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Life time of drill stem

Home Forums Coking Operations Cutting, Drilling, Unheading Drilling Drilling Equipment Life time of drill stem

This topic contains 4 replies, has 2 voices, and was last updated by  Anonymous 12 years ago.

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  • #4009


    We have found that the outside diameter of the drill stem became smaller after four years of running.
    We would like to know the typical life time of drill stem.

  • #7354


    drill stems have a varied life.  They usually fail due to “bending” while drilling and getting caught in a “coke bed that moves”.  Sometimes these are straightened and reused but often just replaced.  Drill stems have also failed due to corrosion at the treaded area.  this is caused most often by high PH water.  Adjust the water, replace the section and that usually does the job.  There have been a few failures in our industry due to poor manufacturers design or production.  the drill stem threads are not cut “deep” enough.   I have not heard of drill stems losing dia to the point they fail or must be replaced except maybe a very rare case.  Sounds like “erosion”.
    I would ensure the metallurgy is correct and that they are being manufactured correctly.  Check the water PH and trend for 6mo.
    Jim Blevins – Chevron

  • #6271


    I don’t have any data on drill stem life.  I do know that several refiners keep a few spare middle sections of drill stem and the top and bottom sections with the flanges or unibolt to minimize the downtime to replace a broken drill stem.  I would wonder if your drill stem guide lacks lubrication or has some sort of defect.  I have heard about more failures due to bending (especially for welded CS stems), and breaking (typically for 4140 threaded stems) during coke bed collapses. 
    Is the drill stem still relatively straight?  If not it may be getting excess bending force applied to it during cutting cycles.  I would also question the type of drill stem guide that you are using. If the reduced diameter is only noticable in a single drill stem for a short span then I would further question how true the stems are.  If the wear is not localized, then I would not suspect a bent drill stem.
    I hope this helps,
    Chris Hackler

  • #5596


    no doubt threaded drill stems are the replacement of the old welded style drill stems. The higher strenght, better corrosion resistance, easier installation, handling and storage are some of the advantages over the old style. The longest reported and witnessed is in COP-Carson four drums were installed in 1982 aprox. and there is still one set running. Short runs may be two years and average is between 5 to 8 years. Also infant mortality can happen due to wrong installation, carefull clean of the threads and proper lubricant must be apply. I t may be a good idea to have the hydraulic torquing machine but not one per facility, better to be a share resource with several facilities.

  • #5331

    Claus Graf

    Five to eight years is a good number. Definetively would change complete after the 10 year mark. If you have an old drillstem and starts leaking at any threaded joint, complete failure may be only minutes away.
    If considering a hydraulic torquing machine, make sure your cutting deck has enough space available to position the tool above the drum. If you have a top unheading device, like a Delta Valve or Z&J, access might be limited. 

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