Turb.sect9.BFP 10Sept07

Medupi Power Station Employer’s Requirements Package No. 3 STG Contract No: 4600008582

Eskom

Employer’s Requirements

One Turbine Generator with auxiliary plant

Section 9 – Boiler Feed Pump Plant

9.1 BRIEF OVERALL PROJECT DESCRIPTION .................................................................................. 3

9.1.1 Function of Boiler Feed Pump Plant (Equipment task) .................................................... 3 9.1.2 Description of the Boiler Feed Pump Plant ...................................................................... 3

9.1.2.1 BFP Drive ............................................................................................................................... 3 9.1.2.2 Alternative BFP VFD Drive Option ....................................................................................... 4

9.1.3 Control and Instrumentation (C&I) .................................................................................. 4 9.1.3.1 General (C&I) requirements for the boiler feed pump plant ................................................... 4 9.1.3.2 Minimum C & I requirements for the boiler feed pump plant ................................................ 4

9.1.3.2.1 Leak-Off (Minimum Flow) Protection............................................................................... 4 9.1.3.2.2 Mechanical Seal Protection................................................................................................ 4 9.1.3.2.3 Vibration Protection........................................................................................................... 4 9.1.3.2.4 Thrust and Journal Bearing Metal Temperature Protection ............................................... 5 9.1.3.2.5 Strainer Differential Pressure Protection............................................................................ 5 9.1.3.2.6 Mechanical Seal Earthing Device ...................................................................................... 5 9.1.3.2.7 Reverse Rotation Detection ............................................................................................... 5

9.1.4 Electrical supplies and other services ............................................................................... 5 9.2 SCOPE OF SUPPLY ................................................................................................................... 5

9.2.1 Design phase ..................................................................................................................... 5 9.2.2 Main equipment to be supplied.......................................................................................... 6 9.2.3 Auxiliary equipment to be supplied ................................................................................... 6 9.2.4 Accessories to be supplied................................................................................................. 7 9.2.5 Spare parts ........................................................................................................................ 7 9.2.6 Tests................................................................................................................................... 7

9.3 TERMINAL POINTS .................................................................................................................. 7 9.4 OPERATIONAL REQUIREMENTS ............................................................................................... 8

9.4.1.1 Operating duty points.............................................................................................................. 9 9.4.2 Operating hours .............................................................................................................. 10 9.4.3 Start-up and shut-down ................................................................................................... 10 9.4.4 Abnormal operating conditions....................................................................................... 10 9.4.5 Further operational requirements................................................................................... 11

9.4.5.1 Fixed or sliding pressure deaerator ....................................................................................... 11 9.4.5.2 Booster Pump ....................................................................................................................... 11

9.5 GENERAL DESIGN................................................................................................................. 12 9.5.1 Casing Design and Construction..................................................................................... 12

9.5.1.1 Main Pump Design ............................................................................................................... 12 9.5.1.2 Booster Pump Design ........................................................................................................... 12 9.5.1.3 Shafts and Impellers.............................................................................................................. 13 9.5.1.4 Pump rotating element .......................................................................................................... 13 9.5.1.5 Thrust Balancing Devices ..................................................................................................... 14 9.5.1.6 Shaft Sealing System ............................................................................................................ 14 9.5.1.7 Bearings................................................................................................................................ 15 9.5.1.8 Couplings.............................................................................................................................. 15 9.5.1.9 Lubrication System............................................................................................................... 15 9.5.1.10 Pump Gaskets and O-Rings .................................................................................................. 16 9.5.1.11 Forces and Bending Moments .............................................................................................. 16 9.5.1.12 Speed increase gearbox (alternative BFP drive option) ........................................................ 16 9.5.1.13 Pump and Interconnecting Pipe Connections........................................................................ 16 9.5.1.14 Leak-off or minimum flow devices ...................................................................................... 16 9.5.1.15 Reheater Attemporating Spray Water Connection................................................................ 17 9.5.1.16 Intermediate Strainer............................................................................................................. 17 9.5.1.17 Commissioning Strainer ....................................................................................................... 18 9.5.1.18 Discharge Non-Return Valve................................................................................................ 18

Turb.Sect9.BFP 10Sept07.doc of 32


9.6 PERFORMANCE REQUIREMENTS............................................................................................ 18

9.6.1 General............................................................................................................................ 18 9.6.1.1 Noise performance................................................................................................................ 19 9.6.1.2 Vibration performance.......................................................................................................... 19

9.6.2 Availability ...................................................................................................................... 19 9.6.3 Dynamic Behaviour of Rotors ......................................................................................... 19 9.6.4 Dynamic behaviour of the stators.................................................................................... 20 9.6.5 Instrumentation for control and condition/maintenance diagnostics...................................... 20

9.7 MAINTENANCE FEATURES.................................................................................................... 20 9.7.1 Sub-assembly replacement times..................................................................................... 20 9.7.2 Material selection............................................................................................................ 21

9.8 VERIFICATION OF SPECIFIED PUMP PERFORMANCE ............................................................... 21 9.9 MAIN BOILER FEED PUMP DRIVE ......................................................................................... 21

9.9.1 Design requirements of the Planetary geared variable speed fluid drive coupling ........ 22 9.9.2 Lubrication system of the planetary geared fluid drive coupling. ................................... 22

9.10 APPENDIX 1 .......................................................................................................................... 25



9.1 Brief overall project description

This document sets out the minimum technical requirements for the boiler feed water pump plant.

