Process Engineering Equipment Handbook Episode 2 Part 5 pps

At the sametime, AssiDomän’s entire holdings of productive forest land were FSC-certified.With the introduction of EMS, each unit set up environmental objectives.Examples of areas covere

are easily dropped and lost For example, a 60-in ID vessel made by this informationsource has only 20 removable parts (not counting the filter cartridges) as opposed

to 235 parts in a conventional design

There are no support arm threads to become stripped, and no support arms Thisavoids the difficult job of removing a collapsed filter cartridge from a support arm.The design of the retainer assembly allows all maintenance work to be donethrough a small closure (below), with substantial savings in first cost as well as inman-hours in removing and resealing the closure

Gas filters are designed for both operating efficiency and clean-out efficiency Tomake the cartridge replacing operation as quick and simple as possible, a quick-demountable filter cartridge retainer assembly is used in all vessels of 30-in shelldiameter and larger The result is a substantial saving in both man-hours anddown-time whenever cartridges are replaced

Not all foreign matter from the gas stream is deposited on the filter cartridges

In any gas filter there is a gradual buildup of rust, scale, and other gas line dirt onthe inner surfaces of the shell, especially at the bottom

This phenomenon is used by directing the incoming gas into a generously sizedinlet chamber (① in Fig F-13), where the abrupt drop in velocity allows the heavierparticles to fall out of the gas stream by gravity before they reach the filtercartridges Thus the filter cartridges’ dirt-holding capacity is used to best advantage

in trapping the hard-to-catch fine particles

The material collected in the shell is removed from gas filters There are nolongitudinal support arms for the filter cartridges, so that when the cartridges areremoved, the filter chamber (② in Fig F-13) is empty of all structural parts Thestandpipes that connect to the cartridge outlets are arranged in a square ratherthan a diagonal pattern, with plenty of room between them for dirt to fall through

to the bottom of the shell In addition, the cartridges and standpipes are positionedwell above the bottom, clear of accumulated dirt

Because of the design of the cartridge retainer assembly and location of thecartridges themselves, all of this servicing can be done by one person, standing

outside the vessel.

Sizing and performance

For this original equipment manufacturer’s (OEM) product range, for instance,series MT multitube filters are built in sizes from 6-in through 144-in shell diameter.They are usually selected for a pressure drop of 1/4to 2 psi (clean), although theycan be selected or designed for other pressure drops

Multitube filters remove 100 percent of all particles larger than 3 microns indiameter and 991/2percent of all particles 1/2to 3 microns.

Construction

Each filter cartridge consists of a small-diameter tube made up of closely packedglass fibers and covered with a knitted cotton sock A perforated metal liner stiffensthe cartridge and maintains its inside diameter against the inward-acting pressure

of the gas

The shell is constructed in accordance with the latest edition of the ASME Code—with stamp A resident National Board licensed inspector is on hand at all times tocheck each phase of construction

Optional features

Customized construction can be provided to meet various state codes and customer specifications An external bypass with rupture disc can be added A davit can beinstalled to facilitate removing the closure head Alternative metals can be usedinstead of the standard carbon steel

In-line Gas Filters*

In-line gas filters (see Fig F-14) generally provide the same gas-handlingperformance as (series MT for this information source) multitube filters They arebuilt in two configurations—vertical (VGF) and horizontal (HGF) (VGF and HGFare both model designations specific to this manufacturer.)

The inlet and outlet nozzles are opposite each other, on a common centerline, near one end of the vessel This arrangement simplifies connections and allowsinstallation in piping runs that are too short for other filter designs

Sizing and performance

VGF and HGF filters are built in sizes from 6-in through 24-in shell diameter Theyare usually selected for a pressure drop of 1/4 to 2 psi (clean) Like the MT filters,they are guaranteed to remove 100 percent of all particles larger than 3 micronsdiameter and 991/2percent of all particles 1/2to 3 microns

