Beam pumping unit with geometry optimized for bearing stress reduction
A pump jack includes a number of standard components that have been sized and configured according to unique relative dimensions to produce a pump jack that reduces structural stress, increases bearing life and permits a lower cost of manufacture. These geometric ratios can be used to express the relative size and spacing of the crankshaft, crank arms, center bearing, equalizer bearing, walking beam and pitman arms. Pump jacks incorporating one or more of these geometric ratios can be sized and scaled for a variety of pumping applications.
1. A pump jack configured to raise and lower a polish rod, the pump jack comprising:
a crankshaft;
crank arms connected to the crankshaft, wherein the crank arms provide a maximum throw length “R”;
a samson post, wherein the samson post supports a center bearing that is spaced from the crankshaft at a total distance “K” and at a horizontal distance “I”, wherein the ratio of the distance “K” between the center bearing and the crankshaft to the maximum throw length “R” of the crank arms is about 3.3;
a walking beam pivotably supported by the center bearing on the samson post;
an equalizer bearing assembly on a rear end of the walking beam spaced at a distance “C” from the center bearing;
a horsehead on the front end of the walking beam, wherein the horsehead is connected to the polish rod at a horizontal distance “A” from the center bearing;
pitman arms connected between the crank arms and the equalizer bearing assembly, wherein the pitman arms have an effective length “P”; and
wherein the ratio of the horizontal distance “A” between the center bearing and the polish rod to the maximum throw length “R” of the crank arms is between about 1.1 and 4.0.
2. The pump jack of claim 1 , wherein the ratio of the horizontal distance “A” between the center bearing and the polish rod to the maximum throw length “R” of the crank arms is about 2.2.
3. The pump jack of claim 1 , wherein the ratio of the horizontal distance “I” between the center bearing and the crankshaft to the maximum throw length “R” of the crank arms is between about 1.8 and 2.2.
4. The pump jack of claim 3 , wherein the ratio of the horizontal distance “I” between the center bearing and the crankshaft to the maximum throw length “R” of the crank arms is about 1.9.
5. A pump jack configured to raise and lower a polish rod, the pump jack comprising:
a crankshaft;
crank arms connected to the crankshaft, wherein the crank arms provide a maximum throw length “R”;
a samson post, wherein the samson post supports a center bearing that is spaced from the crankshaft at a total distance “K” and at a horizontal distance “I”;
a walking beam pivotably supported by the center bearing on the samson post;
an equalizer bearing assembly on a rear end of the walking beam spaced at a distance “C” from the center bearing;
a horsehead on the front end of the walking beam, wherein the horsehead is connected to the polish rod at a horizontal distance “A” from the center bearing;
pitman arms connected between the crank arms and the equalizer bearing assembly, wherein the pitman arms have an effective length “P”, wherein the ratio of the effective length “P” of the pitmans to the maximum throw length “R” of the crank arms is between about 2.5 and 2.8; and
wherein the ratio of the horizontal distance “A” between the center bearing and the polish rod to the maximum throw length “R” of the crank arms is between about 1.1 and 4.0.
6. The pump jack of claim 5 , wherein the ratio of the effective length “P” of the pitmans to the maximum throw length “R” of the crank arms is about 2.7.
7. A pump jack configured to raise and lower a polish rod, the pump jack comprising:
a crankshaft;
crank arms connected to the crankshaft, wherein the crank arms provide a maximum throw length “R”;
a samson post, wherein the samson post supports a center bearing that is spaced from the crankshaft at a total distance “K” and at a horizontal distance “I”;
a walking beam pivotably supported by the center bearing on the samson post;
an equalizer bearing assembly on a rear end of the walking beam spaced at a distance “C” from the center bearing, wherein the ratio of the distance “C” between the equalizer bearing assembly and the center bearing to the to the maximum throw length “R” of the crank arms is between about 1.7 and 2.0;
a horsehead on the front end of the walking beam, wherein the horsehead is connected to the polish rod at a horizontal distance “A” from the center bearing;
pitman arms connected between the crank arms and the equalizer bearing assembly, wherein the pitman arms have an effective length “P”; and
wherein the ratio of the horizontal distance “A” between the center bearing and the polish rod to the maximum throw length “R” of the crank arms is between about 1.1 and 4.0.
8. The pump jack of claim 7 , wherein the ratio of the distance “C” between the equalizer bearing assembly and the center bearing to the to the maximum throw length “R” of the crank arms is about 1.9.