After changing flanges (and O-rings - all brand new) and using the ultrasonic leak detector, we still are not able to maintain the pressure in the main 4" enclosure. We have no more leaks around the penetrators or the screws on the aluminium end cap at that end. There is still a leak around the screws of the dome - and this dome has also been replaced with a spare brand new dome and ring. We have checked that we have not overtightened the ring holding the dome. I think that the dome or the plastic ring has been deformed around the screws.
Any suggestions or replacement for the dome/ring part?