IADC Tricone Bit Classification Codes System
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IADC Tricone Bit Classification Codes System

2023-01-03

IADC Tricone Bit Classification Codes System

IADC Tricone Bit Classification Codes System

The IADC roller cone drilling bit classification charts are often used to select the best bit for a particular application. These charts contain the bits available from the four leading manufacturers of bits. The bits are classified according to the International Association of Drilling Contractors (IADC) code.  The position of each bit in the chart is defined by three numbers and one character. The sequence of numeric characters defines the “Series, Type and Features” of the bit. The additional character defines additional design features.

IADC CODE REFERENCE

First Digit:

1, 2 and 3 designate Steel Tooth Bits, with 1 for soft, 2 for medium and 3 for hard formations.

4, 5, 6, 7 and 8 designate Tungsten Carbide Insert Bits for varying formation hardness with 4 being the softest and 8 the hardest.

Second Digit:

1, 2, 3 and 4 help further breakdown the formation with1 being the softest and 4 the hardest.

Third Digit:

This digit will classify the bit according to bearing/seal type and special gauge wear protection as follows:

1.Standard open bearing roller bit

2.Standard open bearing bit for air drilling only

3.Standard open bearing bit with gauge protection which is defined as

carbide inserts in the heel of the cone.

4.Roller sealed bearing bit

5.Roller sealed bearing bit with carbide inserts in the heel of the cone.

6.Journal sealed bearing bit

7.Journal sealed bearing bit with carbide inserts in the heel of the cone.

Fourth Digit/Additional Letter:

The following letter codes are used in the fourth digit position to to indicate additional features:

A -- Air application

B -- Special Bearing Seal

C -- Center Jet

D -- Deviation control

E -- Extended Jets

G -- Extra gauge protection

H -- Horizontal Application

J -- Jet Deflection

L -- Lug Pads

M -- Motor Application

R -- Reinforced welds

S -- Standard Tooth Bit

T -- Two Cone Bits

W -- Enhanced Cutting Structure 

X -- Chisel Insert

Y -- Conical Insert

Z -- Other insert shape 

The terms “soft” “medium” and “hard” formation are very broad categorizations of the geological strata which is being penetrated. In general, the rock types within each category can be described as follows: 

Soft formations are unconsolidated clays and sands.

These can be drilled with a relatively low WOB (between 3000-5000 lbs/in of bit diameter) and high RPM (125-250 RPM). 

Large flow rates should be used to clean the hole effectively since the ROP is expected to be high.

Excessive flow rates however may cause washouts (check drill pipe washouts). Flow rates of 500-800 gpm are recommended. 

As with all bit types, local experience plays a large part in deciding the operating parameters.

Medium formations may include shales, gypsum, shaley lime, sand and siltstone. 

Generally a low WOB is sufficient (3000-6000 lbs/in of bit diameter). 

High rotary speeds can be used in shales but chalk requires a slower rate (100-150 RPM). 

Soft sandstones can also be drilled within these parameters. 

Again high flow-rates are recommended for hole cleaning

Hard formations may include limestone, anhydrite, hard sandstone with quartic streaks and dolomite. 

These are rocks of high compressive strength and contain abrasive material. 

High WOB may be required (e.g. between 6000-10000 lbs/in of bit diameter. 

In general slower rotary speeds are used (40-100 RPM) to help the grinding/crushing action. 

Very hard layers of quartzite or chert are best drilled with insert or diamond bits using higher RPM and less WOB. Flow rates are generally not critical in such formations. 


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