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Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal Units

h)Emergency stop and control valve position.

i)Main steam and hot reheat steam inlet temperature and pressure.

j)Bearing metal and drain oil temperature.

k)Turbine casing metal temperature.

l)In case of vibration, shaft mounted reference detectors and required supervisory instrument circuitry shall also be provided.

m)Any other measurement necessary for safe and reliable operation of the turbine.

iii)The system shall be provided with suitable hardware and software signal processing and shall be capable of signal distribution and interfacing with other control systems and MMIPIS system.

iv)For all vibration measurements indicated under (ii) above, a Microprocessor/computer based system shall also be provided to achieve the following functions:

a)On-line spectrum/harmonic analysis.

b)Identification of the exact nature of failure resulting in increase in bearing vibration and direct message on the TFT indicating the exact nature of fault e.g. misalignment, shaft crack, bearing looseness etc. through use of intelligent software packages.

c)Storage and comparative analysis of vibrations.

d)Generation/ analysis of bode plot/ orbit plot and time waveform/ nyquist plot/ shaft centre line plot/ cascade and water fall plot.

v)All the vibration parameters as well as turbine supervisory parameters shall also be fed to the turbine control system (TCS) through hardwiring or through suitable link so that all these parameters are suitably displayed on the TG control TFTs. All required I/O cards and other processing modules etc. shall be provided for this purpose.

vi)Test calibration jigs for site calibration of all sensors of TSS shall be provided.

17.3.11BFP turbine supervisory instruments

i)The supervisory equipment/ instruments shall be provided for BFP turbine for detection, indication, recording, monitoring and diagnostics of the following also keeping in view the standard and proven practice of the OEM:

a)Shaft eccentricity.

b)Axial shift, (with three pickups).

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Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal Units

c)Differential expansion.

d)Overall expansion.

e)Speed (triple pickups).

f)Turbine casing and bearing metal temperature for all bearings.

g)Stop valve metal temperature.

h)Bearing pedestal vibration (both in horizontal and vertical direction).

i)Absolute as well as relative shaft vibration measurement in both X & Y direction.

j)Any other measurement necessary for the safe and reliable operation of the turbine.

ii)Duplex K-type thermocouples/ duplex 100 ohm platinum RTD’s shall be provided for the metal temperature and on the thrust bearing faces.

iii)Separate and independent hardware/electronics shall be employed for each of the TDBFPs.

17.3.12HT drives supervisory instruments

Adequate supervisory equipment/ instruments shall be provided for HT drives comprising of ID/FD/PA fans, coal mills, MDBFP, CEPs, CW/ ACW/ DMCW pumps etc. for detection, indication, recording and monitoring of equipment vibrations.

17.4Plant Performance Analysis, Diagnosis & Optimization (PADO) Software

17.4.1The plant shall be provided with a PC based on-line plant performance analysis, diagnosis & optimization (PADO) system incorporating complete thermal design model of each unit.

17.4.2The PADO system perform the following main functions:

i)Calculate thermal performance status of the plant and efficiency of generation using measured data.

ii)Calculate all the key system performance indicators at system level such as heat rate, plant and equipment efficiency, generator output and controllable losses.

iii)Monitor, track and analyze plant emissions such as SO2, NOx, CO and CO2 in real time.

iv)Monitor and analyze ESP and stack conditions such as temperature, humidity, gas flow rate and opacity.

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Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal Units

v)Facilitate obtaining lowest emission while maintaining combustion efficiency.

vi)Evaluate system and component performance degradation to detect worn plant equipment.

vii)Expert system diagnostics using neural and Bayesian belief networks and historical data for quick identification of problem pinpointing down to the component.

viii)Facilitate obtaining controllable parameter settings to optimize given process or activity at the measured operating condition, using state of the art optimization techniques.

ix)What if analysis at system and component level.

17.4.3The PADO system shall also include boiler stress condition analyzer, interactive water and gas chemistry management system and regenerative cycle performance optimization system.

