Industrial Training Report on NTPC DADRI

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JUNE - JULY

2009 Industrial Training Report

SUBMITTED BY: DIGVIJAY SINGH MECHANICAL (FINAL YR.) ROLL NO. 0621640015

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INDUSTRIAL TRAINING REPORT ON ‘ NTPC DADRI’ GAS POWER PLANT

National Thermal Power Corporation Limited National Capital Power Station - Dadri P.O. Vidyut Nagar, District Gautam Budh Nagar - 201 008 (UP)

“NTPC was set up in the central sector in the 1975.Only PSU to achieve excellent rating in respect of MOU targets signed with Govt. of India each year. NTPC Dadri station has also bagged ISO 14001 certification. Today NTPC contributes more than 3 / 5th of the total power generation in India .”

INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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CONTENTS S.NO . DESCRIPTION

PAGE NO . 3

(1)

OVE RVIE W OF NTP C

(2)

SATIO N AT A GL AN CE

5

(3)

INTR ODU CT IO N T O GAS POWER PLANT

6

(4)

GAS TU RB IN E STARTI NG SYSTEM

17

(5)

FUEL SY STEM

19

(6)

SA LIE NT FEA TU RES OF NTP C DADR I

25

(7)

GAS PLA NT OPE RATIO N

26

(8)

HOW DOES A CO MB INED CYCLE PO WE R PLA NT WOR K?

30

(9)

AUT OMA TI ON AN D CON TR OL

46

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(i) Overview of NTPC

NTPC was set up in the central sector in the 1975 in response to widening demand & supply gap with the main objective of planning, promoting & organizing an integrated development to thermal power in India. Ever since its inception, NTPC has never looked back and the corporation is treading steps of success one INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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after the other. The only PSU to have achieved excellent rating in respect of MOU targets signed with Govt. of India each year. NTPC is poised to become a 40,000 MW gint corporation by the end of XI plan i.e. 2012 AD. Lighting up one fourth of the nation, NTPC has an installed capacity of 19,291 MW from its commitment to provide quality power; all the operating stations of NTPC located in the National Capital Region & western have acquired ISO 9002 certification. The service groups like Engineering, Contracts, materials and operation Services have also

bagged

the

ISO

9001

certification.

NTPC

Dadri,

Ramagundam, Vindhyachal and Korba station have also bagged ISO 14001 certification. Today NTPC contributes more than 3 / 5th of the total power generation in India.

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(ii) Station At Glance

NTPC dadri is model project of NTPC . also it tit the best project of NTPC also known as NCPS ( National capital power station ). Situated 60 kms away from Delhi in the District of gautam budh Nagar, Uttar Pradesh. The station has an installed capacity of 1669 MW of power – 840 MW from Coal based units and 829 MW Gas Based Station . the station is excelling in performance ever since it’s commercial operation . consistently in receipts of meritorious projectivity awards, the coal based units of the station stood first in the country in terms of PLF for the financial year 1999 – 2000 by generating an all time national high PLF of 96.12 % with the most modern O & M Practices. NTPC – Dadri is committed to generated clean and green Power. The Station also houses the first HVDC station of the country (GEP project) in association with centre

for power efficiency and Environment

protection (CENEEP) – NTPC

& USAUID. The station has

bagged ISO 14001 & ISO 9002 certification during the financial year 1999 – 2000, certified by Agency of International repute M/s DNV Netherlands M/s DNV Germany respectively INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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1.Introduction To Gas Power Plants Introduction The development of the sector in the country, since independence has been predominantly through the State Electricity Boards. In order to supplement the effects of the states in accelerating power development and to promote power development on a regional basis to enable the optimum utilisation of energy resources, the Government of India decided to take up a programme of establishment of large hydro and thermal power stations in the central sec tor on a regional basis. With this in view, the Government set up the National Thermal Power Corporation Ltd., in November 1975 with the objective of planning, construction, commissioning, operation and maintenance of Super Thermal and Gas Based Power projects in the country. The availability of gas in a large quantity in western offshore region has opened an opportunity to use the gas for power generation, which is an economical way and quicker method of augmenting power generating capacity by natural gas as fuel in combined cycle power plant in a power deficit country like ours. With this intention in mind the Government asked INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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NTPC to take up the construction of Kawas, Auraiya, Anta, Dadri and Gandhar Gas Power Project along the HBJ Gas pipe line. The power plant consists of gas turbine generating units waste heat recovery boilers, steam turbo generator, ancillary electrical and mechanical equipments. The power generated at this power station is fed over 220 KV AC transmission system associated with this project to distribute the power in the various Regions. In the Power Sector, gas turbine drive generators are used. Gas turbines range in size from less than 100 KW up to about 140.000 KW. The gas turbine has found increasing application due to the following potential advantages over competive equipment. • Small size and weight per horsepower • Rapid loading capability • Self-contained packaged unit • Moderate first cost • No cooling water required • Easy maintenance • High reliability • Waste heat available for combined cycle application. • Low Gestation Period • Low Pollution Hazards The function of a gas turbine in a combined cycle power plant is to drive a generator which produce electricity and to provide INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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input heat for the steam cycle. Power for driving the compressor is also derived from gas turbine.

