7/27/2019 Acid Cleaning Procedure for Cleaning of Lub Oil Piping

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Acid cleaning procedure for cleaning of lub oil piping

1.AcidSoakingandPassivationTechnique1.1Fabricatethealkalitank,acidtank,rinsetankandpassivatingtank1no.foreachaccordingto

themaximum dimension of pipe or fitting. The acid tank shall be preferable vertical type to

facilitatetheslagdischarge,andbepreferablecoatedwiththeethoxylineresinoninnerwall.

1.2 Solution preparation: Determine the solution concentration in accordance with the

benchscaleexperiment.Thegeneralmethodasfollowing:

1.2.1Alkaliliquor:Preparethe0.8102NaOHsolutioninalkalitank,add0.2l0

2Na3PO4slowly

andblendevenly,andfinallyaddthe(0.05l)102rinseagent.

1.2.2 Acid liquor: Pour rinsing into the acid tank and add the 30102HCl slowly. Test the

concentration,andpreparetotheratedvalue(511)102byaddingrinsingiftheconcentrationis

toobig,oraddingacidwhereas;afterwardsadd0.2and102inhibitors.

1.2.3Passivatingagent:Preparethe(23)102

NaNQ2intank,addtheadequateNH4OHsolution

tillPHvalueis9.510.

1.3Processofcleaning:

1.3.1Alkali

cleaning:

Soak

the

pipes

and

fitting

into

alkali

liquor

and

maintain

the

temperature

8090for46hrs;theoildirtonpipewallwillbecleanedconsequently.

Theprocessofalkalicleaningcouldbecancellediftheoildirtcontaminationonpipeandfittingis

notsevere.

1.3.2Acidcleaning: raisethe temperatureofacid liquor to6070 (heating isnot required in

particularcondition),soakthepipeandfittingintoacidliquorcompletelyinbatches;thesoaking

time,dependingon thepipediameterand rustcondition, isaround4hrsnormallyand limited

within 8hrs until the rust on pipe wall is completely descaled. Before soaking each batch,

supplement the inhibitor, test the concentration of acid liquor and add acid duly when the

concentrationdecreased.Tofacilitatethecheck,put2nostestsamplesineachbatchtoexamine

theacidcleaningconditionandrateofcorrosion.

1.3.3Rinse(1):Preheattherinsing inrisingtankto4060,soakandrinsethepipeandfitting

treatedwithacidcleaning inthehotwater,andthenflushwithpressurizedhotwateruntilPH

valueofusedflushingwateris>6.Payattentiontoshortenthetimeasmuchaspossibleincase

themetalofpipewallwillagainberustedoncontactwithairforlongtime.

1.3.4Passivating:

Preheat

the

passivating

agent

to

50

60

before

putting

the

pipe

and

fitting

7/27/2019 Acid Cleaning Procedure for Cleaning of Lub Oil Piping

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into it;thepassivatingtime,dependingonthepassivatingcondition,isaround36hrsnormally.

MonitorthePHvaluebyusing indicatorpaper,andaddNaNQ2dulytomaintainthepassivating

quality.

1.3.5

Rinse

(2):

Put

the

passivated

pipe

and

fitting

into

rinsing

with

temperature

above

50

.

After rinsing, theNitrite ion content inwater shallnotexceed lmg/kg; thepassivating film in

silvergreycolourisformedonthesurfaceofpipeandfittingevenlyandingoodappearance.

1.3.6 storage:Dry thepassivated and rinsedpipe and fittingwith compressedair (sometimes

blow dry with compressed air is not necessary for the pipe and fitting rinsed by hot water

becauseof itsown temperature).and thenblock theendsofpipe tightlyand store in indoor

placeforstandby.

1.3.7 The used acid liquor and passivating agent shall be neutralized and checked qualified

beforedischargetopreventtheenvironmentpollution.