11tank Gauging and Oil Accounting

“Tank farm operations.”

TOPICS : TANK

FARM OPERATION & GAUGING •TANK /SAMPLES TYPES & SAMPLING •DIPPING, DENSITY & TEMP. TEMP. MEASUREMENT MEASURE MENT •PREPARATION OF OUTTURNS •OIL ACCOUNTING & LOSS CONTROL •PIPELINE LOSS/GAIN RECONCILATION

STORAGE TANKS TYPE OF TANKS TANKS : MAINLY OF TWO TYPES: •FLOATING ROOF TANKS ( FOR LIQUIDS WITH

HIGH VAPOUR VAPOUR PRESSURES SUCH AS CRUDE OIL, MS) - EITHER SINGLE DECK OR DOUBLE DECK •FIXED ROOF TANKS ( FOR LIQUIDS SUCH AS HSD,

SKO)

STORAGE TANKS TYPE OF TANKS TANKS : MAINLY OF TWO TYPES: •FLOATING ROOF TANKS ( FOR LIQUIDS WITH

HIGH VAPOUR VAPOUR PRESSURES SUCH AS CRUDE OIL, MS) - EITHER SINGLE DECK OR DOUBLE DECK •FIXED ROOF TANKS ( FOR LIQUIDS SUCH AS HSD,

SKO)

Floating Roof Tanks • When the Tank is in operation, the Roof should

always be in floating condition • In resting or semi-floating condition, the tank 

should not be operated • The seal should be checked periodically • The roof should also be checked periodically

(especially during Monsoon) to ensure that there is no water accumulation at the deck.

TANK BOTTOM 

LONG SEAMS

HORT SEAMS

ANNULAR PLATES

SKETCH PLATES

TANK SHELL •SHELL PLATE IS OF VARYING THICKNESS

THICKEST PLA PLATE TE FOR F OR THE LOWEST L OWEST COURSE AND DECREASING THICKNESS FOR UPPER COURSES. •THE PLATES ARE ARRANGED SO THAT THERE IS AN OFFSET BETWEEN TWO VERTICALS •PLATES ARE FLUSH FROM TANK INSIDE SO THAT THAT I.D. OF THE TANK DOES NOT CHANGE. CHANGE . THIS ARRANGEMENT IS ALSO A MUST FOR THE FLOATING ROOF TANKS.

SHELL NOZZLES •INLET NOZZLE •OUTLET NOZZLE •WATER DRAW OFF •PRODUCT DRAW OFF •CLEAN OUT DOOR •ROOF DRAIN •TANK STIRRER NOZZLES/ JET MIXER NOZZLES

INLET AND OUTLET NOZZLES

TANK INSIDE

TANK INSIDE R/F PAD

BOTTOM REINFORCEMENT PLATE

TANK INLET NOZZLE

BOTTOM PLATE

TANK OUTLET NOZZLE

TANK BOTTOM •BOTTOM PLATES USUALLY 0F 8 MM THICKNESS

INCLUSIVE OF CORROSION ALLOWANCE •LAYING SHOULD BE SUCH THAT IT FACILITATES FLOW OF MUCK TOWARDS THE SLOPE (EITHER INWARDS OR OUTWARDS). •MINIMUM WIDTH IS RECOMMENDED TO BE 72 INCH •JOINED BY FULL FILLET WELDING •REINFORCEMENT PLATE IS RECOMMENDED TO BE WELDED WHERE INLET JET IMPINGES ON THE TANK BOTTOM

TANK ROOF DOUBLE DECK FLOATING ROOF •ROOF IS CONSTRUCTED ON TEMPORARY SUPPORTS ERECTED

ON THE TANK BOTTOM •BOTTOM DECK IS KEPT AS FLAT AS POSSIBLE •THE TOP DECK PLATE, USUALLY OF 5 MM HAS SLOPE TOWARDS THE ROOF DRAINS •THE SPACE BETWEEN THE TOP DECK AND BOTTOM DECK IS DIVIDED INTO A No. OF BOXES CALLED PONTOONS. •EACH PONTOON IS A LEAK TIGHT COMPARTMENT MADE FROM •CIRCUMFERENTIAL AND RADIAL BULKHEADS. •THE TOP DECK IS SUPPORTED ON RAFTERS AND TRUSSES. •EACH COMPARTMENT HAS A MANWAY FOR INSPECTION