17.5PLC Based Miscellaneous Control Systems

i)Independent PLC based Control and Instrumentation system complete with all accessories, auxiliaries and associated equipments and cables etc. shall be provided for the safe, efficient and reliable operation of the standalone plant auxiliaries such as turbine lube oil purification system, central lube oil purification system, condensate polishing plant, on-line tube cleaning system and any other such standalone system. Alternatively, controls of standalone plant auxiliaries can be implemented in Plant DDCMIS also as per standard proven practice of the OEM.

ii)Each PLC unit shall be provided with two processors (Main processing unit and memories) one for normal operation and other as hot standby. In case of failure of working processor, there shall be an appropriate alarm and simultaneously the hot standby processor shall take over the complete plant operation automatically. The transfer from main processor to standby processor shall be totally bumpless and shall not cause any plant disturbance whatsoever. In the event of both processors failing, the system shall revert to fail safe mode. It shall be possible to keep any of the processors as master and other as standby. The standby processor shall be updated in line with the changes made in working processor.

iii)The PLC system shall be provided with necessary interface hardware and software for dual fibre optic connectivity & interconnection with station wide LAN for two - way transfer of signals for the purpose of information sharing.

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Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal Units

iv)For PLC system of CPU, two (2) nos. latest version of PC based OWS each with 19" color TFT’s and key boards shall be provided for control & monitoring and programming function. One number heavy duty A3 size color printer shall be provided alongwith OWS. Turbine lube oil purification system, central lube oil purification system and any other such standalone system may be provided with panel mounted unit for control & monitoring and programming function as per proven practice of the manufacturer.

v)Manual intervention shall be possible at any stage of operation. Protection commands shall have priority over manual commands and manual commands shall prevail over auto commands.

vi)Input Output modules shall be provided for all type of field input signals (4-20 mA, RTD, Thermocouple, non change over/change over type of contact inputs etc.) and outputs from the control system (non change over/change over type of contact, 24/48 VDC output signals for energising interface relays,4-20 mA output etc.).

vii)For PLC system, redundant 24 V DC power supply shall be provided. Necessary redundant transformers and redundant chargers with 24 V DC battery back-up shall be provided to derive power supply from 415 V, 3-phase redundant incomers at the input terminals of Power supply cabinets. Each set of PC along with TFT shall be provided with smart type line interactive UPS with battery back up of atleast 30 minute. Alternatively, primary power supply to PLC and PC system can be redundant 230 V AC from smart type line interactive UPS with minimum 30 minutes battery back-up.

viii)The battery shall be sealed maintenance free Ni-Cd type or Plante type Lead Acid batteries with long life and shall be able to provide a backup for atleast 30 minute at full load requirement of the complete control system.

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Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal Units

SECTION-5

MISCELLANEOUS SYSTEMS, PIPING, VALVES, INSULATION ETC.

Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal Units

CHAPTER18

POWER CYCLE PIPING, VALVES AND THERMAL INSULATION

18.1Power Cycle Piping

18.1.1General

i)All the piping systems and equipments supplied shall be designed to operate without replacement and with normal maintenance for a plant service life of 25 years and shall withstand the operating parameter fluctuations and cycling which can be normally expected during this period.

ii)The design, engineering, erection, testing, etc. of the complete piping systems shall be to the requirements of power piping code ANSI B 31.1. In addition to this, requirements as laid down in Indian Boiler Regulations (latest edition) shall also be met completely.

18.1.2Pipe sizing

i)Inside diameters of piping shall first be calculated for the flow requirement of various systems based on velocity limits listed below:

Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal Units

ii)Pressure drop in reheat steam circuit (cold reheat, hot reheat line & reheater) should not exceed 10 % of HP turbine exhaust pressure.

iii)Pipes shall be sized for the worst operating conditions (i.e. maximum flow, temperature and pressure values). In case of BFP suction piping, transient analysis shall be carried out for optimum sizing of the system in order to establish the pipe inside diameter for minimum pressure drop in system to match with the pump NPSH requirement under worst operating conditions.

iv)The design pressure for BFP discharge piping up to and including downstream valve at feed regulating station (FRS) shall be selected such that the minimum calculated thickness for various pipes at design temperature is sufficient for the following conditions, considering allowable stresses as per ASME B31.1:

a)Discharge pressure corresponding to turbine driven BFP trip speed at shut off head condition, if TDBFP characteristics is governing for calculation of boiler feed discharge piping design pressure.

