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FIELD OF THE INVCNTION
The present invention reLates to an improved flexible dosing system for injecting
"Lubncjty additive" adaptable to Gas Turbines operating on Naphtha fuel. The
improved system can adapt severa/ quality of "Lubricity additive$* ayariable In
the market.
BACKGROUND OF THE INVCNTION
Gas Turbines are fequired to operate on vartious types of fuels.
Wherevel .Naptha fuel is readily avaiable and offer significant advantages jn
avaifabjbity and costt becomes attrscttve for use as fuel in Gas Turbine systems.
While Naphtha fuel may offer signiftcant advantages, this fuel has the
characteristic of fow lubricity. Accordigy this particular characteristic of
Naphtha fuel does warrant additional treatment to assure long life of the Gas
Turbine, particularly of ths fuel system components of the turbine
The operating life of a typical fuel system of the Gas Turbine depends on the
lubricating capability of the hydrorarbrm fuels used in the Gas Turbine to protect
bearing and its mating surfaces.
To distribute the liquid fuel flow equally to the combustion chambers, prior art
Gas Turbines use mechanical flow dividers that have very tight tolerance of
internal mating parts; to meter the Fuel flow to the multiple combustion

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chamber these flow theders hove teanvery surcessful in providing a very
tight these of flow division needed to provide uniform distribution of
temperatures from thtf combustjon system and into the turbine sectfcn. As on
today, flow divides ate an essential feature of liquid fuet-fired gas turbines,
For the Gas Turbines operating on Naphtha fuel, a ^Lubricity additive is
generallty to be dosed or injected in to the naphtha fuel for raising the lubricity
parameters to such levels witch are acceptable to the flow dividers.
The following operational consitrain0ts also need attention with respect to
selection of the dosing rate of the lubricity additive" into Naphtha fuel;-
(i) lt the injection rate is too high, gummping of the flow divider will
occur and the flow divider will stop, tripping the turbine,
(ii) If the injection rate is too tow, the bearings of the flow divider will
seize, also tripping the turbine,
(iii) Lubricity properties of Naphtha formulations vary depending on the
particular produclion process adopted by different manufacturers,
(iv) The cost of "Lubricity additiive is considerably high in Gas Turbine
hased plant, and any reduction in additive injection rate if achived,
will lead to significant savings in operational cost of the plant.
Traditionally, Hitec-580 is used as the 'Lubridty additive'. Test? have shown that
H itec-580 additive injection to produce a concentration of 60-75 ppiri [weight by
weight] of Naphtha fuel flow rate into the Gas Turbine is the best overalf rate.
Presently r the following is recommended by the Gas Turhine manufacturers for
the injection of *Hiteo580 additive* for operation of Gas Turbines operating on
Naphtha fuel.

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(i) The lniilal flow rate of then 80 additive is XXX to prOVile a
conestu;ration of 75 ppm weight by weightof Naphtha fuel flow
rate into new gas rubmes, operating on Naphtha
(ii) The flow dividel shall be removed, disassembled and inspscted at
frequent intervals for measuring the rate of deposition. If the initial
concentration of the additive results in excessive deposits, the
injection rate shaii)) be reduced to 60 ppm |weight by wetght). The
evaluation process shall be continued and if tlie excessive deposits
continue to form, the injection rate shall further be reduced while
ensuring that there iS no undue "wear" takcing place in the bearings
of the flow drvidel.
(iii) Under no circumstances the dosing rate shall be lower than 30 ppm
weight by weightjf below which the resultant wear will lead to
very sbort life of the flow divider.
(iv) The cost of additive can be minimized by consistent inspection,
evaluation and tuning of the additive dosing rate to a minimum
extent required.
In addition to Hitec-580, various other * lubricity additives * under different brand
names, are available for Gas Turbines operating on Naphtha fuel. Gas Turbine
users are also pmerimg the available choice «n selection of Vubiitity additive" to
procure the same at competitive prices thus leading to reduction in plant
operating costs,

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Accordingly, various avaitable additives have also been tested by the Gas Turbine
mavuifactures Hawever, in line with the test results, the recommend
maximum and minimum dosage ate of various types of additives differ from
brand Lo brand, compared to bhe standard recommended dosage rate of 30-75
ppm for Hitec-580.
The details of various 'iubrtcity additives" along with their recommended
minmum to maxirnum dosage ate is as per the followmg table.