9.1.1 Function of Boiler Feed Pump Plant (Equipment task)

Three 50% motor driven boiler feed pump sets with Vorecon planetary geared variable speed fluid hydraulic coupling shall be provided to supply feed water via the high pressure feed water heaters to the steam generator (Boiler).

9.1.2 Description of the Boiler Feed Pump Plant

The boiler feed pump plant shall form part of a boiler feed pump station located in the turbine house at ground floor or zero meter level The pump sets shall be located on independent spring-mounted reinforced concrete deck slabs with the suction connections of the booster pumps in line with the centre axis of the feed water tank. The connecting pipes between the booster and main pumps shall be arranged below the pumps and have an integral fine strainer. The lubrication oil system shall include an oil reservoir integrated into the Vorecon. The lubrication oil coolers and filters shall be located separately in the basement below the boiler feed pump sets. The boiler feed pumps shall consist of three (3) parallel sets of a nominal 50% duty flow capacity per set. Each 50% feed pump set comprising of one booster, one main pump, one Vorecon planetary hydraulic coupling and one fixed speed MV motor complete with transfer pipe between booster and main pump. The following shall form part of the supply : base plates or support structure, main pump non-return valve, intermediate strainer, local instruments, leak-off equipment, shaft seal system, lubrication oil system, holding down bolts, lagging, painting, delivery, erection, and commissioning, testing and all other equipment required for satisfactory and safe operation of the plant.

9.1.2.1 BFP Drive Refer Section 9.9.



9.1.2.2 Alternative BFP VFD Drive Option Not applicable.

9.1.3 Control and Instrumentation (C&I)

The general requirements for the control and instrumentation system for the boiler feed pump plant shall be in accordance with in Section 11 of the Employer’s Requirements.

9.1.3.1 General (C&I) requirements for the boiler feed pump plant The entire power station unit including the boiler feed pumps shall be operated from a central control room. The Contractor is responsible for the supply of all necessary tapping points and inline devices as per limits of supply and services and functional diagram in Section 11 to enable correct control of the plant.

9.1.3.2 Minimum C & I requirements for the boiler feed pump plant The following minimum C&I protection equipment shall be provided by the Contractor for the Boiler feed pump plant:

9.1.3.2.1 Leak-Off (Minimum Flow) Protection The primary flow measurement device shall be included as part of the leak-off valve protection to be supplied for each pump set.

9.1.3.2.2 Mechanical Seal Protection A suitable scheme for avoidance of high temperature of the seal faces shall be provided. This scheme shall take cognisance of start-up and shutdown conditions on the pump.

9.1.3.2.3 Vibration Protection

Shaft monitoring equipment for vibration of the main pump in operation shall be provided. Two shaft monitors at each end of each main pump shall be provided together with cabling to the local cubicle. The instrumentation provided should be able to measure phase angle for condition monitoring and be able to be used for in situ balancing purposes. The fixed speed electric motor shall be provided with bearing housing vibration monitoring equipment. The vibration protection system shall be compatible with the condition monitoring system requirements set out in Section 11.



9.1.3.2.4 Thrust and Journal Bearing Metal Temperature Protection

Thermocouples and transmitters with cabling to local panels and appropriate temperature gauges shall be provided.

9.1.3.2.5 Strainer Differential Pressure Protection A differential pressure transducer plus cabling to a local cubicle is to be provided for an early warning of the strainer being dirty.

9.1.3.2.6 Mechanical Seal Earthing Device The necessary earthing device and associated equipment must be provided if required for compliance with 9.5.1.6 below.

9.1.3.2.7 Reverse Rotation Detection The detection of pump rotation shall be by means of a non-contacting type instrument, including cabling and local display.

9.1.4 Electrical supplies and other services

The general requirements for the electrical supplies shall be in accordance with Section 7 of the Employer’s Requirements. The entire boiler feed pump train must be adequately earthed to eliminate stray currents and potential pump trips due to instrumentation/earthing faults.

9.2 Scope of supply

The extent of supply shall include the following:

9.2.1 Design phase

A static and dynamic study of the foundations for the BFP’s shall be submitted by the Contractor.

Thermal shock studies to verify the adequacy of the available NPSH on the suction side of the booster and main pump for the different steady state and transient operating conditions, shall be conducted by the Contractor and submitted to the Engineer for approval.

Dynamic studies and steady state analysis of acoustic or mechanical resonances of the main piping systems shall be conducted by the Contractor for start-up, shut-down and transient modes of the plant

A complete rotor dynamic behaviour study of the boiler feed pump train shall be conducted by the Contractor.



9.2.2 Main equipment to be supplied

• Main pump

• Booster pump

• Planetary geared variable speed fluid drive coupling including all auxiliary equipment needed

• Fixed speed electric motor including all auxiliary equipment needed

• Main pump discharge non-return-valve and attachment to pump casing

• Leak-off valve

9.2.3 Auxiliary equipment to be supplied

• All required structural steelwork supporting the main and booster pump

• All required structural steelwork supporting the electrical motor

• Baseplates as required per set (separate baseplates for main pump - fluid coupling - booster and motor)

• Anchors

• Holding down bolts

• Couplings between main pump, electric motor; gearbox and booster pump

• Design of the foundation block (concrete slab) supporting the pump set assembly

• Spring supports for foundation block

• Minimum -flow (leak-off valve) protection device, including isolating valves, actuators, back pressure regulator and primary flow measurement device.