Construction

Each filter cartridge is made up of closely packed glass fibers covered with a knittedcotton sock The cartridge is stiffened by a perforated metal liner It is held in place

by a longitudinal rod and wingnut

The shell is ASME Code stamped, as in the series MT The O-ring closure allowsquick access to the interior

Flare Stacks (see also Stacks)

A flare stack is a stack that conducts vented gases that are then lit at its top exit

by a burner and ignition system (which has its own fuel supply line) The stack has

to be a minimum distance (worked out as a function of substances being flared andtheir heat-release rates) from the rest of the plant for the purpose of preventingfires, ignition, and secondary damage to other equipment such as storage tanks

Floating Covers

In the petrochemical and chemical industries, evaporation losses from stored liquidproduct can be sizable and costly When these products are stored in tanks, theycan be covered with a movable floating cover that will eliminate evaporation Tank

manufacturers can supply suitable covers for the application in question (see Tanks).

Deforestation that occurs if logging is not done selectively has severe

consequences, including loss of wildlife habitat (see Ecosystem) with consequential

loss of revenue for personnel who work in these areas and soil erosion It is widelyaccepted that had severe deforestation occurred in the rain forest around thePanama Canal, the canal would have been irretrievably clogged with eroded soilsoon after

The forest products industry, therefore, is an industry that could be thoroughlyinterwoven into the community in which it is located As an illustration, the followingextracts adapted from the 1997 AssiDomän company report regarding its corporateenvironmental objectives are included here Further understanding of this material

is evident by reading the sections on Environmental Economics and Pulp and Paper;and the total material summaries, the material on the contemporary forest andtimber industry, and the packaging materials production data in this section

Contemporary Forest and Timber Industry Practices*

In many countries of the world, the forest products industries carry on as before,with developers hastily cutting, clearing, and burning down forest to make their

F-12 Flare Stacks

* Source: AssiDomän, Sweden Adapted with permission.

products This form of production is not sustainable In the United States andCanada, consumption of forest materials in industry is still high compared to thewestern European countries that aim at maximizing the output from forest products, thereby minimizing their use and maintaining other practices that helpensure their raw material supply will be sustainable.

Case study 1: Forestry management at AssiDomän

This case describes typical, sophisticated, state-of-the-art western Europeanmanagement of the raw materials required for forest products See also Tables F-

2 and F-4 through F-6 and Figs F-15 through F-17 Note that measures involvingemissions reduction take on considerably more significance in a country with NOxand SOxtaxes (like Sweden)

Forestry work

 All forest management regions work in accordance with the EnvironmentalManagement System (EMS) standard ISO 14001 This means that they haveestablished a local environmental policy as well as goals and programs for theirenvironmental work EMS registration was not possible for forestry until 1997,

so work is currently focused on ISO 14001

 The forest management regions in Kalix, Älvsbyn, Lycksele, Örebro, andVärnamo were approved for certification in accordance with ISO 14001 See Fig.F-16

 The two timber units started work with the introduction of EMS

 More than half of AssiDomän’s productive forest land area, 1.7 million hectares,was approved during 1997 in accordance with the Forest Stewardship Council’s(FSC) Swedish standard for certification of forestry

 Ecological landscape plans will be drafted for the entire forest holdings by 2002

FIG F-15 AssiDomän operations regions in Sweden (Source: AssiDomän.)

 New directions for precommercial thinning were put into use during the year.Regeneration planning prior to final felling was finished in time for the 1998 fieldseason.

 This source imported 11 percent of the pulp and paper industry’s wood needs inthe form of roundwood and chips during 1997 The imported wood comes mainlyfrom the Baltic states and otherwise from Finland, Russia, Germany, and Brazil

F-14 Forest Products

TABLE F-2 Activities on Corporate Environmental Objectives

Corporate Environmental

To certify the Group’s forest More than half of the forest holdings The remaining forest holdings are expected holdings in accordance with were certified during the year to obtain certification during the first half

That all units will have begun Approx 90% of the units have begun Some 15 units are expected to be certified in the work on introducing EMS this work Some 15 units were 1998 and the remainder in 1999 and 2000.

by year-end 1997 approved for certification according

to ISO 14001 and/or EMAS registration.

