Project Summary

HIFraser was awarded the design and supply of a replacement Oily Water Separator (OWS) and bypass system for a submarine program.

The current units are obsolete and required regular maintenance activities that did not align with the existing submarine maintenance cycles. The customer required a compact system that was able to be retrofitted in the limited space available with extended maintenance periods to align with full cycle docking.



Submarine Oily Water Separator - 2017-2021

Project Overview

  • To meet the customer’s extended maintenance requirements, HIFraser’s Engineering Consulting team designed and integrated a bespoke bypass system to direct any fluid with an oil content of greater than 60% directly to the oily waste tank for storage until docking.
  • This system continually monitors the OWS inlet fluid. Once the threshold is reached, the oily water is automatically redirected to the tank and the OWS unit is shut down.
  • The system has an external electrical control panel and mechanically integrates with the OWS skid including a bypass pump to supplement the transfer pump within the PECOFacet OWS system.
  • With this reduced load on the OWS, the maintenance periods can be extended to meet the submarine’s operational requirements whilst not increasing the overall equipment envelope.


  • Working with a long standing HIFraser partner, PECOFacet, a coalescing plate separator was selected to replace the existing separator.
  • The CPS 2.5B MKIII complies with the MEPC.107(49) IMO regulation allowing treated bilge water to be reduced to an oil concentration of less than 15 ppm, which can then be safely discharged overboard.


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