More about SCR Health Checks


The time to complete depends on the availability of equipment and amount of disruption to the programme, but as a general rule the time to complete a health check can be estimated as follows: allow one half day for each Generator and SCR section plus one half day per  assignment. For example a 4 SCR, 4 Generator system with 2 Mud Pumps, DWA, DWB and Rotary Table = 2 + 2 + 2.5 = 6.5 days.

Typical Scope of Work

A comprehensive health check would include the following:

  • Generator Sections
    • General clean and check tightness of terminations
    • Circuit breaker – secondary injection (optional), settings, contact wear
    • Governor control – running milliamps, actuator adjustment, regulation and control
    • Check pulse pick-up waveform and clean and adjust as required
    • Exciter control – exciter current waveform, voltage regulation and control
    • Load sharing – KVAR and KW load sharing between engines and generators
    • Check AC module protections: UV, loss of pulses, reverse power
    • Check operation of synchroscope, synch check relay, dead bus override, lamps and meters
  • SCR Sections
    • General clean and check tightness of terminations
    • Circuit breaker – secondary injection (optional), settings, contact wear
    • Contactors check tips for signs of burning or arcing
    • Check blowers run freely and without vibration and delivers expected airflow
    • Clean and/or replace filters
    • Check bridge ferrites or reactors and snubber circuits for damage or scorching
    • Sample SCR heatsinks to check for pitting or corrosion (may require further deferred action)
    • Ensure SCR firing is correct and check firing pulse waveforms
    • Check current waveform for signs of faulty SCRs
    • Confirm DC Module current limits and check calibration of SCR ammeter and voltmeter
    • Check fuse microswitch and bridge overtemperature trips and logic indicator display
    • Check operation of Sprocket Slip protection (series motor systems)
    • Ensure SCR assignments operate correctly and contactors operate freely
    • Check signal levels arriving at the DC Module are adequate and there is no significant voltage drop from the Drillers Console
  • Auxiliary Circuits
    • Verify operation of Power Limit circuit and calibrate
    • Check Ground Fault detector circuit and calibrate
    • Check Surge Suppression unit is in circuit and functioning
    • Check HOS battery charger circuit is operating at the correct voltage and calibrate.
    • Ensure HOS batteries are healthy
    • Ensure DC motor blowers and auxiliary starter operate correctly and interlocks and alarms all function as expected
  • Field Supplies
    • Check diodes and transformers for signs of damage or scorching
    • Check field supply waveform is correct with no missing pulses
    • Confirm and adjust field current as required
    • Check operation of field loss relay
    • Confirm operation and adjust Mud Pump load sharing
  • Drillers Console and Foot Throttle
    • General clean and check tightness of terminations
    • Check all potentiometers for signs of damage or wear and smooth operation.
    • Check the Drillers Console PCB and components for signs of damage or scorching
    • Adjust and verify the operation of hand throttle microswitches
    • Calibrate the RT Torque (current) meter and power limit indicator
    • Check the operation of all lamps and replace blown bulbs
    • Check the operation of all pushbuttons and switches
    • Verify purging system and alarm
    • Check the Foot Throttle for correct operation and adjust as required

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