Combined Cycle Combined Cycle power plant integrates two power conversion cycles namely. Brayton Cycle (Gas Turbines) and Rankin Cycle (Conventional steam power plant) with the principal objective of increasing overall plant efficiency.

Brayton Cycle Gas Turbine plant-operate on Brayton Cycle in which air is compressed this compressed air is heated in the combustor by burning fuel combustion produced is allowed to expand In the Turbine and the turbine is coupled with the generator. Without losses the theoretical cycle process is represented by 1’ 2’ 3’ 4’ In the actual process losses do occur. Deviation from the theoretical process, results from the fact that compression and expansion are not performed isentropically but polytropically which is conditioned by heat dissipation (expansion) and heat supply (Compression) caused INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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by various flow and fraction by losses. In the combined cycle mode, the Brayton Cycle is chosen as the topping cycle due to the high temperature of the exhaust of the gas turbine (point 4 in the P.V diagram). In modern gas turbines the temperature of the exhaust gas is in the range of 500 to 550 0C. Reference to the T.S. diagram may indicate the amount of heat that is produced, converted into mechanical energy and extracted from this process. For the evaluation of the cyclic process, two parameters are of greatest importance; 1) Thermal efficiency

2) Process working capacity

Thermal efficiency is obtained from chemical binding energy of the fuel and mechanical energy available at the shaft of the gas turbine. Thermal efficiency ( th ) as follows:

th

= Energy at GT shaft Chemical Energy of fuel = (Q Input. Q output )/ Q Input = 1 — Q Output/ Q Input

Working capacity is also obtained from the difference between INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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the amounts of heat supplied and removed. This is achieved by increasing P2

that is increasing gas inlet temperature T3.

Fig.1

Rankine Cycle The conversion of heat energy to mechanical energy with the aid of steam is carried out through this cycle. In its simplest form the cycle works as follows (fig.2). The initial state of the working fluid is water (point-3) which, at INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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a certain temperature is compressed by a pump (process 3-4) and fed to the boiler. In the boiler the compressed water is heated at constant pressure (process 4-5-6-1). Modern steam power plants have steam temperature in the range of 500 0C to 550 0C at the inlet of the turbine.

Fig.2

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Combining two Cycles to Improve Efficiency We have seen in the above two cycles that gas turbine exhaust is at a temperature of 500–550 0C and in Rankine Cycle heat is required to generate steam at the temperature of 500-550 0C. so, why not use the gas-turbine exhaust to generate steam in the Rankine cycle and save the fuel required to heat the water ? Combined Cycle does just the same. The efficiency of Gas Turbine cycle alone is 30% and the efficiency of Rankine Cycle is 35%. The overall efficiency of combined cycle comes to 48%.

Types of Combined Cycles It is basically of two types, namely Unfired Combined cycle and Fully Fired combined cycle.

Unfired combined Cycle The basic system is shown in figure- 3. in this system the exhaust gas is used only for raising steam to be fed to the steam turbine for power generation. INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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The conventional fossil fuel fired boiler of the steam power plant is replaced with a ‘Heat Recovery Steam Generator’ (HRSG). Exhaust gas from the gas turbine is led to the HRSG where heat of exhaust gas is utilised to produce steam at desired parameters as required by the steam turbine. However, non-reheat steam turbine is the preferred choice for adopting this type of system as usually the live steam temperature for HRSG will be solely controlled by the gas turbine exhaust temperature which is usually around 500 0C.

UNFIRED COMBINED CYCLE FIG-3

In recent development, with the introduction of Dual Pressure Cycles more heat is recovered in the HRSG and steam with higher pressure and temperature can be generated. But higher INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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capital investment and sometimes necessity of supplemental firing system makes the system complex and costly.

Fully Fired Combined Cycle Fig – 4 shows the basic schematic of this cycle. In this system the heat of exhaust gas from gas turbine is used for two purposes as described below: Heat contained in exhaust gas is used to heat feed water to a desire

BOILER REPOWERING EXCHANGER

SYSTEM

Fig. 4 INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

EXHAUST

HEAT

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temperature at the inlet to the boiler. This leads to the reduction or elimination of the extraction steam requirement from the steam turbine. In case, the steam turbine has a larger steam swallowing capacity to generate more power the amount of steam which is being extracted from steam turbine for regenerative feed heating could be made to expand in the turbine to increase its base load capacity and improve the overall efficiency. In case the steam turbine does not have the capacity to swallow extra steam available due to cutting down of extraction, the fuel being fired in the boiler can be cut down to generate less steam by an amount equivalent to steam required for extractions and thus improving the overall efficiency due to less consumption of fuel. Gas turbine exhaust contains about 14 to 16 % oxygen (by weight) and can be used as hot secondary air in the conventional fossil fired furnaces. So the heat required to heat the secondary air will be saved and can be used for other purposes. FD fan power consumption will also be reduced to a great extent.

