PROCESS LEAK DETECTION, RESPONSE & CONTINGENCY PLAN1 GOALS OF THIS PLAN2 IMPACT OF PROCESS LEAKS3 EARLY DETECTION4 LOCATING THE LEAK5 ELIMINATION OF LEAKS6 CONTINGENCY PLAN DURING PROCESS LEAK

GOALS OF THIS PLANDetect earlyReduce negative impact on cooling systemLocate leakIdentify productSpecify countermeasuresReduce leak frequency & severityRecover from effects of leak

RESPONSIBILITYSUPPLIER & USER DEPTT

NOTIFICATIONIf a leak is suspected, the plant operators should notify the unit in-charge and the Vasu personnel.It should be impressed upon everyone that earlier a leak is detected, the less damage it can do.It is better to alert everyone if a leak is suspected rather than wait for positive proof. A false positive report is less damaging to the refinery than a delayed report.

FUTURE This procedure will be reviewed and revised as experience indicates.It is also planned , in future versions, to include comprehensive series of diagrams showing:Color coded heat exchangers that will identify the category of product they cool.Color code frequent leakersIndicate sampling points.

REASONS OF PROCESS LEAKSMECHANICAL FAILURE OF THE COOLERS/CONDENSERS- Gasket failure of the HXs- others

PUNCTURE OF THE COOLERS/CONDENSERS TUBES/TUBESHEET

IMPACT OF PROCESS LEAKS1) DETRIMENTAL EFFECTSProcess leaks increase bacterial slime growth by two mechanisms:- Increased available food-Decreased toxicant (Chlorine)Slime caused two undesirable problems:-Reduced efficiency of cooling tower fill, especially film fill & reduced cooling efficiency of affected coolers/condensers-Under deposit corrosionOne negative effect of process leaks is often not recognized : that is sloughing of corrosion products that occur during leaks of heavy distillates and residual products such as lube oil etc. These pieces of iron oxide are loosened in the circulating lines and can plug tubes and damage circulatory pumps.

IMPACT OF PROCESS LEAKS continues(2) SEVERITYThe severity of undesirable and damaging effects of process leaks depends upon three factors:The Process streamThe concentration of the contaminantThe length of time the leak continues.

IMPACT OF PROCESS LEAKS continues(3) THE PROCESS STREAM> Any hydrocarbon process stream that leaks into cooling water that is lighter than light gas oil will:Consume chlorineIncrease chlorine demandIncrease formation of slimeIf the stream is sour, chlorine consumption and demand is even more pronounced and severe.

IMPACT OF PROCESS LEAKS continues(3) THE PROCESS STREAM-continues:> The effect of heavy gas oil and residual fuel oils and bottoms on the operation of cooling systems is different than for lighter streams.-Cl2 demand lesser than that for Lighter fractions unless theses streams are Sour.Bacteria do not utilize heavy hydrocarbons as efficiently as they do middle and lighter fractions.Very light, volatile hydrocarbons, C1 - C5 tend to be stripped from the water in the cooling tower so their concentration buildup is somewhat limited resulting in less severe effects than middle fractions. Of course, sour, light streams will consume chlorine at a higher rate than sweet streams..

EARLY DETECTIONOPERATOR TRAINING:-It is critically important that operators in each unit be trained when and where and how to test for process leaks and whom and when to notify.* When:daily* Where:each return header* How:Smell- especially if the leak is sourVisual:Foam, Turbidity or milkiness of cooling water denotes heavy hydrocarbons and /or amine.Build up of slime on cooling tower fillChange in appearance or smell of back wash water.

EARLY DETECTION-continuesOPERATOR TRAINING-continues:Test Chlorine to detect reduction in normal concentrationORP unit to test reduction in Oxidant level.Test for H2S to detect a sour leak.Test for ammonia to detect ammonia/amine leak.* Whom to notify : This should include IOCL and Vasu personnel. These persons should be notified as soon as a leak is suspected.----- DONT WAIT until the leak is or is not verified.Name DepartmentTelephone no* Who is responsible for training- Vasu Chemicals will be responsible to train refinery personnel in these leak detection methods during the initial phases.

