Inspecting Pressure Vessels and Piping Susceptible to High Temperature Hydrogen Attack HTHA

1
Inspecting Pressure Vessels and Piping
Susceptible to High Temperature Hydrogen Attack
(HTHA)
HTHA
The steel spool operated for more than 20 years
in high temperature hydrogen service. The pipe
metallographic cross-sections had HTHA heat
affected zone cracks. The cracks were fine,
discontinuous and intergranular. The steel was
decarburised to each side of the crack.
2
HTHA DETECTING THE DAMAGE WITH AUBT
Do vessels in the same circuit also have HTHA
(without any more cutting)?

• The vessels in the circuit were inspected
  non-destructively using advanced ultrasonic
  backscatter techniques (AUBT) developed to detect
  high temperature hydrogen attack (HTHA). For the
  Base Metal, the Techniques Used Were
• Backscatter Technique
• Spectrum Analysis
• Velocity Ratio
• For the Welds, the Angle Beam Spectrum
  Analysis (ABSA) Technique Was Used

3
HTHA DETECTING THE DAMAGE WITH AUBT
In what condition were the vessels?

• The vessels were free of any significant
  damage. Only the cracked piping section had the
  stresses necessary to develop cracks.

HTHA signal