b)Discharge pressure corresponding to motor driven BFP trip speed (frequency 51.5Hz) at shut off head condition if MDBFP characteristics is governing for calculation of boiler feed discharge piping design pressure.

v)With feed regulating station (FRS) located at upstream of HP heaters and no isolating valve provided at inlet of economiser, the design pressure of boiler feed discharge piping at downstream of FRS shall be worked out corresponding to design pressure of the boiler. This shall be for HP heaters provided with spring loaded relief valve(s) or having provision of media operated three way valves at inlet/ outlet of HP heater(s) as per approval of IBR so as to prevent BFP shut off pressure from being communicated to downstream piping system and HP heaters.

vi)The design pressure and temperature, down-stream of any pressure reducing valve upto and including the first block valve shall be the same as that at up-stream of pressure reducing valve. If a pressure relief valve is provided in the down stream of PRV, the downstream piping shall be designed to a lower pressure as per set pressure of the relief valve.

The piping at down stream of de-superheater shall be designed for spray failure condition. The length of piping system considered for spray failure condition shall not be less than the length required for proper spray mixing as recommended by de-superheater supplier.

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Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal Units

18.1.3Material selection

The material used for power cycle piping shall be equal to or better than the following unless specified otherwise:

18.1.4Pipe wall thickness

i)Pipe wall thickness calculation shall be made on the basis of procedure and formula given in ASME B 31.1. Stress values of piping material for calculation shall be selected from tables given in ASME B 31.1. Thickness, thus calculated shall be checked as per IBR formula (where applicable) and the more stringent of the two shall then be selected. In any case the thickness selected shall not be less than the standard thickness specified in ANSI B 36.10. In such cases where thickness calculated does not fall in the standard range of thickness as given in ANSI B 36.10, ID/OD controlled pipes as per ASA-530 shall also be acceptable.

ii)The selected pipe thickness shall not be less than Sch.80 for alloy steel

&carbon steel pipes of sizes 50 NB & below. The selected thickness for SS pipes shall not be less than Sch.40S of ANSI B36.19.

iii)For the piping systems likely to be subjected to two phase flow, i.e. down stream of control valves on heater drain lines etc. and for the length of piping which is required for the proper mixing of spray water at downstream of de-superheater, the selected thickness shall not be less than Sch.40 for pipe sizes above 50 NB but below 300 NB and Sch. STD for pipe sizes 300 NB and above.

iv)To account for losses due to corrosion, erosion etc. during the plant service life, an allowance of 1.6 mm/0.75 mm shall be considered in the minimum wall thickness calculation of pipes as per ASME B31.1/IBR respectively.

18.1.5Layout

i)All high points in piping system shall be provided with vents. All low points shall be provided with drains. Provisions of drains on steam piping shall be as per ASME code TDP-1. Drain lines shall be adequately sized so as to clear condensate in the line and prevent water hammer and damage to turbine due to water induction.

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Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal Units

ii)All piping shall be sloped towards the system low point such that slope is maintained in both hot and cold condition.

iii)The pipe routing shall be such that a clear head room of not less than 2.2 m above the walkways/ working area is available.

18.1.6Stress/ dynamic analysis

i)Flexibility and stress analysis for various piping systems shall be carried out by the contractor as per the requirement of ANSI B 31.1. Analysis results shall satisfy the following:

a)Calculated stresses in the piping system shall be within the allowable limits stipulated in ASME B 31.1 as well as IBR for piping under the purview of IBR.

b)Calculated forces and moments on equipment nozzles/TP shall not be more than the allowable loading provided by equipment manufacturer(s). Flexibility analysis shall also calculate the deflections in all directions (translational and rotational) to enable design and selection of hanger/support system.

c)Besides the flexibility analysis, steam hammer analysis/ dynamic analysis shall also to be performed wherever required to study the effects of fast closure of steam admission valves and safety valve blowing. Requirements of additional restraints/ snubbers to take care of these effects shall be established, and such restraints/ snubbers shall be provided. The effects of seismic and wind loads and adequate support to take care of the same shall be provided.

ii)Cold pulling shall not be used and piping systems shall be so designed that there will be no requirement of cold pull for meeting allowable reaction/ stress values.

18.1.7Specifications for piping and fittings

Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal Units