Editors’ note: This is part 3 of a three-part series on environmental monitoring. Part 1, which explored the first steps in implementing a cleaning/sanitation process, was published in the August/September 2020 issue of FQ&S, and part 2, which reviewed sanitation recommendations after receiving an out-of-specification microbiological result, was published in the December 2020/January 2021 issue.
This is part 3 of a three-part series discussing the link between environmental monitoring and sanitation. In part 2, we provided root cause investigation’s information on equipment and, in this part, we’ll continue to discuss root cause investigations, turning our attention to clean-in-place (CIP) systems.
CIP System Types
There are two basic types of CIP systems:
1. Single-use systems: Typically, this is one tank where the CIP solution is used and then replaced with a fresh solution. An example of a single-use system is a pasteurizer wherein solutions are used a single time to reduce the contamination risk.
2. Re-use systems: In this system, multiple tanks use the wash solution repeatedly to clean multiple circuits. Re-use systems have a higher initial capital cost but may allow for shorter CIP run times or they can be set up to wash two different circuits at the same time, using two supply pumps. Multiple tank re-use systems can lower water and energy cost by having the cleaning chemicals stored in one or two tanks and fresh water for final rinsing in another. A final tank, the reclaim tank, stores the spent post-rinse water after the alkaline wash and may be used as the prerinse water for the next CIP circuit.
CIP systems can be time-based or conductivity- based, which measures chemical concentrations. Time-based controls are simplified in that they receive a signal from the CIP controller and the pumps run for a specified time. The pumps deliver the same volume every cycle regardless of demand.
CIP: Less Is More. The objective of a CIP system is to clean the interior of an enclosed stand-alone vessel and its fittings (tanks, spiral freezers, mixers, blenders) or multiple closed-system vessels within processing line(s) and their connecting pipework. The substantive goal being, counterintuitively, less—less workforce, less water, less disassembly, less downtime, fewer chemical accidents, less chemical waste, and lower operating costs.
Mechanical Action (or, in the CIP World, “Flow”). In part 1 of this series, a “Sinner’s circle” was described that identified the four factors needed for cleaning/sanitation: mechanical action, temperature, time, and chemical concentration. As one factor is altered (decreased or increased), the others are adjusted to compensate. In manual cleaning, mechanical action is created through scrubbing, water sprays, and foaming. In CIP, mechanical action is produced by flowing liquids (flow) to create turbulence, which, in turn, generates convection (energy transfer by mass motion of molecules). Convective energy is more efficient at removing soils because the surface soil’s adhesive force is often less than the force of convective energy (flow plus temperature), leading to the soils being released from the surface more quickly and with a lower temperature and fewer chemicals than when exposed to conductive energy (energy transfer by direct exposure) or temperature and chemicals exposure via soaking. Or, said another way, the amount of time, temperature, and chemicals can be reduced (or their effect is amplified) when flow is present.
How Is Flow Rate Calculated? Flow rates are calculated by two factors:
- Pipe diameter and configuration: This is the largest pipe size diameter in the circuit and flow requirements for all spray devices in the line. Pipe diameters are a critical consideration because they must be completely filled and the solution velocity high enough to produce turbulent flow during both cleaning and sanitizing. While this may sound easy, piping can be a dizzying maze, causing missed diameter size changes.
- Spray balls: Each spray ball will have a gallon/minute rating. If there are four in a line each rated 40 gal/min, the pump for that line will need to deliver 160 gal/min.
What Are Minimum Flow Rates? The minimum flow rate necessary for effective turbulent flow is 5 feet/second. To put this into perspective, it is similar to wiping down a counter with a cloth, therefore highlighting the synergistic attributes when convective flow is applied. Nevertheless, even under the best circumstances, there are areas these flow rates are unlikely to reach—notably at dead ends, 90-degree corners, fissures, and cracks.