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From the abonve table, it Can be comstrued that the *Lubiicity additve* dosting
system - for operation of gas Turbines on naphtha tuel generally needs rusher
special treatment as below:
(i) The dosage flow rate of Lubricity additive 'shall be in accofdance
with Naphtha fuel flow Tata into the Gas Turbine cm weight to
weight bass, in conespendence with the yalations of load on the
Gas Turbine, the Naprlha fiow rare into rile Gas Turbine also
caTtes, The Gas Turbine generally responds instantaneousty lo any
vanartation of lond which is not predictable. Hence, the "Lubricity
saddive' dosing system need to be designed in such a way that the
tow fate of lubricky additive* should be iiistantaneotisty charged
In registration with the variations in flow rate of Naphtha fuel into
the Gas Turbine.
For typical gas Tubinies, the naphtha flaw rate depends on its density and
Catoritic value. The density of Naphthd varies from 0.65 to 0.75 Kg/Lit. The
calorific vafuie of Naphtha fuel is close to i0,000 Kcal/Kg. The turn down
requirement of Naphtna flow rate into the Gas Turbine is 4:1 on volume basis#
Corresponding to the maxmun and minimum flow rates of Naphtha into the Gas
Turbine.
(ii) In additionr the dosage rate of "Lubricity additive* in terms of ppm
is variable for a plant depending on an outrome of the balance of
wear and plugging with respect to the individual Naphtha
formulation used in the plant. Acccrdingfy, the dosage rate of
lubrity additive' varices form 25 ppm to 100ppm ppm, depending on
the bland of lubficity additive" selected.

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The closage rate of "Lubricity'' addillive" in terms of ppnt is -an
outcome nf inspection of Ihe dismanhed fow divrder and will be
maintained constant til the next inspection
However, the lubricity dosing system shall be capable of meeting
the prohable var rtuation in dosing rate in terms of ppm,in addition to
the varnation in Naphtha flow due to diasiges in Jaads on G^s
Turbine.
For a typical Gas turbine, corresponding to maximunm and
minimum dosing rate variation of 100 ppm to 25 ppm, the turn
dovm retfuirement of 'Lubricity additive* dosing is 4:1 on volume
basis.
Further, the lubricity additive dostng rate \s on weight to weight
basts with respect to Naphtha flow into Gas Turbine. The weight of
'Lubricity additive* depends on the density of brand of additive
used. Accordingly, tiie turn down requirement of ^Lubricity
additive' for a density variation of the additive of 0.874 8 to 0.94 is
LI :l,on volume basis,
Accordingly, for & typical Gas Turbine, the combined turn down
reqttjrenient of "Lubricity additive" is 17.6:1, meeting variations in
Gas Turbme load inrtsnding variations in ppm levll of dosing, and
variations in densities of lubricity aciditives.