EARLY DETECTION-continues(2) EARLY DETECTION IS IMPORTANT because process leak can have very severe negative effects on CW treatment program.Loss of FRC to flourish the microbial growth in the system.Slime formation- in CW lines, HXs & CT Fills- leads to- under deposit corrosion by SRB and fouling in the system Bacterial slime in circulating lines and heat exchangers.- reduction in cooling efficiency of Coolers/condenser resulting in inferior quality of Products

EARLY DETECTION-continues(2) EARLY DETECTION IS IMPORTANT- because process leak can have very severe negative effects on CW treatment program-continues-One problem resulting from lube oils, and other heavy hydrocarbon leaks is the sloughing of pieces and chunks of corrosion products in circulating line----these lodge in heat exchanger water boxes causing decreased water flow through blocked tubes These oil also foul cooling tower fill, especially film type fills, reducing the CT EFFECTIVENESS.Ammonia and amine leaks elevate the pH which has three undesirable effectsConsume chlorineReduce the effectiveness of chlorineIncrease the scaling tendency of the cooling tower.

MIC during hydrocarbon ingress

MECHANISM OF CORROSION

The bacteria cause Cathodic Depolarisation by removing Hydrogen from Cathodic sites.

SRBG posses enzymes that are capable of converting Hydrogen and reducing Sulphate

INTERACTION OF AEROBIC AND ANAEROBIC BACTERIA IN PRESENCE OF OIL ( HYDROCARBONS)

(+O2)Aerobic BacteriaLACTIC ACID ( Carbon Source)

(-O2) Fe3SO42 + SRBSSO32 + Anaerobes Pseudomonas Fe+2 + S2

Ferric Ions are SRB Depolarizes Cathode by removal reduced to Ferrousof the Hydrogen Adsorbed on the Metal surface for metabolic purpose

Formation of Phosphides are also noticed in Corrosion Products

A thick black material containing large amounts large amounts of sulphides are formed.

OIL (Hydrocarbons)FeS ( Corrosion Product)Cathodic DepolarisationAnodic Depolarisation

MICROBIOLOGICAL ACTIVITY ANAROBIC SOLUTION OF IRON: ANODIC DEPOLARISATION8HOH = 8H+ +8 OH -4Fe + 8H+ 4 Fe ++ +8OH

CATHODIC DEPOLARISATION SRB Ca SO4 + 8H Ca S + 4H2O

CORROSION PRODUCTSFe++ + CaS + 2(OH-) + H2CO3 FeS + CaCO3 + 2H2O3Fe ++ + 6 OH 3 Fe ( OH)2

SUMMARY4Fe +CaSO4 +2H2O + H2CO3 3Fe(OH)2 + FeS + CaCO3

REFINERY APPLICATIONS SRBC (SULPHATE REDUCING BACTERIA)

IDENTIFYING

Found in Anaerobic conditions (highly localised areas), under deposits/ Tubercles

No Biofilm

Planktonic counts in bulk water much lower are the only indication of viable sessile bacteria. Unreliable as an indicator of active corrosion

Intense localized attack discrete Hemispherical depressions- Interiors of pit are smooth

MS, SS, Al, even, Ti are attacked Cu Alloy- process not well defined

Pits tend to cluster together, overladen to form dimpled surfaces

SRB attackCorrosion Product Metal SulphidesRapid, Spontaneous Decomposition of S-R occurs after samples are removed, H2STherefore only freshly corroded surfaces + HCL H2S rotten Egg Smell or spot test with Na- Azide

SRB Attack on SS

Show well Defined PITSRelatively very little Deposits/ Corrosion ProductsFreshly corroded surface Fes (Block) in PITS Rust stains may surround pits or form streaks running in the direction of flow from the attack site.

LOCATING THE LEAKTHERE ARE TWO APPROACHES-Go first to the exchangers that have historically been leakers.- Work your way back from the main return header to the branch lines and then to the individual heat exchangers.TWO TRICKY SITUATIONS:-Chlorine residuals and ORP readings are not significantly affected by leaks of lube oil and other heavy hydrocarbons. This should be tested in the laboratory.-If the leak is large and the hydrocarbon and/or amine is heavier than C5, the leaking material wont air strip out in the system. In this situation , it is virtually impossible to detect a difference of product contamination levels in exchanger in and out water.-Here , a leak is detected by observing foam, turbidity and oil build up on the fill and in the basin and deposits on the fill.

