Ash Water System

INTRODUCTION: -

The ash water system is used to cater water for various utilities in ash handling system. The water is supplied from the ash water tank through the pumps like BALP pumps / BAHP pumps / FW pump / sump jetting water pumps which are located at Ash Water Pump House and are started & stopped from ASPH control room. Ash water tank makeup make is taken from different sources like Raw water makeup from stage 1 & 2 inter connection, Raw water makeup from stage-2, Ash water recirculation, Treated ash water recirculation, Service water blow down and CHP according to the situation and requirement.

Low pressure ash water system caters water at the following areas (BALP pumps):

• Ash slurry sump makeup.
• Ring header for seal trough makeup / flushing.
• Refractory cooling supply.
• Bottom ash hopper makeup / filling.
• Bottom ash hopper window spray.
• Make up to overflow settling bin.

High pressure water pump caters water at the following areas (BAHP pumps):

• Jet pump fitted below the clinker crusher at the bottom ash hopper.
• Jetting water requirement for bottom ash hopper.
• HP line water supply to feeder ejector and slurry box of economizer and economizer bypass system.
• HP line to economizer ash transfer hopper for jetting purposes.
• HP line to jet pump fitted below the economizer ash transfer hopper.
• HP line bypass connection to bottom ash hopper refractory cooling water and ring header for seal trough make up / flushing water line.
• Flushing connections to bottom ash hopper overflow weir boxes.
• Line for flushing sludge pump discharge lines.

Flushing water pump:

• The flushing water pumps are provided for slurry disposal line flushing purpose.

Sump jetting water pumps caters at the following areas:

• Ash slurry sump jetting.
• Common ash slurry trough jetting arrangement. 

PROCEDURES :
 LINE UP PROCEDURE FOR ASH WATER SYSTEM
PRECONDITIONS

• The AWT level is normal.
• Check no PTW is pending on the equipment and system as well as the associated system like BA HOPPER etc.
• Ensure the CW pumps are running and the blow down valves are open from both the units from CW pump discharge header.
• Check the make up water valve to AWT from CW blow down near AWT is closed.
• Ensure the AWR pumps are in service and water is available to AWT. The makeup valve is motor operated and power supply available.
• Ensure the RAW water makeup valve to AWT is available and on auto at ASPH control room and power supply available.
• Ensure the supply normalization of all AW PUMPS at AWMCC END and check both Sections are normalized individually.
• Before starting the system the SCE is to be informed and the open channel level to be checked.

LINE UP PROCEDURE FOR STARTING ANY PUMP

• Before starting any pump ensure the down stream line is lined up i.e near the BA Hopper or ASPH.
• Check the respective pump suction valve is opened and the pump is vented properly.
• Keep the discharge valve crack open before starting otherwise it will be difficult to open the valve after pump starts.
• Ensure that the DV is not opened fully otherwise the pump will draw high starting current for a longer period and may trip on overload. It is quite detrimental for the motor life.
• Check the EPB is released.
• Now the pump is ready to take start.

AFTER THE PUMP STARTS

• Slowly open the DV till it opens full.
• Check the pump current in ASPH control room that it is with in limits. Other wise check for any other valve opening/closing
• If the pump is not vented properly then it may draw low current. If the other pump discharge valve is open and NRV is not holding then also it may draw high current.
• Check the discharge pressure.
• Check the other pump DV is closed and pump is not rotating in reverse direction.
• Check for any gland leakage/pump or motor abnormal vibration/bearing temperatures. If any immediately inform the ASPH control room/UCB.

ROUTINE CHECKS

• Check running pump has no gland leakage.
• All stand by pump EPBs are released.
• All stand by pump discharge valves are open.

ISOLATION PROCEDURE

• Close pump suction valve
• Close pump discharge valve
• Isolate the power supply.
• Press EPB locally
• Open the pump vent