FIV (flow induced vibration) usually occurs on SB lines. You need to check your flare against AIV (Acoustic induced vibration). There are many guide lines to do this.
You need to get the process department involve asap. In fact, all the input should come from them. They should tell you if you really have a problem.
The basic rule of thumb is to use a thicker header in your case 15.875 mm for 200 diameters downstream the noise source +full wrap in Tee connections. . See guide lines
Look up for the Carruci and Mulle (C&M)r dat +MTD Publication 99/100.

Also do searches on this forum, you will find useful info. Do not rush and go ahead and propose a thicker header. Tell the process department to perform and AIV study for you based on (C&M) and if the noise level for a 36 in line is above 160 Db aprox. You have a problem.

On the unlikely event, according to my expertise, to have a FIV on this type of line .Yes you need to check the forces and the LOF. Restraint the line on change of direction (Stops) and use hold downs where applicable.


Hope this helps