Pulsation Dampener Precharge

Updated: 11-10-2010

Pulsation Dampener Pre-charge Rates

Please note: According to the manufactures (Continental Emsco – PD Series &Hydril – K-10/20 style - Aftermarket KB Series) the formulafor calculating pulsation dampener dry nitrogen pre-charge is 1/3 of your pump pressure, NOT to exceed 650 psi.

The 650psi limit is relatively new procedural advisement because of the increased mud pump pressures in modern drilling. When you add more nitrogen then recommended you are not gaining any benefit of additional pulsation control. The addition of excessive nitrogen causes elongation of the bladder inside the dampener assembly and results in premature failure due to the bladder reciprocating inside the shell with excessivebladder travel. The bladder and its stabilizing hardware (Hydril Style – K-20) hits on bottom discharge port and the cap due to this excessiveelongation, and failures are common with the stretching of the rubber bladder when coupled with  high mud pump pressures. When referring to theEmsco/KB style , the bladder fails due to abrasion with the bottom discharge screen.

This abrasion can be limited but by adhering to proper precharge rates.

We make an effort to “short charge” the bladder to 500psi - 550psi to allow for higher pump pressures with additional bladder travel abilities within the specifications of the bladder.  All  10  and  20  gallon  bladders  achieve  90%+  efficiency  at  400  psi  of precharge therefore  you  are not  creating  harmonic distortion  by  adhering to  this precharge guideline.(MWD Tools)

Note: During recent testing with Patterson-UTI we tested MWD mud pulse telemetry at 550 PSI of  nitrogen precharge and again at 900 PSI of nitrogen precharge. The signal change at thesurface was less than 1%. All MWD tool hands have the ability to set  upper  and  lower  thresholds  for  MPT  to  eliminate  and  or  accommodate  for pulsation “static” therefore this should not call for a deviation of precharge rates.

This circumstance is the same regardless of bladder material or mud base.