Fuels Gas turbines are capable of burning a range of fuels including naptha, distillates, crude oils and natural gas. Selection of fuel (s) INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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depends on several factors including fuel availability, fuel cost and cleanliness of fuel. Natural gas is an ideal fuel because it provides high thermal efficiency and reliability with a low operation and maintenance cost. Liquid fuels, particularly heavy oils, usually contain contaminants, which cause corrosion and fouling in the gas turbine. Contaminants, which cannot be removed from the fuel, may leave deposits in the gas turbine, which reduce performance and add maintenance costs. Dual fuel systems are commonly used, enabling the gas turbine to burn back-up fuels when the primary fuel source is not available. Dual fuel systems can also be designed to fire both fuels simultaneously.

Advantages Plants

of

Combined

Cycle

Apart from the higher overall efficiency, the combined cycle power plants have following advantages: Low installation Cost: power from a combined cycle power plant is approximately 70% of a conventional coal based power plant of same capacity. INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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Low Gestation Period: Power from a combined cycle power plant can be obtained in two phases, i.e. two third power, obtainable from gas turbines, is available within 16-18 months and the balance in next 1 month. This is much lower than the gestation period for conventional thermal power plants, which is around 48-60 months. Better Reliability: Combined cycle power plants are considered to be highly reliable with the reliability factor of 85-90% as compared to 60-65% for conventional coal Fired Power Plants.

2. Gas System

Turbine

Starting

The function of the starting system is to crank the gas turbine upto the required speed until : it becomes self sustaining. One method of starting large gas turbine is by using a motor driven hydraulic starting system. Alternatively, the GTG can be started by using a frequency converter to rotate the generator which drives the turbine for starting. A typical hydraulic starting system for each gas turbine consist of the following: INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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• Starting motor, electric AC induction motor • Hydraulic torque converter • Auxiliary Gear • Couplings The electric starting motor drives the hydraulic torque generator through a coupling. The hydraulic torque converter consists of an impeller, which forces the fluid against hydraulic starting motor. The hydraulic torque converter is coupled to the accessory gear, which is connected to the gas turbine shaft. The torque converter receives hy draulic fluid from hydraulic and lube oil reservoir during operation. When gas turbine reaches self-sustaining speed the starting device is disconnected and shut down. To break the inertia of the starting motor and reduce the starting current a pony motor is provided. Gas turbines of GE and WH designs are provided with starting motor system for cranking purpose. The static frequency converter serves the same function of starting, accelerating running at preset speed by starting the generator as a synchronous motor by feeding variable frequency current drawn from the connected grid. Gas turbines of ABB and SIEMENS make are provided with frequency converter s for the GT cranking and normally 2 * 100% static converters are provided for the power station.

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Black Start System To start a gas turbine in the event of AC-power failure an emergency black start system is provided. It also helps in safe coasting down of the gas turbine and its auxiliaries following a ‘trip’ in the event of grid collapse. The black start system consist of a separate diesel engine or a gas turbine driven synchronous generator connected to station switch gear bus. It can be operated manually from local or remote and also it automatically comes into operation following a black out condition. Capacity of the black start unit should be such that it can supply the total auxiliary power required to start a gas turbine from standstill condition. The NTPC’s Auraiya project gas turbine is provided for emergency black-start purpose and all other projects are provided with diesel generator set for the same duty.

3. Fuel System Fuel System of Gas Turbine The function of the fuel system is to deliver fuel to the INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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combustion chamber(s) of a gas turbine at quantity and pressure as required by the control system

Liquid fuel system The liquid fuel system consists of the liquid fuel storage and handling system. The liquid fuel storage and handling system provides means for unloading , storage and distribution of the fuel oil within the plant and typically composed of the following major components: • • • • • • •

Fuel oil unloading pumps Fuel oil transfer pumps Fuel oil storage tanks Flow meter Strainers Pressure and Level control stations. Distribution piping

The number and size of equipments is site dependant. The storage facility is dependant on such factors as the location of the site, proximity of the oil supply and the reliability of the oil supply. Fuel oil may be supplied to the plant by a pipeline, oil barriages, oil tankers, rail/road or high way trucks. Fuel oil unloading pumps may not be required if the oil arrives by a pipeline, an oil barge, or an oil tanker since they have their own pumps.

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Naphtha Pressurising System By the forwarding pumps,Naptha is pumped upto the GTs and kept under recirculation. For firing the naphtha is the GT,separate pressurising system with high pressure pump, allied filters and m easurements and recirculation system is used. This pressurising is required because in the naphtha burner this fuel is mechanically atomised. There is no other medium like air, etc are used for atomisation.

