Power Gen 2010

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Hydraulic Control Systems in

Gas and Steam Turbines

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2 Industrial Hydraulics | Systems & Engineering

Always the Optimum Solution withSystems & Engineering from Rexroth

Rexroth has set up competence centers for virtually everyapplication area of hydraulic drives and controls: Systems &Engineering. These industry-specic and specialist depart-ments consist of a combination of highly specialized engi-neers, project designers, and other experts. Rexroth cus-tomers are thus able to utilize the extensive applicationknow-how of the world’s leading technology supplier.

Application-focused system solutions are developed here tostate-of-the-art technology—right through to turnkey sys-tems. This means that customers are then able to concen-trate on the core issues of their project design. Systems &Engineering produces the technical details, as it is theintegration, in particular, of demanding drive and controlfunctions, that constitutes the success factors of customer-specic systems.

This unique combination of extensive application know-how and reliable Drive & Control technology is maximizedto the benet of the Rexroth customers. For this purposeSystems & Engin eering is broken down into four essentialcompetencies:

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3Systems & Engineering | Industrial Hydraulics

Civil Engineering Technology

Dredge Technology

Energy Technology

Entertainment Technology

Materials Handling Technology

Motion Technology

Naval Technology

Offshore Technology

Research Technology

Shiplift Technology

Special Technology

Stage Technology

Testing Technology

Transport Technology

Special Projects

Market and application competenceRexroth is able to offer extensive knowledge of the marketwith decades of experience in this branch and accurateknowledge of the demands and wishes of their customers.

Engineering and project competenceRexroth meets all the necessary criteria to enable it todevelop, simulate, and rene systems in an optimum way.In doing so, we take into account all relevant and inter- nationally specic legal stipulations and, furthermore, alsooffer comprehensive risk, insurance, and site management.

Technological competenceWith Rexroth, as with no other supplier worldwide, custom-ers select from an extensive range of rst-class Drive &Control com ponents, such as cylinders, power units, valves,

pumps, and control systems.

International competenceRexroth has sales ofces in over 80 countries, servicecenters in 37 countries, as well as 85 production locationsaround the world. This means that all products and ser-vices are available anywhere and at any time: in close prox-imity to the customer.

www.boschrexroth-us.com

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4 Industrial Hydraulics | Installation

All from One Source:

Hydraulic Control Systems inGas and Steam TurbinesHydraulic closed-loop control devices have a long tradition of use in turbine construc-tion and are certainly one of the “pioneers” of oil-hydraulic closed-loop control technol-ogy in general (e.g. centrifugal governors by J. Watt). Around 20 years ago, and withSiemens in particular, Rexroth started to replace the low-pressure closed-loop control

concept, which had been used up to that point and was based on the bearing lubrica-tion system available, with a high-pressure concept. In turbine manufacture the100–160 bar range is considered to be high pressure.

The most important issues in this range are safety, availabil-ity, and life expectancy of the installations.

Safety:Ensuring that non-permissible operating conditionscan be 100% controlled: If faults are not rectied,this results in machine breakdown and potentiallyaccidents and explosions may occur.

Availability and life expectancy:Ensuring that the generators can operate continuously:The most important issue with power stations is a non-interrupted power supply for maximum output. It mustbe guaranteed that the hydraulic components will lastapprox. 5 – 6 years without failing and causing a turboassembly to break down.

The application of hydraulic systems in gas and steamturbines is explained in greater detail in the followingdescription of turbo assemblies.

In the course of development of power plant techno logy, anincreasing number of so-called combined cycle plants arebuilt (combined process of gas and steam turbine). Withthe combined cycle process, steam is generated with thehot waste gas from the gas turbine by means of a waste-heat boiler, then being fed back to the power generationprocess via the downstream-connected steam turbine. Thisprocess offers a degree of efciency of up to 60%.

Both the control and the safety functions are met usingRexroth actuator technology.

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5Installation | Industrial Hydraulics

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6 Industrial Hydraulics | Hydraulic Control System

Hydraulic Control System

in Gas Turbines

A range of systems is required in thefuel circuit for mastering the closed-loop con trol and safety functions of

a gas turbine. Basically, it is possibleto equip the gas turbine with two fuelsystems, namely natural gas and fueloil. Other fuels such as coal gas,synthesis gas, and naphtha can alsobe used.

The layout of the gas turbine will depend on the applica-tion. One relevant example of a fuel gas system is demon-strated in the diagram far right. As can be seen from thediagram, it is possible to operate the gas turbine in pre-mixor diffusion mode. Using these modes requires applicationof the control and safety devices shown in the diagram.These devices consist of oil or gas valves, which are oper-ated by hydraulic actuators from Rexroth.

These components cover the complete power range of gasturbines from around 25 MW to 340 MW.

