THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS345 E. All, St., New York, N.Y. 10017
The Society shall not be responsible for statements or opinions advanced in papers or in dis-cussion at meetings of the Society or of its Divisions or Sections, or printed in Its publications.Discussion is printed only if the paper is published in an ASME Journal. Papers are availablefrom ASME for fifteen months after the meeting.Printed in USA.
Performance and Reliability Improvements for Heavy DutyGas Turbines
J. R. (BOB) JOHNSTONTurbine Technology Department
General Electric CompanySchenectady, New York 12345
ABSTRACT
Many significant advances in technology have been applied tonew unit production in the past 15 years. These technology im-provements can be applied to field units to achieve increased per-formance, life, and/or reliability.
Several types of improvement are now available for compres-sors, combustion systems, hot gas path turbine parts, and turbinecontrols. This paper provides a summary of performance im-provements available for General Electric gas turbines MS3002,MS5001, MS5002, MS6001, MS7001, and MS9001 and tabulationsof performance for each improvement. Also provided are detaileddescriptions of control modernization designs available for improv-ing the operating reliability of field units.
INTRODUCTION
Many uprate parts packages have been introduced because ofcontinued strong user interest in reduced maintenance cycles, im-proved efficiency, and increased output. This paper will covermany new upratings that have been successfully developedspecifically for field unit application; it will also cover the newupratings that are available as a result of using parts that were de-veloped for later model new unit production.
Additionally many types of control upratings have been intro-duced to improve control reliability of older field units.
MS3002 Performance Improvement Package — Models A thru G
The MS3002 gas turbine was introduced in 1950. Variousdesign changes in combustion and turbine hot gas path designwere introduced over the years as the unit was uprated from theMS3002A through the MS3002 F&G models. Figure 1 lists theperformance characteristics for the various models. This unit hasbeen used for many pipeline and process applications.
An advanced technology upgrade package was developed be-cause of continued strong customer interest in reduced mainte-nance cycles, improved efficiency, and increased output. Figure 2details the MS3002 Performance Improve Package. Figure 3 de-tails improvements in thermal efficiency for the Advance Technol-ogy Parts Package for regenerative cycle units. Considerable fuelsavings are realized with improvements in thermal efficiency to32% for regenerative cycle. Figure 1 also lists uprate potential withthe Advance Technology Parts Package for Models A through G.Figure 4 details expected reductions in maintenance intervals. As
maintenance inspections for hot gas path are extended to 48,000hours, considerable reductions in planned outages and associatedmaintenance costs are realized. Figure 5 is a cross section detail-ing parts that are changed.
MODEL SHIP DATES HP RANGE
FIRING TEMP (F)
% OUTPUT INCREASERC SC
3002 A, B 1951 -56 5000-6700 1450 1450 56%
3002 C 1955-59 to 7600 1500 1500 37%
3002 0 1961-63 to 8000 1550 30%
3002 E, G 1963-66 to 8500 1575 152 23%
3002 F 1966-73 to 9300 1625 1575 12%
3002 H, J 1969- to 14600 1730 1750
Figure 1. MS3002 Models A Thru G Performance History
3002A/B 3002C THRU G
2 Vane Stage 1 Nozzle
GTO 111 Stage 1 Bucket
High-Pressure Turbine Rotor Assembly
Stage 2 Nozzle
GTD 111 Stage 2 Bucket
Low-Pressure Turbine Rotor Assembly
Floating Seal Transition Piece
Turbine Shell
Combustion Liners
Splash Plate Crossfire Tubes
Exhaust Diffuser
Round-the-Corner Combustion
Figure 2. MS3002 Models A Thru G Performance Improvement PackageHardware Changes
Presented at the Gas Turbine Conference and Exhibition, Anaheim, California — May 31 -June 4, 1987
Figure 5. MS3002 Modernization and Upgrade Program
1s1 STAGE SHAFTNiOpMo V
One pipeline customer has purchased 10 performance improve-ment upgrade modification packages for some of their MS3002Cmachines to improve the efficiency of their pipeline operations.Considerable preplanning by the customer, manufacturer, and fieldservice organization personnel resulted in completion of the entireproject on time. Performance tests on the first unit show actualefficiency improvements in excess of those shown on Figure 3.
During the early fall of 1987 an additional upgrade is plannedfor a MS3002F unit in California.
