Description
Product Overview
The Spirax Sarco VB21 is a small, purpose-designed vacuum breaker. It is utilized in condensing vapor (steam) and liquid systems to protect plant and process equipment against vacuum formation while allowing condensate to drain effectively from pipework and storage vessels.
Key Features
- Stainless Steel Construction: Manufactured with an AISI 303 stainless steel body and cap, and an AISI 440C stainless steel valve.
- Tight Shut-off: The precision ground stainless steel valve is held firmly on its seat during normal operating conditions, ensuring a tight shut-off.
- Instant Response: At the point of vacuum, the valve instantly lifts off its seat, drawing air in through the upper chamber to prevent a vacuum from forming. The differential pressure required to open the vacuum breaker is 4.6 mm Hg (0.2 in Hg).
- Food+ Variant: The VB21 Food+ 1/2” version is available with a food contact regulation Declaration of Compliance, meeting (EC)1935:2004, (EC)2023:2006, (EU)10/2011, and FDA Code of Federal Regulations Title 21 standards.
- Non-Maintainable Design: The unit is non-maintainable; in the event of failure, the complete unit must be replaced as no spare parts are available.
Technical Specifications
| Parameter | Value |
|---|---|
| Body Design Conditions | PN25 |
| PMA (Maximum Allowable Pressure) | 25 bar g @ 120 °C (362 psi g @ 248 °F) |
| TMA (Maximum Allowable Temperature) | 400 °C @ 13 bar g (752 °F @ 188 psi g) |
| Minimum Allowable Temperature | -48 °C (-54 °F) |
| PMO (Maximum Operating Pressure for Saturated Steam) | 21 bar g (304 psi g) |
| TMO (Maximum Operating Temperature) | 400 °C @ 13 bar g (752 °F @ 188 psi g) |
| Minimum Operating Temperature | 0 °C (32 °F) |
| Cold Hydraulic Test Pressure | 38 bar g (551 psi g) |
| Flow Coefficient (Kv) | 0.52 |
| System Connection | 1/2” screwed BSP or NPT |
| Air Inlet Connection | 1/8” screwed BSP or NPT |
| Weight | 0.33 kg (0.73 lbs) |
Applications
- Condensing vapor (steam) systems
- Liquid systems
- Food contact processes (VB21 Food+ version)
Installation and Operation
The VB21 vacuum breaker must be installed in a vertical position with the system connection at the bottom. On steam systems, the vacuum breaker should be installed at the highest point in the system where it will not be flooded with condensate.
During cooling, steam begins to condense resulting in a reduction of pressure. The valve remains on its upper seat until the pressure in the upper chamber falls below the air inlet pressure (usually atmospheric pressure). At the point of vacuum, the valve lifts to draw air into the system.
