Lpg Automation

1

Tank Storage Istanbul

11/2010

LPG loading operations

management

Presentation – 09/11 - 2

Automation & metering solutions

1. General configuration of an LPG depot

• Flow metering considerations and requirements

• Health & Safety requirements

• Loading authorization and security systems management

2. Case study

• Presentation of an optimized supervisory and MECI automation and

supervision system for the management of 14 LPG depots including 7

unmanned depots

Agenda

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• LPG transactional bulk transfers can be carried out using standard volume or mass.

• LPG Custody Transfer measurement primary meter must meet an accuracy of 0.6%

(OIML R117 - MID)

• Measure Accuracy depends on maintaining a single phase liquid flow through the

flow meters

Flow meter requirements



• Volumetric flow metering (liters)• PD meter, turbine meter• Ultrasonic flow meter

• Mass flow metering Coriolis (kg, tons)

Flow (volume and mass) metering

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• Primary measurement in volume (PD and turbine meters) • Primary measurement in mass (coriolis meters)• Lack of moving parts, no mechanical wear (coriolis)

• Primary measurement in volume (PD and turbine meters) • Primary measurement in mass (coriolis meters)• Lack of moving parts, no mechanical wear (coriolis)

BenefitsBenefits

• Liquid phase assurance: Pressure drop can cause vapor breakout (flash point)• Mechanical wear due to poor lubricity of LPG (PD and turbine meters)• Units conversion uncertainty problems (mass to volume, volume to mass)• Difficult calibration with volumetric devices (coriolis)• Vibration sensitivity (coriolis)

• Liquid phase assurance: Pressure drop can cause vapor breakout (flash point)• Mechanical wear due to poor lubricity of LPG (PD and turbine meters)• Units conversion uncertainty problems (mass to volume, volume to mass)• Difficult calibration with volumetric devices (coriolis)• Vibration sensitivity (coriolis)

DisadvantagesDisadvantages

Flow (volume and mass) metering



Mass =Volume * Density

Density must be determined !

1- Using an on-line densitometer (expensive solution); the densitometer is directly connected to the flow computer

2- Using LPG conversion tables, 24E and 23E, (produced and published by The Gas Processors Association (GPA) under the designation TP25), or other standards.

The electronic flow computer will convert the volume to standard volume V15 and will compute the transactionnal mass = V15 * D15

Conversion from mass to volume and calculation of standard volume require accurate knowledge of the properties of LPG mixtures.

Volume conversion to Mass

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Measurement by weighing full truck



• Primary measurement in mass • Vapor phase measurement unnecessary• Balance in weight easier• Easy weighting instruments calibration

• Primary measurement in mass • Vapor phase measurement unnecessary• Balance in weight easier• Easy weighting instruments calibration

BenefitsBenefits

• Very expensive solution (weighting bridges, on-board weighting sensors)• Tank trucks volume overfilling not controlled• Tank truck traffic in the loading terminal heavier, more complex supervision system• Safety problem; LPG gas retention on in weighting bridge installation gap

• Very expensive solution (weighting bridges, on-board weighting sensors)• Tank trucks volume overfilling not controlled• Tank truck traffic in the loading terminal heavier, more complex supervision system• Safety problem; LPG gas retention on in weighting bridge installation gap

DisadvantagesDisadvantages

Measurement by weighing full truck

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1 - Loading arm and hose must be constantly full of product in service operation

2 - Liquid phase assurance; LPG gets a high Vapor Pressure. Pressure drop can cause flashing change to two phase conditions, which can distort the measure accuracy.

LPG Vapor Pressure is a mathematical equationAntoine formula, Vapor Pressure in relative bar unit function of temperature:

VP = exp(a-b/(c+t)))-1

Butane C4 H10 a:9,6382297 b:2321,2682 c:256,64 Propane C3 H8 a:8,8258087 b:1897,6525 c:262,79

LPG flow meters operation requirements



Vaporization depends on temperature and pressure of measured product

How to maintain pressure and avoid vaporisation and maintain the liquid phase ?

– Cooling the temperature of the LPG (expensive)

– Maintaining the LPG all over the pipe at a pressure higher than its own Vapor Pressure:

• Holding constant pressure though P > LPG Vapor Pressure at max service temperature

• Holding adjusted pressure though P > LPG Vapor Pressure + 1 bar (dynamic regulation)

LPG flow meter requirements

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LPG is pushed in the piping in order to:

Push out gas pockets To cool the piping installation in order to avoid

gas formation during loading operation

T° Storage

Cooling process

Truck loading operation (1)



The required quantity is pumped under pressure and loaded into the tank truck. In some configuration, the gas phase in the tank is either condensed or returned to the LPG storage.The site system or the batch controller control :

The flow pressure regulationThe flow rate regulation

Storage

Truck loading operation (2)

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Gas phase of the storage is used to push out the liquid of the tank truck

Empty tank gas recovery

Liquid phase

Gas phase

Storage

Tank unloading operation (1)



The direction of the compressor is inverted in order to recover the gas phase of the tank truck.

