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Observation Report

Stage-II - Dry fly ash evacuation system of NTPC Vinhyachal:

Date of Visit : 16/17/19 MAY 2003 Plant Status :500 MW Unit 7 !unnin" # Unit $ % S/D

Main Control Desk Room:

1. The ash evacuation Cycle is continuously operated in auto mode.

2. The control desk ESP hopper number has dual display i.e., display in GEE!

"hen the hopper is not in service and chan#es to E$ as soon as correspondin#

hopper%s &'( opens as per lo#ic.

). *P' hoppers are also are included in the +C pass evacuation system.

-. /CE table 0or hoppers is available on screen 0or each pass 0or repeated

operation o0 the &'( 0or checkin# and clearin# the hopper.. &ech. Ehauster 3 vacuum pump4 load current variations are smooth 3 as per

line vacuum4 and does not cross 0ull load current durin# evacuation process.

5. 6ine vacuum and dry system runnin# hours are available on screen.

7. * pur#e option 0or the dry system is available on screen 0or all passes 0or

checkin# cleanin# dry system e8uipments durin# "et operation mode.

9. Trend history#raph o0 line vacuum versus time is available 0or all passes 0or

the past 2- hours "ith user adustable ; and < scales.

=. 6ockable EP+ 0or the dry system is incorporated 0or ensurin# sa0ety o0 the

"orkin# personnel . This "ill ensure no accidental P6C command can etend tosystem under permit. 3in addition to isolation o0 instrument air and display o0

dan#er ta#s4. The status o0 this EP+ is displayed on screen 0or all passes.

1>.* check list is maintained 0or &'( local operatin# status and leaka#es 3 0ull

closin# openin# durin# evacuation4 in all shi0ts .

11.The PCSC upperlo"er dump #ates are operated in C/SS type and both the

*6T upperlo"er dump #ates operated simultaneously one pair at a time.

12.Timin# o0 any dump #ate is sec open 3e8ualisin# 4 and sec open 3main 4.

1).!o "indo"s ?Start@ menu option available on any computer screen.

/nly S vie" mimicsschemes are accessible 0or operation.1-.* dot matri printer is provided 0or recordin# all alarms o0 the system.

1.Provision is made 0or runnin# both units in dry mode simultaneously throu#h

one set o0 *6Ts o0 each unit 0eedin# to t"o di00erent silos. 3 reducin# silo

pressurisation problem4.

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ESP/ Buffer Hopper Area:

1. *ll the ESP hopper ash conveyin# lines are havin# a 0ied bolted metal #asket

"ith a hole o0 1> mm dia. and all &'( air inlet check valves are maintained

clean to ensure re8uisite air 0lo" 0or ash evacuation 0rom the hopper.2. !o "histlin# sound durin# evacuation.

). The vacuum pump ehaust is havin# silencer . The air and seal "ater are

dischar#ed separately. * canopy is provided 0or (P and motor.

-. The vacuum pump suction line 0lushin# arran#ement is available. 3 +oth (PA(s

closed and 0lan#e at the suction header is opened 0or 0lushin#4

. The (PA((A(+'(A( are havin# po"er cylinder operated actuators.

5. The Bet system B'B( header is provided "ith a ventin# arran#ement.

7. Bater ettin# 0or collector tank dischar#e is taken be0ore B'B( inlet header .

9. There are >- A*Cs 3t"o per nit "ith interconnection4 and provision is made0rom t"o A*Cs 0or 0eedin# to Silo area air re8uirement. Presently >) !o.s

A*Cs are in service 0or nit 7 3nit 9 is under Shut do"n 0or GT problem4 and

>1 !o. A*C 0or Silo area. *ll the A* supply interconnectin# pipin# siDe is

around 59> !b.

=. +'*6T e8ualisin# line bends are shrouded and the *6T and )"ay e8v.valve

is connected "ith a strai#ht pipe. 3"ithout any bend4

1>. +oth *6T 0luidisin# air is supplied 3 throu#h a rin# header 0or each *6T 4 via a

sin#le solenoid valve "ith bypass provision. rom this rin# header the direct

pipin# is done 0or each 0luidisin# pad. !o 0leible hose pipes used.

11.The +'*+ suction 0ilter is vertically mounted directly on top o0 the blo"er.12.The +'*+ relie0 valve is set "ith "ts and the heater is havin# both inout

isolatin# valves.

1).The +' is havin# 5 3side4 and 1 bottom 0luidisin# hot air pads and hot

0luidisin# air supplied throu#h a insulated rin# header.

1-.+a# 0ilter pulse ettin# timin#s : > ms /! and 21 sec./.

1.The pulse ettin# mani0old is provided "ith a local pressure #au#e.

15.The line vacuum T and the impulse line is kept insulated as variations "ere

observed as per ambient temperature.

17.There are >) !o.s T*Cs 3 *tlas Copco , about 1>>>> m)hr , 2.> ksc4 and /neT*C per line is run 0or transportation . The third T*C is standby.

19.The T*C driers are not taken into service. T* line drains are provided at

di00erent points.

1=.The T* line pressure transmitter is provided bet"een T* isolatin# valve and

line ori0ice. 3Separate 0or each nit 7 and 9 4.

2>.The T* line ori0ices are o0 siDe 12> mm.

21.*n additional tappin# 0rom each T* main line 3 be0ore ori0ice4 is connected

0or the *6T e8ualisin# valve T* supply header end point to boost up the T*

pressure 0or the last pass *6Ts "ith isolatin# valves.

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22.&ost o0 the ash pipe conveyin# pipe lines are routed "ith 3in up direction4 - >

bend .The => >vertical portions are limited.

2).*ll the FG( po"er cylinders are havin# canopies.

2-.*ll e8uipments are painted.

2.The dry and "et system to"ers are separate.

Silo Area:

1. There are >) !o.s Silos o0 >> &T capacity.

2. The Silo area is havin# a concreted approach road.

). The entire silo area and vehicle movementparkin# area is concreted.

-. The inlet portion is havin# lar#e pokin# hole.

. !o manual #ate above inlet pneumatically operated #ate.5. An Silo 2 the &CG is replaced "ith a FG( valve.

7. The Silo area A* pressure is maintained 57 ksc. The A* pressure #au#es are

mounted at each silo ba# 0ilter pulse ettin# air mani0old.

+a# 0ilter pulse ettin# timin# : /! time : 12> msec. H / time : 21 sec.

9. * pressure #au#e 3 >->> mm"cl4 is mounted at ba# 0ilter housin# 0or

checkin# silo pressurisation durin# operation.

=. * #rill "ire mesh is 0ied at vent 0an dischar#e.

1>. Silo (ent 0an suction 0rom top o0 the ba# 0ilter is throu#h a pipe and

rectan#ular duct portion is limited at top only.

11. The Silo drain pump motor ratin# is 2 kB . The pit is havin# make up andettin# arran#ement.

12. *dditional >- "ater pumps are provided 0or "ater curtain and spray system.

The re8uired "ater is tapped 0rom ash "ater return system.

1). /ne o0 the S*+ suction pipin# is modi0ied to prevent ash deposition.

1-. Truck loadin# is done 0rom local "ith local Push button controls.

1. Truck loadin# is restricted to 7>9> I only to prevent ash spilla#e.

15. * open shed is provided 0or restin#"aitin# 0or the truck drivers.

SF +E* +( FAS'!*S & AS'% MM( SS&)(/*o++sn"

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