Spirax Marshall Vacuum Breakers VB14 and VB21
Spirax Sarco Vacuum Breakers (VB14 & VB21): Product Overview & SEO Content
Spirax Sarco VB14 and VB21 Vacuum Breakers are small, highly sensitive mechanical valves designed to protect steam-heated process equipment, heat exchangers, and liquid lines from negative pressure buildup. By automatically admitting atmospheric air when internal pressures fall below ambient levels, these valves ensure continuous condensate drainage, prevent equipment implosion, and eliminate system water hammer.
Core Specifications & Material Comparison
|
Specification |
VB14 Model |
VB21 Model |
|
Body & Cap Material |
Brass |
Stainless Steel |
|
System Connection Size |
1/2" (DN15) |
1/2" (DN15) |
|
Air Inlet Size |
1/8" (DN6) |
1/8" (DN6) |
|
Available Threads |
BSP / NPT |
BSP / NPT |
|
Max Operating Pressure ($\text{PMO}$) |
14 bar g (210 psig) |
21 bar g (304 psig) |
|
Max Operating Temperature ($\text{TMO}$) |
260°C (500°F) |
400°C (752°F) |
|
Flow Coefficient ($\text{K}_\text{v}$) |
0.52 |
0.52 |
|
Opening Differential Pressure |
4.6 mm Hg |
4.6 mm Hg |
Key Operational Advantages
- High Sensitivity: Requires a tiny opening differential pressure of just 4.6 mm Hg to break a vacuum instantly upon system shutdown or steam condensation.
- Durable Construction: The brass VB14 offers a reliable solution for standard industrial utilities, while the all-stainless steel VB21 provides higher temperature tolerance and superior chemical resistance for harsher environments.
- Compact Footprint: Compact 1/2" size makes it easy to install directly on equipment nozzles or steam mains.
Primary Applications
- Steam Heat Exchangers & Air Coils: Prevents vacuum formation that holds back condensate, allowing steam traps to drain effectively.
- Jacketed Boiling Kettles & Sparge Systems: Protects vessel shells against collapse during cooling cycles.
- Boiler Feedwater Tanks & Chilled Water Lines: Maintains atmospheric balance and prevents unwanted back-siphonage.
- Process Liquid Piping: Protects pipelines prone to vacuum creation during fluid drainage or ambient cooling.
Installation & Maintenance Best Practices
- Vertical Mounting: Must always be installed in a strict vertical position with the 1/2" system connection pointing directly downward.
- Optimal High-Point Location: Place the valve at the highest point of the equipment or pipeline where condensate will not pool or submerge the valve internals.
- Easy In-Line Servicing: To clean or inspect internal seating surfaces, simply isolate the system and unthread the top cap to clear any trapped pipe debris.