MS5001 Performance Improvement Package — Models A thru P
The MS5001 unit was first introduced in 1957. Various designchanges in combustion and turbine hot gas path design were intro-duced over the years as the unit was uprated from the MS5001Ato the current MS5001P model. Figure 6 lists the performancecharacteristics for the various models. This unit has been used forboth Mechanical Drive and Generator Drive applications.
(1) In the early 1970's, Rating Standards were changed from NEMA (1000 ft. altitude
and 80 F) to ISO (Sea level and 59 F) conditions. To convert from NEMA to ISO
ratings for approximate comparison, multiply NEMA rating by 1.12.
Figure 6. MS5001 Performance History
The initial Performance Improvement Package was designed toapply to Models L through P only. This upgrade package is in-tended to improve efficiency and output and to reduce mainte-nance intervals. Figure 7 details the MS5001 Performance Im-provement Parts Package for Models L through P models. Con-siderable fuel savings are realized with heat rate improvements ofup to 9% (see Figure 9). Figure 4 details expected reductions inmaintenance intervals. As maintenance inspections for hot gaspath are extended to 48,000 hours, considerable reductions ofplanned outages and associated maintenance costs are realized.Figure 8 is a cross section of the parts that are affected. Estimatedoutput and heat rate improvements for MS5001 Performance Im-provement uprates are shown in Figure 9 for MS5001 L through Pmodels. Load equipment load limits must be carefully reviewedfor each application to make sure driven equipment capability isnot exceeded.
2
Dow
nloaded from http://asm
edigitalcollection.asme.org/G
T/proceedings-pdf/GT1987/79276/V005T15A001/2397525/v005t15a001-87-gt-24.pdf by guest on 14 January 2022
Figure 8. MS5001 Performance Improvement Package
500/p
soo/R
500I M
sook
I I I
(SHAFT LIMIT)
5001p
0
20 40 60
80
COMPRESSOR INLET TEMP. (F)
5001 A-K 5001L/LA/M 5001N/P/R
Floating Seal Transition Pieces
Combustion Liners
Splash Plate Crossfire Tubes
2 Vane Stage 1 Nozzle
GTO 111 Stage 1 Bucket
Stage 2 Nozzle
Shrouded Tip Stage 2 Bucket
Stage 2 Turbine Wheel
Turbine Shell
Distance Piece
Stage 1 Turbine Wheel
Outer Combustion Casings
Exhaust Frame
Figure 7. MS5001 Models A Thru P Performance Improvement PackageHardware Changes
Estimated Performance Improvement
Drive
Incremental S Gains
OuLDUL Heat Rate
5001L Generator 31.1 9.1
5001L Mechanical 25.9 7.2
5001LA Generator 20.3 7.5
5001LA Mechanical 17.7 7.2
5001M Generator 14.0 6.5
5001M Mechanical 12.3 7.1
5001R Generator 6.0 2.9
5001R Mechanical 5.7 2.7
5001N Generator 5.1 2.9
5001P Generator 5.1 2.9
Figure 9. MS5001 Models L Thru P Performance Improvement Package
Figure 10 is a list of units that have been uprated as of 12/86.Field performance tests on these units have shown that predictedperformance gains have been met or have been exceeded for eachcase. Figure 11 is a graph of uprate possibilities prepared for oneMS5001 utility customer. A 5001L unit can be uprated by 31% atNEMA (80°F and 1000 ft altitude) conditions with a full upratingto the current MS5001R configuration with the Performance Im-provement Package.
Further review of the Performance Improvement Design Pack-age resulted in a design to apply the uprate to older vintage 5001Athrough 5001K models. This basically involved a new turbine cas-ing in addition to the Performance Improvement Package. Fig-ure 6 also shows original performance for models A through K.The maximum uprating by applying the Performance Improve-ment Package is the 5001R Performance Improvement rating asalso shown on Figure 6. This uprate was originally designed for
one customer to upgrade their MS5001C unit. Ultimately theyelected only to uprate to the MS5001M rating due to parts inter-changeability with their other 5001M units. Another customerpurchased an uprate of their MS5001K unit in Louisiana to aMS5001R Performance Improvement configuration. Figure 12 de-tails the variety of options offered. Ultimately, they elected option5D to provide an uprate of their unit by 63%. Actual improve-ment in performance for this Performance Improvement upratecan vary depending on original unit configurations. Figure 13 listsapproximate output improvements for 5001A through K models.
