MRO Q&A: How Do You Calculate CIP Parameters?
MRO Q&A is a Food Processing series addressing maintenance, repair and operational issues in food plants.
How are the primary clean-in-place (CIP) parameters (i.e. concentration, temperature, flow rate and duration) calculated for a given process?
Due to the complexity and diversity of food processing equipment and the related final products, CIP systems need to be designed for specific applications. CIP parameters such as temperature, concentration, duration and flow rate are chosen after evaluation of the following:
- Composition of the products and type of fouling -- protein, fat, sugar, mineral salts, starch and special additives such as titanium dioxide can be found in fouling material in various proportions.
- Process conditions -- for instance, are we cleaning cold surfaces (e.g., storage tanks and pipes) or hot surfaces (pasteurizer, UHT systems)?
- Type of detergent selected.
- Process design -- line sizes, heat exchanger, tanks, etc.
Based on these different process conditions, there is no primary CIP parameter setup that would fulfill all production and cleaning conditions. However, over the years some parameters have become industry standards. For instance, there is a very high probability that the following parameters would apply successfully to a standard milk HTST (high-temperature, short time) pasteurization process:
- Pre-rinsing with water for 10 mins.
- Caustic wash at 1-2 percent concentration for 30 mins. at 165 DEG F.
- Intermediate rinse with water for 5 mins.
- Acid wash at 0.5-1 percent for 20 mins. at 150 DEG F.
- Final rinse with water for 5-10 mins.
The last parameter, but perhaps the most important, is the flow rate. If the flow is too low, the efficiency of the other three parameters -- detergent concentration, cleaning time and temperature -- might decrease. Approximately 50 percent of all CIP-related problems are due to inadequate flow. The flow must be sufficient to ensure the satisfactory transport of detergent solution to the soiled surface. The soiled surface is also exposed to shear forces (mechanical forces) through the fluid flow, resulting in the removal of soil.
In the CIP literature, it is normally stated that the velocity in a pipe flow must be greater than 5 ft./sec. to obtain good cleaning results. For plate heat exchangers, the CIP flow normally is suggested at 1-3.0 ft./sec. A common recommendation for cleaning of tubular heat exchangers is to use a CIP flow 1.5 to 2 times higher than that during production.
Despite these general suggestions it is always required to evaluate the CIP efficiency on a regular basis to ensure safe production.