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#1 syedimran


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Posted 13 April 2004 - 12:47 AM

We are planning to replace 288 catalyst tubes of our ammonia plant (Haldor Topsoe) primary reformer presently of IN 519 material with HP microalloy 25 35 Nb Ti after almost 25 years of service. Please let me know if we have to replace the outlet hairpin tubes also (alloy 800H) having the same service life. Presently there is no problem with them. Is it normal practice of changing reformer catalyst tubes along with the outlet hairpins?

#2 mbeychok


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Posted 13 April 2004 - 01:44 PM

I strongly suggest that you also post your question in the ComLink forum at www.nh3.org ... a great many experienced ammonia plant operators participate in that discussion forum.

#3 Guest_Ashwani Kaul_*

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Posted 17 April 2004 - 04:47 AM

Dear Imran,

Primary reformer tubes are normally designed for 11~ 12 year life. Obtaining 25 year life from Primary Reformer tubes is noteworthy. Regarding haipins, they do not see high radiant heat flux and ther deterioration rate is somewhat lower than reformer tubes. You should dig out old reports/ NDT tests of hairpins to find out the observations regarding their residual life. In case such tests have not been done previously, you could get the NDT tests done on next turnaround.

In any case, as precautionary measure, you should have 5~10% of hairpins as spare during turnaround test so that if any immenient failures are detected, the hairpins can be replaced immediately before start-up.

Normally, creep, magnetic permeability and metallography tests are done to assess residual life of haurpins. Also, Dye Penetrant Test / UFD can be done to identify weld pinhole cracks.Hardness test is advisable if you feel that the hairpin may have to be nipped because of leaky reformer tube.

Hope this is of use,

#4 Kameswara Rao

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Posted 23 April 2004 - 01:45 PM

The normal life span for reformer tubes is around 10 to 12 years depending upon the temperature and the operating pressure. Higher the temperature lesser the life and vice versa.
The Primary reformer out let gas enter the secondary reformer al most at the same outlet temperature. Hence though the haipin bends wont expose to radiant zone but they are subject to the temperature stress and creep strength. Hence they need be thoroughly inspected and replaced on random check. It is very essential for you to get ready for replacing atleast 20% of them.
If you need any further assistance and clarification you may contact me( I am a retired Senior Engineer operations Ammonia Plant) at e-mail address kkrao22@hotmail.com.
I will get information from our Technical Service people if you provide more information

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