- •MODERN
- •POWER STATION PRACTICE
- •PERGAMON PRESS
- •Contents
- •Foreword
- •G. A. W. Blackman, CBE, FEng
- •Preface
- •Chapters 1 and 2
- •Chapter 3
- •Contents of All Volumes
- •CHAPTER 1
- •Power station siting and site layout
- •1 Planning for new power stations
- •1.1 Introduction
- •1.2 Capacity considerations
- •1.3 Economic considerations
- •1.4 Future requirement predictions
- •1.5 System planning studies
- •1.6 Authority to build a new power station
- •2 Site selection and investigation
- •2.1 Basic site requirements
- •2.3 Detailed site investigation
- •2.4 Environmental considerations
- •2.5 Site selection
- •3 Site layout — thermal power stations
- •3.1 General
- •3.2 Foundations
- •3.3 Site and station levels
- •3.4 Main buildings and orientation
- •3.5 Ancillary buildings
- •3.6 Main access and on-site roads
- •3.7 Station operation considerations
- •3.8 Cooling water system
- •3.9 Fuel supplies and storage
- •3.10 Ash and dust disposal
- •3.11 Flue gas desulphurisation plant materials
- •3.12 Transmission requirements
- •3.13 Construction requirements
- •3.14 Amenity considerations
- •3.15 Typical site layouts
- •4 Pumped storage
- •4.1 Introduction.
- •4.2 Suitable topology
- •4.3 Ground conditions
- •4.4 Site capacity
- •4.5 System and transmission requirements
- •4.7 Heavy load access
- •4.9 Environmental impact
- •5 Gas turbines
- •5.1 Introduction
- •5.2 The role of gas turbines
- •4.7 Heavy load access
- •Station design and layout
- •1 Introduction
- •2.1 Fossil-fired stations
- •2.2 Nuclear stations
- •2.3 Hydro-electric and pumped storage stations
- •2.4 Gas turbine stations
- •3 Future development options
- •3.1 Fossil-fired plant
- •3.2 Nuclear stations
- •3.3 Combined cycle gas turbines
- •3.4 Wind power
- •3.5 Tidal power
- •3.6 Geothermal energy
- •3.7 Combined heat and power
- •4 Station design concepts
- •4.1 Basic considerations
- •4.2 Design objectives
- •5 Plant operation
- •6 Station layout
- •6.1 General
- •6.2 Main plant orientation
- •6.3 Layout conventions
- •.7 Turbine-generator systems
- •7.1 Feedheating plant
- •7.2 Condenser and auxiliary plant
- •7.3 Erection and maintenance
- •8 Boiler systems
- •8.1 Pulverised fuel system
- •8.2 Draught system
- •8.3 Oil firing system
- •8.4 Boiler fittings
- •8.5 Dust extraction plant
- •8.6 Flue gas desulphurisation plant
- •9 Main steam pipework
- •10 Low pressure pipework and valves
- •11 Water storage tanks
- •12 Cranes
- •13 Fire protection
- •13.1 Introduction
- •13.2 Prevention of fires
- •13.3 Limiting the consequences of a fire
- •13.4 Reducing the severity of fires
- •14 Electrical plant layout
- •14.1 Introduction
- •14.2 Auxiliary switchgear
- •14.3 Turbine-generator auxiliaries
- •14.4 Main connections
- •14.5 Transformers
- •14.6 Cables
- •14.7 Batteries and charging equipment
- •14.8 Control rooms
- •15 Heating, ventilation and air conditioning
- •15.1 Introduction
- •15.2 Ventilation of nuclear stations
- •15.3 Smoke and fire control
- •15.4 General layout of HVAC plant
- •16 Air services
- •17 Water treatment plant
- •18 Cooling water plant
- •18.1 General design considerations
- •18.2 Cooling water pumphouse
- •18.3 Main cooling water pumps
- •18.4 Screening plant
- •18.5 Pump discharge valves
- •18.6 Section valves
- •18.7 Discharge pipework
- •18.8 Auxiliary systems
- •19 Chlorination plant
- •20 Coal handling plant
- •20.2 Water-borne reception and discharging
- •20.3 Road-borne reception and discharging
- •20.4 Coal storage
- •20.5 Conveyance from unloading point to station bunkers or coal store
- •20.6 Plant control
- •21 Ash and dust handling plant
- •21.1 Ash handling plant
- •21.2 Dust handling plant
- •21.3 Ash and dust disposal
- •22 Auxiliary boilers
- •23 Gas generation and storage
- •23.1 Hydrogen
- •23.2 Carbon dioxide
- •23.3 Nitrogen
- •23.4 Miscellaneous gases
- •24 Pumped storage plant
- •24.1 Hydraulic machines
- •24.2 Generator-motors
- •24.3 Main inlet valves
- •24.4 Draft tube valves
- •24.5 Gates
- •24.6 High integrity pipework
- •25 Gas turbine plant
- •25.1 Introduction
- •25.2 Operational requirements
- •25.3 Aero-engine-derivative gas turbines
- •25.4 Industrial gas turbines
- •25.5 Gas turbine power station layout
- •26 References
- •CHAPTER 3
- •Civil engineering and building works
- •Introduction