TANK ROOF ROOF DESIGN AND INSPECTION

THE DECK IS SO DESIGNED THAT WITH ALL THE DRAINS INOPERATIVE, IT SHOULD WITHSTAND 10” RAINFALL IN

24 HOURS. THE DECK SHOULD HAVE SUFFICIENT BUOYANCY WITH TWO ADJACENT PONTOONS PUNCTURED. DURING INITIAL FLOATING OF THE ROOF, ALL THE PONTOONS ARE VISUALLY INSPECTED FOR ANY LEAKS OR SWEATING.

TANK ROOF ROOF APPURTENANCES AND FEATURES •ROOF MANWAYS •INSPECTION HATCH •RIM VENT WITH RELIEF VALVE •AUTO BLEEDER VENT •EMERGENCY DRAIN •GAUGE WELL PIPE AND ANTI ROTATION DEVICE •ROOF DRAIN •FOAM DAM •ROLLING LADDER

TANK ROOF FLOATING ROOF - EITHER SINGLE DECK OR DOUBLE DECK TOP DECK SUPPORTING LEGS

SEAL AREA ROOF DRAIN

BOTTOM DECK

TANK BOTTOM FLOATING ROOF - EITHER SINGLE DECK OR DOUBLE DECK TOP DECK SUPPORTING LEGS

SEAL AREA ROOF DRAIN

BOTTOM DECK

Sampling • Important aid to Quality control • For ascertaining the stock conformity to

the relevant specifications • Sampling aids like sample grabber, sample thief, water finding paste, sample containers • Sealing of the sample container with proper seal. Sealing Wax not permitted.

Type of the Samples • Top sample • Upper Sample • Middle Sample

• Lower Sample • Bottom Sample • All Level Sample

• Composite Sample • Water Draw off Line Sample

Bhakti

Samples Sample: A portion extracted from a total volume that may or may not contain the constituents in the same proportion that are present in the total volume. SPOT SAMPLE: A sample taken at a specific location or at specific time from a flowing stream TOP SAMPLE: A sample obtained 15 cm below the top surface of the liquid UPPER SAMPLE: A sample drawn from the middle of the upper one third of the tank contents (or one sixth of the total tank contents)

Samples MIDDLE SAMPLE BOTTOM SAMPLE LOWER SAMPLE: A sample drawn from the middle of the lower one third of the tank contents (or five sixth of the total depth of the liquid. COMPOSITE SAMPLE: A blend of U M and L Samples ALL LEVEL SAMPLES: A sample obtained by submerging a stoppered beaker or bottle to a point as near as possible to the draw off point and raising it at a rate such that it is 75 % - 80 % full as it emerges out of the liquid.

Samples COMPOSITE SAMPLE: The composite sample shall be a mixture of an equal quantity of : U, M and L samples for product depth above 4 Meters U and L samples for product depth between 2M to 4 M Middle sample for product depth below 2 meters.

Sampling Procedure – (p- ½) • The sampling bottle and sample containers shall

always be kept clean. • Before use, they shall be rinsed with the product under sampling. • Only the type of sample required for the relevant

specification to be tested, shall be taken. • The sample quantity collected shall be sufficient for carrying out the relevant tests.

Sampling Procedure- (p 2/2) • Sample shall be taken preferably during the

cooler part of the day and under shade. • The sample container shall be properly closed

and it shall be ensured that there are no leaks. • Sample details shall be entered in the form (as per Appendix-11/Appendix 11A) as applicable and fixed to the container. • Sampling and filling of the sample container

shall be personally supervised by an officer well conversant with the procedures.

