Corrosion testing within Coal Fired sector 1

[CoalFired84]

Gentlemen,

First and foremost thank you for taking a moment to read my question. Though it would be best to reach out to other professional within the industry. My question is as follows:

We are currently looking for the most practical way to test for corrosion that may/may not be present within a fully operational coal fired unit (carbon steel flue liner).

The basic problem is that there is currently a glass borosilicate glass block lining (with asphalt based adhesive) which to this point has done its job wonderfully. However, we are now seeing some "wet spots" where flue gas may/may not be penetrating to the backside of the joint and eventually to the carbon steel substrate.

As I noted there are several obstacles that we would face. They are as follows:
- The unit in itself will most likely remain in operation. Substrate temperature would be under 150 F.
- Because of the interior lining system we would need to test from the exterior of the carbon liner looking in to determine any thickness loss via corrosion.
- The unit itself is approx 400' high and is of varying thicknesses (1-5/16" bottom to 6/16" top)
- There is some unknown corrosion prior to installation of the corrosion resistant lining. Pitting thickness loss etc.

Again, if anyone can lend advice as to what type of testing or what route we should take in evaluating the condition of the steel I would be extremely grateful. I look forward to your responses.

 

[metengr]

CoalFired84;
I think the beat approach is to continue to monitor the carbon steel stack thickness from the exterior. The key will be to establish a re-inspection intervsal to monitor wastage over time to establish a rate and to trend the thickness profile. Perhaps a re-inspection interval of 12 months of the same locations and other new locations should be considered.

 

[CoalFired84]

Metengr,

Thanks for the reply. Is there any particular type of test which you would suggest. Again, noting that we have an interior lining system of approx 2" and that the unit will most likely be in operation.

My fear here is coming up with a test that will give us accurate results with those types of contributing factors.

 

[metengr]

Yes, ultrasonic thickness testing performed on the exterior surface of the carbon steel substrate. You can perform this test at 150 deg F with special coupling, certain transducers and safety precautions.

 

[CoalFired84]

Metengr,

Again my sincere thanks for your help. Also, we've looked into thermal imaging to reference any possible heat loss. What are you or anyone elses thoughts on that process for determining possible problem areas? Thanks again.

 

[metengr]

I agree. Thermal imaging will help to determine hot spots for further investigation and thickness testing.