MBLeakDetection FFinal 1.1

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XXXXXX

TRECATE REFINERY

PROJECT

PIPELINE AUTOMATION IMPROVEMENT

COMPLEX LOGICS & LOOPS NARRATIVES

MASS BALANCE LEAK DETECTION


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TRECATE PIPELINE AUTOMATION ENHANCEMENT PROJECTCOMPLEX LOOPS/LOGICS NARRATIVES

Date: 31 Oct 02

G.P.Cacciaglia - Rev. 1.1

LEAK DETECTION BY MASS BALANCE

IntroductionThe purpose of this specification is to provide the design basis narrative to develop themass balance Leak Detection System (LDS) software for the six major product pipelinesoriginating at Trecate Xxxxxx Refinery. The 20-inch crude line is outside the scope of this

project, since the Quiliano Depot as its originating terminal controls it. Moreover, it has itsown stand-alone leak detection system based on pressure data (Level III - PressureProfiling) as measured by the 11 pressure transmitters disseminated along the pipelinefrom Quiliano to Trecate.

The applications for the six major pipelines, basically similar to each other; will becustomized by pipeline to reflect single system peculiarities. However, this specification

focuses on the general aspect of the application, defining the solution to adopt andaddressing alternatives as appropriate.

Prompt detection of leaks in liquid petroleum pipelines is a matter of great importance toprevent potential disaster in populated areas or contamination of rivers, undergroundwater, etc., regardless the possible economic catastrophic impact.

From the endless statistics and categorizations made from accident reporting, it is


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The pipelines are relatively small sizes, both in diameters and in lengths.Consequently, the linefill itself is rather small, as is its the pipeline transit time.

A prototype of a similar application has been successfully experienced with the 6inch Malpensa pipeline and partly with the 8 inch Reversal pipeline. Particularly, the

linefill stability has been confirmed.To implement the mass balance leak detection application in the control system is afirm requirement. Supplemental/interconnected equipments and/or stand-alonesystems are not accepted.

The mass balance processed for the leak detection should get the signals from theexisting flow meters, respectively the PD Meters at the Refinery and the Turbine

Meters at the Receiving Terminals.Although not in this project scope, it is stated that each meter must have the provingfacilities by the date of project completion (i.e. it is envisaged Malpensa terminal willreplace the existing pipe prover with a Master Meter prover. A follow up isrecommended).

Easy applications, well documented for the refinery maintenance people , is a firm

i b d d bl d h di


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Pipeline OverviewThe pipeline system operated by Xxxxxx Refinery, to transport refined products to thevarious depots sited in Northwest Italy, consists of 6 major pipelines plus 5 additional very

short lines to supply two adjacent depots. The whole system also includes the 20 inchpipeline to supply the crude oil to the refinery and a short pipeline taking bitumen to anEsso depot just opposite the refinery. As far as the mass balance leak detection concerns,the pipelines involved with are limited to the six major product pipelines.

As shown in the figure on theright, these pipelines run

across the flat lowland lyingon the east side of the PoRiver valley, where theoriginating terminal altitude(Trecate) is lower than thereceiving terminals. Anexception is the 8 inch


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Xxxxxxxx terminal (Savona still operates manually) the 8 inch Reversal simulates, as faras the hydraulic gradient of receiving terminals is concerned, a virtual altitude (say 450 to550 metres depending the linefill and pipeline status) sufficient to keep the pipeline wellpacked at all times, such as to avoid slack segments and/or biphase states.

However, these more than 300 kilometers of Trecate pipeline system spread across awide sensitive area, such as to require a system to detect ruptures. Although the prevalentcrossing is through agricultural fields, the routes include dense urban areas and anextensive number of crossings through railways and roads ballasts, as well as river-beds(including the Po River and most of its tributaries).

Pipeline Facilities

Pipeline 8 inch Arluno (values are approx. for the application requirements)

This pipeline consists of 15 km of 8 inch pipeline together with one pump station at Trecateoriginating terminal and metering stations at Trecate and Arluno Terminal.