To implement cost-effective Life-cycle assessments are an important The environmental objective remains The environmental measures based part of the environmental work and Group’s environmental work will be

on life-cycle assessments have been used in product pursued in a holistic perspective.

development and in choice of transport mode.

To achieve ecocycle compatibility An “ash restoration group” has been Field studies and development projects

in the Group’s operations Ash formed to promote the recycling continue.

restoration in large-scale tests of ashes and residual products to the

forest A field study has been started.

To reduce the use of fossil fuels, The environmental objective was not The environmental objective remains As a mainly at the Group’s pulp achieved at most mills in 1997 At result of modernizations and other strategic and paper mills some mills use has increased as a investments in energy and recovery

result of production increases and systems in the mills, the use of fossil fuels higher prices for biofuels than oil is expected to decline progressively up to (due to national energy tax policy) the turn of the century A black liquor and rebuilding work in the plants gasification plant is being designed at The biofuel boiler at AssiDomän Frövi AssiDomän Kraftliner This will yield was rebuilt, permitting increased higher energy efficiency and increase biofuel use Energy-saving measures electricity production from biofuel.

have been implemented at AssiDomän Skärblacka so that oil use will be reduced by 9000 m 3 per year.

To collaborate with carriers in Collaboration with carriers in transport The environmental objective remains Work is projects aimed at greater of both timber and finished products being pursued in prioritized areas.

environmental compatibility Reduced specific transport volume has

and shorter transport distances been achieved by scheduled route

transport Environmental questionnaires are used to evaluate carriers Environmental calculations comprise part of the basis for choice

of transport mode.

To promote the development of Several new packaging solutions with Working toward the environmental objective lighter weight and more common environmental profiles were is integrated in the daily work of

resource-efficient packaging developed during the year Reduced developing new products.

materials and packaging packaging weight is an important

factor in this work.

To participate in and carry to AssiDomän has been represented in the AssiDomän will actively participate in completion the joint sectoral management of the project, which continued activities within the sector’s environmental research project will be concluded in 1998 environmental research.

within SSVL.

SOURCE : AssiDomän.

TABLE F-4 Total Material Summary of AssiDomän Operations: Forest Management Regions (8 Units)

Raw material use

Harvested own forest, excl standing timber, 1000 sm 3 ub 6,190 5,930

of which harvested with own machinery, 1000 sm 3 ub 3,600 3,760

of which harvested by contractors, 1000 sm 3 ub 2,590 2,170

of which harvested with own machinery, 1000 sm 3 ub 120 50

of which harvested by contractors, 1000 sm 3 ub 1,040 930 Total wood raw material, 1000 sm 3 ub 7,350 6,910

Products

Wood to AssiDomän, 1000 m 3 fub 5,020 3,690 Wood, sold externally, 1000 m 3 fub 2,330 3,220 Total wood delivered, 1000 m 3 fub 7,350 6,910

ND = No data available.

1 From own machines 2 Collected oil 3 Over available estimated values 4 Incl 123,000 ha not inventoried previously 5 Certain areas have been redefined in conjunction with ecological landscape planning.

Continued environmental work. All forest management regions and timber unitswere certified according to ISO 14001 during the first half of 1998 At the sametime, AssiDomän’s entire holdings of productive forest land were FSC-certified.With the introduction of EMS, each unit set up environmental objectives.Examples of areas covered by the objectives are: reduced usage of fossil fuels,improved waste management and resource management, and programs for thepreservation of biodiversity in the forest landscape.

