Suitability of Buttress Thread for PV Lid

[pacesetter]

Hi, I am looking into a pressure vessel that uses a 7/45 Buttress thread. It operates at 10 000 psi and has a 14 inch diameter flat lid. They are having problems with the threads seizing. Does anyone have some experience to share with this thread style.

I have read that the distribution of load in the threads can be uneven if it is not perfectly clean and anti-seize is not evenly distributed.

Thanks