The pump station consists of two pumps, giving the pipeline the following two ratecapacities:


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The metering at Trecate consists of 3 PD meters dedicated to Fuels and 2 PD meters forthe ADO (also shared with the 8 inch Arluno). The metering at Arluno consists of oneturbine meter for high viscosity. Both stations are provided with proving facilities.

Arluno transmits metering signals to Trecate by an OMNI flow computer.

Pipeline 10 inch Chivasso (values are approx. for the application requirements)

This pipeline consists of 81 km of 10 inch pipeline together with one pump station atTrecate originating terminal and metering stations at Trecate and Chivasso Terminal.


- Pumping ADO One pump: 250cmh @ 45bar Two pumps: 370cmh @ 80bar

- Pumping Mogas One pump: 280cmh @ 42bar Two pumps: 390cmh @ 73bar

- Linefill 4200cm

The metering at Trecate consists of 4 PD meters. The metering at Chivasso consists ofone turbine meter. Both stations are provided with proving facilities.

Chi i i i l T b OMNI fl


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- Pumping JET-A1 One pump: 80cmh @ 25bar Two pumps: 105cmh @ 45bar

- Pumping JET-A1 Three pumps: 126cmh @ 65bar

- Linefill 600cm

The metering at Trecate consists of 2 PD meters. The metering at Malpensa consists ofone turbine meter. Trecate station is provided with proving facilities; Malpensa is expectedto provide proving facilities within the start-up date.

Malpensa transmits metering signals to Trecate by an Allen Bradley PLC/5.

Pipeline 6 inch Turbigo (values are approx. for the application requirements)

This pipeline consists of 12 km of 6 inch pipeline together with one pump station at Trecateoriginating terminal and metering stations at Trecate and Turbigo Terminal.


- Pumping Fuel Oil One pump: 150cmh @ 47bar Two pumps: 230cmh @ 80bar

- Linefill 240cm

Th i T i f 3 PD Th i T bi i f


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Purpose of the ApplicationThe application LEAK D ETECTION B Y M ASS B ALANCE , for the Trecate Pipeline System, is tolimit the ultimate size of an oil spill to a manageable levels. In the most probable scenarioof a mechanical fault, corrosion leak or minor 3 rd party damage, this application wouldreduce potential spill volumes from a volume of tens, maybe hundreds, of cubic meters toan even more manageable 500 liters, plus the drainage of line contents whose quantitydepends on the location where the rupture occurs.

In the very remote scenario of a full line rupture, this system should provide the earliestpossible warning and shutdown in order to reduce spill volumes from a potential huge

amount of many cubic meters to under 10 m3

(based on an average flowrate of 250cmhand 2 minute response time to shut off the pumps). This excludes, as previously said,drainage of line contents, which is outside of operator s control. An additional investmentfor MOV s along the length of the pipelines would reduce the amount of line contentdrainage (this is not in the project scope).

At this stage, the detection capabilities have only to be provided for steady flowing

di i f h f h i i d f i (idl ) di i d


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short periods of balance samples (i.e. a temp variation as big as 1 / 2 C in 15 minbalance results in a linefill volume change of about 0.01%, equivalent to 1 / 2 m3 for a 5000 m 3 pipeline (worse case). This is insignificant when compared to theLDS thresholds for alarms and cutoffs .


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Pipeline Leak Detection Application (PLDA) PerformancePLDA to be implemented by Pipeline Automation Improvement project provides oil spilldetection during steady flowing lines. Detection functionality for static (idle) conditions andduring transitions is not required at this stage. The table below, therefore, shows theexpected performance limited to flowing conditions.

The application criteria is based on oil spill flow rate rather then on the leak size, which isnot the only function variable (i.e. liquid head also varies substantially).

The PLDA response time is a function of the quantity of spilled oil. The response timeranges from the immediate shutdown for a large spill, detected by a combined

flow/pressure high Rate of Change (ROC), to 15 minute for an oil spill as small as 1% ofthe pipeline flowrate, which is typical for a 5mm diameter hole.

Leak missed by one methodcan be detected by another more sensitive method.

