Clean-in-place (CIP)

Cleaning is bought with four things: the concentration of the detergent, its temperature, the mechanical effect at the surface, and the time you run for. Trade one down and you pay for it in another. That trade is the whole design of a CIP set, and the Tetra Pak dairy handbook lists exactly those four as the variables to work with.

The stage sequence below is the one 3-A's accepted practice for pipelines and cleaning systems sets out, with the dairy handbook's figures for the chemistry. Every plant tunes it, but this is the shape.

The pre-rinse temperature is the one people get wrong first. Hot water on a protein-bearing residue sets it onto the wall, which is why the standard caps the entering water rather than leaving it to the operator.

There is a cost on the sanitising end too. 3-A warns that halogen-based sanitisers, chlorine and iodine, left on surfaces for longer than they need to be may corrode them. On a stainless pump head that shows up as pitting, then as a surface that no longer cleans, and the cycle that was meant to protect the product has begun to eat the equipment.

Three of the four variables belong to the CIP skid and the chemical supplier. The fourth, mechanical effect, arrives as flow, and flow is the pump.

3-A's accepted practice for CIP puts a minimum on the cleaning velocity: a circulating unit should deliver 5 ft/s, which the document gives as 1.5 m/s, as a mean flow velocity per line during cleaning, with enough flow in all cases to keep the lines fully flooded. The dairy handbook gives the working band as 1.5–3.0 m/s in the pipes. Below that you lose the turbulence at the wall, and the chemistry is left doing the job on its own.

3-A publishes the flow that velocity costs, tube size by tube size. Converted to m³/h:

Those are imperial tube sizes, because 3-A is a US dairy standard. A UK plant is more likely to be running ISO 2037 or DIN 11850 tube, so take the velocity and work it against the bore you actually have rather than lifting the flow figure. 3-A also notes that the table suits milk and other relatively low-fat products; on cream, ice cream mix or concentrate you may need to move the velocity or one of the other variables.

Two consequences follow, and both get missed. First, the CIP duty is a separate duty point from the process duty. A line that carries product at 8 m³/h and cleans at 23 m³/h is asking two different things of the pump, and if the process pump is doing both, one of them is being met by accident. Second, the mistake we see most often here is the same one we see everywhere else: margin gets added at each stage of the design, the CIP pump comes out oversized, and it spends twenty years drawing power it never needed.

3-A also requires that the suction intake of the primary circulating pump is flooded at all times during the cleaning cycle. That is the practical form of an NPSH margin, and it is worth reading as the warning it is. A CIP set that draws down its solution tank is running a pump on hot, thin caustic with air in it.

One last detail from the same document, and it is a good tell of a properly specified installation: a pump used solely for CIP recirculation has to carry a plate next to its nameplate stating that it is for cleaning and sanitising solutions only. If a plant has those plates, someone has thought about the separation of the two circuits.

A pump only cleans in place if it was built to. EHEDG's design criteria set out what that means, and read against them a standard industrial pump fails on most counts.

Two of those rows deserve reading twice. EHEDG is careful about the Ra figure, because it is the topography that governs cleanability rather than the reading: rougher than 0.8 µm is acceptable where testing shows the surface cleans anyway, and pits, folds and peened-over irregularities all leave places a cleaning agent cannot reach whatever the number says. And on radii, 3-A allows smaller ones where they are functionally necessary, naming pump impellers as the case, but sets a floor of 1 mm and requires the angle to be accessible for cleaning and inspection. That exception exists because an impeller vane cannot carry a 6 mm root radius and still move liquid.

Hygienic pumps are built this way, and it is most of what you are paying for. A rotary lobe pump or a hygienic centrifugal costs considerably more than a comparable industrial unit, and almost none of that difference is in the hydraulics. It is in the finishing, the seal arrangement and the castings. That is the trade-off, stated honestly: on a duty that never needs validating, you would be wasting the money. On a duty that does, an industrial pump in the circuit is the thing that stops you validating it.

The rest of the hygienic range is built to the same criteria, and the pump is only ever as clean as the pipework it sits in.

Seals fail before anything else on a hygienic pump, and CIP is one of the reasons. A mechanical seal is a running interface sitting in the product path, with two faces held together and a gap between them that product gets into and cleaning fluid has to get back out of. EHEDG thinks the problem is hard enough to warrant its own guideline, Doc 25, on the design of mechanical seals for hygienic and aseptic applications.