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7Hydraulic Control System | Industrial Hydraulics

Fuel gas system for an annular combustion chamber

Example of a diagram for a fuel gas systemfor an annular combustion chamber

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The actuator canaccommodate up tothree positionaltransducers and sixlimit switches.


in Gas Turbines

All hydraulic cylinders aredesigned as low frictioncylinders. The functional

operation of the actuatoris carried out in the cylinderhousing, which is designedas an integrated controlblock.

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All fuel valves are kept open by hydraulic means against adisc spring set arranged inside the cylinder. The spring setcloses the valves safely by mechanical means. The cylindersare designed as double-ended cylinders with double pistonrods. As the oil volume is the same in both cylinder cham-bers, the hydraulic oil can be led via the cylinder housingdirectly to the rear side of the cylinder during the tripfunction (adjusting time 120 – 300 ms). This design meansthat, for rapid switching movements, hydraulic oil does notneed to be fed back to the power unit. As a result, theavailable piping is only required for “normal” control modeand therefore only needs to be designed for minimal ows.

With the exception of the servo valve, all hydraulic valvesused are designed as leak-proof components. On the onehand, a high level of system security (safety cut-out) isguaranteed (all switching valves are seat valves); on theother hand, the leakage ow of the complete system isdrastically reduced (e.g. if the trip actuators are completelyleak-proof). The result is that, in many cases, a hydraulicpower unit with only minimal electric power will sufce forsupplying all the actuators.

As a special feature, all control valves can be tted with a superimposed tripfunction and the valves can match the sealing re quirements of the trip valves.

The principle of a redundant safety function is accomplished with a trip valveand a combined trip-control valve. A second isolating valve is not applied. (e.g.with a control valve that is not leak-proof).

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From its supply, the steam is fed to the HP-part of theturbine via two inlet valve combinations 1.1 and 1.2. Afterthe initial expansion, it is directed via intercept valve com-binations 2.1 and 2.2 into the IP-part. From the IP-part, thesteam is led to the condenser via the LP-stages, from where

it is fed back into the process as feed water.

For handling interruptions or faults, and for particularturbine operating conditions, provision is made for

HP-bypass station 4, IP-bypass station 5 and LP-bypassstation 6. With the bypass stations it is possible to operatethe steam supply independently of the turbine.

The valves installed for turbine control are designed and

built by the turbine manufacturer. The temperature range isup to 550 °C, with the pressure ranging from 8 – 300 bardepending on the position of the valves in the installation.Each valve combination consists of a trip valve and a con-


in Steam Turbines

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Steam turbine assembly

1 Main steam valve combination2 Intercept valve combination3 Buttery valve combination4 HP – Bypass station5 IP – Bypass station6 LP – Bypass station

Fig. 7 shows a typical layout of a steam turbineassembly with the required steam valves

In contrast to a gas turbine, the total thermal power of a steam turbine has to be controlledby means of safety and control devices. With a gas turbine the quantity of fuel fed is closed-loop controlled (e.g. on a small scale comparable with the injection pump on the dieselengine); on the steam turbine, however, the complete steam ow has to be controlled bythe steam valves. The steam valve nominal diameters, the steam pressures, and tempera-tures on these components are many times higher than on the gas turbine. This results in aconsiderably higher force requirement and thus greater diameters and spring forces of thehydraulic actuators used.

trol valve. The safety and control functions are combined ina valve housing, onto which two hydraulic cylinders aremounted.

Rexroth has a complete series of hydraulic cylinders with

spring packs for use with various nominal diameters andpressure stages of these steam valves. The diameter canvary between 110 – 330 mm and the strokes range from50 – 250 mm.

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in Steam Turbines

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As can be seen from the preceding descriptions, Bosch Rexroth is in a position,via its modular system, to supply the complete hydraulic functions required ingas and steam turbines, the closed-loop control, and safety functions for thepower range 25 – 1600 MW. A wide range of relevant reference projects,

together with experience, are available and on hand if required.

The complete actuator design is modular i.e. the diameterrange is covered by three housing sizes and the springforces by appropriate spring package sizes. As both cylindersizes and spring packs can vary, this series meets therequirements of steam valves for turbine powers ranging

from 50 – 1600 MW.

All necessary control functions are realized in a single cylin-der housing, which is designed as an integral control block.Both cylinder chambers are directly connected via thehousing. The corrosion-proof spring packages ensure thesystem is closed and thus safe, once again purely bymechanical means (i.e. cut-off of the steam supply and thusthat of the turbine). The steam valves are kept open byhydraulic means against the disc springs, respective thesteam control valves are position controlled via servo valves.

Each valve combination consists of a trip and a controlpart. Due to the steam cut-off already described, the con-trol actuator is also equipped with a superimposed rapidclosing feature.

Here, too, as with the gas turbine cylinder, the high volumeof oil occurring during trip and shor t switching times is feddirectly to the rear of the double-ended cylinder.

