Spirax Sarco MST21 Balanced Pressure Thermostatic Steam Trap
Note: All certification/inspection requirements are available at an additional cost and must be requested at the time of order placement. This item is available with certification to EN 10204 3.1. Please to request CMTRS with your purchase.
The Spirax Sarco MST21 Steam Traps are a balance pressure thermostatic steam trap featuring entirely stainless steel construction, including the body seal. The welded stainless steel element is self-adjusting over the entire operating pressure range and will discharge condensate at approximately 18°F (10°C) below saturated steam temperature on the standard Fill trap. Options are available for a 40°F (22.2°C) or 7.3°F (-4°C) below steam discharge. The 7.5°F version is also referred to as the "near to steam" (NTS) option. The MST21 Stainless Steel Steam Traps are rate for service up to up to 518°F @ 300 psig (270°C @ 21 barg) and will tolerate water-hammer. The MST21 can be easily disassembled for servicing by unscrewing the body.
The MST21 steam trap is ideally installed in a vertical line with the inlet at the top and the outlet at the bottom. This will ensure that it is self-draining. However, it is also suitable for use in horizontal pipelines. If fitted in a horizontal line, the trap should be preceded by a short drop leg. Trap will be piped inverted (outlet vertical up) when used as an air-vent (NTS-Fill recommended). Full port isolating valves should be installed upstream and downstream of the trap regardless of installation position. Can be used on tracing, drips, sterilizers and a low capacity air vent.
Spirax Sarco MST21 Steam Trap Features:
- Available in 1/4" or 1/2" NPT
- Available with 40°F, 18°F or 7.5°F subcool discharge elements
- Full Stainless Steel Construction (Body, Capsule, and Seal)
- Offered in standard and high capacity
- Serviceable Unit
- Withstands water-hammer
- Can be installed horizontally or vertically
- Max Operating Pressure (PMO): 304 psig (21 barg)
- Max Operating Temperature (TMO): 518°F @ 300 psig (270°C @ 21 barg)
- Max Allowable Pressure (PMA):
- 362 psig up to 248°F (25 barg up to 120°C)
- 309 psig @ 424°F (21 barg @ 218°C)
- 188 psig up to 752°F (13 barg @ 400°C)
- Max Allowable Temperature (TMA): 752°F from 0-188 psig (400°C from 0-13 barg)
 | ||||||
| Part # | Size | Subcool Discharge | A | B | C | D |
|---|---|---|---|---|---|---|
| 1250790 | 1/4" | 40°F | 2.0" (50.5mm) | 0.3" (8.5mm) | 0.4" (10mm) | 1.8" (45mm) |
| 1250690 | 1/4" | 18°F | 2.0" (50.5mm) | 0.3" (8.5mm) | 0.4" (10mm) | 1.8" (45mm) |
| 1251690 | 1/4" | 7.2°F | 2.0" (50.5mm) | 0.3" (8.5mm) | 0.4" (10mm) | 1.8" (45mm) |
| 1250990 | 1/2" | 40°F | 2.4" (61mm) | 0.5" (12.5mm) | 0.06" (14mm) | 1.8" (45mm) |
| 1250890 | 1/2" | 18°F | 2.4" (61mm) | 0.5" (12.5mm) | 0.06" (14mm) | 1.8" (45mm) |
| 1251790 | 1/2" | 7.2°F | 2.4" (61mm) | 0.5" (12.5mm) | 0.06" (14mm) | 1.8" (45mm) |
 | ||
| No. | Part | Material |
|---|---|---|
| 1 | Body | ASTM A743 CF16F/ DIN 17440 X 10 CrNiS 18 9 |
| 2 | Cap | Stainless Steel ASTM A276 Gr 431 |
| 3 | Capsule | Stainless Steel |
| 4 | Spring | Stainless Steel |
| 5 | Spacer Plate | Stainless Steel |
| 6 | Strainer Screen (0.8mm perf) | Stainless Steel |
| 7 | Gasket | Stainless Steel |