Corrosion in a ammonia threw compressor

[Tiquibola]

Dear Sirs,

I would like you can help me to analyse causes for corrosion found in rotors and shell of an ammonia compressor.

The step where corrosion is observed works at 15 Kg/cm2g and 90ºC.

Ammonia is pure and contains a 0,2% of water.

I include photos for observing the corrosion.

Ammonia compressor is new and it was startup last may, almost five months old.

Please could you help me to determine cause of corrosion.

Many thanks.

[zanlog]

thanks for your interesting case study,but i have some question.
what is rotors material?
do you have analysis of corrosion product?
what is temperature range of work?
are you sure about analysis of ammonia?

[Tiquibola]

Thanks for your quick answer.

what is rotors material? We are looking for that data. The photos are of the compresssor shell. The material is nodular cast iron.
do you have analysis of corrosion product? We have found steel wool sings in several samples. After burning analysis is 69% ashes and 39% organics
what is temperature range of work? There is not a range, from the startup the temperature is maintained to 90ºC.
are you sure about analysis of ammonia? It is analysed each day, contain of water can vary up to 0,4%

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[mitsai_3]

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I believe you should analyse steel composition, If alloy % are low such as Cr Ni may be why you found corrosion.
Also if there is a heat/chemical treatment and after someone machined/welded to solve a dimensional problem found I may cause to propert. lost.
Some problems have been related to china made steels who have the % of alloy and rest correct but then some strange % components have been found who give problems when machining or welding.

[zanlog]

i agree with

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[SAMEH ELSAGHER]

Dear Tiquibola*
Thanks for sharing this case
I think you have to inform the rotor material because it is the key thing to identify the damage mechanism
now I know the operating conditions but material of the rotor is important to think about what damage occurred.
From the photos* I can expect that general corrosion which created surface rust layer and i expect that not critical or can cause any problem for the safe running of the equipment however you need to know the reason to avoid subsequent severity.
Please tell us material of that rotor.
Regards