Naphtha drain system Since the flash/fire point of this fuel is very low it is designed to drain the oil from the piping burner etc when the system is stopped. Separate drain tanks are kept at pumping stations, which will collect these naphtha and pump back to the main storage tanks.

Mode of firing It is provided to fire natural gas or naphtha or in mixed mode of the fuel in the GT Combustion Chamber.

FUEL GAS SYSTEM The purpose of the fuel gas system is to take gas fuel from the custody transfer point, process it to the quality and pressure conditions required by the gas turbine and to distribute it and INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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monitor its use. Fuel gas system consists of the off base system and the on base system. Off base fuel gas System The off-base fuel gas system is typically composed of the following major components: • An emergency stop valve at the gas inlet to the plant knock out drum • Filters • Pressure-control station • Distribution piping Optional Components are • Gas metering station • Gas Heaters The need for any of the optional components is dictated by the conditions specific to each individual application. The final supply pressure required at gas turbine is a function of the gas turbine compression ratio and the control valve and nozzle pressure drops. Large gas turbines typically require a gas supply pressure of about Kg/cm2 with pressure regulated with in +10 percent off-set point. The emergency stop valve at the in let to the station is provided to completely shut off the gas supply in an emergency. The gas INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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fuel then goes through a knockout drum. A knock out drum will remove the free liquid and some solids from the gas stream. However, it will not separate out much of the entrained liquids. The liquids separation from gas stream takes place by decreasing the gas veloc ity in its transit through the drum. Impurities collect at the drum bottom and are periodically automatically purged A level controller opens a drain valve which allows the waste to Adrian tank vented to the atmosphere. The filter separators must have minimum of two stages of separation. The initial stage being utilised removal of large liquid droplets and the final stage for mist separation. Any solid particles carried with the gas stream are separated in the first stage . The first stage elements consist of hollow tubes of glass fibers through which gas flows radially from outside. The separation of carried solids and liquid particles is by interception, diffusion and/or inertial impaction of the droplets on the fibers. The liquid droplets coalesced on the surface drain on to the shell and from there to the drain pot. The second stage mist separator is preferably of the vans type in which liquid separation takes place by subjecting the gas path to multiple changes of direction. The gas analysis is carefully checked from the stand point these point of hydrate formation or icing at the pressure reducing station under the worst ambient temperatures prevalent at each site. If there is any tendency for the above, a suitably, rated gas fired indirect heater is provided ahead of the pressure reducing station. The gas heater ensures a gas temperature sufficiently high such that the after pressure reduction the gas temperature is at least 20” C higher than hydrate forming temperature or the gas dew point whichever is higher. The heater normally utilises INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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natural gas for firing. Heat from the fire tube be utilised to heat a water bath in which the U tubes for carrying the gases to be heated are immersed. The control system ensures constant temperature of the outlet gas for gas flows ranging from zero to full gas flow. A full capacity bypass is provided so as to enable operation of the fuel gas system is designed to deliver gas fuel to the gas turbine combustion chamber(s) at the proper pressure and flow rates to meet all the starting, acceleration and loading requirements of gas turbine operation.

Naphtha forwarding system The forwarding system is mainly remote controlled from the GT LCR and CCR. Although there is a possibility to control the main devices locally by a switching the selector switch on local position in the local panel. By means of three way valves a tank selection is possible. To ensure the standby position of the lines keep the value open. The pumps are protected by the automatic recirculating valves. The condition of the strainers as well as of the filters is monitored by the differential pressure indicators and switches. The safety valves protect the line against the line against over pressure.

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4. Salient Features Of NTPC DADRI Gas Project DADRI GBCCPP-STAGE I (817MW) General Layout Plan In the main plant block two modules, each consisting of two GTGs placed on each side of 2 STGs. The central control room is located towards west of the ST hall. The transformer yard Is on the wester side of the turbine hall, with switchyard further down west. Induced draft cooling towers have been located considering the proper flow of cooling water. Nearer to main power house & convenient routing of open return channel to CW pump house. The 220/400 KV switchyard has been located in front of the power station. The 220 KV switchyard control room is accommodated in the central control room itself. Space has been kept for liquid oil installation and oil unloading facilities. The GAIL terminal for receiving gas is located within INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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boundary of plant site.

5. Gas Plant Operation Gas Turbine, WHRB, Turbine Starting Modes

Steam

Basic conditions for plant operation are as follows:• Start up or shut down of G/T, WHRB and S/T of each module is performed separately from the other module (except for S/T gland steam back-up and heating steam back up systems). • Start up/shut down mode is selected freely form among those mentioned. The start up/shut down procedure for WHRB and S/T here mainly describes operating procedure for G/T bypass damper, WHRB inlet damper and remote operated valve necessary for start up and shut down from G/T exhaust gas admission to WHR till rated load operation of S/T. For detail operating procedure for G/T WHRB, S/T auxiliaries and remote operated valve following procedures are followed.

