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:

  • The operator manual states the end of the jet tube should be three inches off the bottom of the bulk tank. The slots on the tip of the jet tube are designed to give the best coverage at this angle. Depending on the bulk tank size, adjustments to the washer legs may be needed to ensure the jet tube is three inches off the bottom of the tank.
  • If the tip of the jet tube is dented or plugged the spray pattern can be altered and may result in a cleaning failure. The tip needs to be kept up off the floor and protected. Options are to hang the washer on the milk house wall or set the tip on a stainless bracket. (see figure 1)
  • The slots on the jet tube are specific to tank size so check your manual to ensure you are using the right sized washer for your bulk tank.
  • Tank washer impellers on these units can wear over time. Although the tank washer may appear to be functioning well, it may in fact not be delivering the required amount of cleaning solution. This situation can be difficult to detect.
  • The auto drain valve can malfunction and cause incomplete drainage between cycles. This will dilute and neutralize cleaning chemicals and affect temperatures of solutions. Cleaning chemicals can also be lost down the drain during tank filling.
  • The agitator paddle needs to turn during cleaning cycles. This ensures all angles of the paddle and tank walls receive proper solution coverage.
  • Keep water supply strainers clean to maximize flow.
  • Keep soap and acid containers clean.
  • Repair any leaks promptly to prevent loss of cleaning chemicals and solutions.

Figure 1. Shows improved storage of the jet tubes to prevent contamination

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.

Cleaning validation

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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