Vessel Inspection Shows Severe Fish Scaling

Glasslined Technologies, Inc. was called to a clients' facility to review the reactor's glass failure. This was a result of the hydrogen ion migration referred to as fish scale in glass-lined processing equipment. Upon arrival, Glasslined Technicians reviewed the extensive wear ring in AR-7 existing in the vessel. The vessel had been subjected to extensive damage on the bottom head including loose glass in the system.

At each inspection, our technicians take pictures and videos of the vessels to reference the damage to the client accurately. With the pictures from this inspection, they found a circle of damage on the bottom head similar approximately 40” ID by 56” OD, 8” wide. The variance along the circumference is less ¼". The position is located 3 ½" outside the span of the CBT hub. The entire area resembled fish scaling.

After an inspection with the data collected, we met with the client to create an initial plan based on the discovered evidence. With this specific vessel we noted the bottom head of the vessel was covered in insulation. The lower sealer ring shows heavy corrosion. The technicians created a list to collect additional evidence to support the analysis.

1. Analysis of Glycol

2. Vessel Inspection of the internal and external parts of the vessel

a. Glass thickness on Bottom Head

b. UT thickness of vessel shell behind the glass

c. UT thickness of sealer ring and Bottom Head

4. Review previous failures related to Glycol

6. Inspect nearby vessels for lower sealer ring corrosion

7. Review process for incompatibility with glass-lined steel

Analysis of Glycol

Glycol was injected in the inlet ports. After the fluid was inside the technicians were unable to remove jacket plug 14 on the Bottom Head due to extensive corrosion. Then they removed the piping at the lowest inlet port and revealed an injection nozzle that had not properly been installed to direct the flow. A significantly low pH event had taken place previously in 2012 which leads to the recording of low pH of 5.5 for the system with sampling taking place at bulk Glycol storage tanks. After the analysis had completed the technicians recommended replacing the pipes, replace pump impeller which failed as result of corrosion, replace a lower sealer ring, and extensive repair the jacket on the glass-lined vessel.

Visual Inspection of AR-7

In a visual inspection our technicians look at the internal and external parts of the vessels, taking pictures and notes during the process, in order to give an accurate description of the vessel.

Internal Inspection Results

Upon inspection of the Top Head, Reactor Shell, Bottom Head, and all the vessels’ accessories, the technicians found the following issues:

· Inside the Reactor Shell, there are two 1 ½" tantalum plugs installed. One was in good condition, but the other showed rust below the plug, indicating a likely leak. This requires a replacement, not a repair. 

· On the Bottom Head it showed a severe loss of fire polish on the middle part of it as well as a small chip resulting in a severe case of fish scale as a result of Nascent Hydrogen.

· The Bottom Nozzle showed light abrasion without a chemical attach. This is caused by light erosion from the solid contact in the solution.

· The AR-7 CBT Hub was installed to high on the shaft which can cause product build up leading to difficulty in the hibernation removal.

External Inspection Results

Upon inspection of the vessel exterior the technicians found the following issues:

· The lower diaphragm showed that the paint of the lower Lealer Ring was missing. This included severe corrosion at the beginning of the ½" coupling with delamination in the area. The outside of the Bottom Head showed extensive rust, and the drain was heavily corroded.

Glass Thickness Measurements

Due to the extensive fish scaling on the vessel a regular spark test at 5000 Volts will not reveal pinholes in the glass. The technician increased the spark test to 14500 volts, and it provided a positive reading on the spark tester with the lowest reading recorded as 29 mils, based on the constant 500v/mil as the dielectric strength for the glass. The steel thickness measurements on the lower sealer ring confirmed a low of .180” vs .375”, whereas a reading of .200” was recorded in several areas on the Bottom Head vs .437” original thickness. This indicates significant corrosion had taken place in the Sealer Ring and the Jacket Bottom Head. If not neutralized, the Hydrogen remaining in the steel or glass bubble structure will continue to evolve.

Final Conclusion

Once the extensive vessel inspection has been completed, our technicians will create a detailed document of their findings, including the pictures and videos taken of the vessel during the inspection. This document will also include recommendations for the client based on the findings and information on preventing future issues. The client can then decide what they would like to do, and we can either provide, most of the time, work on-site or figure out the logistics of getting the vessel or part back to Glasslined Technologies' facility to repair.