| Model | 21-AR | 21-312AR | 21-312VAR |
| Body Material | ASTM A48 Class 30 Cast Iron | ASTM A105 Forged Steel | ASTM A105 Forged Steel |
| Maximum Allowable Pressure | 250 psig @ 450°F (17 bar @ 232°C) |
500 psig @ 750°F (34 bar @ 399°C) 600 psig @ 100°F (41 bar @ 38°C) |
500 psig @ 750°F (34 bar @ 399°C) 600 psig @ 100°F (41 bar @ 38°C) |
| Maximum Operating Pressure | 250 psig (17 bar) | 68 psig (4.7 bar) | 600 psig (41 bar) |
| Connection Sizes | 1/2″ (15 mm) 3/4″ (20 mm) |
1/2″ (15 mm) 3/4″ (20 mm) |
1/2″ (15 mm) 3/4″ (20 mm) |
The 21-AR is a small, economical air vent of high quality. It uses a single lever with a fixed pivot and viton seat, ensuring tight shutoff.
The 21-312 AR/VAR is a forged steel version of the Model 21 with a larger float and higher leverage. Available with screwed, socketweld or flanged connections.