The FSC certification affects AssiDomän’s forestry practices in a number of ways.Some of the more important changes are the requirements on an increasedhardwood fraction and controlled burning on forest land, and the fact that moredeadwood should be left Besides consideration for the environment, the FSC’scriteria also include economic and social consideration One example of the latter

is that consideration be given to reindeer herding

Ecological balance sheet. For the purpose of evaluating how well the forest-relatedobjectives have been achieved, internal follow-up has been done since 1993 in the

Products

By-products for external delivery

Sawdust, bark, chips, 1000 m 3 /m 3 1,210 1.1 1,020 1.0 Pulp chips, 1000 m 3 /m 3 6 2,050 1.9 1,820 1.8

Sawn

Timber

Total

Per m 3

Sawn

Timber

1 Return trips only included for system traffic at sea 2 Hydrocarbons.

Common key figure for transport emissions 3 Excl Central and Eastern

Europe.

form of an ecological balance sheet The balance sheet is a good aid in the furthertraining of forestry workers See also Figs F-18 through F-22

The grades for final felling show that the former trend of improvements from year

to year has been improved This is true for site-adapted forestry as well as for natureand water conservation The number of evaluated categories, as well as therequirements for getting the highest grade for the individual site, have graduallyincreased as knowledge has grown and the criteria for FSC certification have takenfirmer shape An example of a new category for the year 1997 was evaluation ofwhether the nature conservation measures were concentrated and targetedcorrectly within the felled site Only 44 percent of the final felling area received thehighest grade in this respect This is an important, but difficult, category that willrequire further training

On more than 16 percent of the evaluated sites, so many trees have been left onthe productive land that an appreciable portion of these trees are not judged tocontribute to better functional nature conservation Here the production target wasdisregarded, resulting in a lower yield

The 1997 balance sheet showed that on 88 percent of the final-felled area, thebest possible combination of felling method, tree species, and regeneration methodwere chosen

The thinnings in the 1997 balance sheet showed no great changes in gradescompared with 1996 Water conservation improved slightly, however The removal

of hardwood trees in the thinnings decreased since the introduction of the newthinning instruction in 1996 However removals were still too high to meet the long-range target of a 10 percent hardwood fraction of standing timber

Precommercial thinning was included in the ecological balance sheet starting in1998: It is important for tying together the follow-up of stand management duringthe entire rotation period

Approximately 14 percent of the productive forest land area is given specialtreatment for nature conservation purposes in connection with both final felling andthinning This is a reasonable level for preserving and strengthening biodiversity.

The sawmills produce by-products in the form of chips, sawdust, and bark Thesematerials are used as raw materials in pulp and particleboard manufacture or asbiofuels, either at the sawmills or externally

Environmental work list for a sample year (1997)

 Environmental management systems were introduced at six of the nine unitsduring the year The main reason why EMS have not yet been introduced at three

of the units is extensive restructuring of the operations

F-18 Forest Products

FIG F-16 Carbon dioxide balance (Source: AssiDomän.)

FIG F-17 Sawmills and wood processing (Source: AssiDomän.)

FIG F-18 Nature conservation measures on AssiDomän’s productive forest land (Source:

AssiDomän.)

 Niab Hestra and Hasselfors Timber were certified in accordance with ISO 14001.

 Environmental training was carried out for all employees at six units as a step

in the introduction of EMS

 Two units, Hasselfors Timber and Lövholmen, were certified during the year withregard to “chain of custody” for production of sawn timber from raw material fromFSC-certified forestry This means that the origin of the timber can be guaranteedthrough the whole production chain

 Environmental incidents occurred at some of the units during the year Examplesinclude exceeding prescribed noise level and improper handling of contaminatedindustrial sites The incidents were reported to the appropriate authority andremedial plans were prepared and initiated

 Noise-suppression measures were adopted at three units

 Climate-controlled timber watering was installed at three units, leading toreduced water consumption and thereby reduced surface water runoff

 Measures were adopted at four units to reduce emissions of nitrogen oxides andparticulates For example, a new solid fuel boiler with cyclone ejector andelectrostatic filter was installed at one sawmill and a wet scrubber at another

 Waste management was improved by increased source separation at five of theunits

Environmental work scheduled for a typical year (1998). In accordance with ISO 14001,the units adopted environmental objectives for their operations Examples of suchobjectives are to reduce the quantity of spillage and waste, to reduce emissions fromcombustion, to improve oil and fuel management, to adopt noise suppressionmeasures, and to reduce effluent discharges

F-20 Forest Products

FIG F-19 The evaluation of each final felling and thinning results in three different grades: site-adapted forestry (how well the wood-producing capacity of the different growing sites is used), nature conservation, and water conservation Grades are awarded on a five-point scale, where 3 is satisfactory and 5 is the highest grade (Source: AssiDomän.)