• Booster and main pump shaft sealing system

• Self contained lubricating within hydraulic fluid coupling casing: oil systems including oil tank and supports, 2 x 100% duty oil coolers, 2 x 100% on-load cleaning oil filters and pipework, two 100% duty motor driven lubricating oil pumps, (one ac and one



dc) including motors, motor and control gear. Oil filling pump and ac motor

• Oil purification system

• Integral and interconnection lubricating and control oil pipework, valves, supports, etc., including supply, return and drain lines to appropriate connections on motor lubricating oil system and gearboxes oil systems.

• Intermediate strainer complete with associated valves and integral pipework for pressure differential measurement and venting.

• Temporary commissioning strainers for booster pump protection (to be handed over to and kept by Employer after commissioning).

9.2.4 Accessories to be supplied

• A full set of new special tools and equipment for maintenance including handling rigs for installation and maintenance (pull-out trolley device)

9.2.5 Spare parts

Refer to Schedule H.

9.2.6 Tests

Plant tests shall be in accordance with Section 12 of the Employer’s Requirements.

9.3 Terminal points

The main process input and output terminal points shall be decided and clearly defined by the Contractor to ensure that the function and performance of the boiler feed pump plant and its major components may be demonstrated to meet the requirements of the power plant. The following terminal points describe the limits of scope of the boiler feed pump supply:

• Suction and discharge lines of main and booster pumps

• Electrical motors

• Baseplate(s)

• Commissioning and intermediate strainers Turb.Sect9.BFP 10Sept07.doc of 32


• Interconnected pipe between booster and main

• Discharge butt weld of main pump non return valve

• Discharge flange of inter-stage tapping transition piece for attemporating spray water to reheater

• Connections of the lubrication oil supply and return connections to main pump, booster pump, gearbox and electrical motor.

• Inlet and outlet of cooling water requirements to pump cooling jackets, mechanical seal coolers and electrical motor coolers.

• Leak-off return lines to deaerator including leak-off pressure regulators or binary (on/off) valves

• Clean drains and seal leakage systems

• Dirty drains

• Valve actuators

• Electrical as well as C&I junction boxes

9.4 Operational requirements

The Contractor shall ensure that:

a) It shall be possible to operate two pumps in parallel over the entire load range without any limitation on operation.

b) It shall be possible to start up the boiler/turbine unit with one pump and to sustain a part-load condition before automatically introducing a second pump as the load demand increases.

c) On loss of a duty pump the standby pump shall start-up automatically with minimal decrease in unit load.

d) Each pump shall be capable of operating at any rate from minimum flow to maximum flow under all conditions without cavitation and instability or undue vibration and noise. (Vibration and noise values outside of the normal parameters are expected when operating the pump at minimum flow conditions.)

e) The plant shall be required to operate for extended periods at minimum flow operating conditions.

f) The necessary boiler flow quantity for intermediate loads shall be adjusted by speed variation of the variable speed fluid drive coupling.



9.4.1.1 Operating duty points

The Contractor shall cater for four main points in the design as indicated in the attached Table 9.1. The table provides the main turbine and boiler feed pump parameters required for the different operating conditions. The Contractor shall complete the appropriate sections of table 9.1 in Appendix 1 and provide the curves as shown in Appendix 1 as per the VDSS. At feed pump design point (A), the pumps work against the opening pressure of the H.P. by-pass station which is needed to maintain the live steam flow rate at boiler MCR (Refer to Table 9.1 and drawings attached in Appendix 1). The total pump discharge flow rate is then the sum of the live steam flow rate (8) and the attemporating flow rate to the H.P. by-pass station (6) from Table 9.1. The Boiler MCR operating point (B) is determined by the maximum producible steam rating at the corresponding pressures. An additional Turbine MCR operating point (C) is determined by the turbine nominal rating at the corresponding pressures with the full feedwater flow passing via the 100% duty isolating slide valve of the feed control station. Note: optimum feed pump efficiency should be obtained at this point. A further additional operating point designated 'X' is determined by the transient occurring on the loss of one pump set whilst running at duty point 'B’. Under this condition the system resistance is assumed to remain constant with the boiler acting as a pressure buffer for at least 20 seconds. The input speed for the surviving pump shall be increased to its maximum permissible value of by means of the feedwater control system. The increased power required shall be determined by increased flow only, the head being substantially constant. The fixed speed motor and planetary geared variable speed fluid drive coupling shall have sufficient margin to operate at these higher than normal power requirements. A margin of 5 % on flow and 3% on generated head shall be applied to the highest power requirement of the boiler feed pump plant at MCR. The pump efficiency at the operating points (B) and (C) shall be guaranteed. (Refer also to Schedule D-9 for limits of pump performance).



9.4.2 Operating hours

The boiler feed water pumps shall be capable of operating continuously, 24 hours a day, 365 days a year, as well as cyclic operation (12 hours per day, 5 days per week).

9.4.3 Start-up and shut-down

The boiler feed pump plant should be able to start-up and shut down without experiencing any problems and without any special care for base load, load following and 2-shifting operation.

