Troubleshooting tips for bulk tank washers
Bulk Tank Washer Issues
A bulk tank is often a more difficult vessel to clean than a pipeline. Automatic bulk tank wash systems clean by covering the inner surfaces of the tank with a sprayed sheet of cleaning solution. The large surface area of a bulk tank and spray action of automatic tank washers can make it hard to maintain the required 120ºF end temperature on the hot wash cycle. It is generally more difficult to maintain surface temperatures in spraying operations than in pipe flow conditions because of the greater surface to solution ratio.
The scrubbing action in a milk pipeline is achieved by slugging and turbulence. Meanwhile only a small surface area of a bulk tank receives the force of the spray jet leaving much of the cleaning to the cascading action of the solution as it flows down the tank sides. Therefore the mechanical cleaning action is significantly reduced in a bulk tank compared to circulation cleaning of pipelines.
It is critical that all surfaces of the bulk tank receive adequate coverage with cleaning chemicals at proper temperatures and strength particularly since the hot wash circulated by some tank washers lasts only three and a half minutes.
There are a few different generations of tank washers, but the general operation is very similar. Here are a few items to be aware of that can have a significant impact on tank cleaning:
Figure 1. Shows improved storage of the jet tubes to prevent contamination
Bulk Tanks with Spray Balls
Small orifices in a spray ball can clog easily from debris such as straw and bits of plastic. This will cause voids in the spray pattern and result in some surfaces not receiving adequate spray. Keeping a cap on the wash pump hose that connects to the bulk tank is one way of preventing debris and pests from entering the wash pump and bulk tank between washes. Don't let the spray ball act as a system strainer.
Observing one complete cleaning cycle, noting times and temperatures is often useful. The tank washer should be included in the dealer's preventative maintenance checks.
The easiest and most practical way to assess tank cleaning is to inspect the surfaces visually. Stainless surfaces must be dry to detect films of protein, fat or milkstone buildup. A strong flashlight is needed to conduct an effective examination. A blue / rainbow colour indicates a protein film and is difficult to remove. Water droplets clinging to the tank walls may indicate a fat film. Manually brush a small area of the tank with a strong chlorinated alkaline cleaner, then rinse and dry the surface. Critically examine the brushed area. If the brushed surface appears shinier than the adjacent non-brushed area, a film has been removed. Repeat this process with a strong acid and examine again.
Mineral films such as milkstone are removed by acid cleaners. Organic films of fat and/or protein are removed by hot chlorinated alkaline cleaners. If a tank cleaning issue is found, it is important to drill down to the root cause.
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