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Start up Mode The start up mode of G/T, S/T and WHRB shall be selected from among the following as a rule through various other start up modes are conceivable according to power demand and operating principle.

Outline of each start up •

Normal start up mode This mode is two unit (2G/T’s + 2WHRB’s +1 S/T) combined cycle start up mode which, after starting up one each of G/T and WHRB, starts up the other G/T and WHRB and brings the output of G/T and S/T the target output of the module. In this mode, S/T is loaded with one each of G/T and WHRB in operation, and after the initial load is achieved, the pressure control of HP/LP by-pass valves of both WHRB’S is changed to common pressure control and then S/T is loaded up. The timing of starting up the other G/T and WHRB is left to the discretion of the operator, and S/T is kept stand by at the initial load until the pressure control of both WHRB’S is changed to the common pressure control.

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• Rapid start up mode This is a mode of starting up both G/T’s and WHRB’S at the same time, changing the pressure control of HP/LP by-pass valves of both WHRB’S to the common pressure control, then loading up and brining G/T the output of and S/T to the target output of the module is achieved. This mode is used only for start up after right stop or hot start up (with vacuum). In other start up modes; in which the time from G/T start up to S/T loading is long, simultaneous startup is not made to reduce heat lose at start up. • G/T/WHRB additionally start up mode This is a mode of starting up the other G/T and WHRB one until combined cycle of G/T, WHRB and S/T is in operation. In this mode, the HP Steam pressure and temperature of the other G/T and WHRB are raised up those of G/T and WHRB in operation, and then the pressure control of HP/LP by-pass valves is changed to the common pressure control, and S/T is loaded up. INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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• Single G/T/WHRB start up mode This is a combined cycle start up mode of starting up S/T with only one each of G/T and WHRB in operation. The other G/T and WHRB remain stopped. • Individual pressure control Individual pressure control means pressure control made automatically by using HP/LP by-pass valves of both WHRB’s and detecting pressure before HP/LPCV so that HP/LP steam pressure of both WHRB’S will be the same and constant respectively. • Loading of S/T S/T loading rate after HP/LP by-pass are fully closed and HP/LPCV are fully opened is determined by the load change rate of G/T, namely S/T load change rate increases as G/T load change rate increase. (Except for G/T/WHRB additionally start up mode). S/T unloading rate too is determined by G/T load change rate under HP/LP by-pass valves are fully closed and HP/LPCV are fully opened.

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6.How Does A Combined-Cycle Power Plant Work?

Power Generation: Air Inlet  The amount of air needed for combustion is 800,000 cubic feet per minute. This air is drawn though the large air inlet section where it is cleaned, cooled and controlled, in order to reduce noise.

Turbine-Generators:

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 The air then enters the gas turbine where it is compressed, mixed with natural gas and ignited, which causes it to expand. The pressure created from the expansion spins the turbine blades, which are attached to a shaft and a generator, creating electricity.  Each gas turbine produces 185 megawatts (MW) of electricity.  The blades are attached to a rotor, which spins the generator, and makes electricity. Think of a generator as a huge spinning magnet inside a coil of wire. As the magnet spins, electricity is created in the wire loops.

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Heat

Recovery

Steam

Generator

(HRSG) • The hot exhaust gas exits the turbine at about 1100 degrees Fahrenheit and then passes through INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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the Nooter Erickson, Heat Recovery Steam Generator (HRSG).  In the HRSG, there are 18 layers of 100-foot tall tube bundles, filled with high purity water. The hot exhaust gas coming from the turbines passes through these tube bundles, which act like a radiator, boiling the water inside the tubes, and turning that water into steam. The gas then exits the power plant through the exhaust stack at a much cooler 180 degrees, after having given up most of its heat to the steam process.  About 1 million pounds of steam per hour is generated in this way and sent over to the steam turbine through overhead piping. Steam Turbine INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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 The steam turbine is a Siemens Westinghouse KN Turbine Generator, capable of producing up to 240 MW.

It is located on top of the

condenser, across from the cooling tower.  Steam enters the turbine with temperatures as high as 1000 degrees Fahrenheit and pressure as strong as 2,200 pounds per square inch. The pressure of the steam is used to spin turbine blades that are attached to a rotor and a generator, producing additional electricity, about 100 megawatts per HRSG unit.  After the steam is spent in the turbine process, the residual steam leaves the turbine at low pressure and low heat, about 100 degrees. This

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exhaust steam passes into a condenser, to be turned back into water.  By using this “combined-cycle” process, two gas turbines and one steam turbine, we can produce a total of about 600 megawatts of electricity. Emissions Control Selective Catalytic Reduction (SCR)  To control the emissions in the exhaust gas so that it remains within permitted levels as it enters the atmosphere, the exhaust gas passes though two catalysts located in the HRSG.  One catalyst controls Carbon Monoxide (CO) emissions and the other catalyst controls Oxides of Nitrogen, (NOx) emissions. INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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Aqueous Ammonia 

In addition to the SCR, Aqueous Ammonia (a mixture of 22% ammonia and 78% water) is injected into system to even further reduce levels of NOx.

