There are many different configurations and designs. But a general principle applies – cleaning is done without removing process components through flushing the system with cleaning agents. The following terms are used to define the degree of cleanliness:
Physical cleanliness: Removal of all visible dirt from the surface
Chemical cleanliness: Removal not only of all visible dirt, but also of microscopic residues which can be detected by taste or smell but are not visible to the naked eye
Bacteriological cleanliness: Attained by disinfecting
Sterile cleanliness: Destruction of all microorganisms
It is important to note that equipment can be bacteriologically clean without necessarily being physically or chemically clean. A typical CIP run consists of:
- Recovery of product residues by scraping, drainage and expulsion with water or compressed air,
- Pre-rinsing with water to remove loose dirt,
- Cleaning with detergent, Rinsing with clean water
- Disinfecting by heating (steam) or with chemical agents if this step is included the cycle ends with a final rinse, if the water quality is good.
Each stage required a certain length of time to achieve an acceptable result. Four components (Time,
Temperature, Concentration and Velocity) determine the effectiveness of the CIP and are optimized for each application.
An example of CIP systems are single use, 1, 2, 3 or 4 tank system. The number of tanks describes how CIP media is recovered or what detergents are used. Above is an example of a 3 tank system. CIP systems are designed for central or de-centralized systems. Central systems are used for smaller plants where it is practical to use one centrally located CIP and a de-centralized system is often used for larger facilities. As a general rule, separate CIP systems are used for raw and pasteurized product. HTST pasteurizers and UHT systems have dedicated CIP systems. There is also a differentiation between line circuits and tank circuits. Tanks are cleaned using bursts of flow through a spray ball or a rotary nozzle. Cold processes commonly only use a caustic detergent (typically sodium hydroxide) while hot services may use caustic and acid (typically nitric or phosphoric acid) to remove burnt or caramelized deposits. A CIP program for a “hot components” circuit can consist of the following stages:
1. Rinsing with warm water for about 10 minutes.
2. Circulation of an alkaline detergent solution (0.5 to 1.5%) for about 30 minutes at 170 °F.
3. Rinsing out alkaline detergent with warm water for about 5 minutes.
4. Circulation of (nitric) acid solution (0.5 to 1.0%) for about 20 minutes at 160 °F.
5. Post-rinsing with cold water.
6. Gradual cooling with cold water for about 8 minutes.
The circuit is usually disinfected in the morning, before production starts. This is typically done by circulating hot water at 195 to 205 °F for 10 to 15 minutes after the returning temperature is at least 185 °F.
To control the process, flowmeters are used to ensure that the correct flushing action takes place. Note that flow velocity of 5 to 10 ft/sec is common during CIP. This is sometimes overlooked when sizing flowmeters since the flow rate of the process media is usually much lower. Temperature of CIP is closely monitored, if temperature is too low the effectiveness of the cleaning is compromised. As a rule of thumb, cleaning with alkaline detergent should be done at the same temperature, as the product has been exposed to, but at least 160 °F.
Concentration of the CIP detergent is monitored by conductivity measurement. Commonly two points are monitored; the concentrations in the CIP tank and on the CIP return line. The transmitter on the CIP return line controls the CIP diverter valve. Depending on the system, the diverter valve returns the CIP fluid to the CIP tank for reuse or dumps it to drain. The response time and performance of the conductivity transmitter is important. A slow response often results in unnecessary waste of CIP chemical to drain, resulting in higher cost for replacement chemicals, heating of more media and additional cost for water treatment.
What can Endress+Hauser supply for CIP systems?
• Deltapilot S FMB50 – ideal because of small range capability and temperature compensation. Balance tanks see rapid level and temperature changes.
• Liquiphant M – High/low level alarm – prevent the balance tank from overflow or run empty reducing product losses and production downtime
• Capacitance FMI51 – an alternative to Deltapilot S for level measurement.
CIP Chemical storage tanks
• Level measurement with Cerabar M PMC 51, Deltapilot S FMB50. Alternatives are Ultrasonic FMU 50 but look out for foam.
• Conductivity transmitter CLS 54 with CM 44x or CLD 134 for concentration measurement of CIP solutions. Some users prefer pH (accuracy is a little better but additional labor to calibrate and maintain is hard to justify).
• Liquiphant M for over-spill protection.
Chemical (CIP) header tanks
(Small tanks with about 100 to 200 gallon capacity)
• Capacitance FMI51 or Levelflex M.
Ultrasonic may work but foam is often present.
• Conductivity transmitter for CIP concentration (not always used here).
Sanitizer solution tank
• Sometimes pH measurement is used for sanitizer concentration
• Promag 50 H. Promag offers several benefits: True full bore design, no pressure drop and much better turndown. Vortex cannot measure at low flow (cuts off at about 13 gallons/minute for a 2” line). Vortex meters are often sensitive to pipe vibrations.Keep in mind that CIP rinse water for pharmaceutical applications may be ultrapure or even WFI (water for injection) with conductivity too low for magnetic flowmeters. If this is the ase then coriolis meter Promass is used for these applications, for example, Promass 40E, 80E or 80F.
• Conductivity transmitter for CIP return line – CLD 134 or CLS 55 with CM44x. This is used to control diverter valve. Many CIP systems are purely timing based, this can result in a lot of waste. A system controlled by conductivity is far more efficient.
• Liquiphant M FTL 50 H for pump dry-run protection. Primarily applicable if PD pumps are used.
Centrifugal pumps are less prone to damage.
• Temperature – applications can be found at several locations to ensure that correct cleaning temperature is maintained.