1, Great impact on net happened during down stroke.

2, Internal exhaust valve increases down stroke speed.

3, The results showed that the down stroke in the room had been killed in pure love.

4, Deformation of helical buckling appeared on rod during down stroke is also analyzed.

5, Two different approximate functions with the up and down stroke of the piston are integrated to more accurately obtain unsteady flow velocity.

6, Both the down stroke and the up stroke are highlighted in different colors.

7, The stroke frequency can be changed and the up and down stroke will have a stable transition.

8, A counterbalance is used on most pumpers to balance the weight of oil and sucker-rod string on the upstroke and the sucker-rod string on the down stroke.

9, When wells run at one or some of the above states, and the practical down stroke axial load of the plunger is greater than the critical axial load, the wear of rod string and tubing will take place.

10, Step 2 – The material has filled the piston chamber and the piston is ready to start its down stroke.

11, The working principle and characteristics of hydrostatic transmission system with secondary regulation were introduced. The new system can match power perfectly during upstroke and down stroke.

12, The main causes of side-abrasion of a sucker rod in polymer holes are analyzed: It is due to the resistance during down stroke and normal force attached by the polymer.

13, The formula for calculating the liquid shock load in the low sinking depth wells was set up,[http:///down stroke.html] and the formula for the axial load in the down stroke of the plunger was established.

14, This technique eliminates the tube in conventional mechanical lifting, takes hollow rod as the transmission medium and oil flow channel and discharges fluid during down stroke.

15, When the pump cylinder could not be filled with enough liquid, the liquid shock will occur, and the liquid shock load will make the down stroke axial load of the plunger increase.