To avoid chipping the glass during disassembly of the BME kettle's sight glass back valve, begin by loosening, but not fully removing all 4 bolts holding the valve together.
In one hand, hold the valve in the palm of your hand so that the valve handle is pointed down, and TC portion up, and that glass insert is carefully supported by your thumb and index finger. Next, use your free hand to carefully unscrew each nut, and remove each bolt leaving one of the main bolts that protrude through the valve body for last.
Upon removing the final nut, remove the TC flange portion of the ball valve along with it, and place it aside for safe keeping. Then carefully remove the final bolt.
The glass insert should be held safely and securely by your index finger and thumb; set aside for safe keeping.
Then break down the remaining components for cleaning.
Reverse the process for proper reassembly.
Always perform the breakdown over a soft padded surface, such as a pillow, or couch, just in case one of the components gets dropped.