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Hence, the lubriclly additive dosing sestem sheuld be capable of
matching the wide rariations in the tubricitive " flow rate
required,
(iii) As the dising Quantity is very small and the same is sensitive in
terms of choking/wear of the flow divde, the dossing rate shall be
arrurate Hence, there should be a feed back. system to ensure that
the *Lubncity additive" dosaqe is as par the requirement only
Furthe, the companents of the system shall be accurate enough to
ensure accurate dosing.
(iv) The viscos nityf "Lurbkity addittve" is varying from as few as 20 Csl
to 256 Cst, depending on the brand of "Utfbicity Additive*
chosen.normally, there will not be any operations) problem for
dosing pumps for a lubricity lever" of 20 Cst. However, the dosing
pumps shall be capable of operating at high viscosity level of 256
Cst.
(V) As the "Lubricity additive" is avarfabte in the standard barrefsr there
shall be suitable provision fof unfoading the same into the system.
The luibicity Additive" dosing systems- for the typical GAS Turbines opsratiug
the maphtha fuel in practice are normmally designed for one particular "Lubricity
Additive" ie.r Hitec-580 and for a particular dosing rate. These systems constitute
gear type * Lubricity addittve* dosing pumps with automatic speed control of the
pumps with variable lrequency drive.
The above system has a limited turn down of 7:1 only. Hencer this system can
not cater to a wide range of available ""Lubncity additives', with varying required
dosage rates, densities, where a minimum turn down of 17.6:1 is required.

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Further gear pumps have a XXX d^ tiit ve><'.u,i>ii.j >>i
thund is higher thuis thuscalling for higher capacity of the pump when handling higher
viscosity Library addrttive'. which turlher calls iar much hlgliur furndowo
fequtrement.
In there systems manual unlading of "Lubrkity edditve" into the system
storage tank is practiced, which is labor tntensive.
Objects of the Invention:
It is therelore an objecr of the invention to propose an impioved dosmg system
for injeting lubricity additive adaptable to gas turbines operating on naphtha
fuel.
Another object- of the invention to propose an improved dosing system For
injecting lubricity additive adaptable to gas turbines operating on naphtha fuel
which eliminates the disadvantages of the prior art.
A farther objact of the indention to propose an improved dosing system for
injecting lubricating additive adaptable to gas turbines operating on naphtha fuel
which is capable to cater for the variations in vistocities of different types of
available lubricity additives,
A still further object object of the invention to propose an improved desing
system far injecting iubrkity additive adapUbie to gas turbines operating on
naphtha fuel which pvovides medianized unloading of lubricity additives to the
stoiage tank of the system.

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and yetanother which in of the inviertion[ to plopse an improved dosing system for
rejecting lubricity additive adaptable to gas turbines operting on naphtha fuel
which is testel, economic and actuate
Summary of the Inyeptjon
Accordngly, there is provided an improved flexible lubricty additive dosing
system adaptabte to a gas turbine operating on naphtha fuel, comprising an
unioding device having a portabte motor driven baren pump for bansferring
lubricity additive from a barrel to a storage tank, the storage tank being
operably connected to the unoading device via a discharge hose, the barrel
pump is connected to the portable motor drive via a flexible power cable, the
storage tank provided with instrumentations for auto-change - over of gas
Turbine to alternate fuel, in response to alarming signals generated by the
insumenrs provided in the storage tank based tin the available levels or the
lubricity additives in the tank.. Atteast two motor driven dosing pvimps are
provided for metering and dosing a predetermined quantity of lubricity additives
into a fuel supply device of the gas turbine, A puslation dampenr is arranged
for smoothening the additive flow into the system. A flow meter is disposed to
measure the follow rate of lubricity additive to the gas turbine and providing a
flow signal to a dosing control device. A control device is operably connected for
calculating the dosing rate based on instaneous naphtha flow fate into the gas
turbine. the device transmiting corrective signals representative of the flow-rate
once the flow rate measured by the flow-meter mismatches the calculated
dosing rate.

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ORIEF DESCRIPTION OF THE ACCOMPAMYlNG DRAWINGS
1, Figure 01; iS schetnatic diagram of on-base liquid fuel system For a typical
Gas Turbine,
2. Figure 02: is schematir diagram of an improved flexible -"Lubricity
additive" dosing system"- for a Gas Turbine operating on Naphtha fuel,
according to the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
As shown in figure-2, the improved flexible "Lubricity additive' do$ing system-
comprises the following components:
- an Unloading device (2,3,4);
- a Storage Tank (5) ;
- atleast two Motor driven dosing pumps (6);
- a Pulsation Dampener (7) ;
- a Flow meter (8);
- Inter connecting piping and instrumentation circuit; and
- a Control device having Vanable Frequency Drives.
The function and detailed descriptions of above components is as given below:
1.0.0. Unloading device (2,3,4)

