Produces and sells various types of drilling rig matching accessories, which can also be customized according to your needs.
The Selection of the Drilling Parameters
Influence Factors of Rotary Speed
When deciding the specific peripheral velocity of bits, in addition to bit type and bit diameter, other factors such as rock properties, diamond sizes, drilling equipment and core barrels, drilling depth and the structure of drilling holes, should be considered also.
a
Bits Type:
The natural diamond grains on surface set core bit are large and self-sharpening easily, in order to protect the exposed diamond grains, the rotary speed of surface set core bit should be lower than the impregnated core bit.
b
Bit Diameter:
In order to reach a proper linear velocity, the rotary speed of the small diameter bit should be higher than the big diameter bit.
c
Peripheral Velocity:
From the formula of rotating speed, we can find the liner velocity is proportionate to the rotating speed. it means the higher speed of the liner velocity, rotating speed is accordingly higher.
d
Rock Properties:
High rotary speed is suitable for medium hard, complete rock formations; In broken, fractured, mixed formations, with high vibration when drilling, drillers should slow down the rotary speed according to the broken level of the rock; in the soft formations with high drilling efficiency, in order to keep cooling and carry out the cuttings, the penetration speed needs to be limited, as well as the rotary speed.
e
Diamond Sizes:
The larger the diamond size, the quicker the self-sharpening. To avoid the bit face chipped or cracked, the rotary speed of the bits with big diamonds should lower than the bits with small diamonds.
f
Drilling Equipments and Core Barrels:
When the drilling machine is with poor stability and the drill rods have a low intensity, correspondingly, the rotary speed should be slowed down. If the lubricants or other similarities for decreasing the vibration are adopted, the rotary speed could be raised.
g
Drilling Depth:
when the depth of the drilling hole becomes deep, the weight of the core barrels will be larger, the pressure situation is more complex it takes larger power while rotating the core barrels. Hence, in the deep hole, because of the limit of the power and intensity of the core barrels, the rotary speed should be decreased; in shallow hole, conversely.
h
Structure of Drilling Holes:
High rotary speed can be used in the condition that the borehole structure is simple and the clearance between the drill rods and borehole wall is small. On the contrary, the drilling hole with a complex situation, lots of changeable diameters, big space between the drill rods and borehole wall, it causes poor stability and can't use the high rotary speed.
The following are some pictures of core drilling rig accessories：
Frequently Asked Questions
Q:
How does the bit type affect the choice of rotary speed?
Natural diamond grains on surface set core bits are large and self-sharpen easily. To protect these exposed grains, the rotary speed should be set lower compared to impregnated core bits.
Q:
Why do smaller bit diameters require higher rotary speeds?
To achieve a proper linear (peripheral) velocity, smaller diameter bits must operate at a higher rotary speed than larger diameter bits.
Q:
How should rotary speed be adjusted for different rock properties?
High rotary speed is suitable for medium hard, complete rock formations. In contrast, broken, fractured, mixed, or soft formations require lower rotary speeds to reduce vibration, maintain cooling, and properly manage penetration and cuttings.
Q:
Does diamond size impact the recommended rotary speed?
Yes. Larger diamond sizes self-sharpen more quickly. To prevent the bit face from chipping or cracking, bits with larger diamonds should be run at lower rotary speeds than those with smaller diamonds.
Q:
Why must rotary speed decrease as the drilling depth increases?
Deeper holes mean heavier core barrels and more complex pressure situations, which require more power. Due to the power limits and intensity limitations of the core barrels in deep holes, the rotary speed should be decreased.
Q:
How does the structure of the drilling hole influence the rotary speed selection?
High rotary speed is appropriate for simple borehole structures with small clearances between the drill rods and the wall. Complex structures with variable diameters or large clearances cause poor stability, making high rotary speeds unsafe.
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