RFA Bay Class Reverse Osmosis Plant Upgrades

We have been working on the RFA Bay-Class ships since 2014 and have carried out major works, including Reverse Osmosis Plant Upgrades on 3 out of the 4 ships now. 


Our work scope for the Mounts Lyme and Cardigan Bay ships contained four major components:

  1. Site Survey
  2. Upgrades to RO Plants
  3. Control Panel and Carbon Filter upgrade
  4. Regular Health Checks

Engineer Site Survey Visit

To be able to determine the actual scope of upgrade areas, we must conduct a preliminary survey visit with the plant running to:

  • Perform plant tests
  • Diagnose plant faults
  • Survey the plant
  • Discover emergent defects
  • Provide expertise/labour

Our site engineers hold all essential qualifications for onboard and offshore services such as; OPITO BOSIET, Seafarers Medicals, CONDO.

RO Plant Improvements

We performed the following upgrades to RFA Mounts Bay in 2015, Cardigan Bay in 2016 and Lyme Bay in 2017:

  • RO Vessels
  • HP Pump
  • Cartridge Filters
  • Bird (media) Filters c/w frontal pipework
  • Seawater Supply Pumps

New RO Vessels

Old RO vessels exhibited signs of membrane delamination, which​ leads to membrane failure and will require complete replacements.​ By upgrading the RO vessels, potential significant membrane failure is avoiding constant membrane change-outs.​ By reducing the number of RO Vessels from 4 to 3 and subsequently membrane elements from 8 to 6, this resulted in reduced replacement costs. This is achieved by using latest generation high area membrane elements.

APP Pump in Place of CAT Pump

Old Pumps are triplex, positive displacement reciprocating pumps (CAT).​ New axial piston pumps (APP) are upgraded in place.​

CAT pumps are considered more complex in nature, requiring lubrication, belt drive system, suction in-line damper and Nitrogen charged discharge Pulsation damper.

Any of these add additional maintenance burden and numerous points of potential failure.​ For example, the CAT HP pumps for Mounts Bay had an intermittent motor overload fault and occasionally on start-up it would trip.

Cartridge Filter Upgrade

Old cartridge filters were 316 St/St in construction.​ Due to the corrosive nature of seawater, there was excessive corrosion on the filter housing.​ This will ultimately lead to failure.​ New Super Duplex housings were fitted instead, which are highly resistant to corrosion.

Frontal Pipework Upgrade

Old pipework had many leakages (evident from the valve unions) – a potential of snowballing into a bigger issue.​ This was a result of galvanic corrosion by having bronze in contact with St/St with seawater flowing. ​The whole frontal pipework was overhauled and new valves were installed. This also gave the benefit of better access for maintenance.

Seawater Booster and LP Pump c/w Motor Upgrade

Old pumps were 316 St/St and pumped seawater to a break tank. There are common issues of not being able to be hand turned.​ 316 St/St is also not normally deemed suitable for seawater duty and this is evident by the occurrence of leakages.​ Additionally, pumping to break tank is unnecessary as the seawater is 3m above the plant suction. Feed pump could more than adequately provide seawater straight to the filters instead – taking water from the break tank can and does cause operational problems.

We currently still support the Bay-Class ships in:

  • Technical assistance
  • Aftersales support
  • Through life support