NIPSCO Michigan City Generating Station

Transcription

1 NIPSCO Michigan City Generating Station

2 Michigan City Generating Station Located in Michigan City, IN (50 Miles SE of Chicago) Owned by NIPSCO a division of Nisource Inc. Number of employees 90 Capacity ~500 MWg. In service 1974 G.E. Dense Pack Steam Turbine G2 (2008) Steam Generator B&W (UP76) Cyclone fired (10) Originally Oi i designed dfor Bituminous. i Converted tdto PRB 1994 Blend coal 85% PRB, 15% Bailey NOx control: OFA & SCR installed 2003 SO2 control (Proposed FGD 2018)

3 There were NO Injuries with this incident This presentation is in part to give back to the PRB group that has served as a valuable resource PRB Users Group To establish best practices for the SAFE operation and maintenance of PRB coal handling and storage systems based on best available technologies

4 COMBUSTIBLE DUST Despite the very high temperatures developed within a fire, it is not an explosion. Two other conditions must be satisfied in order to ascend to an explosion status. These are: dust dispersed in the necessary cloud concentration and a confinement of the dust cloud within an area. The explosion pentagon provides a representation of these conditions. Heat from bend roller/shaft Counter weight/belt Take up tower enclosure Housekeeping/Scaffolding EXPLOSIONS CAUSES AND EFFECTS Oxygen The three constituents for fire still remain: oxygen, fuel and ignition as depicted on the fire triangle. By having the fuel available as a dust cloud and having the dust cloud contained within a vessel or room, all of the conditions required for an explosion are present.

5 Timeline of events On January 8, 2009 the coal handling department was in the process of dumping 57 coal cars to the coal bunkers, storing out to the storage pile, and blending in a medium-sulfur coal. 8:30 AM - The C-8 belt was briefly shut down while two coal handlers cleaned the coal out of the table and rollers at the bottom. 10:30 AM - C/H Rover was at the tripper floor (top of C-8) noted fire doors closed on C-8 and upon opening them and looking down he noted nothing out of the ordinary (see, smell or hear) 11:30 AM - Coal handlers finished cleaning coal spill at bottom of C-8, nothing noted out of the ordinary 1:30 PM - C/H Supervisor toured the bottom of C-8 to inspect clean up. Nothing noted out of the ordinary 4:30 PM - Bunkers full, C-8 Shut Down. Coal continued to the store out system 4:40 PM - All conveyors were emptied and shut down 4:45 5:24 PM - several employees left & reported for work many parking by the C-8 take up tower, nothing noted out of the ordinary

6 Timeline of events continued 5:25 PM - Numerous employees felt and heard an explosion. Safety Supervisor heard two explosions in rapid succession, saw a bright flash, and felt radiant heat from his office windows The siding on the north side of the C-8 conveyor take-up enclosure had opened. Fire was burning in the C-8 take-up enclosure and began moving rapidly up the conveyor towards the plant

7 5:27 PM The fire department log indicates call received

8 5:32 PM Station Operator noted that there was fire in the entire C-8 conveyor all the way up to the plant. (Fire Protection not activated yet)

9 South take up bend roller/shaft shifted into the conveyor table frame Misalignment switch?

10 It is believed that a cloud of dust provided the fuel for the explosion. The dust cloud was created by either the impact of the tensioning weight hitting the floor or by the belt s violent movement at separation. The dust filled the take-up enclosure and exploded when it reached its ignition source

11 Timeline of events continued 5:30 PM The fire department log indicates fire trucks arriving i at the plant Station employees assist fire department to locate fire hydrants A short delay (~15 minutes) was experienced when the Fire Department those adapter did not arrive on the first truck Operators shut off the dust collectors

12 Timeline of events continued Efforts to keep fire from entering the plant C-9 deluge valve (tripper floor) tripped, supplying water to the fire protection sprinkler heads. Other station employees began to stage fire fighting equipment and hoses in advance for the fire department efforts The bunker area was non-accessible without SCBA s (Limited Visibility) 5:35 PM C-8 fire protection system activated

13 5:45 PM Fire sprinkler header had pulled apart about 100 feet north of the take-up enclosure.

14 5:50 PM Fire department starting applying water to the conveyor fire

15 Fire Break Area (section of conveyor open, no siding)

16 Timeline of events continued 5:50 PM Operations Supervisor reported he heard a quenching sound near the top of C-8 and the fire started to die down. Firemen fought the fire from the top of C-8 and at the take-up enclosure on the ground until it was extinguished 6:17 PM The fire department reported the fire was under control. 7:57 PM The fire department reported fire out. ~10:00 PM Contractor reported seeing flames on the tripper floor dust collector. The fire protection system was set off manually by the Operations Supervisor 11:00 PM- Tripper floor dust collector fire reported to be out by the Michigan City Fire Department.

17 SEVERE STRUCTUAL DAMAGE

18 SEVERE STRUCTUAL DAMAGE

19 All components stripped out prior to lifts Weather (high winds) big factor with lifts (several delays) Severe structural damage (fire) and 35 years of corrosion

20 Scaffolding installed to support sections 3 & 4

21 New conveyor sections were fabricated off site & shipped with all internal components installed

22 Fire Exits added

23 Washdown control panel (16 zones)

24 Fire detection and suppression washdown system CO Monitoring (bunkers were g( existing). Added CO on conveyor

25 Washdown Nozzles spray entire conveyor structure

26 Drains for Washdown (inside)

27 Modifications on side walls to prevent hideout places

28 Drain collection from floor inside

29 Wash down drains final collection Upper sections, belt water collection, and lower sections

30 RECOMMENDATIONS (Actions Taken) Housekeeping Next day cleaning schedule developed from Rover and Supervisor round sheet Installed an efficient and effective wash down system on C-8 conveyor Helper classification added (cleaning with equipment off) Several conveyor systems have been repaired/upgraded Conveyor Systems (belt conditions & tracking) high priority Electrical trip devices (misalignment & trip cords) verified to be operating properly Operating Procedures revised Rover round sheet and duties revised Post walk-downs by coal handling gp personnel at end of the shift (equipment off) Reinstated walk-down of conveyor systems between 7:00 & 9:00 PM each day by security Combustible Dust Assessment entire coal NIPSCO (final reports issued March 2010). Employee training on combustible dust. Fire protection systems Local Fire department tours and equipment gang boxes tripper floor CO Monitoring

31 THANK YOU QUESTIONS