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Valero (26003), Norco

Causal Factor: Power Failure

LDEQ Accident Number
Accident Date
Point Source(s) Notes Amount of Release

Flare No. 1, Flare No. 2
Cause: Power outage due to instrumentation control processors in MSCCU and Alky units. As a result, these units were upset and relieved to the Flares. Power was restored and units brought back on line.

Followup: No

Notes: Once power was restored, Valero operations moved quickly to return to stable operating conditions. Limits for Sulfur Dioxide were exceeded, but no information on quantity was given.


Thermal Oxidizer #2, Flare No 1, Flare No, 2
Cause: Lost primary and alternate power to instrumentation control processers for East Plant. Control valves and other I/O failed to their last recorded position during the power outage. When power was restored, control valves and other I/O returned to their pre-programmed settings causing some process upsets and equipment shutdowns.

Followup: No

Notes: Power restored and controllers returned to stable conditions.


6d 14hr 24m
Coker No. 2 Steam Vent
Flares 1,2,3,4&5
Flares 1,2,3,4&5; 30, 1600, & 3700 TOX; FCCU; GDU; Boilers B-401C, B-401D, & 401-E
Flares 1,2,3,4&5; Coker no. 2 Steam Vent
Flares 1,2,3,4&5; Coker No. 2 Steam Vent; Boilers B-401C, B-401D, & 401-E
Flares 1,2,3,4&5; FCCU; GDU; Boiler B-401C, B-401D, & 401-E
Flares 1,2,3,4&5; FCCU; GDU; Boilers B-401C & B-401D
Flares 1,2,4&5; 30, 1600, & 3700 TOX; Coker No. 2 Steam Vent
Flares 1,2,4&5; Coker no. 2 Steam Vent
Cause: On August 9, 2013, at approximately 22:51 hrs, Valero experienced an interruption in power supply caused by a surge arrestor electrical fault. The interruption caused the shutdown of multiple process units and resulted in excess emissions from the boilers, Sulfur Recovery Units (SRUs), Fluid Catalytic Cracking Unit (FCCU), Gasoline Desulfurization Unit (GD), Coker Unit, and refinery flares. During recovery process of the power loss event, shutdowns occurred to both the Hydrocracker unit (HCU) and Ultra-low sulfur diesel unit (ULSD) resulting in flaring. Both unit shutdowns were related to the shutdown of their recycle gas compressors. The HCU's recycle gas compressor malfunctioned due to a low steam pressure which was directed related to the power loss event. The ULSD shutdown due to a malfunction of the recycle gas compressor's primary lube oil pump, and a delayed response for the startup of the secondary lube oil pump. We are unable to determine if the shutdown of the ULSD was directed related to the power loss event. However, the emission contributed to the HCU and ULSD shutdowns are considered as part of the same power loss event and are included herein.

