CIP is the cleaning of pipework or vessels (tanks) by passing cleaning fluids through the pipework or spraying inside the vessel. The flow rate and volume of cleaning fluids required can be very high and it is most common practice to recirculate and sometimes recover these fluids to make most use of them.
The principles of cleaning are always the same; whether it is manual cleaning of a utensil in a sink or in a dishwasher or the CIP of a vessel. Energy in the form of chemical energy, thermal energy and physical energy are all required to remove the soil from the surface.
With CIP the physical energy comes from the movement or impact of the fluid. In the case of pipework the turbulence of the fluid flowing creates a physical scouring action on the internal wall of the pipe. Turbulent flow is achieved at flow velocities of greater than 1.5 m/s. With vessel cleaning the physical energy comes from the impact or flow of the cleaning fluid over the internal vessel surface.
It is important to note that for equipment to be effectively cleaned by CIP it must be designed to do so. For instance an automatic depositor head designed for CIP will incorporate a mode where all of the depositor head seals become exposed to cleaning solutions. With a normal depositor the head will require full dismantling for manual cleaning and it is not possible to effectively clean this type of depositor by recirculation or CIP.
CIP Set
A CIP Set delivers cleaning fluids (water, detergent and disinfectant) to vessels or pipework that need to be cleaned. The cleaning solutions are routed to the relevant vessel or pipework route by either a flow plate (manual connection panel) or via an automatic valve bank.
Vessel Cleaning
Production vessels come in vast range of sizes. A large brewery or dairy vessel could hold 100,000 litres (for instance a Bright Beer Tank) while a small cooking vessel in a food factory may hold 500 litres. Both can be cleaned by CIP as long as all the vessel internals can be exposed to the cleaning fluids.
With any vessel it is wise to seek advice from a sprayhead manufacturer to ensure the correct sprayhead/s are used to give complete coverage (computer aided design will be used to ensure theoretical coverage).
When vessels have internal structures (e.g. scraped surface paddles in a cooker) it is vital that the sprayhead design and position also ensures coverage of these internals as well as the vessel surface.
Spray devices should be regularly removed for inspection and cleaning.
Internal pipework, vessels, welded joints, unions and valves should all be of a hygienic cleanable standard. Ensure no pooling of liquids in the bottom of the vessel occurs; if feed rate is higher than scavenge rate then consider burst rinsing.
Pipework Routes
CIP feed pump and circuit design should ensure a minimum flow rate of 1.5 m/s. this ensures that the fluid flow in the pipework is turbulent.
Pipework routes should be of consistent diameter. A change in diameter will lead to lower cleaning velocities in the larger diameter pipework and therefore potentially poor cleaning.
CIP flow rates should not be too high otherwise pipe hammer can occur. Pipe hammer is caused by rapid changes in liquid velocity and can lead to seal and pipework damage.
Internal pipework welded joints, unions and valves should all be of a hygienic cleanable standard. Deadlegs should be avoided.
Chemical Choice
A wide range of CIP detergents and disinfectants are available. One common feature to all is that the products are low foaming and in some circumstances act as defoamers. This is particularly important where caustic detergents are used to remove fatty deposits. The reaction between the caustic and fats produces soap which will naturally foam in recirculation situations.
The choice of detergent and disinfectant are based, as in open plant cleaning, on a number of factors including soil type, materials of construction of the surfaces being cleaned, water hardness and many others. In many CIP situations a caustic based, low foam, detergent is used at typically 0.25% to 1% w/v (NaOH) at 65 to 75ºC.
Types of CIP Set
A Total Loss CIP Set recirculates the cleaning fluids through the vessel or pipework to be cleaned. After the end of the detergent recirculation stage the fluid is discharged to drain and not recovered to a storage tank. The buffer tank is generally small (200 litres) and is used to maintain a feed to the CIP feed pump.
A typical cleaning cycle will be (times will vary dependant on cleaning circuit):
Prerinse: feed clean water, to circuit, and return to drain. Feed for 5 mins.
Detergent: feed clean water, until circuit made, and return to buffer tank; while recirculating run caustic dosing pump. A plate heat exchanger is used to heat the solution to the required temperature. Allow to recirculate for 20 mins.
Rinse: feed clean water, to circuit, and return to drain. Feed for 5 mins.
Disinfect: feed clean water, to circuit and return to buffer tank; while feeding water run disinfectant dosing pump. Allow to recirculate for 3 mins.
Drain: drain system and buffer tank
A Recovery CIP Set recirculates the cleaning fluids through the vessel or pipework to be cleaned. During and after the detergent recirculation stage the fluid is recovered to a storage tank and is then available for use on a subsequent clean. There are different degrees of recovery with some sets recovering water in a rinse recovery tank, detergent in the detergent tank and disinfectant in a disinfectant tank.
A typical cleaning cycle will be (times will vary dependant on cleaning circuit):
Prerinse: feed water, to circuit, from rinse recovery tank and return to drain. Feed for 5 mins.
Detergent: feed detergent, to circuit, from detergent tank and return to detergent tank. A plate heat exchanger is used to heat the solution to the required temperature. Allow to recirculate for 20 mins.
Rinse: feed clean water, to circuit and return to rinse recovery. Feed for 5 mins.
Disinfect: feed clean water, to circuit and return to rinse recovery tank; while feeding water run disinfectant dosing pump. Disinfectant dosing for typically 3 mins.
Drain: drain system returning all solutions to the rinse recovery tank.
Cross contamination by CIP
As with an open plant surface the best method of reducing cross contamination by micro-organisms or allergens in closed equipment such as vessels and pipework is to have separate process plant for low risk and high risk plant and also for plant handling allergenic and non allergenic food products. If this is not feasible then the vessels or pipework must be capable of being cleaned free from micro-organisms and allergens (as appropriate), the method validated and then verified on an on-going basis.
An additional cross contamination route exists with cleaning in place because of the commonality of the CIP set which is often used for cleaning many vessels and pipework routes. Any deposits in the CIP set, including filters, may be transferred between cleans.
With Recovery CIP sets the recovered solutions are a potential for cross contamination; but with Total Loss CIP sets the potential for cross contamination is reduced because no solutions are recovered or reused on subsequent cleans.