After dealing with broken racking canes, and leaking o-rings, I decided i needed a better solution for a sight glass/tube. While the racking cane with o-rings works, I had trouble keeping mine from leaking, and it always seemed to start at the worst time (middle of a 12 gallon boil). Here are some pictures of what i came up with. The picture of the elbow shows a piece of vinyl racking tubing which was not used. Also, hose clamps at top and bottom are not shown.
The parts i used were.
1 - 3/8" stainless compression elbow (3/8" male pipe thread to 3/8" compression)
1 - 1/2" to 3/8" stainless bushing (welded in)
3" of 3/8" stainless tubing (stainless racking cane)
17" - 3/8" (i.d.) high temp silicone tubing
2 hose clamps (not shown in pics)
I was concerned with being able to see the liquid level through the thick walled silicone tubing, but this was not a problem. I tested with water, and was able to see the level fine. I will put marks on the kegs at each 1/2 gallon so if the hose ever needs to be changed, it won't need to be re-calibrated. My fittings are all welded in, but could be done weld-less as well.
After coming up with this solution, and much time spent on this forum, I found that someone else came up with almost the exact same idea and was asking about it on here a few years ago, so i linked that thread below.
Now, I have no worries of a broken, melted, or leaking sight "glass" mid-boil. I hope this helps others looking for a better sight glass solution.