Also, the angle at the top of the plunger has been reversed to force sand inward as opposed to outward in the conventional design. Essentially, we have eliminated the funnel, wedge and moved the 60 thousands gap to the bottom of the plunger. Now, the top of the plunger has only a 2 or 3 thousands clearance between the plunger and pump barrel as opposed to the 60 thousands in the conventional design. The likelihood of sand getting between the plunger and pump barrel is slim to none. The plunger now acts like a scraper, cleaning off the pump barrel wall and throwing sand inward as opposed to outward and acting as a giant wedge. The Farr plunger can operate on POC's and timers. When the sand settle out of solution, it falls inside the plunger, rather than on top. With the sand inside, the plunger is free to move upward as the pumping unit starts up. On the first down stroke of the unit, the sand will be flushed out of the plunger and be put back into solution.

The Farr design will not stop your real sand wells from sanding up. If you are producing large quantities of sand, you will still sand up. But, on wells that produce small amounts of sand, you can operate on POC's and timers without sanding up or sticking the plunger. The rule of thumb is: if the volume of sand, which settles out of solution, is more than the inside of the plunger can hold, then you will sand up. If it is smaller, then you will not. Also, when the pumping unit is on, it must remain on long enough to displace the tubing volume by 110%. This way you will insure that the small sand plug, which was in the plunger, will reach the surface. Otherwise, the sand will keep accumulating in the tubing and become more than what the plunger can handle.

The connector on the top of the plunger, which connects the pull rod to the plunger, is 60 thousands smaller in diameter (OD) than the plunger itself. This connector is tapered downward and outward from where the pull rod connects. The smaller diameter allows for a gap at the top of the plunger. The taper on top of the connector creates a funnel. As the plunger moves upward, the sand (or any solids in the produced fluid) is forced down into the funnel and stuffed inside the gap. Now you have an abrasive material between the connector and the pump barrel wall. The sand will eventually migrate down between the plunger and the pump barrel wall. This abrasive material starts wearing on the two metal surfaces, creating lower and lower pump efficiencies. Eventually the pump will not pump the volumes required and will need to be pulled.

Wells which pump, even the slightest amount of sand, cannot operate with pump off controllers (POC) or timers. When sand settles out of solution on top of the plunger, it only takes a few inches of sand to stick the plunger. The angle between the pump barrel wall and the slope of the connector creates a giant wedge. As the plunger tries to move upward, after being shut down, it wedges the sand between the plunger and the pump barrel wall. The harder you try to pull the plunger upward, the tighter the sand is wedged.

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