Followup: Yes

Notes: The power loss caused the Crude Unit and Vacuum Unit to shut down immediately, thus preventing the manufacture of intermediates that feed subsequent process units. Downstream units were placed in circulation mode through manually closing valves, lowering reactor temperature and restarting tripped equipment such as compressors and pumps. Steam production was also increased as available to allow units to continue in circulation mode until power was restored. The HCU and ULSD units were re-started to reduce excess emissions. In addition, the flare gas recovery unit remain in operation during the entire incident to reduce the amount of flared gas. To prevent recurrence, the following procedures will be adopted: 1) Perform thermal scans of the surge arrestors in the Prospect and Good Hope Substation yards. 2) Perform routine thermal scans of the surge arrestors in the Prospect and Good Hope Substation yards. 3) Complete the evaluation of all existing Valero owned surge arrestors in the Prospect and Good Hope Substation yards to determine if they are of the same age and model of the T3 arrestors that have shown signs of degradation. To data, the surge arrestors on T4 transformers have been identified as being of the same vintage and design as the failed arrestors and will be the first targeted for replacement as will all arrestors of this design. 4) Evaluate one of the non-failed surge arrestors removed from service to determine if any degradation has started to occur. 5) Develop a plan to routinely replace all surge arrestors in 230KV service at 10 year intervals. 6) Review this incident and emergency procedures with affect personnel. 7) Evaluate raising the autostart pressure setting on the auxiliary lube oil pump. 8) Evaluate increasing the trip time delay on the low-low lube oil shutdown. 9) Consider installing a valve on the make-up hydrogen at the ULSD unit battery limits to prevent fresh hydrogen from being introduced to the unit during a period of malfunction. 10) Add to existing Emergency Operation Procedure to account for Diamond Green Diesel, which is connected to the ULSD. 11) Contact corporate hydrocracking specialists to determine if the logic should be modified to initiate high rate depressurization upon loss of recycle gas compressor. Reportable quantities were exceeded for H2S, SO2, NOx, and VOCs.
Nitrogen Dioxide: 8,065.0 pounds
Carbon Monoxide: 18,171.0 pounds
Particulate Matter: 336.0 pounds
Sulfur Dioxide: 71,472.0 pounds
Hydrogen Sulfide: 652.0 pounds
Volatile Organic Compounds (VOCs): 3,764.0 pounds
1,3-Butadiene: 12.0 pounds
Benzene: 26.0 pounds
Ethylbenzene: 0.4 pounds
Formaldehyde: 1.0 pounds
Naphthalene: 2.0 pounds
Hexane: 263.0 pounds
Cresol: 0.2 pounds
Polycyclic Aromatic Hydrocarbons: 1.0 pounds
Toluene: 15.0 pounds
Xylene: 9.0 pounds
Phenol: 0.1 pounds
Phenylamine: 0.1 pounds

Flares 1, 2, 3, and 4
Cause: On February 19, 2013, at approximately 04:10, the Diesel Hydrotreating (DHT) Recycle Gas Compressor (K-15-53) malfunctioned resulting in a unit shutdown and a release to the flare of 828 pounds of sulfur dioxide. The GE Multilin relay indicated a short due to apparent moisture intrusion that caused arcing which damaged the insulators and cables. Heavy rain was in the area at the time of the incident.

Followup: Yes

Notes: Safely shutdown the DHT. No pollutants were recouped. Emissions were minimized by restarting the recycle gas compressor. The cables were repaired and the insulators were replaced. A cover for the capacitor cabinet was fabricated to cover the holes due to rust which allowed water inside to prevent any further damage from inclement weather. To prevent recurrence, the following procedures have or will be adopted: 1) Communicate this incident to all affected personnel. 2) Replace the existing cabinet on the next turn-around. 3) Modify the existing roof/cover to provide better protection from inclement weather. (A temporary repair was already completed.) 4) Survey similar cabinets for damage and make required repairs and/or replacements. 5) Establish preventative maintenance program for similar cabinets plant-wide. 6) Determine the necessity of the capacitors for K-15-53 and either replace or remove them. 7) Improve effectiveness of and/or training on the maintenance work process to ensure that repair findings/discovery scope during the course of work that is not addressed at the time is captured in a work order. 8) Draft an emergency operating procedure to address the loss of the recycle compressor. SO2 reportable quantities were exceeded. A report was issued on 4/19/2013 stating that Valero was "unable to complete the investigation within 60-days of the above referenced incident".
Sulfur Dioxide: 828.3 pounds
Carbon Monoxide: 1,450.7 pounds
NOx: 266.6 pounds
Particulate Matter: 11.0 pounds
Volatile Organic Compounds (VOCs): 548.9 pounds
Hydrogen Sulfide: 4.1 pounds

3h 6m
Cause: On August 15, 2014, electrical feed from a power substation tripped offline, causing multiple units to shutdown. An investigation of the incident found the cause to be the failure of a sudden pressure relay on transformer T-3 at the PS-2 substation. This provided a false trip input into the transformer differential relay. The relay logic reacted to the input by isolating the transformer, thus de-energizing power to Buss 3, which shut down several pieces of equipment. Maximum hourly permitted emissions rates for sulfur dioxide, hydrogen sulfide and volatile organic compounds from Flare 1 were exceeded. Neither report includes emissions totals for hydrogen sulfide.

