More and more ships are being fitted with Exhaust Gas Cleaning Systems (EGCS or, more commonly, scrubbers) so that they can use cheaper, heavy fuel without violating regulations. But there is a problem: inadequately protected mild steel is easily corroded by the scrubbers’ highly acidic wastewater. Corrosion of the scrubber overboard pipe is a threat to the integrity of the hull. This often occurs between drydocking. The question is how to effect a repair without going to drydock or going off-hire.

Hydrex and sister company Subsea Industries solved this problem in 2019. We developed procedures to replace the final section of pipe with the ship afloat and without interrupting its schedule. We also developed a proprietary and patented method of preventing the same trouble from recurring.

This technique has been implemented successfully on well over 100 scrubber overboard pipes for some thirty different shipping companies to date – container ships, bulkers, tankers and reefers.

Coating the carbon steel with Subsea Industries’ patented, chemical resistant Ecospeed coating prevents further corrosion. The procedure has been approved by the major classification societies. So as not to interrupt a ship’s schedule, the repairs can be carried out in several stages at different ports of call if necessary. This applies particularly to container ships.

Hydrex has the operation down to a fine art of coordinated and invariable steps and procedures. Mild steel replacement pipes are prefabricated and protected with Ecospeed. Stainless steel is not used, so as to avoid dissimilar-metal galvanic corrosion between hull and pipe.

The results have been successful in every case where coated carbon steel pipes were used to replace the corroded overboard pipes.

Avoid costly damage

Our teams have also replaced pipes preemptively. These pipes were already starting to corrode, and a leak would have been a matter of time. By performing the replacement before the leak occurred, our divers prevented a costly unscheduled repair later.

While it is easy to carry out the repairs with the ship afloat, Ecospeed protection of the scrubber when it is first installed preempts any problems with corrosion when the scrubber is in use.