Table 3
The errors in the different approaches to calculating dynamic hanging loads on polished rod in Sanjiao coalfield.
| Stroke | Measured total load F′ (kN) | API method |
Schafer’s method |
Gibbs’s method |
The proposed method |
||||
|---|---|---|---|---|---|---|---|---|---|
| Calculated total load F (kN) | Error E (%) | Calculated total load F (kN) | Error E (%) | Calculated total load F (kN) | Error E (%) | Calculated total load F (kN) | Error E (%) | ||
| Upstroke | 27.12 | 31.07 | −14.56 | 29.95 | −10.41 | 31.75 | −17.06 | 27.46 | −1.25 |
| 27.43 | 30.04 | −9.52 | 29.45 | −7.35 | 30.96 | −12.86 | 27.69 | −0.95 | |
| 28.88 | 29.29 | −1.42 | 29.09 | −0.72 | 30.10 | −4.24 | 28.98 | −0.35 | |
| 29.11 | 29.06 | 0.18 | 28.97 | 0.47 | 29.66 | −1.89 | 29.16 | −0.17 | |
| Downstroke | 9.37 | 12.47 | −33.08 | 12.58 | −34.30 | 9.24 | 1.41 | 9.26 | 1.17 |
| 10.58 | 12.96 | −22.50 | 13.02 | −23.09 | 9.48 | 10.36 | 10.48 | 0.99 | |
| 11.37 | 13.31 | −17.06 | 13.34 | −17.30 | 9.75 | 14.25 | 11.32 | 0.45 | |
| 11.74 | 13.42 | −14.31 | 13.43 | −14.44 | 9.89 | 15.77 | 11.71 | 0.30 | |