Sunday, April 17, 2011

Current Discussion in our Network: Relevance of Corrosion Monitoring Using LPR for Interpreting Corrosion and Fouling Behaviour of Several Heat Exchangers in a Cooling Water Circuit

Discussion Posted by: Chetan Sangani
Date: 16 Apr 2011

Experts, We are facing a situation where the LPR readings is showing Corrosion of around 13 MPY, Coupons (45days) retrieval is showing 17 MPY, in Cooling water System with Several HE and equipments

The whole system along with the HX are complete Carbon Steel built, under such readings there should have been heavy corrosion that could be seen in the water conditions, but the Return Water shows iron Fe2 Less then 0.4ppm consistently for more then past 3 months. Has anyone faced such experience? In what circumstances the Readings could be misleading?

1 comment:

  1. Manickam Valliappan • There are several factors that decide the usefulness of corrosion monitoring practice. Please provide little more information on the following:
    Type of cooling system and treatment-chemical/non-chemical.
    If it's chemical based treatment, any Iron Dispersant is included in the package.
    Is the present monitoring based on the risks identified for the whole circuit or using the locations and hardware originally designed?
    Frequency of fluid sampling and corrosion monitoring-coupon/probe and the parameters.
    Operation and Maintenance practice of exchangers including the shutdown frequency.

    16 hours ago

    Chetan Sangani • The Entire System is treated Non-Chemically, There are No Chemicals to control the Ph or No Anti-Corrosion Inhibitors, Anti Scalants, Anti-bacterial Chemicals/Chlorine etc. The Coupons are not located in the Main stream but connected via 1/2" plastic pipe for the Main 24"Header. The Monitoring is done on the whole system by checking the Pressures / Temperatures at Critical HX, Performance of the HX and other equipment in the system, Water sampling is done on Daily Basis from the Return Line as well as downstream of HX`s, HX (that can be isolated) are opened for physical observation once in 45 days and they are clear of fouling or Corrosion. The COC is maintained at above 4 with Zero blowdown. The Water sampling results are as below, Visually the return water seems very clear with the following parameters ph-7.2, conductivity- 568, TSS -1, TDS-510, Ca-175, Total Alkalinity - 51, Chloride -135, Free Chlorine- <0.04, Iron 0.211, Turbidity-1, silica as SiO3-0.85, phosphate-0.05, Zinc-0.164. Bacterial count <1000


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