In food, dairy, beverage and pharmaceutical plants, cleaning is not a housekeeping task. It is a critical process step that protects consumers, prevents cross-contamination between batches and keeps equipment performing as designed. Yet cleaning large tanks, long pipelines, evaporators and spray drying towers by hand is slow, inconsistent and often unsafe. This is why Clean-in-Place, or CIP, has become a standard part of hygienic process design.
This article explains the fundamentals of Clean-in-Place (CIP) technology: what it is, the science behind effective cleaning, the stages of a typical CIP cycle, the main system configurations, and how cleaning is verified. We also look at the particular challenges of cleaning spray dryers and evaporators, where heat, powder and concentrated product create demanding conditions.
What Is Clean-in-Place?
Clean-in-Place is an automated method of cleaning the internal surfaces of process equipment, including vessels, pipes, heat exchangers, evaporators and dryers, without dismantling them. Cleaning solutions and rinse water are circulated or sprayed through the equipment at controlled flow, temperature, concentration and time, usually under the control of a PLC.
The alternative, Clean-out-of-Place (COP), involves taking components apart and cleaning them manually or in a separate washing station. COP is still used for small parts, gaskets and items that cannot be reached by CIP, but for large, enclosed systems it is time-consuming and depends heavily on operator skill. CIP was first widely adopted in the dairy industry and is now used across most hygiene-critical sectors, including beverages, breweries, pharmaceuticals, biotechnology, nutraceuticals and processed foods. Many plants use both methods side by side, with CIP for the main process circuits and COP for removable parts.
Why Plants Choose CIP
- Consistency: every cleaning cycle runs the same way, which supports validation and audits.
- Shorter downtime: automated cycles reduce the time equipment spends out of production.
- Safety: operators are not exposed to hot caustic and acid solutions or confined-space entry for routine cleaning.
- Resource efficiency: controlled dosing and recovery of rinse water and chemicals reduce consumption.
- Traceability: recorded cycle data provides evidence that each cleaning step was completed correctly.
The Science of Cleaning: Four Key Factors
Effective cleaning depends on four factors that work together, often described as Sinner's circle or the TACT principle:
- Time: the contact time between the cleaning solution and the soil. Longer contact allows chemicals to penetrate and dissolve deposits.
- Action (mechanical force): the turbulence or impact that physically removes soil. In pipelines, this comes from flow velocity; in vessels, from the impact of spray devices.
- Chemistry (concentration): the type and strength of detergent. Alkaline solutions break down fats and proteins, while acid solutions remove mineral scale and milk stone.
- Temperature: higher temperatures speed up chemical reactions and soften fats, though excessive heat can bake some proteins onto surfaces.
If one factor is reduced, others must increase to achieve the same result. For example, lower temperature may be offset by longer time or higher concentration. A well-designed CIP program finds the most efficient balance for the specific soil and equipment.
Flow Velocity in Pipelines
For pipe cleaning, turbulent flow is essential. A velocity of around 1.5 m/s is widely cited as a minimum for hygienic pipelines, although the right value depends on pipe size, soil type and the guidance followed by the plant. Insufficient velocity leaves soil in place, especially at bends, tees and low points.
Spray Devices for Vessels
Tanks and chambers are cleaned with spray devices. Static spray balls deliver a continuous low-pressure flow that wets the surface and relies on a falling film for cleaning. Rotating spray heads and rotary jet heads deliver higher impact, which suits heavier soils and larger vessels and can reduce water and chemical use. The positioning of spray devices must ensure that every surface is reached, including the underside of nozzles, manways and fittings.
Stages of a Typical CIP Cycle
CIP programs vary by product and plant, but most follow a similar sequence. The concentrations and temperatures below are typical ranges for dairy and food applications and should be adapted to each process and chemical supplier's guidance.
- Pre-rinse: water, often recovered from a previous final rinse, flushes out loose product and soil. This step removes the bulk of residues and reduces the load on the detergent.