Followup: Yes

Notes: At the time of the accident, Valero energized an alternate source of power to supply the equipment. The Diesel Hydrotreater (DHT), Naptha Hydrotreater (NHT), and Continuous Catalytic Reformer (CCR) Units tripped off-line. Valero left them down until reliable power was restored. The FCCU and Crude Units reduced rates to minimize emissions. Flare gas recovery remained in operation to recover some of the gases sent to the flare header. A Root Cause Analysis identified several corrective actions to be taken by Valero, including: 1) Communicate the incident to affected personnel (Estimated completion date: 10/31/14), 2) Work with Electrical Safety and Reliability network (ESARN) to develop a recommendation for routine testing/inspection of sudden pressure relays on transformers(Estimated completion date: 12/31/14), 3) Develop a list of refinery substations that would benefit from MAIN-TIE-MAIN auto transfer scheme and prioritize implementation (Estimated completion date: 12/31/14), 4) Review the power source for refinery analyzers and develop a prioritized list of analyzers that would benefit from moving from a Purchased Power source to a UPS source (Estimated completion date: 12/31/14), 5) Develop a written guideline for restorations of power for the refinery following power loss scenarios at Prospect and Good Hope Substations (estimated completion date: 12/31/14).
Sulfur Dioxide: 6,400.0 pounds


Flare 1
Flares 1, 2, 3
Cause: The fluid cat cracking unit (FCCU) wet gas compressor shut down due to a loss of power that resulted from a transformer short circuit and a circuit breaker malfunction. As a result, flaring occurred from permitted flares 1, 2 and 3. Workers reduced total feed and reactor temperature in the FCCU to minimize flaring until compressors could be restarted. Transformer failed in the EP-03A substation. A relay setting associated with this system was not set properly and allowed the fault current to reach the Good Hope Substation. The fault was cleared by the breaker at the Good Hope Substation. As a result, several other transformers also tripped and upset the FCCU. This accident exceeded maximum hourly permitted emissions for sulfur dioxide, hydrogen sulfide, hexane, and Volatile Organic Compounds at Flare 1 for one hour. Maximum hourly permitted emissions were also exceeded for NOx and carbon monoxide at Flare 2 for one hour. Maximum hourly permitted emissions for sulfur dioxide and Volatile Organic Compounds at Flare 2 for 5 hours. Reportable quantities for sulfur dioxide and propylene were exceeded.

Followup: Yes

Notes: At the time of the accident, emissions were minimized by reducing the overall rate to the unit and reactor temperature. Operators responded by adjusting the power distribution system in order to reestablish the poewr source and restart the compressors. Throughout the event, the Flare Gas Recovery Unit remained in operation to reduce the amount of flared gas. Process changes have been implemented as corrective actions. These include: - updated relay settings - refinery arch flash study and relay setting review - even distribution of four P82-808 pumps across the electrical feed buses - modify MOC checklist to include relay settings and coordination curves - modify PSSR checklist to include relay settings and coordination curves - require all new or changed relay setting requested through CSE with relay setting/coordination curve request form - communicate incident to affected personnel - communicate incident and path forward to CSE electrical engineers, MP electrical engineers and maintenance electrical supervision
Carbon Monoxide: 510.8 pounds
NOx: 93.9 pounds
Particulate Matter: 3.3 pounds
Volatile Organic Compounds (VOCs): 1,229.9 pounds
Hexane: 11.9 pounds
Sulfur Dioxide: 1,645.2 
Hydrogen Sulfide: 8.8 pounds