I have a safety valve exhaust system. The piping at the safety valve exhaust(8") is connected(horizontally) through an 8" pipe(5-6m in length with few bends)to another bigger exhaust pipe(20")which extends 25-30m to the atmosphere and has a silencer mounted(welded to it) at the top. There is no drip pan in the system all the connections are welded.

First Question: Is it an Open Discharge system or a closed discharge system as per B31.1 (Non mandatory appendix)

second Question: For calculating the safety valve reaction forces in system, can i use the same formula as given for calculating reaction force at at the discharge elbow in B31.1 (for open discharge system). Shall i assume this force to be acting vertically on the exhaust pipe (20") and no force acting on 8" pipe? (using, Dynamic load factor=2)

Third question: Will there be any reaction force due to silencer, which needs to be added to the reaction force calculated above.

Fourth question: Many times horizontal reaction is given as acting on safety valve along with the vertical reaction, but there is no such force given in 31.1, how can we calculate horizontal reaction forces.

Think i am asking a lot many questions, but will be very thankful for your replies