Best Available Control Technology (BACT) 

Our annual average concentration of NOx is only 2 parts per million, which is considered the “best available control technology” or BACT by the Air Board.

 As exhaust gas passes out of the exhaust stack, it is continuously sampled and analyzed, assuring that permit limits are being met.

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 With this kind of clean, modern technology, the exhaust stack is only 145 feet high, compared to 500 feet, the height required by older power plants

that

use

less

efficient

emission

technology.  Environmental

and

health

organizations

recognize this technology as a benefit to the community. The local chapters of the American Lung Association and Sierra Club both support the Metcalf Energy Center.

Transmission

of

Generated

Onto the Grid Transformers INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

Power

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 The Gas Turbine and Steam Turbine generators produce power at 13,000 volts.  The transformers take the generated 13,000 volts and “transform” them to 230,000 volts, which is the required voltage needed for transmission to the nearby tower that sends power to the substation.  A small amount of generation is directed to “Auxiliary transformers” which “transform” the generated voltage to a lower voltage, so it may be used by the plant to power our own pumps, fans, and motors. The Metcalf Energy Center requires 12 – 15 megawatts to operate. Switchyard  From each transformer, the power passes underground into our switchyard. The power INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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from all of the generators comes together there, where it is measured, metered and directed onto the grid.  The proximity of the site to a large, existing PG&E substation makes it a good place to build a power plant and the nearest transmission tower is only about 200 feet away. Condenser and Cooling Tower  The purpose of the condenser is to turn low energy steam back into pure water for use in the Heat Recovery Steam Generator.  The purpose of the cooling tower is to cool the circulating water that passes through the condenser. It consists of ten cells with large fans

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on top, inside the cone-like stacks, and a basin of water underneath.  We process and treat the Title 22 recycled water after receiving it from the City, before using it in our cooling tower. The cool basin water absorbs all of the heat from the residual steam after being exhausted from the steam turbine and it is then piped back to the top of the cooling tower.  As the cool water drops into the basin, hot wet air goes out of the stacks. Normally, hot moist air mixes with cooler dry air, and typically a water vapor plume can be formed, one that may travel hundreds of feet in the air and be seen from miles away.

The California Energy

Commission considered this visually undesirable in this community so we added a “PlumeINDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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Abatement” feature, louvers along the topsides of the tower that control the air flow. 

The cooling tower evaporates about three-fourth of the processed, recycled water, then we send about one-fourth of it back through the sewer lines for re-treatment by the City.

 The Metcalf Energy Center purchases 3 to 4 million gallons per day of recycled water from the City of San Jose. Evaporation of this water assists the City in adhering to their flow cap limits and helps to protect the sensitive saltwater marsh habitat of the San Francisco Bay environment from receiving too much fresh, recycled water.

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Water Tanks, Natural Gas Pipeline, Control Room Water Tanks  The largest tank is the Service Water tank. It contains 470,000 gallons of water to be used for drinking, fire fighting and for the high purity water train. The water from the service water tank is pumped to the water treatment building where it then passes through a reverse osmosis unit, a membrane decarbonater, and mixed resin bed demineralizers to produce up to 400 gallons per minute of ultra pure water.  The pure water is then stored in the smaller 365,000-gallon tank until it is turned into steam for making electricity. INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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Natural Gas  Natural gas fuels the combustion turbines. Each turbine can consume up to 2,000 MMBTU per hour.  The fuel comes from the major high pressure natural gas pipeline that runs along the east side of Highway 101, less than 1 mile to the east of our site.  During construction, “Horizontal Directional Drilling” was utilized with careful coordination with many local authorities. The pipeline was built 60 feet underground and passed under highways,

creek,

train

environmentally sensitive areas. INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

tracks,

and

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 The pipeline enters the site just behind the water tanks, where equipment regulates and measures the natural gas composition, flow and pressure.  Gas compressors pump the natural gas though the facilities’ fuel gas system where it is delivered to the gas turbine and the HRSG duct burners at the proper temperature, pressure and purity.

Control Room  From the control room, the plant operators monitor and operate the facility, via the plant’s “Distributed Control System”, with the click of a mouse, viewing graphic representations of all MEC systems on various screens. INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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

The system gives operators both audible and visual signals to keep them informed of plant conditions at all times and to determine when preventative maintenance is required.

7.AUTOMATION AND CONTROL SYSTEM AUTOMATION: THE DEFINITION

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The word automation is widely used today in relation to various types of applications, such as office automation, plant or process automation. This subsection presents the application of a control system for the automation of a process / plant, such as a power station. In this last application, the automation actively controls the plant during the three main phases of operation: plant start-up, power generation in stable or put During plant start-up and shut-down, sequence controllers as well as long range modulating controllers in or out of operation every piece of the plant, at the correct time and in coordinated modes, taking into account safety as well as overstressing limits.

