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.
How Is Flow Generated? Pumps, valves, spray devices, and pipe diameter work together to create a flow rate.
- Valves create flow by pulsing (opening and closing). Flow is created when the pressure behind a closed valve is released. Often, valves are used to direct supply and clean the O-rings of the valves, which rotate when pulsed. Valve placement and pulse timing are also factors in restricting or routing flow.
- CIP systems must be designed with enough pump capacity to exceed soil build-up resistance, allow for valve back-flow pressure, meet spray ball capacity, completely fill pipe diameters, and maintain liquid velocity.
System Analysis and Root Cause Analysis. Poor cleaning is the No. 1 symptom of CIP failures. Other indicators include the creeping up of finished product indicator results (aerobic plate count, coliforms, E. coli, yeast/mold), pre-op allergen findings, a color bleed-through, or cleaning rinse water pH abnormalities. The CIP failures allow for incomplete soil or chemical removal. The longer that soils remain on the surface, the stronger they attach (think of dishes left in the sink overnight versus dishes cleaned shortly after use). Compounding the effect, sanitizers may be less effective because they do not have direct contact with microbial cell walls/ membranes, which is needed for microbial reduction/elimination.
On some CIP systems, software packages can be added that report system functionality, including flow rates, conductivity, temperatures, preventive maintenance prompts, or other sanitation verifications. These reports are valuable to detect system drift, unintended consequences of program changes, or equipment damage. Additionally, since day-to-day interior equipment/circuit inspection after cleaning and before sanitation is difficult or not conducted until preventive maintenance results in disassembling pipes or tanks, these metrics are tools to maintain system effectiveness.
Programming errors or changes can cause incorrect valve pulsing and sequencing, which may send cleaning solution down the wrong flow paths or release excessive amounts of heated solution to the drain. Additionally, incorrect valve pulsing may lead to decreased flow rates. Installation errors, such as incorrectly installed valves, process dead legs, and non-uniform pipe sizes, may result in unsanitary lines and bacterial contamination risk.
Temperatures of liquids that are above parameters for the soil can cause proteins to denature (unfold), exposing bonds that strongly adhere to surfaces. Liquids that don’t meet temperature requirements may not dissolve soils, as in the case of sugar removal. Thermocouples and resistance temperature detectors (RTD) can be used to measure the temperature in the system. As with any temperature measuring device, calibration must be conducted for accuracy.
Conductivity measurements indicate interfaces between ionic cleaning solutions and non-conductive water. Conductivity can be an indication of chemical concentrations and its removal from the system. The meter calibration must be maintained on a routine basis or drift can occur. If chemical concentration is in doubt, test kits provided by the chemical supplier can be used. Ensure that the reagents in the kit are not expired and that kit instructions are followed accurately. As a fast test, pH paper can be used to confirm acid or alkali presence, but should be followed up with a test kit for confirmation. Further, water hardness (calcium carbonate) and any mineral deposit build up will impact the effectiveness of the sanitizers used. Testing the parts-per-million (ppm), mg/L, or grains per gallon of calcium carbonate in the facility water will point chemical suppliers to the needed chemicals and temperatures for maintaining effective and efficient CIP functions (See Table 1, below).
In conclusion, a CIP system can deliver cleaning and sanitizing functionality with reduced operating costs. When issues arise, it is often due to system drift, minor operator adjustments that compound over time, not setting up, or trending metrics. While cleaning performance is a main CIP issue, the root causes are most often caused by reduced flow rate, a main component of temperature and chemical synergistic effect, followed by disparate temperature or conductivity values. Conducting consistent system analysis by measuring key metrics will drive CIP efficiencies and effectiveness.
Dr. Deibel, a Food Quality & Safety Editorial Advisory Panel member, is the chief scientific officer at Deibel Laboratories, where she is responsible for leading the technical staff in research, food safety, and regulatory issues. Reach her at email@example.com. Baldus is food safety program manager for Hydrite Chemical Co. Reach her at firstname.lastname@example.org or email@example.com.
The authors would like to thank Joel Cook and Spencer Lightfield at Hydrite Chemical Co. for their assistance with this article