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EXPECTED PLDA PERFORMANCE

FLOW/PRESS ROC FLOW IMB 1 MIN IMB 5 MIN IMB 15 MIN IMB

LEAK

RATE

SPILL

SIZE

LEAK

RATE

SPILL

SIZE

LEAK

RATE

SPILL

SIZE

LEAK

RATE

SPILL

SIZE

LEAK

RATE

SPILL

SIZE


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System ConfigurationAttachment 1 provides a hardware overview of the leak detection by mass balancesystem. It is primarily based on the pipeline In/Out mass balance, expressing masses asvolumes at standard condition of 1 atm and 15C.

Pipeline and Instrumentation

Pipeline systems operated by Xxxxxx Refinery range from 6 to 12 inch OD lines that spanfrom 12 to 156 kilometers. Only the main pump stations at the pipeline inlet move theproducts, thus no intermediate Booster pump stations are actually in place. Each pipelineterminates at only a single receiving terminal.

These pipelines mainly transport ADO and Mogas at constant flows as mentioned inprevious sections.

Fiscal custody-transfer metering is performed at the Trecate PD Meters using a distincttank prover for white products and another distinct tank prover for black products. Theterminal turbine meters are non-fiscal meters with dedicated master meter prover. The


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Leak Detection System (LDS)

Pipelines are operated from the Refinery Central Control Room in Trecate where the newGUS op/sts will provide the operator with LDS monitoring and control. In addition, aredundant PLC at the RIS, one each the six major pipelines, will perform the LDSapplication.

The software combines the LDS application running on each PLC and the supervisorystations in a fully integrated system. The leak detection application includes data transferwith the flow computers and a database used by the op/st.

Base data for LDS are pipeline In/Out standard flowrates and volumes, whose signals are

computed by flow computers at both local and remote sites. These signals, available byflow computers, are transmitted to the PLC to perform the mass balance and detect theoccurrence of product loss.

The application functions are summarized as follows (ref to attachment 3):

Data acquisition from flow computers

Computation of in/out delta volumes when in Off mode, to bias the balance on its


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Flow rates: 16 bits resolution, to express flowrates in terms of tenths of cubic meters upto 999.9 m 3 .

The GUS Stations should accommodate LDS data in the following ways:

Main p/l The main pipeline graphic display should integrate the one min MB'

Display: balance (continuous MB is also recommended for monitoring purpose).Adjacent to the MB Counter should be provided the switch to turn On/Off the LDS application (a digital unlatched is preferable). The switch symbolshould change color according the LDS status (digital from PLC).Below the MB Counter should be displayed the leak size.

LDS Trends: A special page display should be designed to show the operator the

following trends on separate coordinates, split horizontally. Attachment 9provides an example of such a display:- Both Flowrates- Delta Flowrates- Delta 1 min MB - Delta 5 min MB


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Application Software

The LDS application to be developed is based on pipeline mass balance calculation,expressing masses as volume at standard conditions. Calculations for transient phasesand linefill compensation are not required, nor are characteristics such as momentum andenergy and equation of state. These are assumed not to influence linefill volume, thus noreal modeling is required. The pipelines to be monitored have simple designs and simpleoperations that allow an almost permanent steady state.

Three main methods of leak detection have to be developed, which are: unexpected flowand pressure variations, unexpected net-flowrates imbalance and unexpected net-volumeimbalance. By a comparison of measured values with dynamic thresholds, the applicationwarns the operator through pre-alarms and shutdowns the pipeline in case of highdeviations. Attachment 3 is a schematic of the whole application. It shows the hardwiredI/O as well as the soft I/O exchanged with the GUS op/st.

The predefined threshold represents the minimum leak size detectable for each method ofleak detection for the pipeline operating under optimal conditions. The threshold will varydynamically to reflect percentages of the parameters under control.


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Calculations:

Delta In/Out Flowrates and alarm threshold.

Delta Net Flowrates: )()( OUT IN VnVnVn

Threshold calculation100

5)(%

IN VnT

Alarm Testing ::%T V if

Alarm/Cutoff Enabled Testing : Al LDSif ON

Alarm Activation :'2 Alif

Cutoff Activation :'4 Alif

Flowrate High Rate of Change (Ref. Attachment 7 Lower part)

Rate of Change is performed on flowrate at the originating site and at the receivingterminal," preferably by flow computer:


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diagram is based on two counter registers whose difference is zeroed at 1 minuteinterval. Just before such zeroing the difference is read and stored as the quantityof product measured in the last minute period. Two such functions are required tocover respectively the originating and the receiving terminals. Once both 1 minuteIn/Out volumes are available and are updated at 1 minute intervals, they are

compared to determine the amount of 1 minute imbalance. This figure is thencompared against the alarm and cutoff thresholds.