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1.1.1.0 Function:
Normally, the "Lubricity additive* is available in standard 200/250 liters
barrels(l) the lunction of the unloading device is to transfer Hie "Lubricity
additive" from the ba nel (I) to a storage tank (5) oF the "Lubricity additive*
dosing system.
1.2.0 Components Description*
Atteast one portable motor driven barrel pump (2) with a discharge hose (4) and
a flexible power cable with a plug arrangement is considered as a part of the
"Lubricity additive'dosing system.
In case the tevel of the storage tank (5) is IOW\ atarm will be genetated in the
control room for operate*'s intervation for unloading of "luxicity additive' in to
the storage tank (5) of the dosing system, using the barrel $jurc\p(2). The pump
(2) can unload the barcel (1) about 5 minutes.
The storage tank(5) has sufftcicent recerve capacity for a dayr till the "Lubricity
additive* is reptenished manually.
2.0.0. Starage Tank (5)
2.1.0 Function;
'Lubricity additive0 for ten days openrational requirement of The Gas Turbine can
be accommodated in the storage tank (5).

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2.2.0. Components Description:
Aueast one 450 LiLers storage tanlk (5) is envisaged for a Gas- Turbine (10) The
tank (5) iS provided with required level instruments for:
(1) alarming the operator in case of low lavel in the tank (5) for
reptemshment of • Lubricity additive".
(iii) auto change-over of operation of the Gas. Turbine (10) to alternate fuel
and to trip the dosing pumps (6) in case of low-low-level in the tank
(5). it is not safe for tfie operation of Gas Turbine on Naphtha fuel
system (11) without dosing of "Lubiicity additive". furthel non-
occurience of levei low-low alarm will act as a start permissive for
starting the dosing pump (5).
3.0.0. Motor Driven Docsing Pumps (6):
3.1.0, Function..
To dose the required quantfty of "Lubricity additive "into Gas Turbine fuet suppiy
system, according to the fuel flow rate, while the Gas Turbine is operating on
Naphtha fuel.
3.2.0, Components Description:
As the dosing reqgvines acurate meteing, positive displacement plunger pumps
are ideal choice. Futther, with plunger pumps it is possible to have a higher turn
dawa in flow rate by combined effect of stroke iength variation along with
variable speed operation of the pump.

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Accordingly, acleast two motor driven phunger type reciprocating pumps II
working f 1 standby) if soltable rapacity and head are considered for the
system.
Further, cherk valves with double all wilout, sprms envisaged as a speciall
design in these pumps (6) to catel to higher viscosity requirement of 256 Cst.
These chock valves are suitable for operation on low viscosity of 20 Cst also.
The pump (6) has manual stxoke length setring provision with a turn down ration
of 10:1. ieLi the stroke length can be varied from 10% to 10%. The flow rate of
the pump is proportional to the stroke tength set.
Further, for a given stroke length setting, the flow rate can be varied by
changing the speed of operation of the pump (5),
4.0.0. Putsation Dampenar :(7)
1.3.0 Function:
To smoorhen the pulsating flow in the system
4,2.0, Components Description;
As the flow tharacteristic of a Tecriprocatlng pumps, is puisatin9, a pulsation
dampenef (7) is provided on the discharge line of the pumps (6), so that
smoother flow is ensured in the downstream system. Further, the flow meter(8)
provided in the system also requires a non--pulsating flow for effective operation.

