Timescale
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