Compressor Upgrades — MS5001 Models A thru M and R
In 1970 the basic MS5001 compressor was upgraded by addinga zero stage to increase airflow by approximately 34%. Previous5001 Models A through M, and the more recent 5001R Models,can all be upgraded to the 5001 N/P compressor design by addinga Zero stage. This can be accomplished by changing the compres-sor bellmouth, forward compressor casing, first four stages ofcompressor wheels and blades and by adding variable inlet guide
Customer Model Application No. of Units
Florida 5001P Generator 1
Bahrain 5001LA Generator 2
Holland 5001LA Mechanical 2
Holland 50019 Generator 1
Nigeria 5001P Generator 3
Bahamas 50019 Generator 1
Thailand 5001LA Generator 1
Norway 5001M Mechanical 4
Indonesia 5001N Generator 1
Venezuela 5001P Generator 4
Louisiana 5001K Mechanical 1
Total 21
Figure 10. List of Units Upgraded with 5001 Performance Improvement Pack-age as of 12/86
vanes. It is also recommended that remaining stages of compres-sor blading be changed because of the age of blades and increasedloading on blading resulting from increased airflow. For MS5001Models A thru M, this modification would have to be done inconjunction with a hot gas path upgrade to a 5001R configurationto accommodate the increased airflow. MS5001R units can be up-graded without combustion or flange-to-flange changes.
Several upgrade studies are currently in process for both gen-erator drive and mechanical drive applications for this compressorupgrade. The shaft speed range for mechanical drive application is80 to 105% of 4860 rpm for the lower airflow 16 stage compressor5001 A through M and R units. The higher airflow 17 stage 5001N/P compressor has a more limited speed range of 92.5 to 105%of 5100 rpm to minimize the possibility of surge during unitstartup/shutdown. Thus, with this modification some speed rangeflexibility loss comes with the airflow/output increase. Figure 6shows airflows for all 5001 models. Figure 14 details an upgradestudy prepared for one MS5001R mechanical drive unit comparingan MS5001 advance technology uprating versus a compressor up-grade. An uprate of 34% is possible at site rating conditions of40°F at 5200 rpm with only a compressor upgrade. Figure 11shows a similar comparison for a 5001L utility unit where anuprating of 86 °/u is possible at 80°F when both a MS5001R Perfor-mance Improvement Package and a compressor upgrade are beingconsidered. Similarly the MS5002A compressor can be uprated tothe MS5002B configuration to provide full MS5002B performance.
Models Firing Temp. (F)
Estimated
% Output Increase
A 1755 103%
1755 99%
17 1755 89%
1755 89%
1755 70%
H, J 1755 63%
K 1755 63%
Figure 13. MS5001 Models a Thru K Performance Improvement PackageUprate Potential
High Flow Inlet Guide Vanes — Models5001N&P/5002B/6001A&B/7001B&E/9001B&E
Improvements in inlet guide vane material and airfoil designhave also increased air flow on more recent vintage units. Fig-ure 15 details output increases available from new inlet guide vanedesigns. The new inlet guide vanes are directly interchangeablewith original IGVs. Over the past six years dozens of units of allframe sizes have been upgraded with the 403 stainless steel IGVs.Since the new C-450 reduced camber IGV design airfoil was intro-duced in early 1986, several units have also been shipped with thenewest C-450 IGV airfoil design.
The MS5002B gas turbine was introduced in 1970. Variousminor design changes were introduced to reach the 35,000 hp ISOrating. Because of the interest expressed by many customers, adevelopment program was undertaken to increase the MS5002Brating to 38,000 hp (ISO). This Performance Improvement Pack-age can be applied to all MS5002 A&B units. Figure 16 showscomparison of MS5002 ratings for both original and upratedconfigurations.
Figure 17 is a listing of the MS5002 Performance ImprovementPackage. This uprating package has been sold for severalMS5002B units in Indonesia and is actively being studied byseveral other customers wanting to upgrade their output to meetchanging operational conditions. Figure 18 is a cross section show-ing which turbine parts are changed for this uprating.