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5,0.0 Flew Meter; (8)
5,1.0 Function-
To measure and indicate the flow rate of "Lubricity additive, being doing into
Gas Turbine Fuel system and to provide ths How signal to foe dosing carteor
device (9}.
6.0.0. Interconnecting Piping and Irtfftnmieitbboit:
6.1.0. Function:
All the required inter connecting piping and instrumentation like safety valves,
gauges and transmitters are provided as shown in Figure-2 for monitoring and
safe operation of the system.
7.0.0. Control device with Variable frequency Drives (9)
7-1.0. Function:
The control device of "Lubricity additive" dosing system, does the fallowing
functions, namely:
(i) Corrtrol the speed of the dosing pumps(6), based on signal from a
feed back means (not shown),
(ii) Auto start of the standby dosing pump (6) in case of failure of the
running pump (6),
(ii) Other controls

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(1) Con trolling speed of the dosing pump (6)
The dosing pump (6) has manual slroke length setting provision with a turn
down ration of 10:1 ie.f the stroke length tan be varied from 10% to 100%. The
How rate of the pump (6) is proportional to the stroke length set.
Further, for 3 given stroke length setting, the flow rate can be varied by
changing the speed of operation of the pump.
The initial stroke length of the pump (6) is set as per the "ppm level'of dosing
requited and the flow rate of tte pump (6) is futther tuned by automatic speed
variation of the pump based on the feed back signal with respect the Naphtha
flow rate into Gas Turbine (10), which depends on the load on the Gas Turbine
at that instance
The initial manual stroke length setting for various ppm levels of dosing and for
various "Lubricity Additives" is given in the following table for a typical Gas
Turbine. For this application, the selected capacity of the pump is 0-2 Liters per
hour.
HITRC-580


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Out of the total turh Jown requlreinent of 1/.6.1 , once the stroke length of
dosing pump (6) Is set based on Maphrfrs fuel density and required ppm leveI of
dosing, the 'Lublicity Additive* flow rate only needs to be controlled with respect
to Naphtlta fuel flow rate into Gas Turbine conesponding to operattng load on
the Gas Turbine. The remaining required turn down for meeting this requirement
is in the range of 4:1.
Variable Frequency Drives are considered as part of a power supply system to
the motors of the dosing pumps (6) for automatic changing the speed of the
pump(6)f with respect to valtations in naphtha fuel flow in to Gas Turbine (10),
Vanabie frequency drives have a trun down of 7:1 for changing the speed of the
metering pump, which is well above the required turn down of 4;1.
The Naphtha flow rate into the gas Turbine (10) is measured by a Naphtha flow
meter (14). The Naphtha flow signal is fed into a "Lubricity additive: dosing
control device (9).
This control device [9) constitutes a dedicated Pf-C based panel or the plant DCS.
Jh the contra) device 'Lubricity additive* dosing fate is calculated for a given
'ppm leve-f' based ort irrstantaneous Naphtha flow into the Gas Turbine (10} and ft
is used as 3 variable set point for the control of 'Lubricity additive ""dosing rate.

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The "Lubricity additive" being dosed into into a gasTurbine fuel system (15) is
measured by the lubricity addibve"1 flow* meter (6) and compared with the Set
flow rate, and a corrective signal willbe provided to the variable frequency drive.
Based on tfijs signal the variable frequency drive will vary the frequency of
power supply to the moter of the. dosing pums (6), thus changing the speed of
the pump {6) and the fiow rate of the dosing pump {6) is tuned to Ithe
requirement, by the control device (9).
(ii) Auto Change over of desing pumps:
Corresponding to the 'Lubricity additive" dosing flow required, as calculated by
the control device (9), a flow levle at 20°/ IOWER than required is idertified by
the control device as low rate of dosing. In case of low rate of dosing, due to
failure of running of the dosing pump (6)f as measured, by the "Lubricity
additrve' flow meter (8), the ccnttoi device (9) will start the stand-by pump (6)
and trip the running pump (6)f thus ensuring a continuity of dosing. In case the
stand-by pump (6) doas not start in pre-set time, that is tow-flow condition
prevails, a signal wiH be provided to the Gas Turbine control system (12) to
change over to alternate fuel by actuating a change-over valve (13), for safe
operate of the Gas Turbine U