137 / | HD | FLUID HANDLING |
455 | DF | LINE CONDITION CHANGE RESPONSIVE VALVES {11} |
511 | DF | .~ Direct response valves (i.e., check valve type) {14} |
515 | DF | .~.~ In couplings for coaxial conduits, e.g., drill pipe check valves {3} |
515.3 | .~.~.~ Valve seat threaded into a coupling element |