The above was caused by a very high pressure PNEUMATIC PRESSURE TEST. In the USA we sometimes use pnuematic (Air) tests for very large diameter lines but the design pressures are low ~50. psig, not 2200. psig.

Quote:

The explosion was caused by a sudden flange failure while the workers
were conducting pneumatic testing of a 36 inch diameter line, 600m
long segment, laid out in an S shape.
The testing pressure was 15.6MPa (2,262psi), and the explosion
occurred when the system pressure reached 12.3 MPa (1,784psi).
The explosion was caused by the rupture of a flange at the end of the
test section.