Durapipe assists biofouling problem in nuclear submarines

Durapipe assists biofouling problem in nuclear submarines

PVC-U pipework and valves alongside our top of the range flow monitoring products have been utilised within a new Sodium Hypochlorite dosing system for a Royal Navy nuclear submarine.

The trial system has been designed and built by WES, a leader in providing engineered solutions for the water, wastewater and process industries, and is required to dose Sodium Hypochlorite into the sea water intake cooling water tubes of a nuclear submarine whilst in dock, in order to reduce bio-fouling in the delicate nuclear reactor heat exchanger systems.

Bio-fouling of the seawater intake cooling systems was resulting in operational downtime as a result of bio-fouling related blockages and more disturbingly, microbiologically induced corrosion in the copper alloy seawater systems. The Ministry of Defence undertook laboratory trials to prove that chemical treatment would prevent this and then turned to WES for a solution to the problem of applying the chemical accurately & safely.

There were strict requirements for the system; it could not interfere with the submarine’s other internal systems, it needed to operate whilst being submerged underwater whilst the submarine is dockside and it was crucial that it provided a dose of chlorine proportional to the sea water intake flow rate. As a result, WES designed a secure dockside based storage and dosing unit, with an umbilical cord to the submarine intake, comprising the dosing pipework and control signals running underwater to a buoyant Polyethylene injection assembly.

The Durapipe FlowX3 monitor is an integral component of the system and was particularly suitable due to the IP68 rating of the sensor body allowing the flow sensor to be fitted to the injection assembly and totally submerged in up to eight metres of water. The product is used to monitor the flow of sea water into the intake cooling tubes to ensure the correct amount of chlorine is injected. It is important that the system doesn’t react to tidal surges and the FlowX3 product provides a 4-20mA signal to the dosing system control panel which then interprets the signal and dampens out any non-linear signals and applies a timer function to ensure that flow detected is cooling water intake and not tidal or wave movement.

Another feature which made the FlowX3 particularly suitable was the range of plastic fittings available; a Polyethylene welded adaptor was used on the similar Polyethylene injector assembly which was critical to ensure correct material selection for both resistance to the Sodium Hypochlorite and to allow neutral buoyancy of the assembly in the water for installation. The standard adaptor allows the flow sensor to be removed by divers from the assembly whilst still underwater for inspection.

Commenting on the use of Durapipe FlowX3, WES managing director Kevin Wheeler said: “We required a highly engineered, sophisticated solution to fit into our system and Durapipe provided the perfect product with FlowX3. It was important that the flow monitor could operate eight metres below the water surface, be easily removable by a diver and provide a signal suitable for our control systems to differentiate between tidal surges and genuine sea water flow intake.”

The trial system has been successful and WES is now working with the Ministry of Defence to develop larger systems for wider use across the submarine fleet. The submerged injection assembly with integral flow sensors will be utilised on all future systems and Durapipe is continuing to assist WES with products from the FlowX3 range.

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