Pics of steel tank valve threads

[Cyborg Pirate]

Got my “new to me” LP72’s today. Took the valves off to do a quick look inside. The tank neck has a beveled edge to it rather then a flat seating edge for the oring. Do I need the special beveled ring gasket or does the oring work for both?

 

[BRT]

Got my “new to me” LP72’s today. Took the valves off to do a quick look inside. The tank neck has a beveled edge to it rather then a flat seating edge for the oring. Do I need the special beveled ring gasket or does the oring work for both?

The tank has to have a bevel to hold the o-ring.

 

[Luis H]

Aluminum tanks (in the US) have a square O-ring groove.

Steel tanks have a bevel O-ring groove and the O-ring tends to take a triangular set after time. It was a round O-ring cross-section when it was originally installed. This O-ring configuration is often referred to as a crushed O-ring seal. The compression on the O-ring is higher than in some other configurations.

BTW, I am only referring to US (DOT) cylinders. In other countries they use different O-ring configurations

 

[Cyborg Pirate]

Awesome! This is exactly the answer I was looking for. I thought that it was the case but needed to hear it from someone else. These are US tanks. PST 72’s. 1969 with j valves. I just don’t have any experience with tanks older then 11 years old. Wanted make sure I wasn’t missing anything.

The only steel tanks I have done the VIP on prior to now are my own 3 sets of twins. And they are all less then 3 years old and purchased brand new.