9.4.4 Abnormal operating conditions

The boiler feed pump plant shall be selected and designed to withstand the following abnormal operating conditions: (a) A temporary overload for the duration of approximately 180s on

the failure of a 50% duty feed pump set, e.g. at MCR and at no risk to the pump itself.

(b) Safe operation shall be possible up to a discharge flow of that corresponding to the run-out for one pump at a speed equal to that for normal operation i.e. duty point “C1”

(c) During the occasion of a sudden load reduction on the turbine whilst the deaerator storage tank level is a minimum

(d) To maintain feed flow following a boiler trip from MCR conditions with both super heater and reheater safety valves operating.

The Contractor shall provide pump characteristic curves with the following minimum requirements: (a) Leak-off line (b) Operating limit line (c) Minimum duty speed curve (d) Over speed curve (e) Closed valve discharge pressures at duty point A, B and C (f) NPSH required for 1% and 3% head drop of main pump, (g) System resistance line referred to one pump (h) The different duty points according to Schedule D 9. The above characteristics must apply at the full feed temperature, stated in Schedule D9, and with main pump spray water tapping "open". See Appendix 1 for examples on specimen pump curves. NOTE: Characteristic curves shall be drawn to a readable scale. The Contractor shall supply start-up speed torque curves for the main and booster pumps showing the required torque at any steady-state speed from zero up to full speed at maximum operating temperature. Should an emergency start-up of the standby pump set occur with



special conditions such as leak-off valve closed then this should be indicated on the curve. The opening point of the discharge NRV shall also be indicated assuming the system head remains constant at that corresponding duty. The rotational inertia with the pumps filled with water shall be as entered in Schedule D 9. The maximum reverse speed that can be achieved if the non-return malfunctions shall be as stated in Schedule D9.

9.4.5 Further operational requirements

9.4.5.1 Fixed or sliding pressure deaerator The selection between a fixed or sliding pressure deaerator has a critical effect on the suction behavior of the booster and main pumps during a load reduction/rejection on the main turbine. The operation philosophy of the deaerator for normal and load reduction/rejection conditions shall be provided by the Contractor. The Contractor shall indicate whether a pre-warming and cool down system for the boiler feed pumps are required. The Contractor shall submit a detailed explanation of the proposed system(s), arrangement and controls with diagrams where necessary.

9.4.5.2 Booster Pump The booster pump shall satisfy the NPSH needs of the main pump under all operating conditions. The characteristic curves shall show that this requirement is satisfied, i.e. a series of curves (H vs. Q) with the head drop-off point and the duty point clearly shown for 20% n to 100% n at approximately 20% intervals, (n = maximum speed). The Contractor shall, in his design, cater for a sudden fall in NPSHa at the pump suction (e.g. due to a load drop resulting in loss of steam support to the de-aerator) which may cause flashing in the booster pump. The effect on the main pump of these critical or sub-critical conditions shall be fully analyzed and assessed, refer to section 9.4.5.1. The booster pump suction conditions for normal and extreme operation shall be supplied in Schedule D 9. The suction pressure in Schedule D 9 is based on a height from centerline of the deaerator to 0, 0 m level. The characteristic curves shall be drawn on a readable scale.



9.5 General Design

The boiler feed pump plant design shall be based on experience gained on plant of a comparable size and type which has passed through the experimental and prototype stages and has operated satisfactorily, so that initial problems have been eliminated, safety established and availability proven to be high. The Boiler Feed Pumps shall be designed for maximum reliability for the expected turbine generator life of 50 years and a minimum of 200 000 operating hours. To ensure maximum availability between planned maintenance periods the Contractor shall advise the optimum period between overhauls.

9.5.1 Casing Design and Construction

9.5.1.1 Main Pump Design

The main pump shall be of horizontal, centrifugal, multistage barrel type construction with the rotating element, bearings, mechanical seals, and diffusers and stage casings in the form of a complete cartridge (pull-out). The main pump casing shall be supported at its centerline and shall be free to expand and contract whilst remaining aligned to the driver. The orientation of suction and delivery connections on the booster and main pumps shall be clearly indicated. The pump design shall take into account the stresses due to differential thermal expansion during rapid changes of feed water temperature either from the normal working temperature to cold or from cold to the normal working temperature. The maximum permissible rate of temperature change shall be as stated in Schedule D 9.

9.5.1.2 Booster Pump Design The booster pump casing shall be of the double volute type, supported at its centerline and shall be free to expand and contract whilst remaining aligned to the driver (gearbox). The inlet and outlet nozzles shall be arranged vertically.



9.5.1.3 Shafts and Impellers

The pump shafts shall be forged and fully heat treated to minimize distortion in service. Shaft sleeves shall be provided in the seal area. Impellers shall be fitted on the shaft so as to ensure easy removal. Each impeller shall be statically balanced before fitting to the shaft. After the entire rotating element has been assembled it shall be statically and dynamically balanced to ISO 1940 quality grade G 2.5. Similarly, all couplings shall be statically and dynamically balanced and component parts hard stamped to ensure that after stripping and reassembly, they shall retain their fine state of balance. The booster pump impeller shall be of a single stage double entry type design. The main pump impellers and diffusers shall be manufactured by using the investment casting process (lost wax method) or the extrude honing process, to ensure the wetted hydraulic parts have the required quality surface finish. Either the casings or the impellers shall be provided with renewable wearing rings. If the impeller is not fitted with wearing rings then it shall have adequate material at the wearing surface to permit renewable wearing rings to be fitted. The wearing rings should have good galling properties or have a distinct hardness difference between the rotating and stationary part. The booster pump impellers shall be suitable (without cavitation) for handling feedwater, at the maximum flow rate from the Deaerator/Feedwater tank with the Deaerator at minimum water level i.e. lowest NPSH available. The suction specific speed of the pumps must not exceed 163. The specific and suction specific speed of the pump impellers shall be stated in Schedule D9.

