In chapterDTH Drilling Care & Maintenance – Part One, we introduced following topics:

  • A balanced system
  • Correct drilling parameters
  • Most commoncausesofproductfailures
    • Corrosion
    • Fatigue
    • Galling

In this chapter, the discussion will be continued and following items will be explained:

  • Lubrication
  • Hammer disassembly
  • Drill pipes


  • Correct lubricationduring DTH drillingis extremelyimportant
  • Inadequate lubricationisamajorcause ofhammerwearandfailure
  • Excessive lubricationslowsdownthe pistonandmakesstartupdifficult
  • Use rock drill oil only
  • Modern drill rigs are provided with automatic lubrication equipment injecting oilintotheairstreamsupplied from thecompressor
  • Rate oflubricationisafunctionof hammer air consumption, which dependsonoperatingpressure, and choke size beingused
  • Joints liketopanddriversubs,pinand boxthreadsshallhaveagoodlayerof threadlubricant
  • This willpreventcorrosionandgalling and insure ease of breakout at disassembly
  • Thread lubricantshallcontainatleast 40% metalparticles


  • Hammer storage
    • Clean andlubricateallcomponentswith rockdrilloilandthreadlubricantbefore storage
  • When using foam
    • After usageclean&oilbyblowingdry lubricatedairthroughthesystemupon completionofeachholeorwhennotin use for threehours
  • Water injection or in wetholes
    • Never leavehammerinholeunder. Inspectandserviceevery100hours
  • Periodically test water
    • pH factorabove7
    • No chlorides or sulfides

  • At frequent intervals
    • Re-coat topanddriversubwiththread lubricant

The gap

  • When thedriversubhasbeenscrewedintothe pistoncasewithguidesleeveandretainerring installed,agapmustbevisiblewherethepiston case and driver subjoin
  • The sizeofthegapisnotcriticalbutitshouldnot belessthan0,5mm(0.02”)andnotmorethan 1.0 mm(0.04”)
  • When thegapisatthelowerlevelitistimeto changethepistonretainer If hammer operationcontinueswithnogap,thereisahigh risk of componentfailures

Hammer Disassembly

  • Usethecorrecttoolsintherightspotstodisassemblehammers Clampingoverthreadareaswillmakedisassemblingverydifficult
  • The hammer disassembly procedure and proper tools are shown in below and the fourth picture in right is showing the damaged hammer by un-proper hammer disassembly tools and procedure.

Drill pipes

  • Make surethatdrillpipesareclean beforeaddingthemtothedrillstring
  • Use compressedairtocleantheinterior
  • All contamination indrillpipeswillend up in thehammer
  • Never use bent drill pipes

  • Inspect thelowerconnectioninthetop subtomakesurethethreadsareingood condition
  • Ifyou areputtingonanewstringorasignificant numberofnewdrillrods,anewtopsub is recommended
  • Remove threadprotectors,cleanoffand inspecttheconnectionsfordamage
  • Apply a good quality thread grease
  • Make suretheinsideofthepipeisclean, evenifthepipeisnew
  • Make andbreaktheconnectionsslowly a couple oftimes
  • If resistancetomakeandbreakistoo highbackoffandinspectforthread damageandrigalignment

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