Scrubber Outlet Assembly With Insulative Barrier Against Galvanic Corrosion
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Solution Overview
Problem
Marine vessels face corrosion issues at scrubber outlets due to acidic and high-temperature washwater, particularly from galvanic corrosion between dissimilar materials like stainless-steel pipes and mild steel hulls, despite corrosion-resistant coatings and materials.
Innovation Solution
A scrubber outlet assembly with a pipe having dissimilar electrically conductive materials separated by an electrically insulative barrier, such as a tube made of glass-fibre reinforced epoxy, to prevent galvanic corrosion, and a diffuser to enhance washwater mixing and pH reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dissimilar materials (stainless-steel pipe and mild steel hull) are used at the scrubber outlet, then corrosion resistance is improved, but galvanic corrosion occurs between the dissimilar materials
Solution Approach 1:
An electrically insulative barrier is introduced as an intermediary component between the stainless-steel pipe and mild steel hull. This barrier prevents direct electrical contact between the dissimilar conductive materials, thereby eliminating the galvanic corrosion pathway while allowing both materials to maintain their corrosion-resistant properties.
Solution Approach 2:
The contact interface between dissimilar materials is segmented by inserting the electrically insulative barrier. This segmentation separates the conductive path that would otherwise exist between the stainless-steel pipe and mild steel hull, breaking the galvanic cell formation.
2Reliability
If a corrosion-resistant coating is applied to the pipe and diffuser, then protection against corrosion is improved, but the coating is difficult to apply properly to complex shapes, leaving gaps and weaknesses
Solution Approach 1:
The corrosion protection function is extracted from the complex external coating application process and relocated to the internally exposed barrier surface. The barrier's internal surface provides a simple, accessible geometry that is easy to coat uniformly, eliminating the manufacturing difficulty of coating complex external shapes while maintaining comprehensive corrosion protection.
3Reliability
If the barrier extends to the open end of the pipe, then galvanic corrosion protection is improved, but washwater discharge is blocked
Solution Approach 1:
The barrier is designed with non-uniform extension: it extends axially only to a first position that is short of the open end, providing galvanic corrosion protection at the critical junction area while leaving the open end area uncovered to maintain washwater discharge functionality. This local differentiation of barrier presence solves both requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Reduces the risk of galvanic corrosion and enhances washwater neutralization, protecting the pipe and hull from corrosion while ensuring effective discharge into the ocean.
Implementation Method 1
there is still a risk of galvanic corrosion, such as between the stainless-steel pipe and a mild steel hull of the marine vessel to which it is coupled
Implementation Method 2
A first aspect of the present invention provides a scrubber outlet assembly, the scrubber outlet assembly comprising: a pipe having an inner surface, wherein the inner surface has a first portion made from a first electrically conductive material, a second portion made from a second electrically conductive material dissimilar to the first electrically conductive material
Implementation Method 3
a diffuser is required at the scrubber outlet to increase a level of mixing of washwater with surrounding sea water, thereby to neutralise the washwater as it is discharged into the ocean
Data Source
Figure 1~6
Figure 2A~2B
Figure 3A~3B
AI summary
Disclosed is a scrubber outlet assembly (100), the scrubber outlet assembly (100) comprising a pipe (200) having an inner surface, wherein the inner surface (230) has a first portion (231) made from a first electrically conductive material, a second portion (231) made from a second electrically conductive material dissimilar to the first electrically conductive material, and a region (240) comprising at least a part of the first portion (231) and at least a part of the second portion (232). The scrubber outlet assembly (100) comprises a barrier (300) located inwardly of the inner surface of the pipe (200). The scrubber outlet assembly (100) defines a flow path through the pipe (200) along which washwater is flowable from a scrubber (10) in use, and the barrier (300) fluidically isolates the region (240) from the flow path.