The imbalances in a 1-minute interval are very small values even for substantialleaks as great as 5 % of the max flow. Thus it is important to have very precisesignal resolution.

The 1-minute quantity signals are also used to feed both the 5 and the 15-minutemoving windows, as defined below.

5 Minute and 15 Minute Imbalances (see Attachment 8 for reference)

In addition to the previous LDS, to detect smaller leaks two more imbalancemeasurements have to be realized, respectively for 5 and 15 minutes.


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by means of a group of wrap around registers to be updated sequentially at a paceof 1 minute. Attachment 2 suggests a method to design such a system.

Leak size

As an order of magnitude, the application provides the oil spill flowrate in terms of liters perminute for those leaks detected by the volume imbalance functions. These figures will beobtained by the imbalance register, among the three ones, which first detects the leak. Asthat occurs, then the value that is compared against the threshold will be scaled to obtain avalue in terms of liters per minute.

Detections by rate of change and flowrate imbalance are suitable for medium/large spills;these methods don t provide size values, whose extent can be easily evaluated by thedata available on the op/st (i.e. the trends of flowrates can indicate the magnitude of thespill size).

No suggestions are herein given to develop this function, as it is believed to be simple todesign.

Leak Location

1.1


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ATTACHMENT 1

RedundantPLC

KF-2 KF-2

DH+

LINE SWITCH

CLM

To GUS Stations

RS-232RS-232

NIM

MODBUS

RS-485 RS-485

1.1

SERIAL LINKSERIAL LINK


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ATTACHMENT 2

Reg. 16A

Reg. 15A

Reg. 14A

Reg. 13A

Reg. 12A

Reg. 11A

Reg. 10A

Reg. 9A

Reg. 8A

Reg. 16B

Reg. 15B

Reg. 14B

Reg. 13B

Reg. 12B

Reg. 11B

Reg. 10B

Reg. 9B

Reg. 8B

LEFT RIGHT LEFT RIGHT

DIFF

15 MIN MB


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AUTOMATIC S EQUENCING

Paolo Cacciaglia - Proprietary Page 23 of 30 17/02/2012

ATTACHMENT 3

NOTES:

Metering signals are from flowcomputers, sent to the PLC via serialcomms, both with the same transferrates and programmed as closesequence.

The shutdown by rate of change(ROC) method requires both flow andpressure ROCs above Cutoff thresholdto activate the shutdown. FlowrateROC by itself only cause an alarm.This method works even when theremote comms links are not working.

Precise input signal resolutions are

required, accurate to tenths of a liter.LDS calculation modules also providesignals for digital reading and trendson the GUS op/st. This is not shownon drawings.

PROCESSMEASUREMENTS

FLOWCOMPsPROCESSED

NET VOLUME IN

NET FLOW IN

NET FLOW OUT

ONE MINUTEMASS BALANCE

FIVE MINUTEMASS BALANCE

15 MINUTEMASS BALANCE

CONTINUOUSMASS BALANCE

LDSCALCULATIONS

NET FLOWRATEIMBALANCE

FLOWRATERATE OF CHANGE

NET VOLUME OUT

LOGICS

EN

DIS.

OR

OR

ALL

HFI

SHD

HFI

OR

PRESSURERATE OF CHANGEPRESSURE

ALL

ROC

ALLHQI

SHD

HQI

SHD

ROC

ShutdownHigh VolumeImbalance

AlarmHigh VolumeImbalance

ALARMS &OUTPUTS

TRECATE PIPELINE MASS BALANCE LEAK DETECTION BLOCK DIAGRAM

ALL

ROC

If Enabled

If Enabled

P/L SHUTDOWN


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ATTACHMENT 4

ONE-MINUTE ACCUMULATOR FUNCTION BLOCK DIAGRAM

Registers A are continuous accumulators; Registers B update at each minute to zeroed the one minute accumulator . Before tozero, one minute values are moved to 1 vol registers, whose difference represents the one minute imbalance.

