Cleaning in place
Cleaning in place or CIP as it is commonly known is an extensively used process in the food, dairy, brewing and beverage industries where stringent hygiene regulations are enforced. Equipment is cleaned automatically to high standards using systems designed to clean 100% of the machines interior by removing food solids and bacteria.

A cleaning in place system could include a solution reservoir, a supply pump and a return circuit with a tank or vessel, a spray device and possibly a return pump. Cleaning in place systems typically start with a pre-rinse to remove solids, followed by a chemical wash using a caustic based solution and finishing with a rinse using a sterilising solution to remove the wash chemicals.

Cleaning in place systems offer fast, efficient and reliable cleaning of all types of process plant, a tanker, tank, vat, chamber, hopper or bin may be thoroughly cleaned using spray balls or rotating jet devices to avoid unnecessary and uneconomical filling of vessels with solution. It also removes the need for operators to climb into vessels to carry out manual scrubbing.

Any closed circuit, including piping, pumps, valves, and plate heat exchangers can be cleaned in place with systems designed to clean tanks and/or line circuits.

The following is a typical procedure used when cleaning food processing equipment. The factors that influence cleaning (time, temperature, chemical concentration and mechanical force) and the food soils to be removed will ultimately determine the cleaning procedures selected for use.

Pre-Rinse: Soiled equipment surfaces are rinsed with warm water to remove the loose food soils and pre-heat the stainless steel pipework.

Cleaning Cycle: Removal of residual food soils from equipment surfaces through manipulation of: time, temperature, chemical concentration, mechanical force and the method of cleaning. Alkaline chemical solutions are typically used for the cleaning cycle.

Rinse: Rinsing of all surfaces with cold to hot water, depending on the temperature of the cleaning cycle, to thoroughly remove all remaining chemical solution and food soils residues.

Acid Rinse: A mild acid rinse may be used to neutralise any alkaline residues that remain.

Sanitise: All equipment surfaces are rinsed or flooded with a sanitising agent.

Cleaning in place systems include a recovered water tank where used water from final rinses is stored for subsequent use as a pre-rinse solution. If a disinfectant/sanitise cycle is used then this solution can also be recovered and re-used for pre-rinse purposes.

Using Conductivity to control the Cleaning in place process

Generally two types of cleaning products are used; an alkali cleaner which is essentially Sodium Hydroxide (NaOH), or an acid cleaner which is based on Phosphoric Acid. The cleaning solution is usually heated to 85°C.

The concentrated chemical(s) are held in bulk storage tanks and transferred to dilution tanks where they are made up to the required concentration for cleaning, typically between 1-5% vol/vol. Conductivity measurement is ideal for this application as only one substance is present at a time.

The conductivity sensor is usually mounted in the circulation loop coming from the base of the tank, which is then pumped back into the top of the tank. This also provides the agitation needed to mix the chemical and water together. A heat exchanger is also mounted in the circulation loop to bring the dilution up to the specified temperature.

The CIP make up tank will run continuously to ensure the cleaning process is ready at any time during the day. Depending on production requirements this can be 6 to 8 process cleans per day.

A centralised control system can supervise the cleaning process which involves pumping the product and cleaning chemicals around the pipework and tanks in the system. The product, for example milk or beer is pushed through the system with heated clean water, followed by the cleaning solution, then water followed by a sanitising solution and one final rinse before the process is repeated.

Each of the different solutions has a very different conductivity value making it possible to detect the interface between each of them when they pass a conductivity sensor. Each solution can then be diverted via an automatic valve to a bulk storage tank or to drain as required.

To keep the inside of the pipework clean and for the automatic cleaning process to have maximum effect, it is essential that crevices such as screw threads etc are eliminated. This is achieved by using hygienic or sanitary process fittings. There are several standard fittings used, the most common being Din, Tri-clamp, IDF, and RJT. Any sensor which comes into contact with the product will require this type of process connection.

LTH Electronics offer a range of Electrodeless Conductivity instrumentation and sensors for Cleaning in place applications.

Call us on +44 (0)1582 593693 or email sales@lth.co.uk to find out how we can help you.