- Alkaline wash: a caustic solution, often around 0.5 to 2% sodium hydroxide, is circulated at elevated temperature, typically in the 60 to 85°C range, to remove fats, proteins and carbohydrates.
- Intermediate rinse: water removes the caustic solution and loosened soil.
- Acid wash: where mineral deposits occur, an acid solution, commonly nitric or phosphoric acid at low concentration, removes scale and neutralizes residual alkalinity.
- Final rinse: clean water, or purified water in pharmaceutical plants, removes all traces of chemicals. Conductivity measurement confirms that the rinse is complete.
- Sanitization or sterilization (where required): a chemical sanitizer, hot water or steam reduces microbial load to the required level.
- Drain and dry: equipment is drained fully and, in the case of dryers, dried before production restarts.
CIP System Configurations
CIP systems are designed around the plant's size, layout and hygiene requirements. The main options are summarized below.
| Configuration | How It Works | Best Suited For | Considerations |
|---|---|---|---|
| Single-use (single-pass) | Fresh solution is used for each cycle and then discarded | Heavily soiled circuits, pharmaceutical duties, high cross-contamination risk | Higher water and chemical consumption |
| Re-use (recirculating) | Detergent and rinse water are recovered and reused for several cycles | Dairy, beverage and food plants with frequent cleaning | Needs concentration monitoring and periodic replenishment |
| Compact one- or two-tank units | Skid-mounted system serving local equipment | Small plants, pilot lines, dedicated equipment | Limited recovery capability |
| Centralized multi-tank stations | Separate tanks for water, recovered water, caustic and acid serve several circuits | Large plants with many cleaning circuits | Higher capital cost, longer supply and return lines |
A typical CIP skid includes tanks, a supply pump, a heat exchanger or heater, automated valves, return pumps and instruments for flow, temperature, conductivity and level. The control system routes solutions to the right circuit, monitors each parameter and records the cycle. AKSH's automatic CIP systems are offered from compact single- and two-tank units to multi-tank centralized stations, with flow capacities from 1,000 LPH to over 50,000 LPH, operating temperatures up to 90°C and PLC plus HMI or SCADA control.
Hygienic Design: The Foundation of Effective CIP
No CIP program can compensate for equipment that is hard to clean. Hygienic design principles include:
- Smooth surfaces: polished stainless steel with a defined surface roughness gives soil less to cling to.
- No dead legs: branches and pockets where solutions cannot flow allow soil and microbes to accumulate.
- Full drainability: pipes and vessels should slope to drain points so no liquid pools after cleaning.
- Crevice-free joints: smooth orbital welds and sanitary fittings reduce harborage points.
- Compatible materials: metals, gaskets and seals must withstand the cleaning chemicals and temperatures.
Material compatibility is especially important where chlorides or strong acids are used. Our guide to choosing the right stainless steel grade explains how materials and cleaning chemistry interact.
Verifying and Validating CIP
Cleaning must be proven, not assumed. Plants use several methods:
- Cycle records: logged time, temperature, flow and conductivity for every step.
- Visual inspection: checking accessible surfaces for residues after cleaning.
- Swab tests: ATP bioluminescence and microbiological swabs to confirm surface hygiene.
- Rinse water analysis: testing final rinse water for conductivity, pH, residues or total organic carbon in pharmaceutical settings.
- Spray coverage tests: riboflavin or similar tests to confirm that spray devices reach every internal surface.
In regulated industries, these checks form part of a formal cleaning validation, demonstrating that the CIP program reliably removes product residues, cleaning agents and microorganisms to defined acceptance limits.
CIP for Spray Dryers and Evaporators
Spray Dryers
Spray dryers present unique cleaning challenges. Their chambers are large, they contain dry powder that turns into a paste when wetted, and their ducts, cyclones and bag filters have complex geometry. Effective approaches usually include removing as much dry powder as possible before wet cleaning, using retractable or strategically positioned high-impact spray nozzles in the chamber, cyclones and ducts, and ensuring the plant can be fully drained and dried afterward. Bag filters intended for wet cleaning need sanitary, CIP-compatible design.
