Service Alliance | Solution Partners

Offshore Drilling Rigs: Upgrades, SCR Drives, Retrofits, VFD Drives, Customization

OFFSHORE DRILLING RIG – UPGRADE OF SCR DRIVES – Replaced obsolete DC drive with current Siemens 6RA70 DC drive

  • Replaced the cabinet with a 100% stainless steel, NEMA 4X with air to water heat exchanger
  • Upgraded the control system by adding two Siemens HMI touch panels and a new Siemens PLC
  • Improved the performance of the winch by adding a constant tension feature


OFFSHORE DRILLING RIG – RETROFIT WINCH CONTROLS – Completed retrofit of the anchor winch cabins and controls including the redundant HPU’s for the winch

  • Replaced obsolete controls with modern controls and improved performance and safety
  • Scope of work included survey of existing system, engineering, installation, and commissioning

NSA Nabors3

  • Reused the existing bucket frames and power connections for cost savings
  • Redesigned the internal layout of the new NEMA components
  • Provided new doors and interlock mechanisms for MCC structure
  • Retrofitted existing AEG fused disconnect switches with new ABB E-Max power circuit breakers in the main switchboard
  • Performed Hazardous Area Survey of the Classified Areas and generated a punch list and identified the necessary material needed to make repairs
  • Provided personnel to handle the remedial repairs based on the Hazardous Area Survey


OFFSHORE DRILLING RIG – UPGRADE OF VFD DRIVES – Engineered a solution to remove the existing obsolete storage winch VFD’s and replace them with modern ABB ACS800 drives

  • The engineered solution was designed in modular sections so that the pieces of the system could be lowered through the narrow elevator shaft and into the area for reassembly
  • The system incorporates an all stainless steel air-conditioner for cooling of the drives
  • This NSA solution resulted in considerable savings over previous plans being considered
  • Provided the installation personnel to remove the existing drives and install the ABB package
  • Commissioned the drives
  • The system was designed with optimum serviceability and redundancy
  • The NSA system incorporated assignment contactors to provide a cross-over logic such that all signals are switched resulting in a seamless efficiency to the PLC


OFFSHORE DRILLING RIG – UPGRADE OF SCR DRIVES – Engineered and manufactured redundant SCR drives allowing for spooling cable on and off the drawworks and anchor winches which is particularly useful when rigs are in the shipyard

  • The Siemens 6RA70 SCR drives facilitated this function with the ability to change from a shunt motor or series motor parameter set by a switch
  • The drives have a four quadrant field supply for reversing the fields of the shunt motors
  • The drives are pendant controlled


OFFSHORE DRILLING RIG – UPGRADE CONTROL PANEL – Provided fifth Generator Control Panel and distribution for living quarters and auxiliary loads

  • Packaged switchboard and MCC with transformer in a customer provided module that integrated with other stackable modules
  • Provided commissioning and installation services
  • Integrated tie breaker with existing switchboard line-up to allow the rig the use of the fifth engine package



  • Rental Generators were added to rig to elevate 480 VAC bus load from main engines to provide more power for drilling conditions
  • NSA designed, installed and integrated the panel into the rig 480 VAC switchboard and installed generator plug box in a 18 hour period as an accommodation to the customer
  • NSA later provided personnel to complete the installation of the rental generators, to install cable tray and place and terminate all the necessary power cables and control cables


OFFSHORE DRILLING RIG – CUSTOMIZATION – Engineered, designed, manufactured, installed and commissioned a 1200 HP VFD drive to fit into a foot print of 64 square feet

  • Provided input and output line reactors with assignment switches for redundancy to work with existing VFD
  • Developed encoderless operation sequence for top-drive application on the VFD
  • NSA Houston developed a program to allow the drive to operate without the encoder in low speed scenarios such as making and breaking connections thereby preventing previously encountered encoder failures


OFFSHORE DRILLING RIG – UPGRADE SCR DRIVES – Replaced several obsolete SCR drives with ABB DCS800 SCR drives

  • Engineered, manufactured, installed, and commissioned third 2000 HP Mud-pump SCR
  • The System controlled two GE752 shunt motors with a load share tolerance of less than 1% throughout the entire speed and load range