CIP

What is CIP (Clean-In-Place)?

CIP (Clean-In-Place) is an automated cleaning method in which piping, tanks, heat exchangers and other process equipment are cleaned on the inside by pumping water and cleaning agents through them in a fixed sequence, without dismantling the installation. CIP is standard practice in dairy, brewing, soft drinks, food, pharmaceuticals and cosmetics, wherever product residues and micro-organisms threaten the quality or safety of the next product. Because a PLC drives the valves, pumps and timers while sensors measure every step, CIP is also a typical OT process: reproducible, logged and demonstrable.

CIP = cleaning without taking everything apart: fast, consistent, automated and with evidence for every cycle.

Note: in industrial networking the abbreviation CIP usually means something else, the Common Industrial Protocol. That meaning is briefly explained further down this article.

🧠 How did CIP emerge and why does it matter?

Until the 1950s, closed systems were dismantled, scrubbed and reassembled by hand. That meant hours of downtime every day, and the result depended on the operator. CIP made it possible to keep an installation closed and to automate the cleaning. A modern CIP installation consists of supply tanks for water, caustic and acid, pumps, a heat exchanger, sensors and a control system that runs everything in the correct order.

The main reasons for using CIP:

• Food and product safety - cleaning is a core prerequisite in HACCP and GMP; residues or bacteria in a pipe can cause off-flavours or ruin an entire batch
• Reproducibility - every cycle runs with the same times, temperatures and concentrations, without manual variation
• Less downtime - the line does not have to be opened, so cleaning between batches takes minutes to at most a few hours
• Operator safety - staff do not come into contact with hot caustic or acid and do not have to climb into tanks
• Traceability - cleaning records are stored in a historian, MES or LIMS for audits and batch release
• Sustainability - recovering rinse water and cleaning agents reduces water, chemical and energy consumption

🔄 Which steps does a CIP cycle go through?

A standard CIP cycle consists of a fixed series of phases. The exact values differ per installation and product and are usually recommended by the supplier of the cleaning chemicals; the ranges below are common in the dairy and beverage industries.

Not every cycle includes every step. A light intermediate clean may consist of rinsing and caustic only, while the acid step is added daily or weekly, for example. In pharmaceuticals, CIP is often followed by SIP (Sterilisation-In-Place) using saturated steam at typically around 121 °C.

🔧 Which parameters determine whether CIP works?

Cleaning effectiveness has been described since 1959 by Sinner’s circle, devised by Herbert Sinner, a chemist at Henkel. Four factors complement each other: if one goes down, another has to go up.

For piping, the rule of thumb is a flow velocity of at least 1.5 m/s so that the flow is turbulent; above roughly 2.1 m/s extra velocity adds little according to common practice guidelines. Tanks are cleaned with static spray balls for light soiling or rotating spray heads for heavier soiling and large diameters. Dead legs and poor drainage are the biggest enemy, which is why the guidelines of EHEDG and the US 3-A Sanitary Standards pay so much attention to hygienic design.

🏭 What does CIP look like in a dairy plant?

A typical example from dairy, where milk tanks, pasteurisers and filling lines are cleaned after every production run:

1. The milk tank is empty and the MES releases it for cleaning.
2. The PLC checks through interlocks that the product lines are isolated, so caustic can never enter a product line.
3. The CIP supply pump starts; a variable frequency drive maintains the required flow.
4. Pre-rinse water goes to drain, caustic circulates through the spray ball and back to the caustic tank.
5. Conductivity measurement in the return line determines when caustic turns into water, so that each medium goes back to the correct tank.
6. After the final rinse the PLC checks the final conductivity; only then is the tank released.
7. Temperature, flow, conductivity and time per step are logged as a cleaning record with the batch.

Installations with recovery (re-use CIP) store caustic and acid in tanks and reuse them, saving water and chemicals. Single-use CIP uses each solution once and is common for heavy soiling or in pharmaceuticals, where cross-contamination is unacceptable.

🔗 How does CIP fit into the OT architecture?

In batch systems based on ISA-88, CIP cleaning is a procedure or phase of its own in the batch sequence, often programmed as an SFC. In modular process plants a CIP skid can expose its functions through a Module Type Package. You can read more about the difference between batch and continuous production in Discrete, Batch and Continuous Processes.

🔐 Which requirements apply to validation and security?

