Monel 400 Life Limiting Criteria

[ahafeez3131]

I am a maintenance engineer in a power plant. We have heat exchangers in our process water cooling circuit. The heat exchangers have Monel 400 material tubes. These heat exchangers have given us excellent service for last 30 plus years. Now we want to assess the tube material condition to check their healthiness and estimate when to replace the tube bundle. In this regard we have pulled out one tube out of heat exchanger. Mechanical tests were done on this aged tube. It shows an increase in yield strength, Ultimate tensile strength and hardness , and a decrease in %age elongation.
Based on this result how we can deduce the condition of tube material. Is there a limit of increase in say yield strength, after which it becomes mandatory to replace the tube bundle with a new one. In short is there any Life Limiting Criteria exists on metals Yield Strength, UTS, %age Elongation or/and Hardness.

A. Hafeez

 

[unclesyd]

I would not try to base any replacement on the the parameters given in the OP.
One would normally base the life expectancy of a heat exchanger tube based on the physical condition of the tube by an eddy current inspection. This type inspection will give information on pitting (internal and external), general thinning, and wall loss at the baffles.

 

[EdStainless]

Please don't double post questions.
This is being replied to in the M&M forum

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