NORMAL PUMP OPERATION

As the plunger begins to travel downward, it attempts to compress the fluid, which is non-compressible; thus causing pressure within the closed chamber, which pushes against the bottom of the traveling valve ball, exerting a force to open the ball. When this force is great enough to exceed the force pushing on the traveling valve ball from the fluid column above the pump, the traveling valve ball opens. As the plunger continues downward, the fluid within the chamber escapes through the open traveling valve into the column of fluid above the pump.

FLUID POUND - WHAT HAPPENS

Once again, we have observed that in the real world, "normal" pump operation is unusual and when it does happen, it does not continue for long. Another one of the common occurrences which prevent normal operation is the partial filling of the pump with gas instead of completely filling the pump with liquid. Immediately before the impending fluid pound strike, the plunger of the pump is in the up position and begins to move downward. Moving downward with the plunger are the rod string and the pumping unit mechanical system. All of which have mass and momentum.

Within the pump barrel, is some gas and some liquid. The gas, being lighter than the liquid, floats on the liquid; therefore, it is above the liquid. As the plunger begins its downward travel into the barrel of the pump, it travels only through gas. The gas is compressible and presents no opposition to the falling plunger and rod string mass. The falling plunger and rod string mass travel virtually unopposed toward the liquid in the lower portion of the pump barrel. The traveling valve remains closed due to the greater force from the above liquid column within the production tubing compared to the small force presented by the gas pressure against the very small area of the traveling ball valve within the seat. No gas or liquid is escaping yet from the closed volume within the pump because the traveling valve is still closed.

Eventually, the falling plunger meets the liquid, which is incompressible, and instantly stops. The plunger stops, the rod string attempts to stop, but actually compresses like a spring, snaking and bending within the tubing all of the way up to the surface. Meanwhile, the pumping unit attempts to continue in the downward direction, but instantaneously it can not. The mass of the fluid above the traveling valve ball stopping instantaneously causes the traveling valve ball to seal even more tightly during this instant. The liquid, by nature, can not be compressed. All of these forces come together to oppose one another during an instant. These forces are called transients. And this instant is repeated on every stroke...until something breaks. During observations of many such situations, the resulting fluid pound shattered or cracked steel traveling balls of up to 2 1/4" in diameter, broke ball cages in all directions, and caused "rod shock", which breaks rod strings, particularly those having hydrogen embrittlement due to H2S in the well. These cracked balls and broken cages were collected and are available for examination upon request. All of these things occurred simply because the traveling valve was not opened when it should have been.

DARTT® VALVE - THE CURE FOR FLUID POUND

What went wrong in the "fluid pound" cycle? Again, once we identify what went wrong, we can work to fix it. Well, what went wrong was that the gas within the pump did not present sufficient force to the underside of the traveling valve to open it as it would have opened had the pump been full of fluid. So, to fix the problem, we must open the traveling valve every time the plunger begins its downward stroke and keep it open throughout the entire downward stroke.

What would logically work to prevent this problem would be a device of some sort which would positively open the traveling valve immediately upon the plunger beginning the down stroke and which would positively keep the traveling valve open throughout the entire down stroke.

Positively opening the traveling valve in the down stroke would prevent the instantaneous shock of attempted fluid compression within the pump in the down stroke. Instead this would allow the fluid within the pump to simply leave the pump normally into the production tubing above the pump.

Since pressure is presented in pounds per square inch, the force which the pressure exerts against the traveling valve to open it should logically be increased if one were to cause the natural pressure within the pump to push against an area which is larger than the small area within the seat below the traveling valve, and then use this larger force to force the ball to open. The DARTT® VALVE makes use of this simple principle of hydraulics, the pressure pushing against a larger area to make a larger force, to positively force the traveling valve to open every time the plunger begins its down stroke. The DARTT® VALVE keeps the traveling valve open with this force throughout the entire down stroke. Thus, the simple addition of the DARTT® VALVE to the pump eliminates fluid pound. The net result is reduced in stress on the traveling valve ball, reduced stress on the sucker rods, smoother strokes, longer pump life, fewer sucker rod failures, fewer tubing leaks, fewer pumping unit gear box failures, and lower overall maintenance costs.

Note that with the DARTT® VALVE, the practice of "tagging the pump" in an attempt to jar the ball off of the valve seat are not needed; therefore, the maintenance costs caused by the violent forces set in motion during pump tagging are eliminated. Historically, the operator is reprimanded for not making production. The operator is also reprimanded for tagging the pump. So if the operator has to tag the pump to get production, he cannot tell this to his supervisor. Communication on this topic is suppressed for obvious reasons. Of course tagging the pump puts more stress on the rods, tubing, gear boxes, etc..

One might ask: Where did the gas come from which caused the fluid pound in the first place?

Field investigations have shown that the gas comes from four main sources:

1. Gas from the formation coming into the pumping chamber

2. Gas formed from the "light ends" of the production fluid being exposed to the relative vacuum within the pumping chamber during the up stroke of the plunger.

3. Gas formed from the "light ends" of the production fluid being exposed to the relatively high-temperature of the pump barrel which has been in contact with the moving plunger.

4. Gas formed by the constant movement of the plunger in the barrel which causes gas to break out of solution (similar to that observed after shaking a bottle of soda pop).

Observation of these gas sources shows that there is little, if any, that even the most experienced operator can do to eliminate these gases. The best thing that the operator can do is to be ready to deal with them. The DARTT® VALVE is the very best tool available today to deal with these inescapable realities.

||Brochure| Valve | Gas Lock | Fluid Pound | Heavy Crude | Information | Periodicals | Testimonials | Installation | New Products | FAQ's | Contact Us | Home ||