Chemical composition of A53 and A106 are not the same. A106 has silicon. As stated before, it is considered killed. The reason it is suitable for certain services is that welds that meet hardness requirements(NACE or Code)can be made with A106 with the use of low hydrogen electrods and a preheat...
The main thing you need to look at is the Pipe Wall calculation. The thickness of B31.8 piping varies with population density as accounted for with Basic Design Factor F. B31.4 has no such requirement. Chances are if the B31.8 piping was design for Class 1, it will not meet B31.4. If the B31.8...
Regardless of which type of connection you have, if you have not controlled the bending moments at the connection, the connection will leak. Displacements and moments are smaller at lower temperatures. As the temperature of the line increases so do the bending moments on the line. This basic...
Several thing will cause vibration of a piping system:
1) bad support system
2) improper support of piping connected to recipricating equipment
3) Slug flow, also known as two phase flow
4) water hammer
Velocity by inself is not going to be a problem. If you have a system that is vibrating it...