LOCATING THE LEAK-continuesThis is one of the few situations where sample must be taken and analyzed by the laboratory, usually viscosity and a distillation curve will identify the product, which in turn, will identify the leaking heat exchanger.These situation most often arise from an upset that results in severe overheating of a product that can cause a no of tubes to pop all at once.

CONFIRMATION OF LEAKSCONFIRMATION OF LEAK- By ORP reading or/and - By turbidity level or/and - By testing of oil level in CW samples by LABORATORY or and/ by identifying the product by viscosity & distillation curve.

ELIMINATION OF LEAKSBy ISOLATION OF THE LEAKING HXS

PLUG THE LEAKING TUBE OR REPLACE THE TUBE BUNDLES. (If more than 10% tubes are found leaking or already plugged then TUBE BUNDLES to be replaced for optimum performance of the HXs). NOTE: AS EARLIER THE LEAK IS ISOLATED, LESSER WILL BE PROBLEMS IN CW SYSTEM.

CONTINGENCY PLAN DURING PROCESS LEAKDURING LEAKS OF VOLATILE AND LIGHT HYDROCARBONS:Slug dose Oil dispersant (20-50ppm) depend upon the level of ingressIncrease the dosages of Cl2 & ClO2 Cl2 dosages should not be increased beyond the double of normal dose. ClO2 dosages may be increased for 4-12 hrs to achieve the FRC in the CW. If FRC is not achieved then dose the Non-oxidising biocides also.Reduce the COC to 1.2-1.5 by increasing the blow down rateIncrease the back washing frequency of the side stream filterBack wash the HXs (having low flow) If iron level increase beyond the normal range then increase the dosing rate of Corrosion inhibitor and Polymeric dispersant.Azole (C.I for yellow metals) dosing should be also increasedTBC & SRB to be analyzed as per requirement during the ingress period to know the microbial load and take the corrective actionsORP also indicate the contaminant level in the system

CONTINGENCY PLAN DURING PROCESS LEAK-Contd.ii) DURING LEAKS OF HEAVY HYDROCARBON AND RESIDUAL FUEL OILRemove heavy foam from the CT sump by over flow/ or manual skimming Apply ejector system to remove the oil sludge from the CT sumps or other areasReduce the COC to 1.2-1.5 by increasing the blow down rate/Over flowSlug dose Oil dispersant (50-200 ppm) depend upon the level of oil Increase the back washing frequency of the side stream filterBack wash the HXs (having low flow)Increase the dosages of Cl2 & ClO2 Cl2 dosages should not be increased beyond the double of normal dose other wise it may lead to increased corrosion in the system. ClO2 dosages may be increased for 4-12 hrs to achieve the FRC in the CWNon-oxidising biocides can be dosed depend upon the situation.TBC & SRB to be analyzed as per requirement during the ingress period to know the microbial load and take the corrective actionsORP also indicate the contaminant levels present in the system

CONTINGENCY PLAN DURING PROCESS LEAK-Contd.iii) DURING INGRESS OF AMMONIA/AMINES/H2S:Increase the dosing of Cl2/ClO2 to achieve the FRC in the CW system.If required, dose the Non-Oxidising Biocide also.If iron level increase beyond the normal range then increase the dosing rate of Corrosion inhibitor and Polymeric dispersant.Azole (C.I for yellow metals) dosing should be also increased. Feeding extra azole to the cooling water is of some benefit in lowering copper corrosion rates. However, it is unlikely that the copper corrosion rate will fall to normal levels. While sulphide continuous to get into the cooling water. A significant role that the azole does play is to react with any soluble copper ions to form an insoluble complex. By tying up the copper corrosion the rate of plating onto mild steel minimized.-TBC & SRB to be analyzed as per requirement during the ingress period to know the microbial load and take the corrective actions