PT21 Inverted Bucket Steam Trap (Cast Iron)
A cast iron inverted bucket steam trap with stainless steel internals for equipment drains with medium-to-heavy condensate on intermittent operation, rated to 17.5 bar(g) / 220°C, mounted vertically.
- IBR / ASME standard
- Nationwide service
Overview
The PT21 Inverted Bucket Steam Trap by Pennant Engineering is an inverted bucket steam trap in cast iron construction with all stainless steel internals, best suited for equipment drains with medium to heavy condensate loads on intermittent operation. It works on the density difference between steam and water to give a cyclic discharge of accumulated condensate. The valve and seat are induction-hardened for prolonged continuous operation, giving perfect shut-off with no steam loss. Rated to 17.5 bar(g) maximum allowable pressure and 220°C, fitted vertically with inlet at the bottom and outlet at the top.
Built and supplied by ME Engineering to IBR / ASME standards, with full documentation and nationwide service support.
Technical Specifications
| Model | Size (mm) | Size (in) | Dimensions (mm) | Weight | |
|---|---|---|---|---|---|
| Dia | A | ||||
| PT21 | 15 | 1/2" | 115 | 155 | 3.70 kg |
| PT21 | 20 | 3/4" | 115 | 170 | 4.20 kg |
| PT21 | 25 | 1" | 186 | 282 | 16 kg |
| PT21 | 40 | 1.1/2" | 213 | 300 | 19 kg |
| Component | Material |
|---|---|
| Body | Cast Iron |
| Cover | Cast Iron |
| Bucket Assembly | AISI 304 with CS Reinforcing Ring |
| Valve Seat (Hardened) | AISI 410/420 |
| Valve Pin (Hardened) | AISI 410/420 |
| Bracket | AISI 304 |
| Lever | AISI 304 |
| Plug | Carbon Steel |
| Gasket | Non CAF |
| Bolt | High Tensile |
| Nut | High Tensile |
| Pipe | Carbon Steel |
| Model | Valve (mm) | Capacity (kg/hr) at differential pressure (bar) | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0.25 | 0.5 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17.5 | ||
| PT21-15 | 2.5 | 80 | 100 | 350 | ||||||||||||||||
| PT21-15 | 2.8 | 100 | 115 | --- | ||||||||||||||||
| PT21-15 | 3.2 | 130 | 145 | --- | ||||||||||||||||
| PT21-15 | 4.0 | 150 | 185 | --- | ||||||||||||||||
| PT21-15 | 4.8 | 200 | 270 | --- | ||||||||||||||||
| PT21-15 | 6.4 | 250 | 340 | --- | ||||||||||||||||
| PT21-20 | 2.8 | 100 | 120 | 530 | ||||||||||||||||
| PT21-20 | 3.2 | 125 | 145 | --- | ||||||||||||||||
| PT21-20 | 4.0 | 150 | 185 | --- | ||||||||||||||||
| PT21-20 | 4.8 | 230 | 310 | --- | ||||||||||||||||
| PT21-20 | 6.4 | 300 | 380 | --- | ||||||||||||||||
| PT21-25 | 4.8 | 300 | 380 | 2500 | ||||||||||||||||
| PT21-25 | 5.6 | 400 | 510 | --- | ||||||||||||||||
| PT21-25 | 6.4 | 500 | 640 | --- | ||||||||||||||||
| PT21-25 | 7.0 | 620 | 840 | --- | ||||||||||||||||
| PT21-25 | 7.9 | 900 | 1200 | --- | ||||||||||||||||
| PT21-25 | 9.5 | 1300 | 1550 | --- | ||||||||||||||||
| PT21-25 | 12.7 | 2200 | 2450 | --- | ||||||||||||||||
| PT21-40 | 6.4 | 450 | 550 | 2600 | ||||||||||||||||
| PT21-40 | 7.0 | 600 | 740 | --- | ||||||||||||||||
| PT21-40 | 7.9 | 800 | 940 | --- | ||||||||||||||||
| PT21-40 | 8.7 | 900 | 1075 | --- | ||||||||||||||||
| PT21-40 | 9.5 | 1000 | 1175 | --- | ||||||||||||||||
| PT21-40 | 11.2 | 1200 | 1450 | --- | ||||||||||||||||
| PT21-40 | 14.3 | 1500 | 2000 | --- | ||||||||||||||||
| PT21-40 | 19.0 | 2400 | 2800 | --- | ||||||||||||||||
Applications
Benefits
The inverted bucket mechanism works on the density difference between steam and water, making it mechanically simple and robust with no temperature-sensitive element to fail, so it tolerates water hammer and superheat better than thermostatic or thermodynamic traps.
High condensate handling capacity even at low pressure means a smaller trap size can serve a given load, which reduces cost and installation footprint versus oversizing.
Induction-hardened valve pin and seat concentrate wear resistance on the two highest-wear parts, extending service intervals under continuous prolonged operation.
Perfect shut-off with no steam loss directly saves energy compared to traps that leak live steam when worn, and those losses compound over the operating life of a steam system.
The full internal kit (valve pin, seat, bracket, lever) is replaced as a matched set during maintenance, which restores the trap to as-new performance rather than patching individual worn parts.
Priming instruction at commissioning (cracking the inlet valve to fill the trap with water before steam enters) prevents the bucket from losing its water seal, which is the single most common cause of inverted bucket trap malfunction if skipped.
Cast iron body keeps cost low for general low-to-medium pressure service, appropriate given the 17.5 bar(g) ceiling — for higher pressure or superheat, the cast steel PT23/PT24 variants are the correct step up.
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PT21 Inverted Bucket Steam Trap (Cast Iron)?
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