Cracking mitigation

Mitigation or elimination of corrosion-fatigue cracks involves gaining control of the critical factors that govern the mechanism. 

Ethane enters the pyrolysis section, which comprises a series of cracking furnaces. The ethane is heated as quickly as possible to the cracking temperature and maintained at this temperature for the minimum residence time. In order to lower the hydrocarbon partial pressure and mitigate coke forming in the pyrolysis tubes, steam is added to the ethane prior to entering the pyrolysis section (not shown). 

Kanninen, M.F., et al., (1997). Design and Technical R erence to Mitigate Rapid Crack Propagation in Polyethylene Pipes for Gas Distribution. Southwest Research Institute Final Report (Contract 5088-271-1822) to the Gas Research Institute. 

STATE the three conditions that tend to mitigate crack initiation. 

Corrosion of the outermost rebar may be mitigated by installing CP however, a conventional CP system with anodes installed on the concrete surfaces likely will not be effective because of a dry environment at the anode-concrete interface that does not facilitate current flow caused by electrochemical osmosis. Because the interior of the tunnel is not exposed to rain or splashing sea water, the moisture available would come from the air. Water from inside the concrete would not reach the surface anodes because the surface cracks were sealed. 

CP or other protection systems should be incorporated, if necessary, in the design phase of the ship. CP system is a secondary defense against corrosion when holidays or cracks form in the coating. CP systems use either sacrificial zinc anodes or impressed-current systems to mitigate corrosion. Other corrosion prevention equipment and materials are inert gases to drive out corrosive gases. Corrosion inhibitors are also used. 

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