CW SYSTEM

-
CW SYSTEM
Purpose
The purpose of CWP system Presentation  is to provide the operating personnel with necessary information to safely operate and maintain the CWP  system & associated equipment.
The scope of the Presentation covers an overview of the CWP System, System  Description, Normal Operation, Start-up / Shutdown, Emergency Operations & Alarms, Instrumentation & Process Control, Interlock & Protection

The cooling water pump (CWP) sat  Power system is provided for each unit. & all pumps is  located CW House Building.

Overview
Purpose of the Circ Water (CW) system
The purpose of Circulating Water Pump (CWP) is to remove the heat rejected to the Main Condenser by the low pressure turbines exhaust steam. 
CWP transfers the heat from the Main Condenser to the atmosphere via natural  draft cooling towers.

NEED OF COOLING TOWER :
In Power plant, cooling tower cools down the hot water of Turbine Condenser by the process of evaporative cooling and sensible heat transfer. This cold water is recycled into the system again for condensation of exhaust steam in Condenser.
Condenser act as heat load and cooling tower plays an important role in maintaining vacuum in condenser.

Normal Operation, Start-up and Shutdown
Check List
Pre-requisites: - 
Check the following before starting up the CWP System
Electrical Distribution System is in service and all the related Switchgears and MCC are ready.
All work permits or hold orders for the plant systems are cleared
All equipment is in a safe condition to operate and is ready for operation.
All instrumentation and control system (DCS) are available and lined up.
All annunciations and interlocks are available.
Power supply line up is completed.
All equipment is aligned for remote operation from CCR. (where applicable)
All set points on the DCS are normal.



Emergency Operation and Alarms
Cooling Water Pump Trip
If the cooling water pump trips due to any reason, an alarm is initiated in the DCS (common trouble alarm). With the tripping of one CW pump, standby pump will come into the service. Operator needs to investigate and rectify the cause of malfunction.
If cause for the tripping identified in the short time, operator needs to reset pump status from the DCS & pump will be kept on the standby. However, if the cause has not been identified in short time, operator needs to isolate the pump.

ALARMS
The CWP  System alarms can be monitored from the DCS operator interface console alarm graphic display.
The following system conditions are alarmed through the DCS :-
1. Running Pump Trip
2. Discharge Header Pressure Low .
3. CWP motor Winding Temperature Hi
4.CWP motor Winding Temperature Hi Hi
5.CWP Motor DE Bearing Temperature Hi
6. CWP Motor DE Bearing Temperature Hi-Hi
7. CWP Motor NDE Bearing Temperature Hi
8. CWP Motor NDE Bearing Temperature Hi-Hi
9. CW Pump DE Bearing Temperature Hi
10. CW Pump DE Bearing Temperature Hi-Hi
11. CW Pump NDE Bearing Temperature Hi
12. CW Pump NDE Bearing Temperature Hi-Hi

START PERMISSIVE

1)CWP Sump level not low (not less than < 4.5 MTR)
2)Pump discharge valve closed .
4)Pump and motor bearing temperature is not high.
5)Motor winding temperature is not high.
6)Motor  vibration not high.
7)Emergency stop push button not operated.
8)Reverse rotation not operated.
9)Switch Gear Available.

CW Pump Discharge Valve, (HOPD)
A motor operated butterfly valve is installed on the discharge side of each CW pump.  This discharge valve allows its respective pump to be isolated from the common discharge header during plant operation.  The valve will automatically open on pump start and close on pump shutdown.  It is also interlocked with the pump such that if the valve reaches full closed the pump will trip off.

CW Pump Discharge Piping
Underground pipes Provided direct CW pump discharge flow to the Main Condenser inlet water boxes.
CW Water Box Inlet Isolation Valve,
Each half of the Main Condenser can be isolated from the CW pump discharge header through, motor V/V operated, butterfly valves Near condensor.

START-UP
CW Pump criteria fulfill all Check List with Start Permissive all are found ok than call the operator nearby pump & as requirement kept start .
CWP circulating water pumps.
Both CW pumps are not required during start-up, except in isolated cases. Only one pump may be sufficient during rolling, synchronization and part load operations.
Start of the second CW pump may be around 90 MW, unit Load.


Pump will be tripped / stopped if any of the following conditions occur:
CW  level low low.
Pump suction valve not open.
Pump discharge valve not fully open within a preset time after pump starting.
Bearing temperature (either pump or motor) high high.
Motor winding temperature high high.
Vibration of the bearing of either pump or motor high high.






















Comments

Post a Comment

Popular Posts

HPBP & LPBP

-
Image
HP Bypass Station 1:- HP/LP bypass system can handel 60% of boiler load. 2:- HPBP valve is a combined pressure reducing and desuperheating station valve 3:- Spray water is tapped from BFP discharge  and spray controled by spray control valve. 4:- HPBP dumps the depressurised and desuperheated steam with suitable parameter into CRH line. 5:-Can operate without coordinate with turbine. 6:- Allows quick raising of steam parameters at a level acceptable to turbine for rolling operqtion during start up. 7:-Oil supply unit is installed for operation of HPBP & LPBP valves  8:-Supply oil pressure is maintained at 160 kg/cm2 by the pump and accumulator unit. Modes of HP Bypass Operation 1:- Boiler start-up with TG set at stand still. 2:- Rising of steam parameters to a level acceptable to turbine for rolling. 3:- Turbine start-up and loading while steam flow gets transferred to the turbine 4:- Parallel operation with turbine on load rejection. 5:- Allowing boiler operatio
Read more

APRDS in THERMAL POWER PLANT

-
Image
OBJECTIVE Auxiliary steam is the steam that is required for various auxiliary requirements in a power plant. A part of main steam is tapped off for auxiliary steam station from MS/CRH line, after pressure reducing and de-superheating up to 16 Kg/cm 2   & 320 °C. At the HT header (16 16 Kg/cm 2    & 320⁰C) and then at the LT header (16 Kg/cm2 & 210⁰C) through desuperheater b/w the HT & LT headers. Spray water quantity required for the temperature reduction of the steam is controlled by separate spray water valve (taken from CEP discharge). TYPES OF STATIONS System consists of  two auxiliary  steam pressure reducing and desuperheating stations (APRDS). High capacity PRDS (LTPRDS)  with tapping off steam from main steam line or CRH line . Low Capacity PRDS(LTPRDS)  from HT header. APRDS SERVICES Auxiliary steam system is designed to provide steam for following systems. 1:-  Turbine  &  Turbine auxiliaries . 2:-  Boiler auxiliaries . 3:-
Read more

CONDENSATE EXTRACTION PUMP (CEP) IN A THERMAL POWER PLANT

-
Image
CONDENSATE EXTRACTION PUMP (CEP) Its Importance in Thermal Power Plant It handles water from hot well. The characteristic of that pump is that it handles water from vacuum.  Berceuse the condenser and the hot well are in vacuum bellow atmospheric pressure. No other pump has this characteristic to handle in such condition. It takes water from vacuum pressure and delivered above atmospheric pressure.   It is a vertical turbine type pump which is multi stage. It deliver water from hot well to deaerator. They may be used to pump the condensate produced from latent water vapors in any of the following mixtures: Steam condensed (exhaust from LP turbine) in condenser Make up water (dumped in condenser hot well from condensate storage tank) Flash box water LPDFT water HPDFT water Drip from ejector Drip from LPFWH   CEP for a 200 MW unit:- Each unit has been equipped with three nos. of condensate pumps installed vertically at minus four meter level in to the turbine hall.
Read more