In the food industry, the EU food hygiene regulation (EC) 852/2004 requires effectively cleaned equipment and HACCP-based procedures; in the Netherlands the Netherlands Food and Consumer Product Safety Authority (NVWA) supervises compliance. In pharmaceuticals the requirements are stricter:

• EU GMP Annex 15 (revised version in force since 1 October 2015) requires cleaning validation: a visual check alone is not sufficient, limits for product residues must be based on a toxicological evaluation, and for automated cleaning the normal operating range of the utilities must be validated. Dirty hold time and clean hold time must also be defined.
• FDA rule 21 CFR 211.67 requires written procedures for cleaning and maintaining equipment, with corresponding records.
• Electronic records of CIP cycles fall under 21 CFR Part 11 and EU GMP Annex 11, which means data integrity, audit trails and a system validated according to GAMP are needed.

From a cybersecurity point of view a CIP installation is interesting because it doses hazardous chemicals close to product lines. A manipulated setpoint, a disabled interlock or a falsified cleaning record can lead to a product recall or a safety incident. Good practice is therefore: CIP control in its own zone with network segmentation, recipe changes through change management and version control, and safety functions that do not depend on software alone.

🧱 What else does CIP mean in industry?

The same abbreviation has three meanings in the IT/OT world. In this knowledge base, links to CIP in the context of Rockwell equipment usually refer to the protocol.

The Common Industrial Protocol is an object-oriented, media-independent protocol with a producer-consumer model, managed by ODVA. It forms the application layer of EtherNet/IP (default TCP port 44818 and UDP port 2222), DeviceNet, ControlNet and CompoNet, and is therefore the foundation of the Rockwell Automation ecosystem with ControlLogix and Allen-Bradley equipment. Extensions include CIP Safety for functional safety, CIP Security for encryption and authentication, CIP Motion and CIP Sync.

❓ Frequently asked questions

What is the difference between CIP and COP?

CIP (Clean-In-Place) cleans an installation on the inside while it stays closed and assembled. COP (Clean-Out-of-Place) means that parts are dismantled and cleaned separately, for example in a wash tank or parts washer. Many plants combine both: CIP for pipes and tanks, COP for small parts such as gaskets and filling nozzles.

How long does a CIP cycle take?

A full CIP cycle with caustic, acid and final rinse usually takes roughly one to two hours in the dairy and beverage industries. A short intermediate clean between similar products can be considerably faster. The exact duration depends on pipe length, soiling, temperature and the chosen concentrations.

Which cleaning agents are used in CIP?

In CIP, sodium hydroxide (caustic) is the main agent against fat and protein, followed by nitric or phosphoric acid against scale and milk stone. Disinfection is often done with peracetic acid or hot water, and enzymatic cleaners are also used for sensitive materials such as membrane filters. Concentrations are monitored with conductivity measurement and recommended by the chemical supplier.

How do you check whether a CIP clean was effective?

The effectiveness of CIP is checked per cycle using the measured values for temperature, flow, time and final conductivity. In addition, plants use ATP swabs, samples for TOC or microbiology, and during validation a riboflavin test that shows under UV light where the spray device fails to clean properly. In pharmaceuticals, formal cleaning validation according to EU GMP Annex 15 is mandatory.

Why is CIP relevant to OT security?

CIP is relevant to OT security because a PLC doses hot caustic and acid next to product lines and the cleaning record serves as quality evidence. Manipulating setpoints, interlocks or logs can result in contaminated products, recalls or injuries. Segmentation, change management and audit trails limit that risk.

Is CIP the same as the Common Industrial Protocol?

No, Clean-In-Place and the Common Industrial Protocol only share the abbreviation CIP. Clean-In-Place is a cleaning method, while the Common Industrial Protocol is the ODVA communication protocol underneath EtherNet/IP and DeviceNet. The context, for example dairy versus Rockwell networks, shows which meaning is intended.

📌 In summary

CIP (Clean-In-Place) is the automated, validated cleaning of closed process installations, in which a PLC monitors time, temperature, chemistry and flow for every step and records each result.

A good CIP installation combines hygienic design, the right sequence of steps (rinse, caustic, acid, final rinse, disinfection) and reliable measurement of conductivity, temperature and flow. Through integration with SCADA, Historian and MES, CIP provides the evidence for GMP compliance and batch release. Because the control system doses chemicals and creates quality records, CIP deserves the same OT security as the production processes themselves.