2.7MW HV VSD Pump Motor Upgrade Functional Design

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Melbourne Water engaged GHD to design the replacement of a 70 tonne, reciprocating gas/diesel engine with a 2.7MW HV, VSD electric motor to drive a pump at Melbourne Water’s Eastern Treatment Plant.

The project required GHD to develop a functional (75%) design after considering various options in order to provide a clear basis upon which to commence the subsequent Detailed Design development. The engagement included developing a cost estimate for implementation under a Design and Construct contract arrangement.

As well as scoping the new equipment and works, a significant scope item was determining demolition interfaces for the redundant pipework, heat recovery boilers and other equipment associated with the removed engine on Pump 5 and a similar engine on Pump 4 (Pump 4 was no longer required).

Several challenges that GHD faced for this project were to:

  • Understand how the 70 tonne engines would be removed and assess any impacts on the surrounding equipment/structure during removal
  • Identify a suitable location of the new VSD within the existing site and building
  • Minimise impact on the operation of the existing three pumps while undertaking the works
  • Develop concept designs for the new room to house the VSD
  • Assess modifications required to the old engine foundations (which provided vibration dampening) to enable the new electric motor to be mounted as well as the coupling modifications to the motor
  • Assess the impact on the existing building structure, and options for cooling of the VSD and motor
  • Determine modifications to existing 6.6KV switchboards to connect the new pump and minimize the effect on the existing site harmonics levels

The design developed by GHD included creating a new Switchroom to house the high voltage (6.6kV) variable speed drive in an area made available with the removal of redundant heat recovery boilers in the OPS building. GHD provided all design services that included HV and LV electrical systems, control system, structural assessment and mechanical ventilation design as well as detailed construction sequencing to minimise impact on the operations of the other thee pumps at the OPS while the upgrade works were undertaken.

The project was successfully implemented and commissioned in June 2017.

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