9.5.1.4 Pump rotating element The first critical speed of the rotating element, including the effects of lubrication, bearings, bearing supports, and coupling half, shall be not less than 30 percent above the normal pump operating speed for new clearances and still in excess of 110% under worn-clearance conditions (150% of new clearance condition). The impellers shall be mounted on the shafts by means of keys, and shall be locked axially by distance sleeves and nuts.



The relative pump clearances for new and maximum worn-out clearances between all rotating parts and casing parts shall be stated in Schedule D 9. The Contractor shall provide a pump efficiency vs. clearance chart indicating how the efficiency of the pump deteriorates with increase in clearances. An additional chart indicating estimated (but preferably based on proven measurements and operating experience) pump efficiency deterioration vs. operating hours shall also be included in the Schedule D.

9.5.1.5 Thrust Balancing Devices The booster pump shall be designed and equipped with a fixed axial (thrust) bearing arrangement. The axial forces generated by the main pump impellers shall be counteracted by a balance piston-throttling bush device in combination with a double acting axial (thrust) bearing arrangement of the direct spray type design. The balance water shall be returned back to the intermediate pipe between the booster and main pump, upstream of the intermediate strainer.

9.5.1.6 Shaft Sealing System Cartridge type mechanical seals together with the associated seal cooling equipment and pump jacket cooling equipment shall be provided, including but not limited to: seal pumping ring, magnetic separator, coolers, duplex filters, piping, valves and temperature sensors, instrumentation and protection as necessary Both seal and jacket cooling systems shall be cooled by water taken from a closed circuit auxiliary cooling water system, to be supplied by others. The cooling water requirements and heat loads shall be stated by the Contractor. Details of the sealing arrangement including associated equipment shall be described with the aid of a sketch. If a mechanical seal earthing device is required to maximise seal life, then the Contractor is required to justify this and describe the mechanical seal earthing device. The seal face material must be compatible with the quality of the feedwater as listed in the Chemistry standard for coal fired units with once-through boilers, Eskom Standard – GGS 0209. The mechanical seal face material shall be capable of operating for a minimum of 30 000 hours.



9.5.1.7 Bearings

All radial bearings for the pumps shall be of the forced oil lubricated, sleeve type design. The thrust bearing shall be of the pivoted pad type, capable of taking equal load in either direction. The quantity of oil flow required and the temperature rise shall be stated in Schedule D9. The booster and main pump radial sleeve and axial (thrust) bearing assemblies shall be mounted in housings arranged externally from the pump casing. Radial and thrust bearings shall be equipped with means to provide remote metal temperature indication and high temperature alarm warning. The extent of supply shall include the local instrumentation and the initiating devices for remote alarm indication. Refer to Section 11. Both radial and thrust bearings shall be designed to accept without damage reverse rotation of the pump to whatever speed can be reached should the pump main non-return valve malfunction. The double acting axial (thrust) bearings shall be of the direct spray type design. All bearings shall be designed for pump set run down without lube oil supply.

9.5.1.8 Couplings Flexible membrane couplings of a proven design shall be provided to connect the main pump; electric motor, gearbox and booster pump shafts. The couplings shall be capable of accommodating the maximum expected expansions, misalignment, axial movements and forces, and shall have suitable torsion characteristics. The design torque shall be well above the rated motor torque (including driver service factor) and shall be determined considering the motor start-up torque as well as the motor torque at motor seizure. All couplings shall be from the same manufacturer. Suitable coupling guards shall also be provided.

9.5.1.9 Lubrication System Refer Section 9.9.2.



9.5.1.10 Pump Gaskets and O-Rings

No O-rings shall be permitted for any sealing purposes on the internals of the pumps. The only O-rings permitted shall be the ones utilized in the mechanical seal and they shall be of the heat resistant type and specifically designed and selected to withstand temperatures above 200 oC. Where O-rings are used on the oil system they shall also be of the heat resistance type and compatible with the oil. (No O-rings to be provided on any hot parts of the pumps.)

9.5.1.11 Forces and Bending Moments The pumps shall be designed to withstand forces, bending and torsion moments applied to each suction and delivery branch by the piping system. The maximum allowable forces and moments of the pump branches shall be stated in Schedule D 9.

9.5.1.12 Speed increase gearbox (alternative BFP drive option) Not Applicable.

9.5.1.13 Pump and Interconnecting Pipe Connections The delivery connection on the main pump shall be butt-welded. For pump connections orientated vertically adaptors welded to the pump casing shall be provided to penetrate through the foundation block. The adaptor for the main pump shall be welded whilst the adaptor for the booster pump may be attached using flanges at each end.

