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*                             HAZARD ALERT                          *  
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*  Produced by:  Saskatchewan Human Resources,                      *  
*                Labour and Employment                              *  
*  Provided by:  Canadian Centre for Occupational Health and Safety *  
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SERVICE RIG WORKER BURNED IN AN EXPLOSION WHILE MONITORING  
WELL CIRCULATION  
  
  
*** SERIOUS INJURY:  ***  
  
  A service rig worker on a rig tank trailer received second and third  
  degree burns to his face and upper body when vapours from well returns  
  ignited during circulation.  
  
  
*** CIRCUMSTANCES:  ***  
  
  The lease location was relatively level with sparse tree and brush  
  growth.  Weather conditions were +28C with a 3km/hr wind.  Wind  
  direction was variable.  
  
  Blow out preventors were installed.  The circulation tank (rig tank),  
  pump and diesel drive motor were mounted on a trailer 29 metres from  
  the well (see photo).  The distance between the circulation tank and  
  pump drive motor exhaust was 8.4 metres.  The victim was stationed at  
  the pump controls.  
  
  As circulation commenced, concentrated gas vapours from circulated  
  returns drifted from the tank towards the pump and diesel drive motor.  
  
  An explosion followed.  Based on an investigation, it would appear  
  that the most probable source of ignition was the drive motor.  
  
  
*** PREVENTION:  ***  
  
  Section 350(a) of 'The Occupational Health and Safety Regulations'  
  requires that when the pump is circulating hydrocarbons the air intake  
  and exhaust of the pump motor must be located not less than 6 metres  
  from the rig tank.  
  
  Despite the fact that the tank and motor were separated by 8.4 metres  
  an explosion occurred.  The investigation suggests that the unusual  
  combination of high temperature (+28C) and low wind (3km/hr;  
  direction variable) were significant factors.  Therefore, well  
  circulation procedures should be re-examined to prevent a recurrence.  
  
  It is recommended that employers prepare, implement and enforce  
  procedures that require employees to follow strict safety precautions  
  or cease work whenever environmental conditions may contribute to a  
  hazard.  Workers should be instructed and experienced in these  
  procedures which should include:  
  
      1.  The use of directional wind monitoring devices;  
      2.  The use of an alternate storage tank to separate well fluids  
          from possible sources of ignition;  
      3.  The circulation of the fluids down the flowline if applicable;  
      4.  Disconnection of DC power sources to the mobile trailer, if  
          applicable;  and  
      5.  The use of a poor boy degasser.  
  
  
Alert Oct. 11/89  
  
  
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