- •2 Geotechnical investigations
- •2.1 General and desk studies
- •2.2 Geophysical investigations
- •2.3 Trial excavations and boreholes
- •2.3 Trial excavations and boreholes
- •2.4 In-situ tests
- •2.5 Groundwater investigations
- •2.6 Ground description and classification
- •2.7 Laboratory tests
- •2.8 Factual reports
- •2.9 Interpretation of site investigations
- •3 Seismic hazard assessment
- •3.1 Geology
- •3.2 Earthquakes
- •3.3 Crustal dynamics
- •3.4 Ground motion hazard
- •3.5 Ground rupture hazard
- •4 Types of foundations
- •4.1 Isolated column foundations
- •4.2 Strip foundations
- •4.5 Piled foundations
- •4.5 Piled foundations
- •4.6 Caisson foundations
- •4.7 Anti-seismic foundations
- •5 Foundations design and construction
- •5.1 Concrete
- •5.2 Bearing pressures and settlement
- •5.3 Test piling
- •6 Foundations for main and secondary structures
- •6.1 Boiler house foundations
- •6.2 Turbine hall foundations
- •6.3 Turbine-generator blocks
- •6.4 Basement of ground floor
- •6.5 Track hoppers
- •6.6 Chimney foundations
- •6.7 Cooling tower foundations
- •6.8 Reactor foundations
- •7 General site works
- •7.1 Flood embankments
- •7.2 Roads
- •7.3 Drainage
- •7.4 Railways
- •7.5 Coal storage
- •7.3 Oil tank compounds
- •7.7 Ash disposal areas
- •8 Methods of construction
- •8.1 Site clearance, access roads and construction offices
- •8.2 Underground construction
- •8.3 Groundwater lowering
- •8.4 Excavating machinery
- •8.6 Formwork and reinforcement
- •8.7 Mixing and placing of concrete
- •9 Direct cooled circulating water systems
- •9.1 Civil engineering structures in direct cooling systems
- •9.2 Culverts
- •3.3 Pumphouse and screen chamber intake
- •9.4 Cooling water tunnels
- •9.5 Submersible cooling water structures
- •9.6' Maintenance considerations
- •10 Harbours and jetties
- •10.1 General
- •10.2 Types of harbours and jetties
- •10.3 Construction of harbours and jetties
- •11 Loadings
- •11.1 Definitions
- •11.2 Imposed loads due <o plant
- •11.3 Distributed imposed loads
- •II. 6 Reduced loadings in main beams and columns
- •11.4 Cranes
- •11.5 Wind and snow loads
- •12 Steel frames
- •12.1 Steelwork
- •13 Reinforced concrete
- •13.1 General
- •13.2 Formwork
- •13.3 Reinforcement
- •1^.4 Design of reinforced concrete
- •12.2 Design of members
- •12.3 Connections
- •12.4 Protection of steelwork
- •13.5 Movement joints
- •13.6 Curing
- •13.7 Precast concrete
- •14 Prestressed concrete
- •14.1 Prestressing
- •14.2 Prestressed piling
- •14.2 Prestressed piling
- •14.3 Prestressed concrete pressure vessels and containments
- •15 Brickwork and blockwork
- •15.1 General
- •15.2 Bricks
- •15.3 Mortar
- •15.4 Brickwork
- •15.5 Blocks
- •15.8 Openings
- •15.6 Blockwork
- •16 Lightweight walling systems
- •16.1 Sheeting
- •16.2 Insulation
- •16.3 Fixings
- •16.4 Durability
- •17 Roofing
- •17.1 Structural elements
- •17.2 Insulation and weatherproofing layers
- •17.3 Application to power stations
- •17.4 Durability
- •17.5 Rainwater disposal
- •18 Finishes
- •18.1 Floor finish considerations
- •18.2 Types of floor finish
- •18.3 Finishes to walls and ceilings
- •18.4 Wall tiling and other special finishes
- •18.5 Internal painting
- •18^6 External painting
- •19 Turbine hall and boiler house construction
- •19.1 General
- •19.2 Structural considerations
- •19.3 Erection of steelwork
- •19.4 ''Cladding
- •19.5 Ventilation
- •19.6 Floor and wall finishes
- •20 Reactor construction
- •20.1 Reactors
- •20.2 Reactor buildings
- •21.2 Control room building
- •21.3 Gas turbine house
- •21.4 CW pumphouse
- •21.6 Workshops and stores
- •21.7 Offices, welfare blocks, laboratories and similar buildings
- •22 Chimneys, cooling towers and precipitators
- •22.1 Chimneys
- •22.2 Cooling towers
- •22.3 Precipitators
- •23 Architecture and landscape
- •23.1 General power station architecture
- •23.2 Landscape considerations
- •23.3 Preparatory works
- •23.4 Landscape layout
- •24 Regulations
- •24.1 Government instruments
- •24.2 Factories Act
- •24.4 Building regulations
- •24.5 Nuclear station licensing
- •25 Civil engineering contracts
- •25.2 Forms of contract
- •25.3 Contract strategy
- •25.4 Contract placing
- •25.5 Contract administration
- •25.6 Budgetary approval and control
- •26 References
- •Appendix A
- •SUBJECT INDEX