Accordingly, the connections to the hydraulic power unitare only designed for closed-control operation, as no oilneeds to be fed back to the power unit during the tripfunction. Modular hydraulic power units, matched to theparticular system and with the relevant performance data,are also available.

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14 Industrial Hydraulics | Power Units


Power Units forGas and Steam TurbinesSupply hydraulic pressure for control of fuel and gasvalve actuatorsSteam turbine safety and control systemsElectronic control systems for the auxiliary functions forturbines such as gas diverter control, turbine starters,

and steam bypass stationsRedundant motor pump groups and valving for uninter-rupted continuous safe operationTrip controls for fast shut down in the event the load onthe turbine is lostLow noise designs possible – 85 dB(A)Jacking/lube oil supplyTurbine starting

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15Power Units | Industrial Hydraulics

Power Unit AccessoriesAll Rexroth sites worldwide operate in accordance with the same standards. Thisguarantees a supply of spare parts at every production site worldwide.

Rexroth has a worldwide unique range of spare parts forpower units – such as anges, screw ttings, measuringand display devices, lters etc.

There are group-own production sites, subsidiaries, country

units, sales ofces and service centers in over 80 countriesaround the world. You can be assured that your power unitsare being maintained throughout their complete service life– and beyond: from installation and maintenance rightthrough to modications and modernization.

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16 Industrial Hydraulics | Accessories

Blocks, Plates, …

Multifunctional SystemComponentsWhether check, pressure control, ow control functions,combined pressure-check functions, or rapid traverse andcreep functions—Rexroth offers ready-to-install hydrauliccontrol plates in modular design for your power unit. Thismodular solution offers a high level of variability, even in

combination with complex functions. Segments with branchor customer- specic circuits can also easily be integrated.

Standard or Special DesignsIn cooperation with the customer Rexroth developmentengineers transform the required functions into a detailedand optimally matched hydraulic schematic. Using in-housedeveloped simulation programs all process steps are testedand matched under dynamic loading conditions, and thencombined to form logical functional units.

Manifold Assemblies for Power Generation include:Safety trip modulesTurning gear blocks

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17Accessories | Industrial Hydraulics

Quality Determines the FunctionExperienced design engineers, prod uction specialists, andassembly workers guarantee smooth func tional operation ofthe subassembly. Not only all of the components, but also

the complete subassemblies are tested once more beforedispatch and installation.

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19Intelligent Hydraulics | Industrial Hydraulics

IntelligentHydraulics inNew Dimensions

Whether it’s a case ofraising or lowering loadssmoothly, undertaking linearor rotational movements,achieving even acceleration

or accurate positioning,maintaining preset speeds,transmitting power orlinking motion sequences— in fact, wherever economi-cal power is required, thisis where hydraulics comesinto its own.

Rexroth is the technologyand market leader in indus-trial hydraulics with anextensive product programand proven applicationsknow-how. With the widestselection of hydraulic prod-ucts in the world, Rexrothwill provide you with stan-dard products, application-orientated systems, andcustomized solutions of thehighest quality. Further-more, with the aid of thelatest micro electronics,Rexroth has made hydrau-lics even more powerfulthan ever.

Rexroth is the ideal partnerif you want to develophighly efcient machinesand production facilities— from the rst point of con-

tact right through to com-missioning and across thecomplete life cycle. Teamsoperating worldwide willtake on the complete proj-ect design work of yoursystems, even producing aturnkey solution, if required.

Whether it’s competentsupport on the telephone,urgent repairs or supply ofspare parts, or a calloutby one of our engineers— whichever service yourequire, experienced per-sonnel and a worldwideservice network will guaran-tee that the problem isswiftly solved.

Using hydraulic drive andcontrol technology fromRexroth will help youbecome more competitivethan ever.

Efcient HydraulicsPaired with Multi-

technology Compe-tence

Intelligent hydraulics in new dimen-sions: As leading supplier in industrialhydraulics, Rexroth takes an outstand-ing position with components, sys-tems, distinct application know-how,

and high engineering competence.

With Rexroth, you can choose from the world’s largestproduct range of application-related systems and custom-ized special solutions of high quality. In conjunction withadvanced microelectronics, Rexroth has made hydraulicseven more efcient. The products can be easily integratedinto modern machine concepts, are extremely powerful andfeature high energetic efciency. Being a supplier for alltechnologies, Rexroth always offers the ideal application-specic drive solution. Rexroth is your ideal developmentpartner for highly efcient machinery and production facili-ties—from the rst contact through to commissioning andover the entire life cycle. Teams who are active all aroundthe world assume the complete engineering of your plantand machinery, if requested, until maturity for series pro-duction or turnkey handover. With multi-technologicalcompetence and the use of drive and control technologyfrom Rexroth you will be more competitive than ever.

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Bosch Rexroth CorporationHydraulics2315 City Line RoadBethlehem, PA 18017-2131Telephone (610) 694-8300

Facsimile (610) 694-8467www.boschrexroth-us.com

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Power Gen 2010