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During stable generation of power, the modulating portion of the automation system keeps the actual generated power value within the limits of the desired load demand. During major load changes, the automation system automatically redefines new set points and switches ON or OFF process pieces, to automatically bring the individual processes in an optimally coordinated way to the new desired load demand. This load transfer is executed according to pre- programmed adaptively controlled load gradients and in a safe way.

AUTOMATION: THE BENEFITS

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The main benefits of plant automation are to increase overall plant availability and efficiency. The increase of these two factors is achieved through a series of features summarized as follows: 

Optimisation of house load consumption during plant start- up, shut-down and operation, via: 



Faster plant start-up through elimination of control errors creating delays. Faster sequence of control actions compared to manual ones. Figures 1 shows the sequence of a rapid restart using automation for a typical coal-fired station. Even a well- trained operator crew would probably not be able to bring the plant to full load in the same time without considerable risks.

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



Ensure and maintain plant operation, even in case of disturbances in the control system, via: 





Co-ordination of house load to the generated power output.

Coordinated ON / OFF and modulating control switchover capability from a sub process to a redundant one. Prevent sub-process and process tripping chain reaction following a process component trip.

Reduce plant / process shutdown time for repair and maintenance as well as repair costs, via: 

Protection of individual process components against overstress (in a stable or unstable plant operation).

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 Bringing processes in a safe stage of operation, where process components are protected against overstress

PROCESS STRUCTURE

Analysis of processes in Power Stations and Industry advocates the advisability of dividing the complex overall process into individual sub-processes having distinctly defined functions. This division of the process in clearly defined groups, termed as FUNCTIONAL GROUPS, results in a hierarchical process structure. While the hierarchical structure is governed in the horizontal direction by the number of drives (motorised valves, fans, dampers, pumps, INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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etc.) in other words the size of the process; in the vertical direction, there is a distinction made between three fundamental levels, these being the: 

Drive Level



Function Group Level



Unit Level.

To the Drive Level, the lowest level, belong the individual

process

equipment

and

associated

electrical drives. The Function Group is that part of the process that fulfils a particular defined task e.g., Induced Draft Control, Feed Water Control, Blooming Mill Control, etc. Thus at the time of planning it is necessary to identify each function group in a clear INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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manner by assigning it to a particular process activity. Each function group contains a combination of its associated individual equipment drives. The drive levels are subordinate to this level. The function groups are combined to obtain the overall process control function at the Unit Level. The above three levels are defined with regard to the process and not from the control point of view.

CONTROL SYSTEM STRUCTURE

The primary requirement to be fulfilled by any control system architecture is that it be capable of INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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being organized and implemented on true processoriented lines. In other words, the control system structure should map on to the hierarchy process structure. BHEL’s PROCONTROL P®, a microprocessor based intelligent remote multiplexing system, meets this requirement completely.

SYSTEM OVERVIEW

The control and automation system used here is a micro based intelligent multiplexing system This INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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system, designed on a modular basis, allows to tighten the scope of control hardware to the particular

control

strategy

and

operating

requirements of the process Regardless of the type and extent of process to control provides system uniformity and integrity for:



Signal conditioning and transmission



Modulating controls

CONTROL AND MONITORING MECHANISMS

There are basically two types of Problems faced in a Power Plant INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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 Metallurgical  Mechanical Mechanical Problemcan be related to Turbines that is the max speed permissible for a turbine is 3000 rpm , so speed should be monitored and maintained at that level Metallurgical Problem can be view as the max Inlet Temperature for Turbile is 1060 oC so temperature should be below the limit. Monitoring of all the parameters is necessary for the safety of both:  Employees  Machines

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So the Parameters to be monitored are :  Speed  Temperature  Current  Voltage  Pressure  Eccentricity  Flow of Gases  Vaccum Pressure  Valves  Level  Vibration PRESSURE MONITORING

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Pressure can be monitored by three types of basic mechanisms  Switches  Gauges  Transmitter type

For gauges we use Bourden tubes : The Bourdon Tube is a non liquid pressure measurement device. It is widely used in applications where inexpensive static pressure measurements are needed. A typical Bourdon tube contains a curved tube that is open to external pressure input on one end and is coupled mechanically to an indicating needle on the other end, as shown schematically below. INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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Typical Bourdon Tube Pressure Gages

Transmitter types use transducers (electrical to electrical normally) they are used where continuous monitoring is required Normally capacitive transducers are used INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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For Switches pressure swithes are used and they can be used for digital means of monitoring as swith being ON is referred as high and being OFF is as low.

All the monitored data is converted to either Current or Voltage parameter.

