Ammonia Purge Near Miss. Jason Clarke, Gulf Power Co.

Transcription

1 Ammonia Purge Near Miss Jason Clarke, Gulf Power Co.

2 Four generating units 2-82 MW MW MW Plant Crist Overview All four units run through a common scrubber The two large units utilize SCR technology and have anhydrous ammonia injection systems

3 11/5/2014 Incident Overview SCR System Owner put in a Clearance request to replace multiple pressure relief valves on the ammonia system according to maintenance strategy schedule.

4 11/10/2014 Incident Overview Plant Operations discovered a small ammonia leak during the nightshift. Operations barricaded the area from a safe distance and placed a clearance on the system thereby isolating ammonia.

5 11/11/2014 (Dayshift) Incident Overview With the ammonia system out of service and no pressure on the system, the location of the small leak could not be determined. The various pressure relief valve replacement job was completed as planned. As the system was returned to service, no leak was detected.

6 11/11/2014 (Nightshift) Incident Overview The same crew working the previous night noticed that the leak reappeared.

7 Subsequently, the following events occurred that same night: Incident Overview The operations team leader contacted the team leader on call, which informed him to contact the manager on call. The manager on call was notified and instructed the operations team leader to contact the emergency response contractor to make the necessary repairs.

8 2130 hours Incident Overview The contractor arrived on plant site and made contact with the operations team leader and proceeded to the leak site. It was determined that the leak was coming from a hose that was located on the grating. This hose was attached to a fitting that was used to purge ammonia from the system prior to performing needed work.

9 Incident Overview The perceived lack of necessary parts did not allow the contractor to make the immediate repairs. However, the contractor did temporarily mitigate the situation by placing the hose in a drum of water.

10 Incident Overview Drum of water Valve Hose

11 2300 hours Contractor left the plant site. Leak was determined to be mitigated and system left in service hours Incident Overview Plant operations visually determined that the ammonia leak had reappeared Calls placed to plant environmental group

12 Incident Overview The information conveyed from environmental compliance was that the ammonia system could be isolated and left out of service until the morning for protection of personnel. Lastly, it was suggested to contact the system owner to inform him of the current situation.

13 2345 hours Incident Overview Operations team leader made contact with the system owner. The system owner informed the team leader that the parts necessary for repair were on plant site.

14 Incident Overview The system owner also confirmed that a C&R technician, which was working on plant site that night, was capable of making the repairs.

15 0120 hours Incident Overview C&R employee approached the area of the leak and found that the hose was no longer vented into the drum of water. Instead, it had come out of the water and was located on the top of the drum.

16 Incident Overview Drum of water Valve Hose

17 0130 Incident Overview The C&R employee placed the hose back into the drum of water, unaware that a small amount of liquid ammonia was in the hose. Consequently, the mixture of ammonia and water reacted causing a plume of vapor.

18 Incident Overview Latent Conditions Bleed off hose was never removed from equipment from prior outage. Hose discharge elevation allowed accumulation of liquid NH3. Recognition for potential of liquid ammonia accumulation in the hose. Lack of awareness to level of reaction.

19 Latent Conditions Specialized contractor successfully performed same task earlier in the night. Specialized contractor successfully performed same task with only respirator as task specific PPE. Time of event event occurred on night shift. Infrequent task Incident Overview

20 Repair expectations Latent Conditions Criticality not identified: Identification and repair of leak on Tuesday day shift Condition report not generated upon discovery of the initial ammonia leak. Limited visibility Incident Overview

21 Incident Overview Latent Conditions T.L. had multiple concerns (Distractive Environment ) Inaccurate Risk Versus Reward Assessment Hose did not appear secured to barrel of water by contractor. Operations team leader was not aware of onsite material.

22 Root Causes Hose used for purging ammonia left in place from previous outage Ammonia valve leaking by Incident Overview Chain of command protocol/experience

23 Incident Overview Corrective Actions Purge checklist procedure for ammonia system and miscellaneous ammonia purging. Inspect and repair leaking valve Perform broadness review of other similar valves in the system

24 Incident Overview Corrective Actions Technical evaluation for upgraded purging equipment/system Supervisors and managers, in discussion of this RCA with their employees, are to emphasize the importance of full circle communication (chain of command and subject matter experts). Technical Evaluation: Event Notification to Generation Fleet for review

25 Incident Overview Purge flange Valve

26 Incident Overview Questions?