CONTROL UPGRADES
The control systems for early model gas turbines consisted of acombination of pneumatic and hydromechanical devices. With theadvent of MS5001 Model M and MS3002 Model H turbines, thecontrol system was completely redesigned to an electronic and hy-draulic configuration known as the SPEEDTRONICTM control sys-tem. Since its introduction in 1969, the SPEEDTRONIC controlsystem has undergone changes from the initial Mark I to the cur-rent state-of-the-art Mark IV. There is growing customer interestin upgrading older. control systems with state-of-the-art electroniccomponents and subsystems. Although the complete Mark IVsystem may be an attractive alternative to those gas turbine usersrequiring high reliability built in through redundant systems andsensors, some customers consider such a complete conversion tooexpensive.
Consequently, General Electric has developed a series ofofferings designed to upgrade an existing General Electric gas tur-bine control system to a system better suiting a customer on atight budget. Figure 19 is an application guide for the control up-grade systems.
Option I
Upgrading of selected components and subsystems on the fuelregulator control system is the most basic control upgrade. It con-centrates primarily on those areas most difficult to maintain or tokeep calibrated, or those that can no longer be replaced in kind,
TM Trademark of the General Electric Company.
Figure 17. MS5002 A and B Performance Improvement Package HardwareChanges
namely temperature control, over-temperature protection, and fuelgas pressure ratio control.
Option I provides a modular approach whereby one or moresubsystems may be upgraded in varying degrees. Improvement isachieved through the use of solid state electronics and the elimina-tion of worn and antiquated control air components while still re-taining the fuel regulator. The result is a simpler control systemwith improved reliability, accuracy, and maintainability.
Temcon I
Temcon I is a solid-state electronic module designed to func-tionally replace a portion of the fuel regulator temperature controlsystem. It is a direct replacement for the original temperaturetransmitter. The total system consists of a power supply, a mil-livolt to current (MV/I) converter, and a programmer.
Temcon I offers flexibility in adjustment along with significantlyimproved accuracy and reliability not found in the existing originaltransmitters. With the original transmitters no longer available asproduction units, Temcon I offers immediate spare parts availabili-ty.
Temcon II
Temcon II consists of a solid-state electronic control moduleand a manual/auto controller designed to replace the pneumaticdevices found in the control air panel relating to the temperaturecontrol system, i.e., computing relay, derivative relay, totalizer,and controllers (fuel and nozzle). Temcon II is used withTemcon I to accommodate the functions necessary for two shaftgas turbines incorporating nozzle temperature control andcompressor discharge bias fuel temperature control as well as sin-gle shaft gas turbines utilizing compressor discharge bias.
5
Dow
nloaded from http://asm
edigitalcollection.asme.org/G
T/proceedings-pdf/GT1987/79276/V005T15A001/2397525/v005t15a001-87-gt-24.pdf by guest on 14 January 2022
OPTION I
- Temperature Control - TEMCON I, II, III
- Temperature Protection - TEMPRO
- Fuel Gas Control - GASCON I, II
OPTION II
- Simplex SPEEDTRONIC Turbine Control Panel
OPTION III
- MK IV with single sensors
Pre-SPEEDTRONICTM Units MK I Units MK II Units
(Not (Not
Applicable) Applicable)
(Not Available)
Figure 19. Application Chart for Control Upgrades
The Temcon II electronic module simplifies temperature con-trol calibration over the existing pneumatics system, while at thesame time offers a significant improvement in accuracy and reli-ability.
Temcon III
Temcon III is comprised of motor-driven actuators used to re-place the pneumatic-actuated temperature override bellows on thefuel regulator and, on two-shaft machines, the pneumatically ac-tuated H.P. speed setpoint rheostat. The high resolution of thestepping motors used in Temcon III offers faster and more accu-
rate response.These electronic actuators make up the final step in total elimi-
nation of control air to the temperature control system, resultingin reduced calibration drift, which increases accuracy and overallreliability of the turbine control system.
Tempro I
Tempro I is a solid-state electronic module designed to provideover-temperature protection for gas turbines with existing pneu-matic over-temperature protection systems and replaces the ETTA(exhaust temperature trip and alarm) system and the earlier pneu-matic protection system as the latest GE spare parts replacementdevice. The Tempro package includes an operator interface panelconsisting of indicators for monitoring over-temperature signals(averaged or selected) and light indication for peak operation,differential alarm and over-temperature alarm, and trip signals.
