Symmetric Casing Drilling System

The Symmetric Casing Drilling System consists of three parts: central pilot bit, casing shoe and symmetrical ring bit. The central pilot bit drills away the center part of the hole and guides the drill string, incorporated with a sacrificable symmetrical ring bit make a full face drill bit. The casing shoe is welded or threaded to a casing pipe, which is pulled down by the impact of the DTH hammer and central pilot bit. The symmetrical ring bit and casing shoe assembly is locked into central pilot bit with a hammer shank, and the ring bit is to drill the segment the casing to advance down the hole. The pilot bit’s upper shoulder engages the shoulder of the casing shoe.

DTH hammer’s impact energy is transferred through the pilot and ring bits, crushing rock, part of impact energy advances casing. On completion of drilling and casing, the drill string with pilot bit is retrieved by a slight reverse rotation to unlock the bayonet coupling. The ring bit stays in the hole, and can be recovered only if the casing is retrieved. Drilling continues to the desired depth in the bedrock using a conventional drilling.

Symmetric Casing Drilling System Features and Advantages:

1. 1)      Stable and reliable working performance

2. 2)      Full face head design for faster penetration and straighter hole

3. 3)      Less torque is required than eccentric drilling

4. 4)      Can drill in vertical, horizontal or any direction

5. 5)      Minimize disruption to the drilled hole

6. 6)      Effective cuttings removal

7. 7)      Unlocking-relocking easily

8. 8)      Easy to operate and system security

9. 9)      Varied ring bit diameters to suit different casing requirement

10. 10)   The less vibration of drill rig