9.5.1.14 Leak-off or minimum flow devices The main pump of each boiler feed pump set shall be provided with a leak-off or recirculation system rated at 25% of rated BFP flow (To be confirmed during detailed design). The pump leak-off system shall include a pneumatic operated minimum flow valve and an orifice plate as a back pressure regulator to protect the pump set against overheating at low flows. The primary flow measurement device shall be provided in the intermediate pipe between the booster and main pump. The device shall be installed in a manner to allow removal for calibration. The pressure reducing components of the leak-off devices shall be so designed as to reduce noise and vibration to a minimum and to eliminate cavitation. The pressure reducing function and isolating function of the leak-off valve shall be provided in an integrated valve body.



The back pressure regulator shall be fitted upstream of the deaerator inlet to avoid flashing and shall be designed for a mass flow which is at least 10% greater than the minimum mass flow (leak-off) of the pump. The leak-off or recirculation connection shall be taken from the feed delivery piping between the main pump and the non-return valve upstream of this valve, and shall not be connected to either the pump discharge branch or the non-return valve body. This connection shall be so designed and arranged as to eliminate vibration due to fluid flow into and through the connection. The details of the leak-off valve, actuator and back-pressure regulator shall be listed in Schedule D.9.

9.5.1.15 Reheater Attemporating Spray Water Connection An interstage take-off feature shall be provided on each main pump for reheater attemporating spray water requirements. The maximum quantity and pressure of the spray water required shall be specified in Schedule D 9 (from boiler Contractor). The pressures corresponding to the part-load pump duty shall be as stated in Schedule D 9. The isolating valves and non-return valves together with lengths of piping and any other fittings between the valves and the tapping points shall be supplied by the Contractor.

9.5.1.16 Intermediate Strainer A strainer of the basket type shall be provided between the booster and main pump and shall be removable for cleaning purposes. The construction of the strainer shall be fine stainless steel mesh supported by a perforated plate of adequate strength. The mesh size shall be selected such that the main pump is adequately protected. The free surface of the coarse screen together with the fine screen shall be at least 4 times the pipe’s cross-sectional area. The strainer body shall be provided with two tapping points for differential pressure measurement as well as a vent valve at the highest point including drain piping to a locally mounted tundish. The differential pressure shall be remotely monitored. The strainer bodies shall be designed and hydrostatically tested in accordance with the relevant pressure requirements. The casing design shall be in such a manner, that the normal allowable forces and moments on the suction nozzle are not influenced by this strainer. The strainer design data and pressure loss calculation for a clean and a blocked strainer shall be provided and listed in Schedule D 9. Removal of the strainer for maintenance purposes shall be possible without dismantling the connecting pipe work. Sufficient space should



be provided below the pump’s foundation and include a support frame for easy removal and cleaning purposes of the strainer.

9.5.1.17 Commissioning Strainer A temporary commissioning strainer of stainless steel material shall be provided and installed immediately upstream of the booster pump to protect it from debris throughout the commissioning phase. The perforation diameter shall not exceed 5 mm and the overall strainer pressure drop shall not exceed 1.6 m head at normal duty. As this strainer shall be transferred to succeeding units following commissioning, sufficient strainers, in total for one of the power station units (i.e. three strainers) shall be included. The make-up pieces (suction line-pipe) which shall replace the commissioning strainers shall be provided by the Contractor.

9.5.1.18 Discharge Non-Return Valve The Contractor shall provide a discharge non-return valve of the in line straight through type for the main pumps. The Contractor shall provide and install the transition piece between the pump and the NRV. The technical details of the NRV shall be included in Schedule D 9.

9.6 Performance requirements 9.6.1 General

The motor and gearbox selected and offered to drive the BFP set shall have sufficient margin to operate at all operating conditions which require higher than normal power requirements. The power station units shall be operated with modified variable pressure, i.e. with the live steam pressure and consequently the pressure at the pump’s discharge will vary as the load varies. The three 50% duty feed pump sets for each turbo-generator unit shall be designed for variable speed from a variable speed fluid drive coupling. The pumps shall have a stable and drooping characteristic with increase in output and shall run satisfactorily in parallel with each other over the full range of speed. The zero flow head at the design speed shall be between 110% and 125% of the duty point head. (To be confirmed during detailed design). The zero flow pressure when running at full speed (with no leak-off) whilst handling water at the design inlet temperature shall be stated in Schedule D 9.



Following a hot shut-down the rotating element of the pumps shall remain free to rotate i.e. the radial clearance shall still be sufficient to preclude any interference between parts.

9.6.1.1 Noise performance The noise generated by the plant shall comply with Section 2.31.2 of the Employer’s Requirements. The expected pump and motor noise levels shall be entered into Schedule D 9. The levels shall be for normal operation as well as during leak-off operation.

9.6.1.2 Vibration performance Refer to sections 2.31.1 and 12 of the Employer’s Requirements

9.6.2 Availability

The boiler feed pump Plant shall be designed to a required availability of > 99,5% of the main turbine running hours. This target is achievable if the recommended maintenance plan is implemented. The pump supplier shall supply availability and reliability figures of similar plant (reference plant) installed world-wide.