19 Turbine hall and boiler house construction
19.1 General
The walls in older power stations built before 1939 were usually of brickwork, built with a solid plinth course and with brick piers to carry the loads from floors, roofs, etc. Roofs were pitched and consisted of wrought iron and, later, steel roof trusses carrying timber or angle iron purlins with slated roofs. Floors were supported on cast iron joists the ends of which were supported on padstones built into the brickwork or supported on circular cast iron columns. Floors were of timber joist and board construction except for those required to carry heavy loads where cast iron plates or continuous brick arches spanning between cast iron beams were used. The introduction of rolled-steel members and later reinforced concrete enabled the main buildings to be constructed using a structural frame, in which the walls ceased to form structural elements but served mainly to insulate and exclude the weather. Flat roofs of reinforced concrete or precast concrete units covered with asphalt became common anil floors were of reinforced concrete, or where heavy loads were to be carried, concrete reinforced by small section rolled-steel joists. The latter is termed filled joist construction.
Compound sections using one or two rolled sections with additional plates riveted to the flanges, and riveted plate girders made up from flat plates jointed by angles were introduced to carry the increased loads on columns and beams. The cladding became a plinth of brickwork to withstand mechanical damage with bitumen-coated, galvanised corrugated steel or asbestos sheeting to the wall$ and roofs. Lighting and ventilation were obtained by incorporating steel windows or areas of patent glazing in walls and roofs. The offices and other ancillary buildings were usually combined on the main elevation of the station, and the facing of brickwork and artificial stone on these buildings was usually extended to the whole of the main buildings on this elevation in order that a good external appearance was presented.
In the period since 1946, the standard walling con struction of brickwork gave way to a number of turbine halls being built with reinforced concrete frames and roofs. Precast concrete, in-situ concrete and composite construction were used, and the use of concrete shell roofs with concrete columns and beams resulted in many excellent buildings.
Until recently it was common practice to plan the construction of a power station in two sections, the first section often being commissioned before the second was commenced. Problems presented by this form of construction included difficulties due to differential scttlemerfi of foundations owing to the settlement in the second section lagging behind that of the first. Re levelling of crane rails was necessary and provision had
Turbine hall and boiler house construction
to be made for movement between all interconnected parts of the building and plant. A temporary gable end had to be provided to the completed first section and this usually took the form of a steel frame covered with cladding.
Several power stations have been built in the past using a semi-outdoor construction for the boilers. A structure was not provided to house the boilers with this arrangement, although hutments and covered stair cases, gantries and walkways were provided to protect operators, when working on the boilers. When these power stations were built, brick walls and concrete roofs were the accepted methods of construction for main buildings and hence considerable capital savings were effected. These savings are not so apparent when outdoor boiler construction is compared with the more modern method of boiler house construction using lightweight cladding. Outdoor construction also has the disadvantage that many repairs have to be carried out in the open and extensive scaffolding may be necessary for work at the higher levels. There are also obvious objections to this type of construction on aesthetic grounds and it is unlikely to be used in this country in the future.
Although brick and steel chimneys have been used in the past, concrete is used for chimneys on projects now under construction. For chimneys in excess of 90 m high concrete construction becomes cheaper than brick.