Weathering of Volatile Samples • Density • RVP, RON • Distillation  –  IBP  –  Recovery % Vol at 70, 100, 180 deg C

Sampling • Avoid vapor loss of samples due to

evaporation, particularly the retention samples  –  Direct exposure to sun-light/heat  –  Air Current

Gauging Procedures- (p 1/3) The Gauging operations include: • Measuring volumetric quantity of the

tank by dipping or ullaging • Recording the temperature of the

product • Measuring the density of the product

Gauging Procedures- (p 2/3) Method for recording gross and water dips: Apply water finding paste to the bob, 2 cms above the previous water dips. Apply oil finding paste around the range of  estimated Gross Dip. Lower the bob through the Gauge Hatch, till the reading is 30 cms short of the reference height. Weight for the ripples to subside and then slowly lower the bob until it just touches the datum plate. Raise the Tape and note the Gross Dip and the water dip.

Gauging Procedures- (p 3/3) In tanks, where water dip is maintained, it should be at least 2 cm above the Datum Plate. In case of tanks where water level is below the Datum Plate, the same shall be checked through the Centre Hatch. For tanks which are to be kept bone dry, the same shall be assured by draining product through water draw off lines.

Layering in storage Tanks • Heavier product in lighter product • Interface Heavier at the bottom • Circulation of product – Jet Mixtures

Master Instruments • Master instruments :

Hydrometers, Thermometers • Validity : 5 Years • In-use instruments : Yearly comparison and records.

Calibration • Calibration of Hydrometers and

Thermometers: Calibration to carried out at 3 – 4 points in the instrument’s range • If the error is within +/- 0.0005 at 15

deg C • If the error is within +/- 0.5 deg C

PRODUCT LOSS CONTROL • Petroleum Products being volatile, product

loss is unavoidable under certain circumstances. But these losses can be minimised. • The losses erode profit. • They cause safety hazards and pollute the

environment.

PRODUCT LOSS CONTROL • Identify the cause and initiate steps to

eliminate it. • Regular Inspections and Preventive

Maintenance • Awareness of employees.

Factors contributing to Pipeline Losses • Defective Gauging Equipment/ 

Gauging errors/ Accounting errors • Sludge/ Water in the tanks • Gauging Errors • Migration of Product • Pilferage/ Leakage in the Pipeline

Control on Pipeline Losses At the Pumping end: • The tanks should be free from water/ sludge • Proper settling time (Minimum 24 Hrs) to

be given to the tank  • Positive segregation from other tanks • Pumping of hot product to be avoided • Use of standard Gauging Equipment. The

same equipment to be used for Opening and closing operations.

Control on Pipeline Losses At the Receiving end: • The tanks should be free from water/ sludge • Water dips to be noted before and after the

receipts (Care to be taken for rain water) • Positive segregation from other tanks • Use of standard Gauging Equipment. The

same equipment to be used for Opening and closing operations.

OIL ACCOUNTING • CALCULATIONS ACCORDING TO ASTM,

ARE BASED ON THE PROCEDURE WHERE A VOLUME MEASURED AT A GIVEN TEMPERATURE IS RECALCULATED TO A VOLUME AT THE STANDARD TEMPERATURE USING VOLUMETRIC CORRECTION. THIS CORRECTED VALUE IS CALLED STANDARD VOLUME. THE MASS OF THE PRODUCT IS OBTAINED BY MULTIPLYING THE STANDARD VOLUME BY THE PRODUCT’S DENSITY AT

STANDARD TEMPERATURE.

ASTM TABLES THE CORRECTION FACTORS ARE AVAILABLE IN THE FOLLOWING ASTM TABLES: • TABLE 53 A : CORRECTION OF OBSERVED DENSITIES TO DENSITY AT 15 DEG c OF CRUDE OILS • TABLE 53 B : CORRECTION OF OBSERVED DENSITIES TO DENSITY AT 15 DEG c OF PRODUCTS • TABLE 54 A : CORRECTION OF VOLUMES TO 15 DEG C AGAINST DENSITY AT 15 DEG c FOR CRUDES • TABLE 54 B : CORRECTION OF VOLUMES TO 15 DEG C AGAINST DENSITY AT 15 DEG c FOR PRODUCTS