The design answer is to move the difficult geometry out of the product. Alfa Laval's LKH UltraPure is built that way, with an external shaft seal carrying few wear parts and spring-mounted on the atmospheric side, on a pump Alfa Laval states is designed for CIP and certified to EHEDG. A flushed double seal goes further and puts a barrier fluid behind the faces. Both cost more than a single internal seal, and both are the right answer on a duty that has to be cleaned to a standard.

The failure to watch for during CIP itself is dry running. A mechanical seal needs liquid to lubricate it. Hot caustic is thinner than the product the pump was set up for, a circuit that loses its flood pulls air, and the seal goes in minutes. On a plant that cleans nightly that is a failure mode with an opportunity every day of the year.

Then the elastomers, which are chosen by the cleaning chemistry as much as by the product. EPDM is the standard hygienic elastomer and copes well with caustic, but EHEDG's own note against it is that it is not oil and fat resistant. Fluoroelastomer handles fat and runs to 180°C; perfluoroelastomer goes above 300°C and costs accordingly. A fatty product cleaned with hot caustic can leave you caught between the two, which is exactly why the medium and the CIP recipe both have to be on the enquiry. Specifying elastomers against the product alone is how you end up replacing seals every few months and blaming the pump.

"EHEDG certified" on its own does not tell you the equipment can be cleaned in place. The class does. EHEDG's wet-processing scheme, Type EL, splits on precisely this question:

Class I is the one that means CIP. A Class II certificate is a real certificate and says something worth knowing, but it says the equipment comes apart to be cleaned. If a specification asks for a CIP-cleanable pump and a quotation answers with "EHEDG certified", the class is the question to ask next.

Cleanability is tested rather than asserted. EHEDG Doc 2 sets out a method for assessing in-place cleanability in which the equipment is soiled and cleaned alongside a standard reference pipe in the same test, and judged against it. Doc 17 covers the hygienic design of pumps, homogenisers and dampening devices specifically.

On the American side, 3-A Sanitary Standards 02-12 covers centrifugal and positive rotary pumps, and the 605 accepted practice covers the installation and CIP of processing equipment and hygienic pipelines. Equipment that meets a 3-A standard can be authorised to carry the 3-A Symbol.

None of those certificates are ours to issue. They belong to the manufacturer and to the specific build they had assessed, in the same way an ATEX certificate does. What we can do is name the certified build, get you the manufacturer's certificate against the model string on the quotation, and tell you when nothing we carry is certified to the class you need.

CIP, COP and SIP get used loosely and they are not interchangeable. Deciding which your process needs happens before you specify the seal, not after.

CIP circulates cleaning fluids through the assembled plant. Nothing comes apart. This is the default across food, dairy and beverage, and it is what the CIP duty pages cover in selection terms.

COP, clean-out-of-place, means dismantling the parts and cleaning them in a tank or cabinet. It is not a failure state. Some components genuinely cannot be mechanically cleaned, and 3-A's practice says as much, listing fittings and valves that should be cleaned and sanitised by hand. EHEDG EL Class II is the certification that matches this way of working. The cost is labour, downtime and the reassembly, and every strip-down is a chance to leave a gasket out.

SIP, sterilise-in-place, follows the clean with steam to sterilise the equipment. It is a separate requirement with its own assessment method. EHEDG Doc 5 covers in-line steam sterilisability, and the aseptic classes require both that and bacteria tightness. 3-A recognises steam as a sanitising route too, at 15 minutes after the drainage at the outlet reaches 76.7°C, or five minutes after it reaches 93.3°C.

SIP changes the pump specification, not just the procedure. The build has to take the steam temperature and pressure, the elastomers have to survive the thermal cycling as well as the chemistry, and the seal faces move relative to each other as the head heats. Most food and beverage duties need CIP alone. Pharmaceutical manufacture and aseptic dairy need CIP and then SIP. Confirm which before you go out to quotation, because retrofitting SIP capability to a pump specified for CIP usually means a different pump.

Two duties, not one. The process duty in the usual terms: flow, total dynamic head, the medium, its temperature, its viscosity and whether it is shear-sensitive. Then the CIP duty, which most enquiries leave out: the cleaning flow the circuit needs, the tube bore it has to reach velocity in, the caustic and acid concentrations and their temperatures, and the cycle time.

Say whether the pump also drives the CIP circuit or whether a separate circulating pump does. Say whether SIP is required. And say whether the specification calls for EHEDG or 3-A, and to what class, because that decides which builds are eligible before the hydraulics are looked at.

If the plant is existing and the problem is that a pump keeps failing rather than that a new one is needed, send the model and the serial number off the nameplate and tell us what the cleaning cycle does. Seal failures on hygienic duties are more often a cleaning or suction problem than a pump problem, and where that is what we find, that is what we will tell you.