How to use core barrel correctly to get longer drilling footage and penetration rate , operating rock core barrel fitting at kelly bar of rotary drilling rig is similar with oil well drilling, but rotary drilling rig doesn't have mud/water fluid system, rock chips can not circulated to ground. After many tests in foundation rock piling projects, we got below experiences that may help you to save cost of drilling tools, protect dynamic and hydraulic system of rotary drill rig and speed up projects process.
1.Clear Hole Bottom
Clear hole bottom before putting rock bucket into hole.Hard materials like iron may break the Tungsten Carbide Inserts(teeth).
2.Low slowly
Lower slowly before bucket touching bottom,because the bottom may not flat. If all weight is loaded by part of cutters,arms of bearing may be broken. Rotating bucket before touching bottom.
3.Pressure
Not press bucket after touching rocks. Keep low rotating speed after touching rocks. Rotating at normal speed after breaking-ring is established stably. Increase load on bucket by impulse type pressing. Make sure not overload.
4.Load of Roller Cones
Load range of 133mm roller cone bits is 3-5 tons. Operators could calculate according to quantity of roller cones, then considering weight of kelly bar and other heavy parts loading on roller cones bits. Press bucket by impulse type without overload.
5.Check after each lifting
Check the Cone-Top, Arm-Top and teeth at initial stage.
The primary teeth should wear earlier than cone body, arm-top, cone-top. Arm-top and Cone-top should not wear at initial stage.Welding problem makes wear unusual.
Check and compare wear speed of each cones.
Wear faster means the position higher/outer/inner. Welding problem makes unusual.
6.Failure handling: Teeth Fracture
Hard materials at bottom. Overload. Low grade tungsten carbide.Teeth too long.
Solutions: Clear hole bottom, reduce load, change shorter teeth.
Failure handling: Bearing Lock
Check water cooling at hole bottom. Bearing shock in lowering bucket too fast. Check overload on bucket. Bearing seal broken due to arm-top wear. Rock breaking ring too wide or too narrow. Change new cutters after lock.
Failure handling: Cone Drop
Change new cutters after worn out. Check the condition of cutters every 3 lifting to find potential failure at earliest time. Fish drooped cutters after loss.
7.Rotating speed
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Diameter of Rock Bucket(mm)
|
Bucket-RPM(Lower Limit)
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Bucket-RPM(Upper Limit)
|
|
800
|
13
|
27
|
|
1000
|
10
|
21
|
|
1200
|
9
|
18
|
|
1400
|
7
|
15
|
|
1600
|
6
|
13
|
|
1800
|
6
|
12
|
|
2000
|
5
|
10
|
|
Note:
1>Bucket-RPM is calculated according to RPM of single roller cones. RPM of single roller cones ranges from 50 to 100.
2>Load of each single roller cones is 3-5 tons, upper-load and upper-RPM can not be used at the same time.
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