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The Plant standard for current and voltage are as under  Voltage : 0 – 10 Volts range  Current : 4 – 20 milliAmperes We use 4mA as the lower value so as to check for disturbances and wire breaks. Accuracy of such systems is very high . ACCURACY : + - 0.1 % The whole system used is SCADA based

INPUT

4-20 mA ANALOG INPUT MODULE

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MICRO PROCESSOR

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ALARM

We use DDCMIC control for this process. Programmable Logic Circuits ( PLCs) are used in the process as they are the heardt of Instrumentation.

HL switch

Start low

Pressure in line

LL switch

pump

Pressure ElectricityAN D Level Level High High level Electricity OR

Stop Pressure

Electricity

BASIC PRESSURE CONTROL MECHANISM

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Hence PLC selection depends upon the Criticality of the Process

TEMPERATURE MONITORING We can use Thernocouples or RTDs for temperature monitoring Normally RTDs are used for low temperatures. Thermocoupkle selection depends upon two factors:  Temperature Range  Accuracy Required Normally

used

Thermocouple

Thermocouple:

INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

is

K

Type

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Chromel

(Nickel-Chromium

Alloy)

/

Alumel

(Nickel-Aluminium Alloy) This is the most commonly used general purpose thermocouple. It is inexpensive and, owing to its popularity, available in a wide variety of probes. They are available in the −200 °C to +1200 °C range. Sensitivity is approximately 41 µV/°C. RTDs are also used but not in protection systems due to vibrational errors. We pass a constant curre t through the RTD. So that if R changes then the Voltage also changes RTDs used in Industries are Pt100 and Pt1000

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Pt100 : 0 0C – 100 Ω ( 1 Ω = 2.5 0C ) Pt1000 : 0 0C - 1000Ω Pt1000 is used for higher accuracy The gauges used for Temperature measurements are mercury filled Temperature gauges. For Analog medium thermocouples are used And for Digital medium Switches are used which are basically mercury switches. FLOW MEASUREMENT Flow measurement does not signify much and is measured just for metering purposes and for monitoring the processes ROTAMETERS:

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A Rotameter is a device that measures the flow rate of liquid or gas in a closed tube. It is occasionally misspelled as 'rotometer'. It belongs to a class of meters called variable area meters, which measure flow rate by allowing the cross sectional area the fluid travels through to vary, causing some measurable effect. A rotameter consists of a tapered tube, typically made of glass, with a float inside that is pushed up by flow and pulled down by gravity. At a higher flow rate more area (between the float and the tube) is needed to accommodate the flow, so the float rises. Floats are made in many different shapes, with spheres and spherical ellipses being the most INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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common. The float is shaped so that it rotates axially as the fluid passes. This allows you to tell if the float is stuck since it will only rotate if it is not. For Digital measurements Flap system is used. For Analog measurements we can use the following methods :  Flowmeters  Venurimeters / Orifice meters  Turbines 

Massflow meters ( oil level )

 Ultrasonic Flow meters 

Magnetic Flowmeter ( water level )

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Selection of flow meter depends upon the purpose , accuracy and liquid to be measured so different types of meters used. Turbine type are the simplest of all. They work on the principle that on each rotation of the turbine a pulse is generated and that pulse is counted to get the flow rate. VENTURIMETERS :

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Referring to the diagram, using Bernoulli's equation in the special case of incompressible fluids (such as the approximation of a water jet), the theoretical pressure drop at the constriction would be given by (ρ/2)(v22 - v12). And we know that rate of flow is given by: Flow = k √ (D.P) Where DP is Differential Presure or the Pressure Drop. CONTROL VALVES A valve is a device that regulates the flow of substances (either gases, fluidized solids, slurries, or liquids) by opening, closing, or partially obstructing INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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various passageways. Valves are technically pipe fittings, but usually are discussed separately. Valves are used in a variety of applications including industrial,

military,

commercial,

residential,

transportation. Plumbing valves are the most obvious in everyday life, but many more are used. Some valves are driven by pressure only, they are mainly used for safety purposes in steam engines and domestic heating or cooking appliances. Others are used in a controlled way, like in Otto cycle engines driven by a camshaft, where they play a major role in engine cycle control.

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Many valves are controlled manually with a handle attached to the valve stem. If the handle is turned a quarter of a full turn (90°) between operating positions, the valve is called a quarter-turn valve. Butterfly valves, ball valves, and plug valves are often quarter-turn valves. Valves can also be controlled by devices called actuators attached to the stem. They can be electromechanical actuators such as an electric motor or solenoid, pneumatic actuators which are controlled by air pressure, or hydraulic actuators which are controlled by the pressure of a liquid such as oil or water. So there are basically three types of valves that are used in power industries besides the handle valves. They are : INDUSTRIAL TRAINING REPORT BY DIGVIJAY SINGH Email Id- singh_digvijay89_yahoo.in

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

Pneumatic Valves – they are air or gas controlled which is compressed to turn or move them



Hydraulic valves – they utilize oil in place of Air as oil has better compression



Motorised valves – these valves are controlled by electric motors

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