Tempro I offers a much improved response time for an over-temperature condition compared to pneumatic temperature sens-ing. Calibration drift is virtually eliminated and a more accuratetemperature profile is established. The end result is more reliableover-temperature protection.
Gascon I
Gascon I consists of an electronic module designed to convertthe existing pneumatically controlled and actuated pressure ratiovalve into an electronically controlled pneumatically actuated speedratio valve. The system is intended to interface with the currentpressure ratio valve through the use of an electro-pneumatic valvepositioner. The controls, except for the valve positioner, are solidstate and do not require control air.
Gascon I does away with a portion of the control air devices as-sociated with the existing gas control system. It also converts theexisting pressure ratio system into a speed ratio system. Thisspeed ratio system has distinct advantages over the pressure ratiosystem:
1. Turbine ignition with a speed ratio system is more controlledand stable as compared to a pressure ratio system because ofthe linear function of speed vs. the nonlinear function ofcompressor discharge pressure (PCD) at crank speed.
2. A more stable acceleration is attained using compressor shaftspeed (a linear function) as a setpoint for maintaining P2 pres-sure vs. PCD ( nonlinear function).
3. PCD, in a pressure ratio system, is directly affected by am-bient temperature. In comparison, at a given high-pressureset speed (NHP), P2 remains constant in a speed ratio systemregardless of ambient temperature change.
Although the speed ratio valve itself remains pneumatically ac-tuated, the accuracy, speed, stability, and reliability of the elec-tronic speed ratio system provides a significant improvement incomparison with the original system.
Gascon II
Gascon II is a further extension of Gascon I. It converts thepneumatically actuated gas control system to one that is actuatedhydraulically. This system replaces the existing three gas valveswith a single body, combined stop/speed ratio, and control valve.Included with the Gascon II arrangement is a fuel gas skid and anelectronic control module.
This system completely replaces all gas system control air de-vices with electronically controlled components. It also eliminatespneumatically actuated valves and replaces them with a single bodycombined valve assembly. Calibration is less complex and calibra-tion drift virtually eliminated. All this results in faster and moreaccurate response of the fuel gas system.
Option II
A progressive alternative to the Option I upgrade is the hybrid,nonredundant microprocessor-based control system called the Sim-plex SPEEDTRONIC System. A Simplex SPEEDTRONIC controlupgrade is used primarily to upgrade the fuel regulators controlsystem in its entirety, including elimination of the fuel regulator.Depending on the user's needs, this hybrid system may also beused to replace SPEEDTRONIC Mark I or Mark II systems.
The SIMPLEX SPEEDTRONIC control system upgrade incor-porates microprocessor-based controls and performs thecomprehensive functions of turbine control, sequencing, monitor-ing, protection, and operator interface plus optional capabilities.Features of the Simplex SPEEDTRONIC control panel include
— 36 in. x 36 in x 90 in. panel designed to fit existing panel
— Operator interface:
— CRT Display
— Membrane Switch Panel
Auxiliary Backup Display
Emergency Stop Push Button
— Printer
6
Dow
nloaded from http://asm
edigitalcollection.asme.org/G
T/proceedings-pdf/GT1987/79276/V005T15A001/2397525/v005t15a001-87-gt-24.pdf by guest on 14 January 2022
— Single Microprocessor Unit or MEM (Medium ElectronicModule) for carrying out the functions of control, sequencing,and protection. One additional processor board, located in theMEM, is used exclusively for over-temperature protection.
— Application software programmed in PROMS to allow a certainamount of field programming flexibility.
— Thermocouple Input Module — up to 14 thermocouples.
— Two Contact Input Modules — up to 128 contact inputs each.