Packaging Materials

A closer look at the manufacture of two common packaging materials enables abetter understanding of the need for environmental policy to develop as an integralpart of increased design sophistication

Barrier coating

There is a great need for fiber-based packaging with some kind of barrier againstmoisture or grease The environmental work within the business area is beingfocused on the development of packaging solutions where new material

FIG F-20 Seed and plants management (Source: AssiDomän.)

combinations permit more efficient resource utilization and where the barriercoating method is environmentally compatible See Table F-3.

The environmental issues given top priority are:

 Solvent-based inks, barrier chemicals, and adhesives. The possibilities ofreplacing these with water-based products are being explored

 Waste and residual product management. The possibilities of utilizing reject and production waste to a greater extent for energy recovery and materialrecycling are being explored For example, the plant in Timrå has a well-functioning system for conversion of combustible process waste to marketable

F-22 Forest Products

FIG F-21 An ecological model “footprint.” (Source: AssiDomän.)

FIG F-22 AssiDomän’s first delivery of FSC-labeled sawn timber products went to England in November 1997 The FSC trademark indicates that the products come from well-managed forests, independently certified in accordance with the rules

of the Forest Stewardship Council (SGS-C-0081) (Source: AssiDomän.)

energy raw material, and several plants have installed systems for collection orincineration of solvents.

 Noise from plants and transport. Noise abatement measures are beingimplemented at several plants

 Energy use. All mills are using exclusively fossil fuels as a thermal energysource Most of the fuels consist of fossil gas Oil will be replaced whereverpossible Environmental targets for reduced energy use are established annually

 Transport A large portion of the business area’s environmental impact comes

from transport operations Ways to improve transport are being investigated

Sack manufacture

Sacks are made from paper based on unbleached or bleached sulfate pulp The sacksare mainly used for packaging building materials, food, chemicals, and animal feed.(See Table F-7.)

The trend is toward lower paper weights per unit volume and fewer layers in thefinished sack, at the same time as the strength requirements on the paper haverisen A mixture of recycled fiber, which is weaker, is rare A new grade withapproximately 10 percent better strength properties was launched in 1997.Lower packaging weights mean lower raw material, energy, and transport needs.This also means reduced emissions to air and water

The introduction of environmental issues systems (EMS) is under way and hascome farthest at the German plants, which achieved environmental certification/registration See Fig F-23

Prioritized environmental issues in connection with sack manufacture are:

 Inks and adhesives The introduction of ink rooms will reduce consumption of ink

and waste as well as associated transport Water-soluble inks and adhesives willgradually be introduced

 Wastewater, polluted with inks and adhesives Existing treatment systems will

be optimized and new ones introduced

 Energy use Reducing energy consumption is an environmental objective at many

mills Fossil gas is the principal source of thermal energy At Sepap, steam fromthe nearby pulp and paper mill is used as a source of heat

 Waste management Training of personnel and good control has led to a reduction

of process waste Waste plans exist at many plants

 Noise Abatement measures have been introduced at plants in Italy and

Germany

Carton material production data (production site: AssiDomän Frövi)

 The aerated lagoon was converted into a long-term aerated activated sludge plant.Treatment efficiency with regard to both phosphorus and COD is expected toincrease considerably compared with the previously used treatment plant Whenthe converted treatment plant was put into operation, a large quantity of sludgewas released from the old treatment plant The discharges exceeded the permitguidelines

 A number of internal process measures were introduced This will lead to reduceddischarges of COD to water, reduced emissions of particulates and sulfur dioxide

to air, and reduced discharges of odorous substances See also Fig F-24

 Production of TCF-bleached pulp, in which bleaching takes place without chlorine-containing chemicals, began in 1997

 A study was made of the animal life on the bottom of Lake Väringen The resultsshow that bottom conditions have improved steadily over the past few decades

 In connection with the development of the EMS, contractors who work at the millhave received training in environmental practices

Reference and Additional Reading

1 Soares, C M., Environmental Technology and Economics: Sustainable Development in Industry,

Butterworth-Heinemann, 1999.

