Hello Brothers,
The company that i work for specializes in leak sealing on pretty much any component from standard pipes, fittings to bespoke designs.

One of the methods for leak sealing a flange joint is to peen wire in the flange gap and drilling and tappings into the flange thickness and pumping leak sealing compound through a form of an injector.

We have always assumed that drilling and tapping a small hole would not cause a significant stress onto a flange and to this date (well over 40 years of leak sealing) there have not been any incidents with flange failure through this method.

However, i have always wondered how the stress would get affected if we drilled and tapped well over 10 holes into the flange thickness and even at one point, i was asked by a client how the hole would affect the flange.

Therefore, i wanted to request from anyone who has experienced this situation and could point me out to any standards that are available or any literature ( Post grad projects, flange stress analysis calculation sheets ) that i can refer to, to determine the effects of drilling multiple holes into flanges or through flange thicknesses.

Any help will be very much appreciated.

regards,
Sandeep