Metering for City Gas Distribution

8/2/2019 Metering for City Gas Distribution

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By

MANJUNATH

(R030307003)

M-tech(GE)


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Introduction to company

Synopsis

System description

Metering for city gas distribution

Classification of flow measuring devices

Meters used in Adani energy limited

Description of the meters

Billing of domestic meter

Selection of meter

Meter installation

Costing of domestic connection

How a customer can steal unregistered gas

Precautions to stop tampering of meter


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Overview of the Adani groups Adani Mundra Port

Adani Real Estate

Adani Energy Limited

Adani Agro

Adani Wilmar Limited

Adani Power

Adani Logistics Limited

Adani Energy Limited

Gas Distribution

Adani group initiated Gas Distribution Business with a goal of providing safe,convenient, reliable and eco friendly fuel to.

Industrial

Commercial

domestic and

transportation sectors


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Fuel supply of AEL PNG

CNG

Places Ahmedabad

Vadodara

Network of AEL < 110 KM of steel pipeline


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Gas supplier to AEL

Petronet LNG

NIKO

GSPL grid to AEL


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Synopsis

This internship report deals with the metering for city gas distribution and its study

Meters used in AEL

Meter mechanism and installation

pressure and temperature parameter which has to be considered while billing

Increasing the meters efficiency


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System description

The system description involves the total arrangement or network in doing citygas distribution business.

City Gate Station

Odorization

District regulating station

Industrial Metering and regulating station

CNG station

Pipeline Network

CGS

Gas Filtration skid

Pressure reduction skid

Flow metering skid


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Metering of gas

It refers to measuring gases based on the volumetric measurement, velocity,thermal and calorific method.

AEL do volumetric and velocity based measurements of the gas supplied to thecustomer

inlet outletmeter


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Classification of metering devices

1. DP meters

> Orifice meter

> Venturi meter

> Pitot tube meter

2. Positive displacement meters> Diaphragm meter

> RPD meter

> Piston type gas meter

3. Velocity meters

> Turbine meters

> Ultrasonic meter


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Meters used in AEL

Senior Orifice meter

Diaphragm meter

RPD meter

Turbine meter

Senior orifice meter:

This meter is used to measure the gas with high flow rate. Senior orifice has veryless turndown ratio i.e of 10:1

Differential pressure cells: the DP transducer measures the differential pressuresand converts it into electrical signals, as a input to flow computer.

AEL use, DANIEL patented Orifice which gives DP values to the flow measuringmachine BOSS.

The patented equation is

Qh = Fb*Fa*Fr*Y1*Fh*Fm*Fpv*Ftf*Fpb*Ftb*Fgr*hw*Pf

Fb = basic orifice factorFa = orifice thermal expansion factor

Fr = Reynolds number

Ftb = temperature base factor

Fg = specific gravity factor


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Fpv = super compressibility factorFh = gauge location factor

Pf = flowing pressurehw = water head due to pressure


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Diaphragm meter:

This is a positive displacement meter which measures the gas by holding andreleasing mechanism of fixed volume .

The flexible material used for this meter is a diaphragm made up of a syntheticfabric called reinforced nitro rubber

Lever and linking mechanism are connected to the dial called index box whichshows the amount of gas consumed by the customer.

Following figure shows the internal structure of the meter


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Reading the meter

The below figure registers cubic meters and here the first five digits give the

quantity up as far as the decimal point. They are again surrounded by a thick black

band. The last three digits represent the number of decimeters. The last digit

representing0.1dm3 per sub-division.

Meter index


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Rangeability Of Diaphragm Meter:

It can be used to measure very less flow rate, which is desirable for the domestic

purpose.

The rangeability is Qmin 0.016 m3/h, Qmax 2.5 m3/h to Qmax 65 m3/h

Pressure should be max of 0.1bar.

AEL use diaphragm meters from Actaris company.

Correction factor for diaphragm meter:

Volume and temperature Correctors will be fitted to all meters operating above 75mbar and with a flow range of above 20 SCM/h.

For flow below 20 SCM/H PD meters will be installed without volume andtemperature Correctors.

For these meters flow rate obtained is multiplied by correction factor given as


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V1/V2= (P2*T1) / (T2*P1)

V1 = std volume

P1 = std pressure

T1 = std temperature

V2 = measured volumeP2 = measured pressure

T2 = measured temperature

Corrected flow = measured flow* correction factor. (standard condition scmh).


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to calculate correction factors for different mechanical meters(diaphragm)

Input

base pressure P1 = 1 Atm

1.01325 Bar

1013.25 Mbar

base temperature T1 = 25 C

0.075 Bar

operating pressure P2 = 75 Mbar

operating temperature T2 = 25 C

Output

corection factor v1/v2 = 1.074019 for pressure in mbar

corection factor v1/v2 = 1.074019 for pressure in bar


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Turbine meter:

Turbine gas meters are flow meters

flow of gas turns a turbine wheel, and thus, the rotating speed of the turbine isproportional to the linear speed of the gas.

