Typical location of CUI corrosion on Pressure Vessel and Storage Tank

Likely Location of CUI for Vessels – Bottom of Horizontal Vessel; 

The risk area for the Corrosion Under Insulation (CUI) for the Pressure Vessel, which is horizontal (Horizontal) is the bottom (Bottom) of the Vessel, which is where water will be trapped under the Insulation.

CUI corrosion on pressure vessel.png

CUI corrosion on pressure vessel 1.png

CUI on Insulation Support Ring of Vertical Vessel and the Design for Minimize CUI;
In an example of the result is corrosion An Under Insulation (CUI) Downtown Insulation Support Ring Of Vertical Vessel , especially the Support Ring in the zone belowWhen water is added to the Insulation of water to flow down by gravity. And imprisoned in the Insulation Support Ring makes the atmosphere remove this happen CUI violence.
CUI corrosion on pressure vessel 2.png

The design method to reduce the CUI occurrence at the Insulation Support Ring suggested by the API and NACE is to allow gap ( Gap) between the Support Ring and the Shell so that water can flow through it. Therefore, the water does not get trapped in the Support Ring. Therefore, the design of the Support Ring in this way can help reduce the severity of CUI at the Support Ring area.

CUI corrosion on pressure vessel 3.png

Likely Location of CUI on Tank – Tank Lower Shell;
Area of Tank Shell adjacent to the Tank Bottom As Potentially Corrosion Under Insulation (CUI) serious because it is an area where water can accumulate and be trapped. It is also the area Insulation may be exposed to direct water Foundation them.
In the API RP 575 Storage Tank Inspection Practice, it is recommended that the Operating Temperature of the most severe CUI is between 43 – 93 C. Therefore, the tank that is used in the above temperature range should first be examined.
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Design of Insulated Tank Shell and Skirt for Minimize CUI “Gap at the Bottom”;
This can be done by leaving a gap or “Gap” between the Insulation and the Bottomto prevent water to accumulate and accumulate in the said area, causing severe Corrosion . Prevent insulation from going Water occupies Bottom ‘s look at a sample below:

CUI corrosion on pressure vessel 5.png
CUI corrosion on pressure vessel 6.png
CUI on Top Headdue to Water Ingress and Trapped at the Junction of Insulation Jacketing;
In Case examples are – Heat exchanger, Corrosion Under Insulation (CUI) due to water entering the junction of Insulation Jacket the Top Head and Flangeon Silicone Seal deterioration, including the design of the junction of Insulation Jacketing where water can be easily passed. Therefore it causing this point to contain water. In addition, the air can easily pass through, causing severe CUI .
CUI corrosion on pressure vessel 7.png
From many examples of Case CUI, we find that the basic principles in specifying the location of the CUI.  Let us imagine that where can the water enter? If water enters the insulation , where will it be? And where can the weather go through? At that point there is a chance of a severe CUI .
CUI corrosion on pressure vessel 8.png
Design of the Junction of Insulation Jacketing between Top Head and Flange to Prevent CUI;
From the Case above, we can see that Insulation Jacketing Design is very important in preventing Corrosion Under Insulation (CUI). By designing a good Insulation Jacketing , it can prevent water getting into Insulation when Silicone Seal deteriorates.
CUI corrosion on pressure vessel 9.png
Change in design of junction between Top head and Flange insulation
The picture is an example of the design of the junction of the Insulation Jacket between the top head and the flange that can prevent water entering the insulation when the Silicone Seal deteriorates.

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