Cast Iron
Armstrong 980 Series inverted bucket steam traps (including models 981 and 983) offer two sizes of cast steel traps with in-line horizontal pipe connections and integral strainers. They are available with a choice of screwed, socketweld, or flanged connections. The inverted bucket is known as the most reliable steam trap operating principle, providing efficient condensate drainage for virtually all types of steam-using equipment.
A unique leverage system multiplies the force provided by the bucket to open the valve against system pressure. The mechanism is free-floating and has no fixed pivots to create wear or friction. Because the mechanism is located at the top of the trap, no dirt can collect on the orifice. Small particles of dirt are held in suspension until discharged by the full differential purging action when the bucket sinks, pulling the valve off the seat.
The discharge orifice is surrounded by a water seal, preventing live steam loss. Automatic air venting is provided by a small vent hole in the bucket, which provides continuous automatic air and CO2 venting at steam temperature. Inverted bucket traps drain continuously, although discharging intermittently, allowing no condensate backup. They are also resistant to water hammer.
Maximum Operating Conditions
- Maximum allowable pressure (vessel design): 600 psig @ 650°F (41 bar @ 343°C)
- Maximum operating pressure: 600 psig (41 bar)
Materials
| Component | Material |
|---|---|
| Body | ASTM A216 WCB Cast steel |
| Internals | All stainless steel—304 |
| Valve and seat | Hardened chrome steel—17-4PH (H900) |
| Strainer | Stainless steel—304 |
| Test plug | Carbon steel |
Options
- Internal check valve: Stainless steel internal check valve (add CV to model).
- Thermic vent bucket: Available for 983 only, maximum operating pressure 250 psig (17 bar) (add T to model).
- Scrub wire: Vent wire (add BVSW to model).
- Blowdown connection: NPT connection (add E to model).
Dimensions and Weights
| Model No. | 981 | 983 |
|---|---|---|
| Pipe Connections (in) | 1/2, 3/4 | 3/4, 1 |
| Pipe Connections (mm) | 15, 20 | 20, 25 |
| Test Plug (in) | 1/2 | 3/4 |
| "A" Flange Diameter (in / mm) | 4-1/2 / 114 | 7-1/4 / 184 |
| "B" Height (in / mm) | 8-5/8 / 219 | 12-5/16 / 313 |
| "C" Face-to-Face, Scr or SW (in / mm) | 5-3/8 / 137 | 7-3/4 / 197 |
| "D" Bottom to Inlet (in / mm) | 4-13/16 / 122 | 7-9/16 / 192 |
| "E" Blowdown Connection (in) | 3/8 | 3/4 |
| Weight, Scr or SW lb (kg) | 11-1/2 (5.2) | 43 (19.5) |
| Weight, 600 Class Flanges lb (kg) | 18 (8.2) | 50 (22.7) |
INFO
Face-to-face dimensions for Class 600 ANSI Flanges vary by connection size. Other flanges are available on request, including ANSI raised face, flat face, or ring joint flanges.
Capacities
Model 981 Capacity
Model 983 Capacity
Maintenance
WARNING
Equipment under pressure - Operating temperature > 100°C. Make sure the trap is cold before handling!
Mechanism Adjustment
OK Alignment:
Incorrect Alignment:
The mechanism should be adjusted as shown above. When correctly aligned, the lever can be moved sideways the same distance to the right as to the left. If the guide pin is not in the middle of the orifices, adjust by slightly hitting with a hammer.
Internals Maintenance
- Unscrew bolts and nuts and lift the cap. The body can remain connected to the steam line.
- Clean or replace the bucket or mechanism (valve and seat).
- Replace the gasket.
- Put the cap back on the body and screw bolts and nuts.
Screen Maintenance
- Unscrew strainer retainer.
- Clean or replace strainer screen.
- Replace strainer gasket.
- Screw strainer retainer.
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