| 137 / | HD | FLUID HANDLING |
| 455 | DF | LINE CONDITION CHANGE RESPONSIVE VALVES {11} |
| 511 | DF | .~ Direct response valves (i.e., check valve type) {14} |
| 516.11 | DF | .~.~ Single head, plural ports in parallel {2} |
| 516.15 | | .~.~.~ Annular head {1} |
| 516.17 | DF | .~.~.~.~> Central post on seat {2} |