— Analog Input Modules — up to:
• 6 servo valves
• 4 pressure transducers
• 6 LVDTs
• 2 Speed Signals
• 6 Vibration Inputs
— Flame Detector Module
— Optional Synchronizing Module
The control design criterion for the Simplex SPEEDTRONICControl System was to increase starting reliability, maximize tur-bine parts life, and maintain good unit availability. The provenhistory of General Electric Gas Turbine application usage of mi-croelectronics is well established from the combustion monitor ofthe mid-1970s to the now state-of-the-art industrial gas turbinecontrol system, SPEEDTRONIC Mark IV. The SimplexSPEEDTRONIC Control System employs the same high technolo-gy microelectronics as the SPEEDTRONIC Mark IV. Comparedto the earlier electrical/pneumatic control devices of the fuel regu-lator and the analog Mark I/Mark II controls, microelectronic digi-tal controls are in themselves a significant improvement in reliabil-ity. The standard inherent diagnostics keep the operator informedof the control status. Power-up, self-checking routines ensure thatcontrol is available and if a problem exists, the control will identifyits source so that quick repair can be accomplished. Mean time torepair is, therefore, significantly reduced over previous systemsbecause of these diagnostic routines. The highly accurate digitalcontrol computations of the hybrid system soften the start-upthermal-mechanical cycle over an analog control system, and thushelp to increase parts life of hot gas path components.
Integrated system automation is another possibility to whichthis option lends itself. The optional RS232 port and hard-wire re-mote allows for interface with many computer control systems forhigher level plant control.
Option III
The SPEEDTRONIC Mark IV control system is the mostcomprehensive control upgrade available to date. The controlpanel is the same used on all current production General Electricgas turbines. Its major distinctions over any other control upgradepackage are:
1. Improved availability/reliability
2. Improved on-line diagnostics.
Running reliability has been achieved by the fundamental ar-chitecture of the SPEEDTRONIC Mark IV panel, which has two-of-three voting for the critical control functions by three indepen-dent microcomputers. A fourth computer is called the communi-cator, which coordinates the data from the three control comput-ers, receives noncritical sensor inputs, controls the operation ofthe operator interface, and performs other noncritical functionsnot assigned to the three redundant microprocessors.
While all older GE gas turbines offer opportunity for Mark IVcontrol system upgrade, those with SPEEDTRONIC Mark I and
Mark II are particularly adaptable with a minimum impact on cur-rent configuration. Changeout of a Mark I or Mark II controlpanel to the Mark IV control, and changing only those on-baseelectrical devices necessary to support that upgrade results in a 3to 1 predicted improvement in reliability (forced outages per year)compared to the existing control system.
Mark IV NonRedundant Sensor Arrangement
The configuration with minimal unit changes (nonredundantsensor arrangement) can be accomplished with relative ease.Three basic areas of modification are required:
— Panel changeout
— Limited device changeout/add-on
— Limited electrical wiring changes
The Mark IV panel measures 54 in. wide x 36 in. deep. This issomewhat larger than most Mark I and Mark II panels and mustbe considered in panel replacement. Most panel interfaces havebeen kept similar to the older Mark I and Mark II units, and thusdo not require significant change.
CONCLUSIONS
Today's highly competitive economic climate has stimulatedconsiderable interest in improving the performance and reliabilityof existing Gas Turbine power plants as well as reducing mainte-nance costs. The large population of GE-designed MS3002,MS5001, MS5002, MS6001, MS7001, and MS9001 gas turbines in-cludes many excellent candidates for modernization programs.Such upgradings are justifiable not only for their economicbenefits, but also for the improved reliability, availability, andspare parts commonality they offer to the gas turbine user.
References
1. Allen, R.P., and Smit, H.C.M., New Technology Uprating ofProcess Compressor and Generator Drive Gas Turbine, ASMEPaper 86-GT-40.
2. Johnston, J.R., and Freeman, M.A., Performance and Reliabili-ty Improvements .fir MS3002 GE Gas Turbines, GER3515(1986).
3. Johnston, J.R., and Freeman, M.A., Performance and Reliabili-ty Improvements for MS5001 and MS5002 GE Gas Turbines,GER3516 (1986).
4. Jurczynski, G.E., Controls Upgrade for GE Gas Turbine,GER3514 (1986).
5. Gas Turbine Control Modernizations, GEA-11550 (5M 6/85).
6. A Breakthrough in Replacement Parts Technology for GeneralElectric MS5001 Gas Turbine, GEA 11230A (2M 6/83).
7. Tomorrow's Technology Today for your MS3002 Gas Turbine,GEA 11447 (1M 7/84).
8. Whittaker, R.A., Application of Advanced Technology to In-Service Gas Turbines, ASME Paper 85-GT-148.
7
Dow
nloaded from http://asm
edigitalcollection.asme.org/G
T/proceedings-pdf/GT1987/79276/V005T15A001/2397525/v005t15a001-87-gt-24.pdf by guest on 14 January 2022