The movement is mechanically transmitted to the totaliser through the magneticcoupling, which shows the reading.

For the flow calculation an electronic device is connected called EVC, electronicvolume converter

It gives readings in standard conditions

It got good turndown ration and accuracy i.e 50:1

Qmin= 10m3/h to Qmax = 400 m3/h


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Internal arrangement of meter


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EVC


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Selection of meters:

Collection of data on load pattern

CRITERIA FOR SELECTION OF METER

Following criteria shall be considered for the Best match,

Contractual requirement

Rangeability or Turndown ratio

Accuracy requiredSuitability of meter with quality of gas available

Pressure requirement

Calibration & maintenance requirement

Size & weight

Installation and maintenance constraints

Operability

CostGas quality

Filtration

Filtration at 50 microns should be fitted to all metering system operating atpressure above 75 millibar and 16SCM/hr


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SN Type of meter

recommended

Working pressure Flow range Type of customer limitation

Bar M3/ Hr

Min Max Min Max

1. Diaphragm Meter 0.0 0.2 .016 30 Domestic Commercial &

Small scale Industry with

pressure requirement less tha n

75 mba r only

Bigger Sized,

Expensive for high flow

No Pressure & tempera ture

compensation

2 Rotary Positive

Displacement Meter

0.0 16 30 1000 Commercial & Industrial Requires:

a) 50 m icron filtration Gas

Quality

b) Lubrication Maintena nce

3 Orifice Meters

With Single

Transmitter

1.5 200 none large .Industrial customers with

flow Turn down

Ratio within 3 :1

a) In- accuracies b). Regular

calibration.

c) Long straight length of pipe

Orifice Meters

With Double

Transmitter

1.5 200 none Bulk customers &

Transportation custody transfer

meters

A) In- accuracies. b). Regular

calibration.

c) Long straight length of pipe

4 Turbine meters 2bar 500 40000

Hi cost, gas qua lity.

5 Ultrasonic Meter 7bar 99 1500 none Bulk customers &Transportation custody transfer

Hi cost, gas qua lity.


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Meter installation

The installation starts from the piping from CGS to the customer

The pipeline from CGS to DRS is of galvanized iron pipe or Corrugated stainless steel

tubing (CSST)

At DRS pressure is reduced from 26 bar to 4bar

After this PE pipes are lined with service regulator up to the customer basement.

Again a galvanized iron pipe (20 t0 30mm) to the meter, with regulator and pressuregauge. Copper pipe (12mm) is line inside the kitchen up to burner or water heater.

Meters should be installed at least 1m above the ground and should be inside thecustomer property

Good ventilation should be provided, safety cover or a box with sealed .

For the industries purpose we create a skid, which includes meter, regulator, pressuregauge and EVC


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Costing of domestic connection:

S.N Item Description Unit Qty. Consider/Conn. Rate Rs./Unit TOTAL Cost

1 G.I.Pipe 1/2" NB Mtr 10 50 500

2 Copper pipe Mtr 12 45 540

2 G.I fitting 1/2" NB Nos 30% of pipe cost - 150

22 Copper fitting cost Nos 30% of pipe cost 162

3 RCC guard Nos 1 100 100

4 1/2" Isolation Valve Nos 1 125 125

5 Meter regulator Nos 1 300 300

6 Domestic meter Nos 1 1209 1209

7 Ball cock(gas tap 6.4mm) Nos 1-consider one point

only

150 150

8 Rubber tube Mtr 1 50 50

9 MDPE 20 mm dia Mtr 5 20 100

10 MDPE 32mm dia Mtr 12 25 30010 MDPE fitting Nos 2-coupler 20 dia & 1

saddle 32X20

- 590(500+90)

11 Labour cost of GI piping Mtr 18 22 396

12 Labour cost of PE installation Mtr 17 35 595

13 Service regulator cost No 1/50conn 9000 180


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How a customer can steal unregistered gas:

The customer can steal extra gas or unregistered gas by adjusting or by changing

the gear wheels behind the index, in case of diaphragm meters.

For a particular customer company do some registration about the demand, basedon which it decides to deliver fixed amount of gas with respect to pressure. A sipleway a customer can take more gas by adjusting the pressure.

Temperature can also play a vital role in stealing the gas. This can be done bydecreasing the inlet line temperature.

In EVC based meters in the battery or the solar panel got failed for a short timethan at that instant, it stop recording the meter readings, as a result stops

converting it into standard conditions. The customer used gas is not recorded inthe EVC

In case of the diaphragm. If the diaphragm of the meter is punctured, then there isa possibility of flowing extra gas to the customer


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Precautions to stop tampering of the meters:

Always check for the meter sealing.

Meter reader should check the pressure settings and any variations in that.

And he should check for the temperature variations.

Check the battery and panel conditions of the EVC type meters.

Cross check the reading of EVC meter manually with the displayed one.

Check the set points of the EVC like super compressibility and base pressure and

temperature conditions.


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Date post:	06-Apr-2018
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Metering for City Gas Distribution

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