Precleaning & Passivation Procedure

Precleaning & Passivation of Heat Exchnagers Introduction: All new equipment or equipment taken out for maintenance in cooling water system should be precleaned to remove grease, oil, corrosion products, mill scale scale and dirt. dirt. Clean Clean surfac surface e enable enable corr corrosion osion inhibi inhibitor tors s to establ establish ish a uniform protective passivation lm. Failure to remove debris can result in deposition on critical heat exchanger surfaces during start up. assivation assivation of  the metal reduces the initial corrosion reaction that occurs at start up and faci facili lita tate tes s the the esta establ blis ishm hmen entt of cor corrosio osion n inhi inhibi bito torr prog progra ramm mme. e. !ith ith traditional pre cleaning method separate pre lming "passivation# step is recom recommen mended ded to prom promote ote a rapid rapid format formation ion of prote protecti ctive ve lm to retard etard corrosion corrosion of the metal surfaces. re$clean re$cleaning ing procedu procedures res non$negoti non$negotiable able since passivati passivation on procedu procedures res are only e%ective on clean metal surfaces assivation of carbon steel heat exchangers is so important that it should be a non$negotiable part of start$up. lants may choose to conduct passivation procedures by isolating a single heat exchanger or circulating chemicals in the entir entire e cooling cooling water circuit circuit,, depend depending ing on the number number of new heat exchangers exchangers or the number of new tubes. AquaC quaChe hemi mie e prec precle lean anin ing g and and pass passiv ivat atio ion n prog progra ramm mme e safe safely ly deposits, corrosion corrosion products and leave passivated metal surfaces.

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Advantages: &. Cleans heat transfer surfaces and hence ensures maximum maximum heat transfer. transfer. '. recleaning recleaning ensures that no debris or loose corrosion corrosion product product is left which can block tubes or deposit on heat transfer surfaces during operation. (. assivation assivation ensures that metal metal surfaces are not directly directly exposed to corrosive corrosive )uid and hence prolong equipment life. *. assivation assivation to certain extent protects equipment from from corrosion corrosion during upsets like low p+, +ydrocarbon leak etc

Prepared By : Surjeet Kumar

Uncleaned & Unpassivated CS Surface CS Surface

Precleaned & Passivated

Procedure: Degreasing/ Dirt Removal  &. Flush system with potable water till water at outlet of exchanger is visually clean and - of outlet water is equal to - of inlet water. '. Add surfactant/ chelating agent to remove oil 0 grease and loose products at recommended dosage level and circulate for & hour. (. 1rain circulating solution completely. *. 2epeat step ' 0 ( again. tep ' should be continued for ' hours. Passivation &. Add polymeric dispersants at recommended dosage in circulation tank. '. Add passivation chemical at recommended dosage in circulation tank. (. 3aintain p+ in range of 4.4 5 6.7 by using mild acids. 8t is recommended to use acid corrosion inhibitors. *. Circulate above solution for 9 hours. 4. 1rain passivation solution completely from heat exchanger.

Prepared By : Surjeet Kumar

6. -horoughly )ush heat exchanger with Cooling !ater. :. 8mmediately after through )ushing heat exchanger should be taken in line within '* hours. 9. -o speed up passivation procedure following actions can be taken; $ 3aintain circulating water temperature of :4 5 97 1eg C. $ +igher dosing of polymeric dispersant is done to keep passivation chemicals in soluble form. $ Circulation should be done for * 5 4 hours.

Time ine for Completing Precleaning & Passivation:

!e"uirements: &. '. (. *. 4. 6.

-ank for circulation Circulation ump Flexible +oses and adapter connections +eating arrangement for maintaining temperature 8nlet 0
Prepared By : Surjeet Kumar

A"uaChemie Specialt# Services for Precleaning & Passivation: &. 3echanical systems for precleaning 0 passivation. '. Chemicals for precleaning 0 passivation. (. upervision of complete activity along with required analysis to ensure precleaning and passivation. *. -ests to ensure proper precleaning and passivation. 4. Complete precleaning reference.

0 passivation

report

for

record

and future

The center and right pipes sho$ incomplete pretreatment and passivation% Preferred is the pipe at left

Prepared By : Surjeet Kumar

Important ote: &. Chemical requirement is calculated based on circulation loop volume. '. Chemical requirement 0 procedure varies with 3
Prepared By : Surjeet Kumar