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Key design features for optimum performance are:

  1. Cutting Structure
  2. Bearing Design
  3. Shirttail Protection
  4. Gauge Protection
  5. Air Circulation System
  6. Back Flow Valve
  7. Carbide Insert Profiles 

tricone drill bit pic

 

Design of Cutting Structure:

Cutting Structure is designed to suit drilling condition. Governing design parameters for designing a new cutting structure are:

1. Carbide Insert

a. Top Profile
b. Bottom Profile
c. Size
d. Projection
e. Grip Length
f. Spacing Width
g. Number of Inserts
h. Carbide Grade

2. Number of Rows
3. Bearing offset
4. Intermesh groove clearance

 

rock roller bit desgin pic

 

Cutting Structure is designed for optimum results in the field, by eliminating tracking and off center rotation and also to provide a fast rate of penetration, high durability and long bit life.

 

Bearing Design

There are two basic bearing designs used in construction of air bearing rock roller bit.

  1. Roller Friction Ball Bearing
  2. Double Roller Ball Bearing

bearing design

 

Gauge Protection

Bit gauge and heel area is well protected with wear resistant gauge insert. Gauge inserts are strategically placed on gauge surface of the cone and are extended out from steel surface to assist the heel row and also trim the bore hole wall to maintain full gauge hole. In abrasive application where gauge rounding takes place double gauge is used.

  1. Single Gauge
  2. Double Gauge

Gauge Protection

 

Shirttail Protection

To Protect the shirttail under high abrasive applications, extremely wear resistant hard facing is applied on leading edge and tungsten carbide are added to protect the leg wear. Customized shirttail layout is decided based on drilling condition.

  1. Only Shirttail Hard Facing
  2. Only Shirttail Inserts
  3. Combination of shirttail hard facing and shirttail inserts

Shirttail Protection

 

Air Circulation System

Importance of air circulation system is to clean the hole, cool the bearing and carry the cutting out. Air pressure is critical for bottom hole cleaning. Pressure drop across the bits should be maintain a excess of 30 psi. General thumb rule is for every 100 feet depth there will be 10 psi of pressure loss. For optimum bit life nozzle should be selected to hold the pressure near maximum. In order for the drill bit to perform at its best and have excellent rate of penetration always the bottom of hole should be clean. Air velocity is one which moves the cutting out from the bottom. General thumb rule is a velocity between 5000 to 8000 feet per minute is optimum for cleaning the hole. From simple formula Q=AV, we can determine what volume of air (Q) is necessary to give desired velocity (V) for give annular area (A)

Air Circulation System1

 

Nozzle configuration is such that the air is directed between the cones towards the corner of bore wall and bottom hole. With this configuration all energy is focused directly on formation and cleans the gauge and multiple inner rows of the cone.

Air tube configuration is such that it supplies equal volume of air to bearing for cooling.

 

Back Flow Valve

The valve operates during drilling process, as air flows into the bit shank the valve plates and return spring are moved down by the air allowing the air inside. When the air flow stops the valve plates is returned to its original position by the return spring and is in close position. This ensures that bearing does not contaminate due to reverse flow.

Back Flow Valve

 

Carbide Insert Profile

Carbide insert profile designed by exploding individual attributes like bottom profile, top profile, profile shape, grip length, projection, various radii and angles. Each attribute is tested and fine tuned to give the best drilling result with minimum insert breakage and wear. Proprietary insert grades are used for higher durability, aggressive cutting, reduce the cone shell erosion and keeps the bit for longer runs.

Tougher and wear resistant insert are designed such that maximum material removal rate attained per revolution of tooth to achieve higher penetration rate.

 

Different Sample Profiles

Different Sample Profiles

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Branch Locations:

  • Witbank (Head Office)
  • Pretoria (Drill Tools Division)
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  • Mozambique LTD
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