Stand-Off Gap Excessive or Does Not Close Upon Minimal Make-Up or Difficulty Breaking Out
* Clean and inspect threads for excessive foreign or wear debris.
* Accelerated wear may be due to damaged accessories - inspect accessories (e.g. adapter subs).
* Rods of different manufactur are to be separate and do not interchange these rods.
* Threads are deformed from overload or excessive load during make and break. Inspect string for damage and discard rods with deformed threads. Overload or difficult breaking may be due to poor choice of thread compound (see lubrication and cleaning and break-out).
* Deformation due to hammering damage (see break-out) or stabbing damage (see stabbing).
* Inspect string and discard damaged rods.
Fatigue Failures or Cracked Pins or Boxes (See Fatigue Strength)
* Extraneous hoop stresses (see glossary) caused by deformation due to hammering damage (see break-out), stabbing damage (see stabbing), excessive foreign debris, or wear debris in the joint (see thread wear).
* Box shoulder deformed due to overload leaving pin or box unsupported. Overload may be due to poor choice of thread compound(see lubrication and cleaning). Consider upgrade to AU rods.
* Bend stresses have exceeded the fatigue strength of the joint. Bend stresses are caused by excessive steering, excessive hole deviations or caves, or helical whirling (see midbody wear). Do not exceed deviation ratings. This may have been compounded by high pullback loads at depth or excessive make-up. Plan deviations to occur at portions of the string that are under low pullback(e.g. avoid the upper portion of a deep hole string).Fatigue strength may have been exceeded in previous application and joint has now reached limit (see memory and fatigue strength).
* Rods run in loose (joints not closed) due to insufficient make-up or to excessive stand-off gap (see causes of excessive stand-off).
* Box wear life exceeded. Inspect string for excessive wear (see wear life).
* Rods string has suffered from hydrogen embrittlement (see glossary). Replace rod string and use non-metallic thread compound.
* Rods are of different manufacture. Separate all rods by manufacturer and do not interchange.
Leakage (See Fluid Seal)
* Box bulging due to excessive hoop stresses (see glossary) imposed by thread, potentially from overload.
* Evident by polished areas on one side of box or thread jumping in the extreme case. Overload may be caused by poor choice of thread compound(see lubrication).
* Box wear life exceeded leading to overload.Inspect string for excessive wear.
Thread Wear or Galling (See Thread Wear)
* Thread compound has failed to prevent mating thread surfaces from interacting. This is due to either a poor or diluted compound or poor lubrication practice. Upgrade thread compound or increase frequency of cleaning and re-lubing joints.
* Thread contact pressure is excessive. For stab flank wear, reduce feed rate/pressure and/or increase rotation during make and break.
* For load flank wear, increase feed rate and/or reduce rotation during make and break. Rods with significant load flank wear should be discarded.
* Accelerated wear may be due to damaged accessories; inspect accessories for damage or wear (e.g. adapter subs).
* Thread wear life exceeded. Accelerated wear may be due to damaged accessories; inspect accessories (e.g. adapter subs). Inspect string for excessive wear.
External Shoulder Wear or External Shoulder Flared/Rolled Over
* Box shoulder flared and/or pin outer shoulder rolled over due to overload.
* Overload may be due to poor choice of thread compound (see lubrication).
* Box shoulder wear life exceeded. Inspect string for excessive wear.
Box Wear or Box Bulging or Thread Jumping (See Box and Midbody Wear)
* Box bulging due to excessive hoop stresses (see glossary) imposed by thread, potentially from overload.
* Evident by polished areas on one side of box or thread jumping in the extreme case. Overload may be caused by poor choice of thread compound(see lubrication).
* Box wear life exceeded leading to overload.Inspect string for excessive wear.
Premature Midbody Wear or High Drilling to Que
* Hole deviations (e.g. rotary drilled holes, wedging, or down-hole monitoring) induce increased contact pressure and friction between string and hole or casing wall.Improve lubrication of string to compensate.
* Hole has oversized or ‘cave’ sections allowing the string to elastically bend or buckle under load increasing contact pressure and friction.
* Reduce drilling loads or rotation speed to compensate or repair hole.
* High pullback or thrust load combined with high rotation speed has caused the string to elastically or permanently bend, increasing contact pressure and friction against the hole or casing wall.
* Evident by polished or heavy wear on one side of string in a slow spiral pattern (e.g. spiral has a multiple length pitch). Reduce drilling loads and/ or pullback.
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