The Spirax Sarco M21Si/M21Vi ISO is a reduced-bore, one-piece industrial fluid isolation ball valve with ISO mounting and EN 1092 PN40 flanged connections, available in sizes from DN15 to DN150. The valve body is rated PN40. It is suitable for sectional shut-off and maintenance isolation in saturated steam and most industrial liquid lines, and must not be used as a control valve.
M21Si/M21Vi Industrial Fluid Isolation Ball Valves, Three-Quarter View | Spirax Sarco
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M21Si/M21Vi ISO Reduced-Bore Industrial Fluid Isolation Ball Valve | Spirax Sarco
Reduced-bore, one-piece ball valve for sectional shut-off and maintenance isolation in saturated steam and industrial liquid lines.
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Specifications
- Valve function
- For industrial fluid isolation; not for use as a control valve
- Valve design
- Reduced-bore, one-piece ball valve
- Installation standard
- ISO mounting
- Nominal size
- DN15, DN20, DN25, DN32, DN40, DN50, DN65, DN80, DN100, DN150
- Flange connection standard
- EN 1092 PN40
- Flange face-to-face standard
- DN15-DN100 complies with DIN 3202 F4; DN25-DN150 complies with BS 2080
- Valve body design pressure rating
- PN40
- Maximum allowable pressure
- 40 bar g @ 120°C
- Maximum allowable temperature
- M21Si: 260°C @ 0 bar g; M21Vi: 230°C @ 0 bar g
- Minimum allowable temperature
- -29°C
- Maximum operating temperature
- 260°C @ 0 bar g
- Minimum operating temperature
- -29°C
- Maximum operating pressure for saturated steam
- M21Si: 17.5 bar g; M21Vi: 10.0 bar g
- Maximum cold hydrostatic test pressure
- 60 bar g
- Leakage class
- ISO 5208 Class A / EN 12266-1 Class A
- Anti-static standard
- Complies with ISO 7121 and BS 5351
- Valve body material
- Galvanized steel ASTM A216 WCB or stainless steel ASTM A351 CF8M
- Ball material
- Stainless steel AISI 316
- Seat material
- Carbon- and graphite-filled PTFE (PDR 0.8) or unfilled PTFE
- Flow coefficient Kv
- DN15: 10; DN20: 10; DN25: 30; DN32: 40; DN40: 81; DN50: 103; DN65: 197; DN80: 248; DN100: 581; DN150: 735
Application scenarios
Sectional isolation and maintenance shut-off in industrial saturated steam pipelines
The M21Si/M21Vi is a reduced-bore, one-piece ball valve for isolation only. It can be used to isolate sections of saturated steam mains and branch lines, or to provide maintenance isolation upstream or downstream of steam-using equipment. The maximum operating pressure for saturated steam is 17.5 bar g for the M21Si and 10.0 bar g for the M21Vi. The valve meets Class A leakage requirements in ISO 5208 and EN 12266-1.
Isolation and shut-off in industrial liquid pipelines
This valve series can isolate pipelines carrying most industrial fluids, including industrial liquid transfer lines and circuits. It is intended for sectional shut-off and must not be used as a control valve. The maximum allowable pressure is 40 bar g at 120°C. The valve body has a PN40 design pressure rating, and the range covers DN15 to DN150 with EN 1092 PN40 flanged connections.
Selection points
Different steam temperature and pressure limits by model
Although both the M21Si and M21Vi have PN40 valve bodies, their maximum operating pressures for saturated steam are 17.5 bar g and 10.0 bar g, respectively. Their maximum allowable temperatures are 260°C and 230°C, respectively, with both temperature ratings applying at 0 bar g.
Reduced-bore, one-piece ball valve design
Both the M21Si and M21Vi use a reduced-bore, one-piece ball valve design. Do not select them as though they were full-bore ball valves of the same nominal size.
Two flange face-to-face standards
The face-to-face dimensions for sizes DN15 to DN100 comply with DIN 3202 F4, while those for DN25 to DN150 comply with BS 2080. Select the configuration according to the pipeline size and required face-to-face standard.
Two valve body material options
The valve body is available in galvanized steel ASTM A216 WCB or stainless steel ASTM A351 CF8M to meet different valve body material requirements.
Installation & maintenance notes
For industrial fluid isolation only
The M21Si/M21Vi is for industrial fluid isolation and shut-off only. Do not use it as a control valve for throttling or flow regulation.
Observe saturated steam operating pressure limits
For saturated steam service, check the operating pressure limit for the model: the M21Si has a maximum operating pressure of 17.5 bar g, and the M21Vi has a maximum operating pressure of 10.0 bar g.
FAQ
Can this M21Si/M21Vi ball valve be used as a control valve?
No. The M21Si and M21Vi are reduced-bore, one-piece ball valves intended primarily for industrial fluid isolation. They must not be used as control valves.
What are the main differences between the M21Si and M21Vi, and how should I choose between them?
The main differences are the seat material and the configurations available for each model: the M21Si series uses a reinforced PTFE-PDR 0.8 seat, while the M21Vi series uses an unfilled PTFE seat. Both are also available with galvanized steel or stainless steel valve bodies. Confirm the specific configuration against the model and application conditions.
What connection type and size range are available for this ball valve?
The product uses standard ISO mounting and has EN 1092 PN40 flanged connections. Available sizes are DN15, DN20, DN25, DN32, DN40, DN50, DN65, DN80, DN100, and DN150.
Which temperature and pressure limits should I consider when selecting the valve?
Check the valve body design conditions, maximum allowable pressure, maximum allowable temperature, and maximum operating pressure for saturated steam. The M21Si and M21Vi have different allowable operating conditions. Confirm the specific configuration against the model and application conditions.
What should I keep in mind when installing and maintaining this valve?
Follow the installation and maintenance instructions supplied with the product. When ordering replacement parts, specify the valve size and model for the corresponding seats, seals, and other available spare parts. Confirm whether the required version is DN15-DN50 or DN65-DN150.