2) Gas phase recycling Gas

Storage

Tank unloading operation (2)

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• General site gas, flame and smoke detections

(emergency alarms)

• Synchronization of the valves and pump status

(emergency shut down valves)

• Over & under pressure sensors

• Overflow probes

• Tanks level control

H&S requirements - Overall LPG site



• Loading arm safety break

• Loading arm settled valve

• Loading arm pressure switch

• Vehicle grounding system

• Overfilling detection sensors

• Dead-man control

• Metering defaults

H&S requirements - LPG loading position

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Truck overfilling sensor:In addition to visual rotating gauge, tank truck can be equipped of an overfilling sensor (optical, magnetic , radar)The safety control system automatically stops the filling process when the overfilling level is reached

Dead Man safety device:At a regular time interval, the operator must manifest its presence on the site actuating the dead - man device.In case of non presence action, a sound alarm is actuated.If the situation last, the general safety alarm is actuated for the site safety and alarm to safety services

Earthing connection;A specific grounding control device does not allow loading operation if not connected

H&S requirements - operator cabinet

Case study :

Optimization of metering,

automation and supervisory

for LPG depots

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2-Case study : Automation of loading & unloading stations

Overview

Final user A French Major Oil Company

Location France

Application

-Supervision and automation of 15 butane, propane & LPG depots

including 7 unmanned facilities (without permanent employee)

-Automation of loading & unloading of LPG, butane, propane

local and distant tank farm supervision, remote maintenance



Overview

Main depots

Unmanned depots

Headquarters


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Overview

Main depots 150 à 500 m3Supplied by rail or tank trucks

Unmanned depots 100 m3 maxiSupplied by tank trucksControlled by related main depot

Headquarters Remote maintenance Possibility to control all the depotsStock reconciliation in mass




Overview: unmanned depot

Operator cabinet

Access control for trucks and drivers

Operator cabinetLoading area

Unloadingarea


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Depot access control

Driver identification

Biometric identification at the inlet of the depot

Fingerprint readers are used to allow

only accredited drivers to enter the facility




Depot access control

Trucks identification at the inlet of the depot

Semi passive tag technology

Microwave based communication The tag echoes its identification code when receiving a 2.45 GHz carrier emitted by the antenna

Hand free detection


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Loading operations : operating procedure

The driver is identified via a smart card reader

The driver key-in loading data via MMI

- mass preset value and medium

- Actual tank filling rate

-Truck plate number

The system calculates and display the maximum allowed quantity to be loaded

The driver must then connect security devices (grounding system, tank level switch)

He will then be allowed to press the “Dead-man” & the “Start loading” buttons




Loading operation : operator cabinet

Card reader

Man – Machine Interface

Dead-man detectionGrounding detection

Tank truck level detection

Emergency stop button

Total mass display

“Start loading” button


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Metering systems

1-Measuring system with turbine meter

-Measurement of volume at operating pressure & temperature

-Measurements of operating pressure and temperature

-Calculation of operating density from P, T & API MPMS 11.2.2.M table

-Calculation of masse

Advantage: Easy to calibrate (volume against ball prover, P, t)

Weak point: Not a direct mass measurement

Can lead to error if product quality is not constant




Metering systems : ball prover calibration


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Metering systems

2-Measuring system with massflowmeter

Advantage: Direct measurement of mass

No need for P & T custody transfer approved measurements

Weak point: Calibration against prover

needs also measurement of reference density




Metering system: typical mass metering skid

Massmeter transducer

Massmeter converter

Control valve for line pressure adjustment

Motor valve


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Metering systems : flow computer (FC) functionalities

1-Calculation of loaded quantities, batch control, transactions data storage,

2-Blending control for LPG preparation

The driver enter the quantity of LPG to be loaded

The FC calculates the quantities of butane and propane to be loaded

The batches of butane and propane are loaded successively

3-Communication




Metering systems : flow computer functionalities

4-Additive injection control

Injection of ethyl mercaptan for odour or of proprietary compounds for road fuels

5-Line pressure control

The FC calculates the saturation pressure of LPG from P & T measurements

It defines a pressure set point (Psat + 1 bar) controlled by control valve

6-Calibration operation management


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Automation and supervisory system functionalities

1-Automation of loading and unloading operations

Management of loading/unloading cycles

Loading authorization according to company quotas

Security devices management

2-Communication with the truck driver

Operating instructions, error and warning messages

3-Communication with headquarters and dispatching




System architecture for main depot

Remote maintenanceSupervisory PC and data base

Truck indentification

Badge reader

Fingerprintreader

PLC

Printer

Printer events

Printer Bill of lading

PSTN

Sécurity dev.


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System architecture




Thank you for yourattention,

Q & A ????

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Lpg Automation

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