STS mixing units are a simple design with limited moving parts or consumable pieces. The basic system works with a pump that draws fluid from the reservoir tank. The fluid then exits the pump and by building pressure and velocity, forces the fluid through the filter / shear and into the mixing chamber. The fluid enters the mixing chamber through a nozzle and exists through a venturi. As the fluid enters the venturi, it creates a vacuum in the mixing chamber to aid in introducing the dry product from the hopper into the mixing chamber and fluid stream. As the fluid passes through the venture, it carries the dry product with it and back into the reservoir tank.

As the fluid travels through the filter / shear, a set amount of fluid is taken from the fluid stream and forced, with pressure, to the internal tank jets inside the reservoir tank. Multiple tank jets distribute the fluid through out the tank to “stir up the tank.

STS mixing units can discharge fluid to the drill rig or another reservoir by allowing some fluid from the filter /shear to be discharged and controlled by a valve.

A good rule to follow when troubleshooting: Everything before the pump is being sucked, “has vacuum". Everything after the pump is being blown, “has pressure”.

These simple steps can be followed when trouble shooting a mixing unit that is not mixing as well as it should. By following these simple but necessary steps in order, you’ll be able to resolve the problem quickly.
     
  1. Drain the reservoir tank completely and check that there is no build-up of old drill fluid or foreign debris around the suction elbow of the tank. This will cause a restriction on the amount of fluid that can be drawn (sucked) by the pump and therefore not have enough fluid to get the high velocity of fluid through the mixing chamber.
     
  2. On the above-mentioned tank suction line, on the outside of the tank is a lever-operated butterfly valve that controls the flow from the tank. The opposite side of the valve is the removable drain cap. Remove this cap and, with a flashlight, visually look at the valve flap inside and make sure there’s nothing attached or wedged to the flap (like rags, plastic, etc.). Now rotate the handle and make sure the flap opens and closes fully. Sometimes the stem connecting the inside valve flap and handle breaks and although the handle moves to the open and closes position easily, the flap inside may not be opening fully.
    Break-out of the tank suction line demonstrating how to deal with debris in the flap.
  3. Now that we’ve determined the pump is getting a full flow of fluid from the tank, the pump is the next step.

On Monarch pumps, remove the front cover of the pump. See that there is nothing inside that looks unusual. Look at the gap between the impeller and the volute face. If the gap is 1/8 of an inch or more, the impeller needs to be shimmed or replaced. Follow the instructions in the manual for this. If all this is OK, then reinstall the front cover and move on to the next step.

On a Gorman Rupp pump, remove the suction flange from the pump casing and check the gap between the impeller and the wear plate. If the gap is 1/8” or more the impeller needs to be shimmed or replaced. Follow the instructions in the manual for this. Remove the pump casing and look for anything inside which may be obstructing the impeller.
     
    Break-out of modified Gorman Rupp pump to demonstrate obstruction to the impeller.
     
  4. Remove and clean / check the filter shear. Reinstall
     
    Patented technology shear filter break-out demonstrating how to check and clean the shear filter.
     
  5.  Remove the Tee and venturi from under the hopper. Check that there is nothing stuck inside of the venturi and nozzle like a bag knife or a water bottle cap. Clean any old build-up inside of the Tee. Reinstall all the components. 
     
    Break-out of the Tee and venture demonstrating the place to look for obstructions. 
     
  6.  Fill tank back up with water, make sure pump is primed (open hopper valve to remove air) and start engine / motor. With the engine at full speed, open the hopper valve and the water should be flowing through the nozzle with little spray back and a roaring sound. 
 
STS offer their product line on a lease basis. You can get the best mixer in the HDD industry on a lease
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