolerances within groove standard, use a relevant WPS for the joint.
Example WPS and to be reported in MIPS
If use of permanent backing with groove tolerances within the groove standard, use a specific WPS for welding with permanent backing.
Example WPS 80-02PB. This to be reported in MIPS
If buttering is needed, Use a WPS for buttering layer and continue the rest of welding according to the main WPS for the joint. Example WPS 80-02Buttering and WPS Both WPS to be reported in MIPS
If buttering is needed and the joint is fit up with permanent backing, WPS for buttering and a WPS for welding with permanent backing shall be used.
Example 80-02Buttering and WPS 80-02PB. Both WPS to be reported in MIPS
Eddie Flatås