We are in the process of identifying the Corrosion risk loops of Liquid 520 kTA ethylene capacity Naphtha Cracker Plant , which is the mother plant of our Petrochemical complex . The exercise is a part of our endeavor to implement an RBI approach thru inhouse effort . Can anyone , having knowledge or experience in the subject matter (Corrosion risk loops identificaation ) or having awareness of licensor's guidelne , can give me inputs on this ? regards , SHAMIK

In order to progress along with the Corrosion risk loop, it is important to know, which RBI system is being used. Different RBI systems accommodates the corrosion loops differntly. Most of the advance RBI systems treat equipment and piping circuits seperately and identification of the corrosion loop becomes more systematic. It is recommended to perform the corrosion risk mainly for the piping and treat the equipments as an individual identity. Some of the guidelines for the corrosion risk loop formation for piping circuits are given below. API-571 and API-581 shall be considered to determine the corrosion rates and various probabilities of damages. 1. Treat piping from one equipment to another equipment under one loop. Since mostly the corrosion characteritics of the fluids remains unchanged from one equipment to another, the loop takes most of the parameters in account. 2. In the event of any injection point treat downstream and upstream piping sections under different piping circuits. 3. Break the piping circuits when the temperature changes are more than 10 Deg C. 4. Break the piping circuits when the pressure changes more than 50 psi. 4. Break the piping circuits at the valves which restricts the flow as normally no flow. 5. Treat the psv inlet and psv outlet pipings as different circuits. 6. Change the circuit when the piping material, schedule and thicknesses changes. 7. Change the loop when the flow velocitie changes for NH4HS corrosion, amine , sulphuric acid etc for the process streams where the corrosion is velocity dependent. 8. Change the loop with the process change. 9. Change the loop when there is change in the insulation(CUI). 10. For the utilities like cooling water system, the cooling water heat exchangers with the leaking history and tube bundle failures shall be taken two circuits for cooling water inlet and outlet pipings. I hope the above guidelines give some basic insight to treat piping corrosion risk loop determination. Regards, Shabbar Hussain Senior RBI Engineer