Spund Settings — Decision Aid¶
FUERST WIACEK Version 1.0 | Reference — pressure values per fermentation stage | Frequency: as triggered (per stage transition)
Purpose¶
The spund (pressure relief / regulator on top of every FV) sits at different setpoints depending on what stage the tank is at. Setting it wrong is a real risk — too low during fermentation will cause uncontrolled blow-off; too high during packaging-ready will mean the line can't draw cleanly.
This page is a decision aid, not a procedure. It tells you what value the spund should be at for what stage. The procedure for actually adjusting the spund lives in the relevant SOP for that stage.
The Decision Tree¶
What stage is the tank at?
│
├─ Tank empty / mid-CIP → 0 bar (spund off)
│
├─ Filling (knockout active) → 0.2 bar (water-filled spund)
│
├─ Active fermentation → 0.2 bar
│
├─ Spunded conditioning → 1 bar (e.g. lagers, West Coast warm DH)
│ (CO₂ being captured for natural carbonation)
│
├─ Cold crashed / pre-carb → ~1 bar via CIP arm top pressure
│ (top pressure added if tank dropped below 1 bar after crash)
│
├─ Carbonating (bubbling CO₂) → 1 bar (spund vents passively as bubbling adds gas)
│
└─ Carbonation complete → → 0.5–0.6 bar (packaging-ready hold)
reduce head pressure
Per-Stage Reference¶
| Stage | Spund value | Set when | Source SOP |
|---|---|---|---|
| Tank empty / mid-CIP | 0 bar | Before tank CIP starts; before opening manway | Tank CIP |
| Knockout — tank filling | 0.2 bar, water-filled | After end of knockout, before glycol cooling on | Wort Knockout |
| Active fermentation | 0.2 bar (continues from knockout) | Held throughout fermentation | Fermentation Monitoring |
| Spunded conditioning (lagers, certain styles) | 1 bar | When recipe calls for natural carbonation hold | Recipe-specific |
| Pre-carb top pressure | ~1 bar via CIP arm | Before starting carbonation bubbling, if pressure dropped | Carbonation — Pre-Conditions |
| During CO₂ bubbling | 1 bar (spund vents passively as gas is added) | Throughout the bubbling cycle | Carbonation |
| Packaging-ready / Ready For Filling | 0.5–0.6 bar | After CO₂ in spec, before advancing Botec to Ready For Filling | Carbonation — In Spec |
Common Adjustment Triggers¶
These are the moments where a brewer specifically needs to change the spund:
| Trigger | From → To | Why |
|---|---|---|
| Tank CIP complete, ready for knockout | 0 → 0.2 bar (water-filled) | Set during end-of-knockout sequence |
| End of fermentation, beginning to crash | 0.2 → 1 bar (only if recipe spunded) | Capture CO₂ for natural carbonation |
| Cold crashed, tank below 1 bar pre-bubbling | rebuild to ~1 bar via CIP arm | Carbonation requires ~1 bar before bubbling starts |
| CO₂ in spec post-bubbling | down to 0.5–0.6 bar | Packaging draws cleanly at this pressure |
| Tank emptied, ready for CIP | down to 0 bar | Required before opening manway / starting CIP |
Common Errors and Fixes¶
| Error | Symptom | Fix |
|---|---|---|
| Spund left at 0.2 bar through carbonation | CO₂ keeps blowing off, won't reach target | Reset to ~1 bar before bubbling. Carbonate again. |
| Spund left at 1 bar after carbonation | Packaging line foaming / drawing erratically | Vent down to 0.5–0.6 bar via CIP arm. Re-check before next packaging run. |
| Spund left at 0 bar mid-fermentation | Tank pulled in air, loss of clean CO₂ blanket | Stop. Restore 0.2 bar water-filled. Discuss contamination risk with brewmaster. |
| Spund 1.5–2 bar during Tank CIP rinse | Liquid blown out uncontrolled | Set 1.5–2 bar only during the water rinse step of CIP, then return to 0 before sterile air purge. See Tank CIP — water rinse. |
Quick Reference Card¶
For when you're at the tank with a phone in hand:
| State | Spund |
|---|---|
| Empty / CIP | 0 |
| Filling / fermentation | 0.2 |
| Spunded conditioning | 1 |
| Pre-carb top pressure / Carbonating | ~1 |
| Packaging-ready | 0.5–0.6 |
| Tank CIP water rinse step (only) | 1.5–2 |