IADC Dull Grading System

Daily Operations > Drillstrings Section > Components Tab - Bits

The IADC Dull Grading System allows for detailed recording bit performance of pulled bit condition. This system allows the user to note the physical condition of a bit for bit performance evaluation.

IODL
	I	Inner Rows	Linear Scale
	O	Outer Rows	Linear Scale
	D	Dull Characteristics	Dull Characteristic Codes Table
	L	Location	Location Codes Table
BGOR
	B	Bearing Seals	Bearings/Seals Codes Table
	G	Gauge
	O	Other Characteristics	Dull Characteristic Codes Table
	R	Reason for Pulling Bit	Reason Pulled Code Table

Linear Scale

A linear scale from 0-8 is used to record the amount of cutting structure wear on the Inner and Outer Rows of teeth. An 8 means that there is no usable cutter left, 0 means that there is no wear and a 4 would denote 50% wear on the teeth. When grading a dull bit, the average amount of wear in each area should be recorded. Calculate the Inner Row by averaging the grades of all the individual cutters in the area. For example, if there are five cutters in the inner area graded as follows:

Cutter 1 = 4; Cutter 2 = 4; Cutter 3 = 5; Cutter 4 = 7; Cutter 5 = 8

The Inner Rows (I) field is calculated as follows:

(4 + 4 + 5 + 7 + 8)/5 = 5.6

See Inner Rows, Bit Component topic.

See Outer Rows, Bit Component topic.

Dull Characteristics Codes Table

Use the following codes in the Dull Characteristics (D) and Other Characteristics (O) fields:

BC*	Broken Cone	LC*	Lost Cone
BT	Broken Teeth/Cutters	LT	Lost Teeth/Cutters
BU	Balled Up	OC	Off-Center Wear
CC*	Cracked Cone	PN	Plugged Nozzle/Flow Passage
CD*	Cone Dragged	RG	Rounded Gauge
CI	Cone Interference	RO	Ring Out
CR	Cored	SD	Shirttail Damage
CT	Chipped Teeth/Cutters	SS	Self Sharpening Wear
ER	Erosion	TR	Tracking
HC	Heat Checking	WO	Washed Out - Bit
JD	Junk Damage	WT	Worn Teeth/Cutters
LN	Lost Nozzle	NO	No Major/Other Dull Characteristics
*Show Cone Number(s) Under Location.

See Dull Characteristics, Bit Component topic.

See Other Characteristics, Bit Component topic.

See Location, Bit Component topic.

Location Code Table

Use the following codes to describe the location of the cutting structure's Dull characteristic.

C	Cone	G	Gauge
N	Nose	A	All Areas
T	Taper	M	Middle Row
S	Shoulder	H	Heel Row

See Location, Bit Component topic.

Bearing/Seals Code Table

Use the following codes to describe the condition of the bearings or seals.

Non-Sealed Bearings
0	No Life Used
8	All Life Used
Sealed Bearings
E	Seals Effective
F	Seals Failed
No Bearing
X	Fixed Cutter Bit

See Bearing Seals, Bit Component topic.

Reasons Pulled Code Table

Use the following codes to describe the reason the bit was pulled.

BHA	Change Bottomhole Assembly	FM	Formation Change
DMF	Downhole Motor Failure	HP	Hole Problems
DSF	Drillstring Fatigue	HR	Hours
DST	Drill Stem Failure	PP	Pump Pressure
DTF	Downhole Tool Failure	PR	Penetration Rate
LOG	Run Logs	TD	Total Depth/CSG. Depth
RIG	Rig Repair	TQ	Torque
CM	Condition Mud	TW	Twist-Off
CP	Core Point	WC	Weather Conditions
DP	Drill Plug	WO	Washout-Drillstring

See Reason for Pulling Bit, Bit Component topic.