Agitation can be either jet or mechanical. Jet agitation utilizes a portion of the pump’s output to stir up the tank. Mechanical agitation, utilizes paddles (usually of stainless steel) on a shaft that is turned by belts and pulleys connected with the engine.
Jet agitation is cheaper to install and service, and is sufficient for most applications. Mechanical agitation, which can add $500 - $1000 to the cost of your rig, is best for mixing heavy granular, or non-soluable, materials.
This entry will focus on jet agitation. We will discuss mechanical agitation in a future blog.
Volume:
Jet agitation requires a pump that has output volume sufficient for your spray application PLUS the volume required to agitate the tank.
Rule of Thumb – Most liquid materials require 8% of tank volume for agitation. Most granular or non-soluable materials require 12%. For example, to agitate a 200-gallon tank that you will be mixing a liquid concentrate into, you need 8% times 200 gallons, or 16 gallons per minute (gpm), for agitation.
Agitation boosters reduce the volume required by creating jet action. Most commonly used boosters are 3X (5X are also available). This means that instead of 16 gallons per minute, we need 16 divided by 3 or 5.33 gpm.
You need to select a pump with output equal to the desired spray volume PLUS the required agitation volume. If you need to spray at 5 gpm, you need a pump that will provide at least 10.33 gpm (5 gallons for spray plus 5.33 for agitation in this example). You actually want a pump that will do more than this because the rated output is for a new pump with no restrictions. Actual output will almost always be lower.
Plumbing:
Some equipment providers plumb the agitation on the pump return. We strongly believe this is a bad idea. Some pump manufacturers (e.g., Hypro, Udor) specifically warn against this as it creates back pressure that can affect the pumps performance. Regardless, it is a bad idea because return lines cannot have shut off valves on them (Note – centrifugal pumps are the exception). Because you can’t shut off the line, if the pump requires service when the tank is full, you will have to dump the tank since you can’t shut off the line. We recommend separate lines with the return to the top of the tank and the agitation to the bottom. It is sometimes helpful to put a gate valve on the agitation line so that the agitation can be easily adjusted. This is also an easy way to adjust the pressure of your spray line. More agitation means less pressure on the spray line.
Agitation Jets:
Jets must be positioned to ensure that the entire tank is agitated and no dead spots exist for material to settle. Be sure to fill the tank and observe the agitation pattern before accepting the rig from your supplier.
Hope this helps.