The first cooling towers consisted of a timber frame built over concrete cooling ponds, the outside of.the frames being covered with wood boarding. Timber stacks were provided inside to ensure adequate cooling of the water. Steel was also used but corrosive condi tions were so severe that in spite of maintenance paint ing the average life of a steel tower was only 8 years. Concrete was then adopted for cooling tower construc tion and the first concrete towers were similar in shape to the timber towers. These towers were superseded by the hyperbolic concrete towers, which although smaller were of the same pattern as those now being constructed.
The main buildings superstructure for a modem 2000 MW power station is unique in size and associated loads when compared with other projects carried out by building and civil engineering contractors. The design of the buildings is the result of co-ordinated efforts by civil engineers, architects, quantity surveyors, land scape architects, steelwork and reinforced concrete designers, services engineers and other specialists. Similarly the execution of the work on the site results from the combined efforts of steelwork, civil engineer ing and building contractors and also the many other specialist contractors and suppliers of materials.
All work on the superstructure of the main building is usually carried out under three m :in contracts:
•The structural steelwork contract which includes cladding and roofing.
267
Civil engineering and building works
•The painting contract.
•The building and civil engineering work eontracl
which |
includes |
floors, |
brickwork, |
finishings, |
services, etc. |
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|
|
The programme requirements for many types of build ings are simple from the client’s viewpoint, starting and finishing dates being the only limitations placed on the contractor. This type of programming is especially applicable where buildings are to be occupied by personnel who move in on completion, and can ;ils<> be used for structures such as chimneys and cooling towers. The programming of contracts for the boiler house and turbine hall is, however, much more com plex. Although the commencement and completion dates for the various contracts can be established from the overall project programme, many intermediate completion dates must be established to ensure that foundations and cover are available for a multitude of plant erection contractors and sub-contractors and electrical contractors to proceed.
19.2 Structural considerations
The total weight of structural steelwork required for the frame of a power station depends upon the plant layout and other factors which include the provision or omission of a basement and the use of reinforced concrete columns to the turbine hall. Hence the weight of steelwork for a 2000 MW station expressed in terms
Chapter 3
of plant capacity varies considerably from 12 t io 19.5 t per MW.
The basic dimensions of the boiler house and turbine hall are decided by the plant layout, and work cannot proceed on the design of the structures until this is established. When this stage is reached, development of the plant details and finalisation of the building design can develop together.
Because of the long beam spans and the heavy loads on columns and beams, structural steel frames arc
.normally used, although composite constitution in which reinforced concrete may be employed for turbine hall columns and for the frames of associated struc tures. Figures 3.51 and 3.52 show cross-sections through the steel frames for unit 1 and unit 2 respec tively at Thorpe Marsh power station, which were com pleted in the early 1960s. The longitudinal arrangement of the turbines resulted in the turbine hall crane having a span of 24.5 m.
In stations completed before 1960, boilers were slung from the main steelwork, the top beams of the large portals of the boiler house providing support for the boilers and roof whilst the columns formed the outer wall of the boiler house. The weight of a boiler in the newer 2000 MW power stations often exceeds 13 000 tonnes, and the span of the boiler house is so large that intermediate columns are introduced to reduce the span of the steelwork carrying the boilers. The boilers are carried by slings from the overhead sling deck, supported on columns which transfer the load to the foundation. For unit 1 at Thorpe Marsh the columns on
1 Al IK'T G1HDLHS
FORMING UOILLH
SUPPORTING STEELWORK
268
Turbine hall and boiler house construction
Fig. 3.52 Section through Thorpe Marsh power station unit 2
lines D and E, as shown in Fig 3.51, are used to support the boilers and for unit 2 the weight of the boilers is carried on the columns in lines C, H and J, as shown in Fig 3.52.
It is only after consultation with the steelwork contractor that decisions on the type of members to be used can be made. Certain contractors asso ciated with plate manufacturers favour box members, whereas others can tender more economically on the basis of rolled sections. Compound members were used throughout in the frame for unit 1 at Thorpe Marsh and although similar construction methods were used for the turbine hall of unit 2, box members have been used in the boiler house construction. Lattice girders have been used to support the roof of the turbine hall for both units.