ASTM TABLES TABLE 53 B: GIVES THE VALUE OF DENSITY IN KG/CU.M AT 15 DEG C CORRESPONDING TO A HYDROMETER READING AT OBSERVED TEMPERATURES OTHER THAN 15 DEG C. TWO CORRECTIONS ARE NECESSARY AND HAVE BEEN APPLIED: THE CHANGE IN VOLUME OF GLASSS HYDROMETER WITH TEMPERATURE (STEM CORRECTION) CHANGE IN THE VOLUME OF PRODUCTS WITH TEMPERATURE

ASTM TABLES TABLE 54 B: GIVES THE VOLUME CORRECTION FACTORS FOR CONVERTING PRODUCT VOLUMES OBSERVED AT TEMPERATURES OTHER THAN 15 DEG C TO CORRESPONDING VOLUMES AT 15 DEG C.

ASTM TABLES If the Hydrometer Reading for a Gasoline at 22 deg C is 733 kg/m. cu, what is the density of  gasoline corrected to 15 deg C.

738.7 KG/  M CU

ASTM TABLES If the Hydrometer Reading for An HSD at 30 deg C is 836 kg/m. cu, what is the density of HSD corrected to 15 deg C.

846.0 KG/  M CU

ASTM TABLES What is the volume at 15 deg C of 55000 cu M at 30 deg C of heating oil the density of which at 15 deg c is 845.7 kg/m cu.

54336.7 m cu.

Out turns FOR CONE ROOF TANKS: 1. From the Dip Memo, calculate the Gross Dip Quantity and water Dip quantity 2. Compute Net Oil at Observed Temperature 3. Compute 15 deg C Density from the observed sample Temperature and the hydrometer Reading 4. Compute VRF against Observed Tank  Temperature 5. Compute WRF (subtract 0.0011 from Density at 15 deg C) 6. Calculate volume at 15 deg C by: V (obs temp)xVRF 7. Calculate MT by : V at 15 deg C x WRF

Out turns FOR FLOATING ROOF TANKS: 1. All the steps as in cone roof are involved with one extra step i.e. Roof correction. 2. Volume displaced by the Roof = Weight of  roof / Density of the product

3. The displaced volume is subtracted from Gross oil to get the Net oil at Observed temperature.

Out turns Prepare an OTR for the following data: Tank No. 3 Type : Cone Roof  Product : HSD Parameters

Opening

Closing

Gross Dip

61.1 cm

415.7 cm

Water Dip (c)

0.0 cm

0.0 cm

Tank Temp.

18.0 deg C

21.5 deg C

Sample Temp.

18.0 deg C

21.0 deg C

Observed density 0.829

0.831

Out turns Prepare an OTR for the following data: Tank No. 11 Type : Floating Roof  Product : MS Parameters

Opening

Closing

Gross Dip

295.5 cm

1396.5cm

Water Dip (c)

NIL

Nil

Tank Temp.

17.0 deg C

16.5 deg C

Sample Temp.

16.0 deg C

15.0 deg C

Observed density 0.745

0.740

OIL RECONCILIATION • •

• • •

• • •

• •

A COMPARISON OF OPENING AND CLOSING BALANCES OPENING BALANCE CONSISTS OF QUANTITY PUMPED QUANTITY UNDER PUMPING OPENING LINEFILL CLOSING BALANCE CONSISTS OF QUANTITY DELIVERED QUANTITY UNDER DELIVERY CLOSING LINEFILL ALL QUANTITIES ARE VOLUMES AT 15 DEG C

Form No. OP 28 INDIAN OIL CORPORATION LTD. (MARKETING DIV.)

TANK NO.

IOC

3

OUT TERN FOR RECEIPT

BONDED

OT NO. 3133 LOCATION : DELHI DATE : 21.01.2004

PRODUCT : HSD

BEFORE RECEIPT

AFTER RECEIPT

DATE

14.01.2004

17.01.2004

TIME

14.15 HRS.

10.00 HRS.

TANK TEMP. IN DEG.C

18.0

21.5

SAMPLE TEMP. IN DEG. C

18.0

21.0

SAMPLE DENSITY

0.829

0.831

DENSITY AT 15 DEG.C

0.8310

0.8350

OIL & WATER HEIGHT/LTS

61.1 cm. /  628723 Ltrs.