9.6.3 Dynamic Behaviour of Rotors

a) Dynamic Bending Behavior Of Each Rotor

Shaft critical speed and response calculations shall be prepared and presented for the main pumps. An up-to-date computer code shall preferably be used to perform the calculations which must include the bearing support stiffness and damping coefficients. The amplitude of vibration of each stage along the rotor length for the full speed range (33 &1/3 to 100%) shall be stated. Where possible, mode shapes for the "wet" and "dry" case shall be plotted for each considered speed. An additional shaft calculation shall be conducted for “worn” clearance conditions. The critical speed for the complete BFP train should be below the minimum speed of the motor/main pump at minimum flow conditions.

b) Shaft Line Torsional Behavior The Contractor shall carry out a rotor dynamic analysis of the full drive train including the driving equipment to demonstrate the torsional compatibility of all the components and shall submit the results of the



analysis to the Employer. This analysis shall include for lateral and torsional oscillations taking into account the motor shaft torsional inertia, the motor bearing damping characteristics and the transmission of these through the coupling. The contribution of voltage pulsations from the motor to the vibration characteristic shall be included in determination of the overall response characteristic.

9.6.4 Dynamic behaviour of the stators

The natural frequencies of the bearing housings shall be well in excess of the pump running speed and the stiffness shall be great enough to provide a deflection much smaller than the bearing oil film thickness to avoid reduction of the shaft critical speed. For speeds at or above 5000 rpm, journal bearing design shall be of the anti-whirl type to eliminate bearing induced vibrations. Bearing spans shall be kept to the minimum practical.

9.6.5 Instrumentation for control and condition/maintenance diagnostics

The Contractor shall indicate the minimum instrumentation needed for control and condition monitoring. It is the intention of the Employer to use plant instrumentation to determine and evaluate the performance of the boiler feed pump plant. The Contractor shall provide a list of instrumentation needed to measure the different parameters to determine the pump set’s performance. The method on how this is to be determined shall also be provided by the Contractor.

9.7 Maintenance features

9.7.1 Sub-assembly replacement times The Contractor shall provide the maximum times to replace the following pump equipment or sub-assemblies: a) maximum time for replacement of the complete pump cartridge b) maximum time for replacement of a mechanical seal, booster

and main pump c) maximum time for replacement of a journal bearing, booster and

main pump d) maximum time for replacement of a thrust bearing assembly,

booster and main pump e) maximum time for cleaning an intermediate filter f) maximum time for replacing the main coupling g) maximum time to replace electric motor (fixed speed)



h) maximum time to replace the planetary geared variable speed

fluid drive coupling Note: the times should be based on a pump that has cooled down to below 45 oC.

9.7.2 Material selection

The materials selection in the construction of the equipment and accessories shall be the responsibility of the Contractor and shall be suitable for the severity of the service intended and the stated life of the plant. As a minimum the following materials of construction shall be adhered to: Booster pump

Volute casing Cast (13-4 Cr Ni) stainless steel

Shaft Forged 13% chrome steel Impeller Cast 13% chrome steel

Main Pump

Barrel casing Forged low alloy steel

Shaft Forged 13% chrome steel Impeller Cast 13% chrome steel Diffusers Cast 13% chrome steel

The choice of materials shall be based on proven experience. The materials selected for construction must be compatible with the quality of the feedwater as listed in the Chemistry standard for coal fired units with once-through boilers, Eskom Standard – GGS 0209 The particulars of material construction for the pump components shall be listed in Schedule D 9.

9.8 Verification of specified pump performance

Refer to Section 12 of the Employer’s Requirements

9.9 Main Boiler Feed Pump Drive This BFP drive will consist of a planetary geared variable speed fluid drive coupling coupled directly to the main pump for step-less speed regulation of the main pump. The planetary geared variable speed fluid drive coupling will be driven by a fixed speed electric motor



(1500 rpm). The booster pump to be connected on the other end of the electric motor shaft. All shaft ends shall be coupled via flexible membrane couplings.

9.9.1 Design requirements of the Planetary geared variable speed fluid drive coupling The 50% duty electrical driven boiler feed pump sets shall consist of: main pump, planetary geared variable speed fluid drive coupling, electrical motor (constant speed, 1500 rpm) and booster pump. All shaft ends shall be coupled via flexible membrane couplings. The hydraulic coupling shall be driven by a fixed speed electric motor (1500 rpm). The main pump shall be driven by the electric motor via a planetary geared variable speed fluid drive coupling. The planetary geared fluid drive coupling shall be capable of giving smooth and steady speed variation and regulation over the entire speed range requirements of the pump. The planetary geared variable speed fluid drive coupling shall be designed for the lateral and torsional oscillations of the complete drive train shaft during transient and starting torque conditions of the fixed speed motor see paragraph 9.6.3. The planetary geared variable speed fluid drive coupling shall be rated for the maximum duty of the main pumps, see paragraph 9.4 It shall be capable of withstanding, without damage, reverse rotation at any speed. The geared fluid drive coupling and its auxiliaries shall be designed to reduce inherent time lags to a minimum. The scoop tube of the fluid drive coupling shall be electro-hydraulically operated. The response of the fluid drive coupling and scoop tube must be such that it meets all the operating conditions as specified in paragraph 9.4.

