WorldWide Drilling Resource

50 FEBRUARY 2015 WorldWide Drilling Resource ® Dull Grading: A Simple and Effective Practice Adapted from Information Provided by rock-drill-bit.com Dull grading the condition of a rock bit when it comes out of the hole is an important but of ten over looked field operation. At many mines, the decision to change the bit is left up to the drilling professional, who is given very little guidance. This means most bits get changed after they are completely worn out and have been operating at low efficiency for an extended period of time. The operator can save a great deal of money by establishing a program of close examination and grading of used bits, and applying a few simple rules based on this information. Significantly reduced penetration rate at the end of a bit's life is inevitable when the cutting structure becomes ineffective through breakage or wear. Based on drilling practices used, bit grading provides an evaluation of the bit’s performance and dulling char- acteristics. When done as a matter of routine, this basic procedure provides data with the potential to significantly lower drilling costs and increase effi- ciency. Dull bit assessments can be made quickly, but it is important for this data to be gathered by someone with rea- sonable judgment and accuracy. Examinations include both the cutting structure and bearings. Bit l ife doesn’t have to be total ly ex- hausted before dull grading. The purpose of grading is to de- termine the condition of the dull bit, and assess what’s happening to the bit while in use. In grading a dull bit, its condition is best recorded using a simple but accu- rate code. Properly graded bits and a com- pleted bit record of the well drilled are important aspects of evaluating a drill bit's performance. Without this infor- mation, deciding how to improve per- formance is, at best, a shot in the dark. The bottom l ine: when properly collected and recorded, facts gathered from dull rock drill bits yield exception- ally valuable information about correct- ing unprofitable practices, including help choosing the right bits for specific jobs in the future. The International Association of Dri l l ing Contractors establ ished an eight-point dul l grading system so drilling professionals and bit manufac- turers can accurately evaluate a bit’s performance. The eight-point system is used on both tricones and fixed cutter bits. A complete grading chart can be found at the following Web site: http://www.rock-drill-bit.com /iadc.html#IADC DULL GRADING ~ The Centerline 7 1/2” x 10” hydraulic drive duplex mud pump ~ Fits in the place of a common 5” x 6” duplex ~ weighs 1000 lbs less ~ pumps twice the rated flow~at over twice the rated pressure ~ Centerline Manufacturing Co. 903-725-6978 ~ www.centerlinemanufacturing.com ~ Mud pumps for the 21st century ~ Monopumps models rated: 180 gpm Duplex models rated: 300 gpm Triplex models rated: 450 gpm 500 or 800 psi models available in aluminum or iron. U.S. Pat. #6,769,884 and others pending ~ Centerline mud pumps are getting the job done from Canada to Australia, China to Peru ~ Centerline Manufacturing is proud to be your complete stocking source for American Manufacturing mud pump parts!! 4< /*2'3* "& > > > > ,'< ? /2+ '6* /3+6 /3+6 ')1/3- " " !8=2+ /7843 4* 4* ')1/3- !+8 5)7 !8'3*'6* $'2:+ 9((+6 6':+2 $'2:+ 9((+6 !+'87 9((+6 $'2:+ 37+687 #6+8.'3+ $'2:+ 37+687 $'2:+ !56/3- ! ! $'2:+ 4:+6 '71+8 ? !;/:+2 ')1/3- ? !+6/+7 ? !+6/+7 ? !+6/+7 ? !+6/+7 ? !+6/+7 ? !+6/+7 < /3+6 < /3+6 < /3+6 < /3+6 < /3+6 6/)+7 !9(0+)8 "4 .'3-+ %/8.498 48/)+ !@ @ < < < < < “Act as if what you do makes a difference. It does.” William James