Hi All,

We have Existing Carbon Steel Flare Header of DN 1000 size with thickness of 10mm ( C.A 1mm), Design/Operating temp. 120/45 degC

Client is looking forward to make a hot tap of DN400 size on this existing DN1000 flare header which is resting directly on steel without a shoe/cradle.

The concern is during Hot tap procedure , As an applied load is increased due to installation of DN400 pipe, the load might ultimately become large enough to cause the pipe to become unstable, ovalise and buckle.

As we know, the buckling capacity of thin walled pipe is dependent on "O.D to thickness" ratio. Normally when D/t ratio does not exceed 80, then steel pipe will not buckle and no reinforcement rings are required as pipe is thick enough to carry high loads.

Client cannot shutdown the flare line & wants to avoid these stiffner rings . Avoiding welding of stiffener rings on the running flare line is understandable, but these are required as per secondary checks we made for two adjacent supports near tie-in point due to high vertical loads.

Can anyone suggest an alternate way to solve this issue?