While it may be tempting from an economical viewpoint to apply new hardbanding over worn and 'cracked' hardbanding, the likelihood of incurring additional problems is quite high.
An offshore Russian drilling contractor's drill pipe showed signs of wear and traverse cracking of a popular titanium hardbanding product. Duraband NC (a non-cracking hardband) was chosen for re-application and Hardbanding Solutions Europe was asked to oversee the work of removal, repair of the tool joints and application of Postalloy Duraband NC. Despite the fact that Duraband NC is non-cracking, re-application over existing worn and cracked hardbanding carries numerous risks that the pipe owner was not willing to take. Complete removal was the only rational option. The old hardbanding on box and pin tool joints was removed down to the tool joint base material by machining. MPI was then used to ensure that all cracks were removed. Following recommended preheat temperatures, a Postle product, HBBU, was applied to recover the original tool joint outside diameter dimensions. Postalloy HBBU is a low alloy hardbanding wire that matches the physical properties of the tool joint. A further machining procedure was conducted to recover exact OD dimensions.
MPI was used again to ensure that new cracks were not initiated. Duraband NC was then applied over the Postalloy HBBU per Postle's hardbanding manual. Slow cooling procedures were implemented to ensure that HAZ hardness values did not exceed 40 Rockwell C. The ?nished hardbanding was again subjected to MPI to ensure that cracks did not develop.
It is far more prudent to completely remove the old hardbanding, repair and build up the tool joint as needed, and then apply Postalloy Duraband NC. If Duraband NC was selected as the initial hardband, this problem could have been avoided.
Adapted from a press release by Louise Mulhall
Read the article online at: https://www.oilfieldtechnology.com/product-news/20072016/duraband-nc-hardbanding-rescues-damaged-drill-string/