Low Magnetic Signature SWRO Refurbishment

How we refurbish and look after low magnetic signature SWRO plants.

Backstory about the SWRO

Since 1997, Salt Separation Services has been at the forefront of designing and manufacturing low magnetic signature Sea Water Reverse Osmosis (SWRO) plants for the Naval sector.

Low magnetic signature is a critical requirement for applications such as mine countermeasure vessels (MCMVs). We have supplied over twenty of this type of RO plant to the Royal Navy, each capable of producing 7.2 m3/d potable water.

There are currently three different configurations of these plants in service. Over the years, Salt Separation Services has supported, overhauled and refitted these specialised SWRO plants across multiple projects, ensuring their intended performance and maintaining longevity.


We were approached by a customer to carry out a refurbishment and modification of an existing SWRO plant. The modification was necessitated by the need to relocate the plant to a different platform.

Initial Assessment and Strip Down

Our first step in the refurbishment process involved a strip down and inspection of the plant. This standard service allows us to identify any emergent defects that could impact the refurbishment and overhaul. The detailed inspection ensures that all components are in good condition and fit for continued use or identifies parts that need replacement and/or repair. 

Modification for New Location

Given the constraints of the new location, several modifications were required:

  1. Orientation Change: The orientation of the RO vessel stack was changed from horizontal to vertical. This involved creating replacement or modified framework and pipework to ensure that the plant could fit into the new location and be maintained effectively. 
  2. Feed Source Adjustment: The new installation location provided a higher feed pressure, eliminating the need for a dedicated feed pump that was previously installed before the media filter. 
  3. Control Panel Modifications: With the removal of the feed pump, it was necessary to modify the control panel by removing the feed pump control. Additionally, to accommodate the increased feed pressure, we installed a pressure-reducing valve on the RO inlet with a suitably related pressure safety valve. 

Factory Testing and Documentation

Upon completion of the modifications, the plant underwent rigorous factory testing to ensure it met all operational standards and performance criteria. We also provided a comprehensive documentation pack, which included a new operation and maintenance manual tailored to the refurbished plant’s configuration. 

Project Challenges and Delivery

This project posed significant challenges due to the tight timescales for completion and the logistical complexities of the end destination. Despite these challenges, the plant was shipped on schedule and commissioning was successfully completed before Christmas, much to the satisfaction of the customer. 

The latest iteration of these plants (which have been supplied to a foreign navy) include automatic media filter backwashing, automatic start-up and shutdown as well as automatic flushing, removing the requirement for RO membrane preservation.