AKSH's hygienic spray dryers integrate CIP spray devices in the chamber, cyclones and ductwork, with PLC-controlled multi-stage wash cycles, and our multistage spray dryers can be supplied with retractable cleaning devices and polished SS316L surfaces. Products with strict food safety requirements, such as egg powder, place particular demands on cleaning, as discussed in our article on egg powder spray drying food safety.
Evaporators
Evaporators concentrate products at elevated temperatures, which encourages fouling on heat transfer surfaces. Regular CIP restores heat transfer and capacity. Falling film evaporators require cleaning solutions to be distributed evenly across every tube, which calls for careful design of distribution systems and adequate flow. Our article on common evaporator fouling problems and how to prevent them covers the link between fouling and cleaning in more detail, and AKSH's industrial evaporators are designed with cleanability in mind.
Automation and Data in Modern CIP
Automation is what makes CIP repeatable. A PLC-controlled system runs stored recipes for each circuit, controls valves and pumps, maintains temperature and concentration, and stops or extends a step if any parameter falls outside limits. Inline conductivity sensors confirm detergent strength during washing and the absence of chemicals during final rinsing. Integrating CIP with the main plant control system gives a single view of production and cleaning, a theme we explore in our article on how PLC and SCADA automation improves spray dryer consistency. Browse our automation and control range for related systems.
Reducing Water, Chemical and Energy Use
CIP can account for a significant share of a plant's water, chemical and heat consumption, so its efficiency is worth reviewing regularly. Common improvements include recovering final rinse water for use as the next pre-rinse, reusing caustic and acid solutions where hygiene rules allow, and switching from static spray balls to rotary jet heads in large vessels, which can clean with less liquid. Optimizing step times based on real cycle data, rather than generous fixed durations, avoids running solutions longer than needed. Heat recovery from hot return solutions and good insulation of tanks and lines reduce heating demand. Each change should be confirmed by verification testing, since savings must never come at the expense of cleaning effectiveness.
Troubleshooting Common CIP Problems
When cleaning results deteriorate, the cause usually lies in one of the four cleaning factors or in the equipment itself:
- Residues after cleaning: check flow velocity, spray device condition and detergent concentration; a blocked spray ball or worn pump impeller can reduce mechanical action.
- Scale build-up: review the frequency and strength of acid washes and the hardness of the water used.
- Long cycle times: look for slow heating, undersized return pumps or poorly drained circuits that dilute solutions.
- Chemical carry-over: confirm that final rinse conductivity limits and sensor calibration are correct.
- Inconsistent results between circuits: verify valve sequencing and routing, since a leaking valve can divert flow.
Reliable instruments are the basis of all these checks. Calibrated temperature sensors, flow meters and conductivity probes linked to a PLC, such as AKSH's instrumentation, automation and control systems, turn every cycle into a data record that makes troubleshooting faster and more objective.
Why AKSH Engineering
AKSH Engineering Systems Pvt. Ltd., based in Ahmedabad, Gujarat, has been designing and manufacturing drying, evaporation and turnkey process plants since 2013, with more than 100 installations in India and export markets. Our team of technocrats, with over 100 years of combined experience, designs CIP as an integral part of the plant rather than an afterthought. We build CIP skids in-house with SS304, SS316 or SS316L construction, orbital-welded piping, dead-leg-free layouts and PLC recipe management with data logging, and we integrate them with our spray dryers and evaporators as well as with existing plants.
Conclusion
Clean-in-Place combines chemistry, temperature, time and mechanical action into an automated, repeatable cleaning process. When it is supported by hygienic equipment design, the right system configuration, careful verification and good automation, CIP protects product safety, reduces downtime, saves water and chemicals and provides the records that audits demand.
If you are planning a new hygienic process line or want to improve cleaning on existing dryers and evaporators, contact the AKSH Engineering team. We will help you design a CIP solution that fits your products, your plant and your compliance requirements.
