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The following sections describe some ways of monitoring the cleaning process. Many basic inspection processes can be carried out by the farmer. If malfunction of the cleaning unit occurs, it should be adjusted by a qualified service man.
The water temperature is an essential part of the cleaning process. Too low temperature could result in improper cleaning. It is of utmost importance that the water temperature is maintained above a certain level during the circulation phase. In many countries regulations prescribe which temperature to maintain. This temperature should be at least 40°C (104°F), in some cases, however, up to 60°C (140°F) is required.
With an open water trough it is easy to check the water temperature with a common thermometer. It could be somewhat harder to do this manually when the trough is covered. In these cases, often the cleaning unit is equipped with a temperature sensor and a display that shows the water temperature.
If the cleaning is unsuccessful, soil could be visible at different points in the milking plant. A manual inspection is therefore always an appropriate way of discovering a possible malfunction. The Table below describes some different kinds of deposits which could occur.
| Kind of deposit |
Description |
| Fat |
Greasy, oily apperance of surface |
| Protein |
Blue-rainbow hue varnish-like |
| Milkstone |
White to yellow deposits |
| Iron |
Red to brown or black |
| Bacteria |
Red or pink/purple colouring or staining |
| Rubber fragments |
Black or blackening residues |
Often you can suspect insufficient cleaning at some well defined points. The differences between plants can vary largely, however. Therefore, it is difficult to give detailed general information about difficult-to-clean points, but the fact is that milkmeters often are difficult to clean and pipelines usually are easily cleaned.
Long before the result of unsatisfactory cleaning is visible, the plant could be unacceptably dirty. Therefore, other methods for assessing the cleanliness are needed. Most of these methods use bacterial growth as an indicator for the assessment. These methods are, however, time-consuming and in some cases also rather difficult to perform. In the future, we will probably have fast and safe methods for the assessment of cleanliness, which will be a valuable tool for the inspection of the cleaning process.
For those parts of the milking plant which are transparent it is possible to visually inspect the water flow. Examples of such parts of the milking plant are the clusters, milk-meters, recorder jars, pipelines and the receiver. Due to stainless steel pipelines, however, it is common that large parts of the plant are difficult to inspect visually.
It is important that all milking units are rinsed by approximately the same amount of water and that all pipe sections are properly flooded. By measuring the amount of water in the milk sampler, usually used for monthly milksampling, you can see the distribution of water between the milking units during cleaning.
For those cleaning systems using a controlled slug flow, it could be appropriate to investigate the slug flow pattern. Since transparent pipelines are seldom in use, these investigations have to be performed with a vacuum recording instrument. The recording instrument must be equipped with either a printer or a data logger. The appearance of a slug is easily discovered by a significant vacuum pressure drop. The velocity and length of the slug could be determined by simultaneous measurement at two locations about ten metres apart in the pipeline. The measurement should be performed at those locations in the system where it is probable that poor flow will occur.
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