Fuel Gas Conditioning System(s)

One of the most important features of a fuel system is that it be acceptably freefrom moisture or liquid droplets (if the fuel is gaseous) and other impurities (if thefuel is gaseous or liquid) A typical system is outlined here.*

F-24 Fuel Gas Conditioning System(s)

FIG F-23 At AssiDomän Sepap, one of Europe’s biggest manufacturers of sack paper and sacks, pollution abatement measures have been approved for a total of MSEK 200 (Source: AssiDomän.)

* Source: Peerless, USA Adapted with permission.

F-24 Key environmental data for AssiDomän Frövi (Source: AssiDomän.)

When gas pressure regulation and heating is not required, a filter separator orvertical dry scrubber is recommended to remove the entrained solid and liquidcontaminants from the gas upstream of the turbine (see Fig F-25) The vertical dryscrubber is a high-efficiency multicyclone separator with constant pressure dropand no replaceable internals Due to a limited turndown ratio, it is recommendedthat a separate scrubber be installed upstream of each gas turbine When specified,

or necessitated by variable flow conditions, a filter separator is often used Sincethe elements must be periodically replaced, a duplex configuration consisting of two

100 percent units is recommended when protecting two or more gas turbines Aswith all of our fuel gas conditioning systems, full instrumentation for local and/orremote monitoring can be supplied for either manual or fully automatic systemoperation

When gas is received from a transmission line at a much higher pressure thanrequired by the turbine, pressure regulating stations are included in the systemdesign as shown in Figs F-26 through F-30 The simplest package consists of asingle skid with one or more 100 percent capacity pressure regulating valves (PRV)placed upstream of the separator(s) This is shown in Fig F-26

In most cases, the PRVs must be protected from liquid slugs, which could bepresent in the gas supply line A vertical gas separator is the primary choice toremove both liquid slugs and mist Duplex filters or filter separators are located

F-26 Fuel Gas Conditioning System(s)

FIG F-25 Position of vertical dry scrubber upstream of gas turbine (Source: Peerless.)

FIG F-26 Pressure regulating station (PRS) upstream of vertical dry scrubber (Source: Peerless.)

FIG F-27 Vertical gas scrubber upstream of pressure regulating station (Source: Peerless.)

downstream of the pressure regulating station to complete the system as shown inFig F-27.

Figures F-28 and F-29 show the addition of heating and metering Whenpractical, all equipment is mounted on a single skid to facilitate ease of erection atthe site If individual turbine metering is a requisite, manufacturers supply eachmetering station on a separate skid that is easily installed in the field

Figure F-30 is an example of a system requiring compression of the gas upstream

of the turbine Some manufacturers offer a precompression gas conditioningpackage, as well as pulsation dampeners and a high-efficiency vertical absolute separator downstream of the compressor Some manufacturers also offer bothanalog and digital simulations to solve dampening and vibration difficulties

FIG F-29 Metering station upstream of gas turbine (Source: Peerless.)

FIG F-30 Pulsation dampeners upstream and downstream of compression station (Source:

Peerless.)

Typical Range of Gas Conditioning Separators*

Vertical gas separators

Definition: Vertical vane-type separator with inlet baffle for high liquid loads with

liquid removal efficiency of 100 percent for particles of 10 microns and larger SeeFig F-31

Filter separators

Definition: Vertical or horizontal two-stage separators for removal of solids and

liquids with liquid removal efficiency of 100 percent for particles of 8 microns andlarger and 99.5 percent for particles of 0.5 to 8 microns

Solids removal efficiency: 100 percent for particles that are 3 microns and larger

and 99.5 percent for particles that are 0.5 to 3 microns

Multitube filters

Definition: Vertical or horizontal single-stage filters for removal of solids

Solids removal efficiency: 100 percent for particles that are 3 microns and larger in

size and 99.5 percent for particles of 0.5 to 3 microns in size

Vertical dry scrubbers

Definition: Vertical multicyclone separator for removal of solids and liquids with

liquid removal efficiency of 100 percent for particles of 10 microns and larger

F-28 Fuel Gas Conditioning System(s)

FIG F-31 A vertical gas separator followed by two duplexed horizontal multitube filters is used to protect two gas turbines

in Nigeria Piping and valves downstream of filters are stainless (Source: Peerless.)

