What is the MINIMUM number of bolts that can be removed from an 8-bolt flange when a slip blind is inserted for hydrotesting?

When hydraulic testing a piping system, it's essential to maintain a secure and reliable connection while inserting a slip blind. The minimum number of bolts that can be safely removed from an 8-bolt flange during the insertion of a slip blind is four. This is because a flange must retain sufficient bolts to ensure that the integrity of the connection is maintained and to prevent any leakage during the hydrotest. With four bolts remaining, there is enough support to secure the flange and resist forces that might cause misalignment or leakage during testing.

Removing fewer than four bolts risks compromising the stability and tightness of the flange, which could lead to failure in maintaining the pressure required for a hydrotest. Thus, it is crucial to adhere to best practices which indicate that at least four bolts should remain in place to ensure safety and effectiveness during the hydrotesting process.