DRILL RODS
DRILLROD |
O.D. |
I.D. |
WEIGHT 10 FOOT ROD |
ROD RADIUS |
DRILL ROD DRAG FACTOR |
DRILL ROD DRAG COMPARED TO BQ (PERCENT) |
|---|
AQTK |
1.760 |
1.470 |
24.000 |
0.880 |
21.120 |
46% |
|---|---|---|---|---|---|---|
ATW |
1.750 |
1.440 |
26.000 |
0.875 |
22.750 |
50% |
BTW |
2.230 |
1.910 |
34.500 |
1.115 |
38.468 |
84% |
BQTK |
2.188 |
1.910 |
32.000 |
1.094 |
35.000 |
76% |
BQ |
2.188 |
1.810 |
42.000 |
1.094 |
45.938 |
100% |
NTW |
2.880 |
2.530 |
50.500 |
1.440 |
72.050 |
158% |
NQ |
2.750 |
2.380 |
52.400 |
1.375 |
72.050 |
157% |
HTW |
3.580 |
3.210 |
67.800 |
1.790 |
121.362 |
264% |
HQ |
3.500 |
3.060 |
76.900 |
1.750 |
134.575 |
293% |
PQ |
4.500 |
4.000 |
117.000 |
2.250 |
263.250 |
573% |
This chart uses the dimensions and weights of the various drill rods to predict how much torque is required to turn the different sized drill rods. (in proportion to other sized drill rods). The frictional drag is assumed to be proportional to the weight of the rod times the radius of the dragging surface of the rod.
The chart shows that it will take about half as much torque to turn an A size rod string as a B sized one. This does not mean it will take half the horsepower, because an A rod string usually has to turn faster as well.
The chart predicts that it will take 24% less torque to turn a BQTK rod string as a BQ one, because of the lighter weight. While NQ only takes about 57% more torque than BQ it is amazing that HQ will probably take almost three times the torque of BQ.
I realize that often the drag from the drill string can be cut in half just by greasing the rods, but this chart might I think give an idea of the amount of drag from different rod sizes.
Nigel Spaxman