* Source: Peerless, USA Adapted with permission.

Solids removal efficiency: 100 percent for particles of 8 microns and larger, 99

percent for particles of 6 to 8 microns, 90 percent for particles of 4 to 6 microns,and 85 percent for particles of 2 to 4 microns See Fig F-32

Vertical absolute separators

Definition: Vertical single or two-stage separator for removal of solids and very fine

mists with liquid removal efficiency of 100 percent for particles 3 microns andlarger, and 99.98 percent for particles less than 3 microns

Solids removal efficiency: 100 percent for particles of 3 microns and larger, and 99.5

percent for particles of 0.5 to 3 microns

Line separators

Definition: Vertical vane-type separator with liquid removal efficiency of 100

percent for removal of particles 10 microns and larger

Fuel Systems; Fuel Flow Control

One* of the most common types of fuel flow control is electrohydraulic control Thereare electrohydraulic control solutions for differing environments, including low-pressure and potentially explosive conditions

FIG F-32 System installed in Saudi Arabia includes one vertical dry scrubber followed by two pressure regulating valves and a line separator A condensate drain tank is mounted alongside (Source: Peerless.)

* Source: J.M Voith GmbH, Germany Adapted with permission.

Modern industrial gas turbine systems require precise fuel dosage for the lowestpossible NOx emissions Each application requires the right actuator and valvecombination to achieve exact, uniform fuel distribution to the burner See Figs F-

33 and F-34

The controller needs to be:

1 Inherently reliable (robust construction and low-pressure hydraulics)

2 Equipped with single-stage signal conversion which results in fast, accurateresponse times

3 Equipped with an oscillating magnet and minimized bearing forces to avoidstatic friction effects

4 Easy to install because the magnet and control electronics are all one unit

5 A control with availability of 99.9 percentThe actuator is only one of the components necessary for accurate flow control Somecontrols OEMs cooperate with leading valve manufacturers to offer a total controlsystem All valves and actuators are factory mounted and aligned to reduce labor-intensive adjustments during commissioning

Balanced valves have low force demands Trip time of the complete valveassembly is less than 200 ms and the related increase in pressure is absorbed bythe valve

Valves are available with soft seals as well as with bellows for gaseous fuels.For optimum performance and safety, electrical components face a burn testoperated under “cold” conditions (See Figs F-35 and F-36.)

Electrohydraulic actuators utilize an integrated position regulator that provides

a true position signal

Other assembly features generally provided by actuator OEMs include:

1 Minimal interfaces

2 Valves designed to run without additional breakaway thrust, even after long, continuous operation

3 Flange mounting for easy assembly

F-30 Fuel Systems; Fuel Flow Control

FIG F-33 Electrohydraulic actuator in a U.S power station (Source: J.M Voith GmbH.)

4 Fail-safe design

5 Explosion-proof design

6 Controlled emergency trip

7 Ease of commissioning and installation

8 Low maintenance

9 Compact design

F-32 Fuel Systems; Fuel Flow Control

FIG F-35 Schematic of gas turbine fuel system – = control valve assembly, G = generator, T =

gas turbine (Source: J.M Voith, GmbH.)

FIG F-36 Functional schematic of control valve assembly X 0 = pressure P A at I = 0 or 4 mA; X 1=

pressure P A at I = 20 mA; K p = proportional amplification; F M = magnetic signal/force; F 1 = feedback

force/signal to controller; F A = hydraulic cylinder force (Source: J.M Voith, GmbH.)