Effectiveness of Rinse Water during In-Place Cleaning of Stainless Steel Pipe Lines

The 1st step of any Clean-In-Place (CIP) operation is a prerinse with water. The purpose of this step is to remove the bulk of food material remaining in the processing lines after production period has ended. It is known that this prerinse step can be a very water intensive process. The objective of this investigation was to measure the influence of CIP parameters (flow characteristics, water temperature, and contact time) on the effectiveness of prerinse water in removing dairy-based deposits from stainless steel pipe surfaces and to compare the rinse effectiveness of unused to reused rinse water. A pilot-scale CIP system was operated to rinse 304 stainless steel pipe sections of 3 different pipe diameters. The velocity of the rinse water was varied from 0.72 to 2.26 m/s. The rinse water temperatures were 22 degrees C, 45 degrees C, and 67 degrees C. The contact times between rinse water and deposited film were 20 and 60 s. Rinse effectiveness was expressed as the ratio of the amount of protein residue removed from the pipe surface during rinsing, as compared to the magnitude of the initial protein deposit. The rinse effectiveness varied from 73.1% to 94.9% for the range of the CIP parameters investigated. High velocities of rinse water provided a higher level of rinse effectiveness. Increasing the rinse water temperature from 23 degrees C to 45 degrees C improved rinse effectiveness significantly (P < 0.05). This impact was not significant when the water temperature was increased from 45 degrees C to 67 degrees C and at higher rinse water velocities. Similarly, longer contact time provided less improvement in rinse effectiveness at higher temperatures and velocities as compared to lower temperatures and velocities. There were no significant differences in rinse effectiveness when comparing reused and unused water (normal tap water) within the range of velocities evaluated. Practical Application The rinse steps are important components of the CIP operation and have direct impact on the amounts of water and energy used for the entire processing operation. The efficiency of rinse water can be improved significantly by the selection of appropriate combinations of operating parameters. For example, higher velocities of rinse water (2.26 m/s) provide significant improvements on rinse effectiveness when compared to current commercial practice (1.52 m/s). The careful selection of rinse water temperature and velocity can result in overall reductions in water and energy used for cleaning operations. The reuse of water for a 2nd or 3rd pass provides additional opportunities for reducing water requirements without influencing effectiveness.