Reg. A

Reg. B +

Flow Computer Refinery + 1 vol in

Reg. A

Reg. B +

Flow Computer ReceivingTerminal

+ 1 vol out

1 clock First

Second

1 Unbal.


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ATTACHMENT 5

PipelineFlowRate

IN

PipelineFlowRate

OUT

5% FlowCalculation

DELTAFlow RateIN - OUT

F > 5%F

Leak detect

ENABLE

ON 2 ON 2

High Flow

ALARM

High Flow

Shutdown

FlowROC

Flow3 %

Flow6 %

ROC >3 %

ROC >6 %

ROC>3%

ALARM

ROC>6%

CUTOFF

PIPELINE SHUTDOWNFLOWRATE IMBALANCE


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ATTACHMENT 6

Counter Pulses

IN

Counter Pulses

OUT

Leak detect

ENABLE

IN - OUT ACTUALVOLUME

IN - OUTTRANSIT.VOLUME

Accumulator TOTAL IN

Accumulator TOTAL OUT

IN - OUTCOMPENS.

VOLUME

6 Threshold

9 Threshold

5Threshold

8Threshold

Leak detect

ALARM

Leak detect

CUTOFF

Totals > XX cmh Comm. On

CONTINUOUS VOLUME IMBALANCE

ELIMINATED


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ATTACHMENT 7

PipelineFlowRate

IN

PipelineFlowRate

OUT

5% FlowCalculation

DELTAFlow RateIN - OUT

F > 5%F

Leak detect

ENABLE

ON 2 ON 2

High Flow

High Flow

FlowROC

Flow3 %

Flow6 %

ROC >3 %

ROC >6 %

ROC>3%

ALARM

ROC>6%

CUTOFF

PIPELINE SHUTDOWN

FLOW RATE OF CHANGE CUTOFFFLOW IMBALANCE AND FLOW RATE OF CHANGE CUTOFFs


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ATTACHMENT 8

Counter Pulses

IN

Counter PulsesOUT

Last Minute

TOTAL

1 5.842 5.783 5.904 5.825 6.176 5.847 6.228 6.009 6.0510 6.0211 5.9812 5.9713 6.0114 6.00 A T

C H O U T

L A S T 1 5 M I N U T E S V O L U M E

1 5.842 5.783 5.904 5.825 6.176 5.847 6.228 6.009 6.05

10 6.0211 5.9812 5.9713 6.0114 6.00 B A

T C H

- I N

- L A S T 1 5 M I N U T E S V O L U M E

Last Minute

TOTAL

First InLast Out

ShiftRegister

First InLastOutShift

?

15 min

}} ?

5 min

?

15 min

}} ?

5 min

Q

5 min

Q

15 min

Q

1 min

ALARMThreshol

d

ALARMThreshol

d

ALARMThreshol

d

CUTOFFThreshol

d

CUTOFFThreshol

d

CUTOFFThreshol

d

ON ON

ALARM CUTOFF

Disabling the Leakdetection causes bothshift registers to reseto zero and stay in such

a status until theapplication is resumed.In the latter event, bothregisters restart storing

he new data from thelast minute volumecounters.

5 AND 15 MINUTES IMBALANCES


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ATTACHMENT 9


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ATTACHMENT 10

1.26% - Leak Simulation

-1,000

-0,750

-0,500

-0,250

0,000

8.00 8.06 8.12 8.18 8.24 8.30 8.36 8.42 8.48 8.54 9.00 9.06 9.12 9.18 9.24 9.30 9.36 9.42 9.48 9.54 10.00

time

mc /h

5% Threshold for 1 min



1 minute imbalance

5 minute imbalance

15 minute imbalance

Trends simulates a leak of 51 l/min on a flowrateof 246 mc/h. Equivalent to 1.26Leak is detected in 10 min by the 15 minuteimbalace methode. Oils spill is =510 liters

MBLeakDetection FFinal 1.1

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