CIP (Cleaning-in-Place) Guide for Dairy Plants
A practical guide to CIP (Cleaning-in-Place) in dairy processing — chemicals, sequences, temperatures, concentrations, validation, and troubleshooting.
What is CIP?
CIP (Cleaning-in-Place) is a method of cleaning the interior surfaces of pipes, vessels, PHEs, and other equipment without disassembly. It uses a sequence of rinses and chemical solutions circulated at controlled concentration, temperature, flow rate, and time.
The 4 Factors of CIP (TACT):
- Temperature — heat accelerates chemical reaction
- Action — flow rate ensures mechanical scouring
- Concentration — sufficient chemical strength
- Time — adequate contact time
Standard CIP Sequence
For Milk Processing Equipment (Pasteurizer, PHE, Tanks)
| Step | Solution | Temperature | Time | Purpose |
|---|---|---|---|---|
| 1 | Pre-rinse (water) | Cold/ambient | 5–10 min | Remove bulk residue |
| 2 | Caustic wash (NaOH 1–2%) | 70–80°C | 20–30 min | Remove protein/fat |
| 3 | Intermediate rinse (water) | Warm | 5 min | Remove caustic |
| 4 | Acid wash (HNO₃ 0.5–1%) | 60–70°C | 15–20 min | Remove mineral deposits, sterilize |
| 5 | Final rinse (water) | Cold | 5–10 min | Remove acid |
For Homogenizer, Separator
Homogenizer valve seats and separator bowls: Higher caustic concentration (2–3%), longer time, or manual cleaning of heavily soiled parts.
Chemical Concentrations
| Chemical | Type | Working Concentration | Temperature |
|---|---|---|---|
| Caustic Soda (NaOH) | Alkali | 1–2% (10–20 g/L) | 70–85°C |
| Nitric Acid (HNO₃) | Acid | 0.5–1% | 60–70°C |
| Peracetic Acid (PAA) | Sterilant | 0.1–0.2% | Cold |
| Chlorinated Alkaline | Combined | 0.5–2% | 50–70°C |
| Phosphoric Acid | Acid | 1–2% | 55–65°C |
Flow Rate Requirements
For effective cleaning, turbulent flow (Re > 10,000) must be maintained throughout the circuit.
Minimum CIP velocity: 1.5 m/s in all pipes
For a 50mm ID pipe: Flow rate needed = 1.5 × π × 0.025² × 3600 = 10,600 L/h minimum
CIP Validation
1. Conductivity Monitoring
- Caustic CIP: Conductivity sensor tracks solution return; low return conductivity = diluted by product soil
- Rinse: Conductivity of final rinse = conductivity of make-up water (confirms caustic removed)
2. Temperature Verification
- RTDs at CIP supply and return must meet minimum temperature throughout
3. Microbiological Swab Testing
- Weekly or after modified CIP: Product contact surface swabs for TPC, coliforms
- Target: < 1 CFU/cm² for critical surfaces
4. Allergen Testing (if applicable)
- After product changeover between allergen and non-allergen products
Common CIP Problems & Solutions
| Problem | Likely Cause | Solution |
|---|---|---|
| Protein deposits (grey/yellow film) | Insufficient caustic concentration or temperature | Increase NaOH% or temperature |
| Mineral deposits (white scale) | Insufficient acid or hard water | Increase acid% or add descaler |
| Microbial failure after CIP | Poor rinse, dead legs, cold spots | Check flow paths, add sterilant step |
| High foam in CIP tank | Foam in product lines entering CIP | Extend pre-rinse, add defoamer |
| Short CIP life of circuits | pH drop too fast | Check for gross soil, pre-clean, or increase concentration |