9.9.2 Lubrication system of the planetary geared fluid drive coupling.

The oil supply shall be incorporated in the planetary geared fluid drive coupling consisting of a shaft driven main lube oil pump, emergency/start-up AC motor driven auxiliary lube oil pump (to be identical to the shaft driven lube oil pump), oil reservoir with integral heater, lube oil coolers, filters, sight glasses, and supply and drain piping and necessary instrumentation. The lube oil requirements to the bearings of the booster and main pump, the hydraulic gear coupling and the electric motor shall be supplied from the fluid drive coupling. All the connecting piping shall be supplied by the Contractor. The lubricating tank/oil reservoir and pipework to the filter shall be in carbon steel. The material downstream of the filter shall be of stainless steel. The oil shall be supplied to all bearings when the feed pumps are in operation and on standby. When in standby, the electrically driven lube oil pump shall be in operation supplying the required lube oil to all the bearings. The A.C. motor driven auxiliary lube oil pump shall start



automatically in the event of failure of the shaft driven lube oil pump or low speed operation when the discharge pressure of the shaft driven lube oil pump is not sufficient to meet the required pressure. In the event of reverse feed water pump rotation, the system shall be such that oil shall still be supplied to all bearings by the auxiliary lube oil pump. In the event of loss of electrical power, the shaft driven lube oil pump shall supply all necessary lubricating oil until the boiler feed pump set runs down to a stop. Changeover between the motor driven and shaft driven lube oil pumps shall be without hunting of pumps or without pressure and flow disturbances. The oil reservoir/sump shall be incorporated into the gear box casing of the planetary geared fluid drive coupling and shall have the necessary vent and drain connections. It shall be designed to avoid excessive aeration or turbulence of the oil during circulation. Suction connections of the auxiliary lube oil pump shall be arranged to draw oil from the lower part of the reservoir and the connection from the main shaft driven lube oil pump shall be positioned to allow a reserve capacity of oil in the system. The oil reservoir/lube oil tank may be incorporated into the main-pump & hydraulic gear coupling base plate assembly. It shall be preferred that the oil reservoir shall not require excavation into the foundation. A level indicator and level switch shall be located on the oil reservoir. A sight glass flow indicator shall be located in the lube oil return line from each bearing. All instrument signals shall be made available to the plant control system for monitoring, alarm, and sequencing purposes. All instrument signals shall be wired to a common terminal box mounted on the pump skid. The actual lube oil tank capacity in the stationary and in the operating conditions to be stated. The maximum and minimum lube oil tank levels to be indicated and stated in Schedule D 9. Access to lubrication systems shall be such as to permit maintenance, draining and refilling without contamination of the new lubricant and without the removal of any guarding facilities. A facility for cleaning the tank is to be provided and additional flanges and valves including connecting pipes to be provided for the connection to a permanent oil purifier. A permanent centrifugal type of oil purifier shall be provided for the three pump sets (shared). It shall be capable of separating and purifying the oil charge for each of the 3 pump sets in approximately eight hours. Selection of the oil for cleaning shall be by manual pushbutton switching from the control room. The elevation of the oil reservoir relative to the oil return lines (gravity flow) shall ensure that there is no pressure build-up in the return lines that could lead to bearing housing and lube oil line leakages. The oil flow to the respective bearing and lubrication points shall be achieved by pipes and fixed orifices only. No valves shall be installed in the supply lines to the respective bearings for flow adjustment.



A duplex type oil filter shall be provided. It shall be integrated in the lube oil system of the planetary geared variable speed fluid drive coupling and shall have a manually operated three way change-over valve. The switch over from one filter unit to the other shall be possible without affecting the pump set's operation and oil flow to the respective bearings. It shall be possible to remove and replace a “blocked” filter element during operation. A remote measurement of the differential pressure shall be provided. Electrical heaters capable of heating the oil from 15°C to the minimum required temperature for start-up in approximately 6 hours, shall be provided for each reservoir. The volume of the oil tanks must be adequate to allow for release of entrained air in the oil. Both the bearing pedestal and oil supply lines to the bearings of the electrical motor shall be electrically insulated. The details of the planetary geared variable speed fluid drive coupling shall be included in Schedule D 9.



9.10 Appendix 1



Table 9.1: Project Alpha 50% Boiler feed pump set technical data

Operation Conditions For Different Boiler Rating (%) No

Description

Unit A

Design B

100 Boiler MCR

C 97

Turbine MCR

D 90

E 80

F 70

G 60

H 50

I 40

X

Diagram reference

Appendix 1 Drawing 1

& Drawing 2

Remarks

1 Unit Live steam flow kg/s 8 Total (2 EFP’s)

2 Unit HP bypass spray water flow kg/s 6 Total (2 EFP’s)

3 Unit Re-heater spray water flow kg/s 9 Total (2 EFP’s)

4 Pump set HP discharge flow kg/s 2 Per pump set

5 Pump set HP discharge flow l/s 2 Per pump set

6 Pump set re-heater spray disch flow kg/s 5 Per pump set

7 Pump set re-heater spray disch flow l/s 5 Per pump set

8 Pump set suction flow kg/s 1 Per pump set

9 Pump set suction flow l/s 1 Per pump set

10 Pump set HP discharge pressure kPa 2

11 Pump set re-heater spray disch pres. kPa 5

12 Pump set suction pressure kPa 1

13 Pump set HP generated head kPa 2&1

14 Pump set HP generated head m 2&1

15 Booster NPSH avail (without strainer) m 1

16 Booster NPSH avail (with strainer) m 1

17 Pressure in feedwater tank kPa 1

18 Feed water temperature oC 1 In deaerator

19 Feed water density kg/m3 1 In deaerator


Turb.sect9.BFP 10Sept07

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Transcript of Turb.sect9.BFP 10Sept07