Heavily corroded scrubber pipe. Image Credit: Hydrex
Hydrex Underwater Technology (Hydrex) says it has recorded an increase in repairs to the pipe work and overboard outlets of those ships that have exhaust gas scrubbers installed.
The company cites work it recently carried on two 270m shuttle tankers as a recently example, saying the wash water from the scrubbed exhaust gases had corroded the pipework, resulting in water ingress.
The issue was identical for both vessels, it said.
"We have noted an increase in repairs to corroded pipework and outlets, which does appear to correspond with the increase in the number of ships fitted with scrubbers," said Dave Bleyenberg, Hydrex Production Executive.
"These systems remove harmful sulphur oxide compounds from the exhaust gasses of marine diesel engines burning high-sulphur heavy fuel oils. However, the resulting residue removed from these gases can have a rapid and highly corrosive effect on the scrubbers' internal pipework and outlets."
Dave Bleyenberg, Hydrex Production Executive
the resulting residue removed from these gases can have a rapid and highly corrosive effect on the scrubbers’ internal pipework and outlets
Hydrex notes that in the most recent case, repairs to the tankers were carried out while the vessels were alongside and remaining in operation. To prevent against further corrosion, a chemical resistant coating was applied to the internal surface of the repaired pipework.
"Taking into account the nature of the process taking place inside a scrubber, this is essential for a lasting protection of the pipe," said Bleyenberg.
"Corroded scrubber pipework and discharge outlets is a serious problem, and we're seeing more and more of it," Bleyenberg added.
"Our divers are certified wet and dry welders as well as technicians, which allowed us to carry out the complete repair work on both of these shuttle tankers, including creating the new diffuser. By doing everything ourselves and on-site the tankers were able to remain on standby to mobilise when needed."
Exhaust gas cleaning systems, more commonly known as scrubbers, allow vessels to achieve an equivalent level of compliance with sulfur regulations while burning otherwise noncompliant fuel.
With the global sulfur cal falling to 0.50% from January 1, 2020, scrubbers are expected to form an important part of the compliance picture.