415.7 cm. /  3483008 Ltrs.

WATER HEIGHT/LTS.

0.0 cm. /  0.0 Ltrs.

0.0 cm. /  0.0 Ltrs.

VOLUME REDUCTION

0.9975

0.9946

NET OIL LTRS. AT (N) NET OIL LTRS. AT 15 DEG.C NET OIL QTY. IN MT

628723 627150 520.470

3483008 3464200 2888.796

NET QTY. RECEIVED

BATCH NO = HSD HSD-309UL

AT NATURAL

AT 15 DEG. C

MTS.

2854.285 KLS

2837.05 KLS

2368.326 MTS

SUMMARY BONDED RECEIPT FROM PIPELINE EX-MATHURA FOR INDIAN OIL CORPORATION LTD.

PIPELINE

MARKETING

CENTRAL EXCISE

DETAILS OF CALCULATIONS VOL. IN KLS AT VOL CORR. UPTO DATUM GROSS QTY. IN LTRS. ROOF CORR. IN LTRS. WATER QTY. IN LTRS.

61.1 cms = 628723 8 = 0 : : :

415.7 cms = 34830086 = 0

628723 0 0

CERTIFIED THAT THE PARTICULARS GIVEN ARE CORRECT PLACE ______NEW DELHI _______DATE __________PLANT TERMINAL MANAGER REGD. OFFICE : G-9 ALI YAWAR JUNG MARG, BANDRA(EAST) BOMBAY – 400 051(INDIA)

3483008 0 0

Form No. OP 28 INDIAN OIL CORPORATION LTD. (MARKETING DIV.)

TANK NO.

IOC 11

OUT TERN FOR RECEIPT

OT NO. 4547 LOCATION : DELHI DATE : 23.01.2004

BONDED

PRODUCT : MS BEFORE RECEIPT

AFTER RECEIPT

DATE

17.01.2004

21.01.20042

TIME

10.15 HRS.

07.30 HRS.

TANK TEMP. IN DEG.C

17.0

16.5

SAMPLE TEMP. IN DEG. C

16.0

15.0

SAMPLE DENSITY

0.745

0.740

DENSITY AT 15 DEG.C

0.7458

0.7400

OIL & WATER HEIGHT/LTS

295.5 cm. /  1407233 Ltrs.

1396.5 cm. /  6378777 Ltrs.

WATER HEIGHT/LTS.

0.0 cm. /  0.0 Ltrs.

0.0 cm. /  0.0 Ltrs.

VOLUME REDUCTION

0.9978

0.9983

NET OIL LTRS. AT (N) NET OIL LTRS. AT 15 DEG.C NET OIL QTY. IN MT

1352250 1349275 1004.805

6323423 6312673 4664.434

NET QTY. RECEIVED

AT NATURAL

AT 15 DEG. C

MTS.

4971.173 KLS

4963398 KLS

3659.629 MTS

BATCH NO = MS MS-311PG

SUMMARY BONDED RECEIPT FROM PIPELINE EX-MATHURA FOR INDIAN OIL CORPORATION LTD.

CENTRAL EXCISE

PIPELINE

MARKETING

DETAILS OF CALCULATIONS VOL. IN KLS AT VOL CORR. UPTO DATUM GROSS QTY. IN LTRS. ROOF CORR. IN LTRS. WATER QTY. IN LTRS.

: : :

295.0 cms =1404974 0.5 cms = 2259 = 0

1395 cms = 6372021 1.5 cms = 6756 = 0

1407232 54982 0

6378777 55354 0

CERTIFIED THAT THE PARTICULARS GIVEN ARE CORRECT PLACE ______NEW DELHI _______DATE __________PLANT TERMINAL MANAGER REGD. OFFICE : G-9 ALI YAWAR JUNG MARG, BANDRA(EAST) BOMBAY – 400 051(INDIA)