Figure 3.53 shows the cross-section through the structural steelwork for West Burton power station on the centre line of the boilers. This is a 2000 MW station with a longitudinal arrangement of the four 500 MW sets which gives a crane span in the turbine hall of 38.5 m. The boilers are supported from the columns on lines D, F and G, and all the columns in the boiler house and turbine hall, together with the main beams in the boiler house, are box members. A longitudinal arrangement of sets usually results in large spaces between boilers which in the ease of West Burton have been used to accommodate the bunkers. Figure 3.54 shows the cross-section through the steelwork on the centre line of the bunkers. The roof beams used for the
turbine hall at West Burton are of triangular section and lattice construction. The compression members of the roof beams are at the apex of the triangle and the tension members at the bottom, which is level with the roof, the beams thus forming a triangular shaped pent house in which glazing and ventilation is provided.
Figure 3.55 shows the cross-section through the 2(KX) MW power station at Fawlcy. This station also has a longitudinal arrangement of sets and the span of the turbine hall crane in the station is 48.75 m. The main roof beams to the turbine hall are box girders and the roof deck is level with the underside of the main beams.
Even longer spans, up to 60 m, result from the trans verse arrangement of sets on other stations. This arrangement presents problems when the heavier loads associated with larger sets are considered and the use of two crane tracks involving a further line of columns carrying two crane rails has been developed. The posi tion of this extra line of columns is not necessarily central, its actual location depends upon the lifting arrangements for the turbine and generator. At Ferry bridge C power station, where this arrangement has been used, the smaller span crane is located over the generators which is advantageous owing to the greater loads on this crane. On this station, the central columns extend to the full height of the turbine hall and are used to support the roof in addition to the crane rails, thus reducing the spans of the main roof beams.
Wind pressures of 1400 N/m2 can result in total horizontal loads up to 15001 on the face of a boiler
269
Civil engineering and building works |
Chapter 3 |
Fig. 3.53 Section through West Burton power station
house and wind girders and bracing i^ necessary to |
19.3 |
Erection of steelwork |
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resist these forces. The main columns are often located |
The design |
and |
fabrication |
of the steel frame is |
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at centres in excess of 12 m. and large section sheeting |
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governed |
largely |
by available |
fabrication |
techniques, |
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rails are necessary to |
carry the weight |
of the cladding |
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transport |
facilities |
and lilting |
equipment. |
Hence box |
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and resist the wind loading on such a span. It is usual |
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columns are manufactured in lengths not usually exceed |
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therefore to introduce |
intermediate |
columns to |
give a |
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ing 13 m. Sections of members such as roof trusses may |
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sheeting rail span usually between 2.75 m and 4.5 m. |
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be assembled into a complete member before it is lifted |
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The main roof beams in the boiler house and turbine |
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at the site. Columns of a cross-section 2 m by 1 m are |
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hall support the |
roof |
structures which normally |
consist |
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often used and beams are up to 4 m deep. The weight |
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of lightweight |
decking |
supported |
on |
rolled |
section |
of sections |
delivered to site is |
normally limited by the |
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purlins. Some of the |
more recent |
stations have been |
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capacity of the works and site cranes. |
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provided with a |
roof |
of |
precast |
concrete units |
to the |
Although the use of large tower type cranes is being |
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boiler as these have been found |
to |
be |
less susceptible |
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tried |
out, |
the normal crane arrangements |
for erecting |
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to mechanical damage. |
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steelwork are shown in Fig 3.56. Derricks up to 50 t |
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Beams and columns are used at intermediate levels |
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capacity are used for steelwork erection, although |
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to support floors, pipework and items of plant. Open |
special erection methods involving the use of catheads |
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grid flooring is normally used for floors, gantries and |
on the top of columns arc sometimes used for lifting |
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staircases above operating floor levels as this permits |
special beams in excess of the crane capacity. It will be |
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easy flow of air. The boiler house operating floor and |
apparent from the arrangement of the cranes shown, |
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also the floors around the sets in the turbine hall are |
that in many cases two cranes can be employed for a |
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normally of reinforced concrete construction. Solid |
single lift as in the case of the turbine hall main beams. |
floors are often constructed from precast concrete units The derricks are usually supported on trestles known as
or a combination of precast concrete units and in-situ |
gabbards, and the whole structure mounted on bogies |
concrete to facilitate speed of erection and avoid |
travelling longitudinally along the boiler and turbine |
difficulties in supporting shuttering at such a height. |
buildings. As erection for one boiler is completed, the |
Permanent shutterings of rigid galvanised sheet units |
derricks move away and are finally dismantled outside |
are sometimes used. |
the buildings on completion of the steelwork erection. |
270
Turbine hall and boiler house construction
l;Ki. 3.54 Suction through West Burton bunkers
198 12 m
55 47 m
Fig. 3.55 Section through Fawley power station
271