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Valero (1238), Meraux

Causal Factor: Equipment Design

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

API Seperator
Cause: On October 9, 2012, Valero experienced excess emissions of hydrocarbon vapor at the API Separator. Approximately 7 AM that morning, Valero personnel coming into work noticed an unusual odor that was traced to periodic openings of the pressure relief valves on the covered bays of the API Separator. After discovering the release of light hydrocarbon vapors to the atmosphere, Valero applied water sprayed on the area and began to search the refinery for the source of light hydrocarbons. Valero determined the source to be the water draw line off the ROSE Water Knock-Out Drum. The normal path for this water draw line is from the Water Knock-Out Drum to the Oily Water Stripper then to the API Separator. During this event the Oily Water Stripper was shutdown and bypassed so the Water Knock-Out Drum was sent directly to the API Separator. The ROSE unit was in the process of being inventoried with pentane prior to unit start-up. Valero believes that the water level went low in the Water Knock-Out Drum, possibly due to a faulty level indication, and a water/pentane mixture was pumped directly to the API Separator. The pentane then vaporized in the bays of the API and lifted the relief valves. Valero has determined the root causes of this incident to be: 1. Inadequate Procedure: The ROSE start up procedure lacked any steps verifying that the OWS is operating prior to ROSE start up; 2. Poor Equipment Design: The Water Knock-Out Drum level control bridle is susceptible to plugging due to dirty water in the drum. Valero has also determined the following to be contributing factors to this incident: 1. It is difficult to detect hydrocarbons leaving the ROSE unit in the water sent to the OWS. The pentane content of the water stream was not recognized by operations and there is no detector or alarm to notify operations. 2. The API Separator pressure indication was not working properly and provided no warning. 3. The OWS was offline due to lack of feed. The OWS does not have a standby operating mode for low, intermittent flows.

Followup: Yes

Notes: Valero submitted a verbal report on October 9, 2012 and a written report on October 16, 2012, with a follow up report on December 10, 2012, and a final follow up February 6, 2013. The duration of the event lasted 8.25 hours.
Pentane: 32,654.0 pounds


North Flare
Cause: Incident occurred following Hurricane Isaac at the North Flare during start up of the Hydrocracker unit. Valero has determined the cause to be the system design of the Hydrocracker/Hydrotreater Unit. Under normal operations, gases produced in the Hydrocracking/Hydrotreating Reactors, including H2S, are completely stripped out by steam in the Ore-Fractionator Stripper and sent to amine contractors for treatment; they do not pass into the Fractionator and on to the Fractionator Overheard Receiver. Consequently, the Fractionator Overhead Receiver was not designed with gas handling capabilities. Manual venting to the flare is the only available method of controlling an increase in pressure caused by gas carryover from the Pre-Fractionator Stripper. The design deficiency becomes apparent during unit start up because gases are produced prior to the ability to introduce stripping steam to the Pre-Fractionator Stripper. Stripping steam cannot be introduced until the unit is at the proper operating temperature. Operational experience has shown that even once stripping steam can be introduced, its use is limited at the low charge rates during a start up because excess steam causes erratic flows in the heater passes and delays the completion of the start up. A contributing factor in this event was that De-Asphalted Oil (DAO), a higher sulfur content feed, was introduced to the Hydrotreater prior to reaching adequate stripping steam rates in the Pre-Fractionator Stripper.

Followup: Yes

Notes: Valero will engineer and install a "start-up vent" that will direct the gases vented from the Fractionator Overhead Receiver to be collected by the refinery's HiJet, treated for H2S removal, and used in the refinery fuel gas system. Valero will also revise the Hydrocracker/Hydrotreater startup procedure to delay the introduction of DAO into the Hydrotreater feed until adequate stripping steam rates have been established. According to the LDEQ's list of reportable quantities, the reportable quantity for sulfur dioxide is 500 pounds.
Hydrogen Sulfide: 1.0 pounds
Sulfur Dioxide: 1,102.0 pounds

North Flare, South Flare, and #2 SRU Incinerator Stack
Cause: Valero experienced excess emissions of SO2 and H2S at the North Flare, South Flare, and #2 Sulfur Recovery Unit (SRU) Incinerator Stack due to a sudden electrical transformer failure that cut power to several process areas within the refinery. Valero determined the root cause to be an electrical failure caused by water intrusion into the air terminal chamber on the 13.8 KV side of the transformer and inadequate insulation on the bus bar and connections. It appears that when the transformer was installed the 13.8KV incoming cables were too short to reach the transformer bushing so a field designed buss work and air terminal chamber was used. This locally designed air terminal chamber proved inadequate to protect the transformer breaker were improperly set and allow too much current to flow to the fault which caused voltage to sag across the reinfery and unnecessary tripped loads that upset other units.

Followup: Yes

Notes: The refinery initiated shutdown procedures for all affected units and followed the MACT UUU SSM Plan to recover the #2 Sulfur Recovery Unit (SRU) and #2 Tail Gas Treater (TGT). The #2 TGT was bypassed during the upset and subsequent startup. All refinery transformers were visually inspected for signs of water intrusion. Water was found in one other transformer of the same design which was removed and the air terminal box was sealed. The damaged transformer was replaced and a new overhead cable was used to replace the underground cable that was too short. Relay trip settings were changed to better coordinate and protect equipment and prevent unnecessarily upsetting other units. Valero has initiated a project to design and install appropriate terminal boxes in place of the locally designed ores for the three remaining transformers of the same design on site. According to the LDEQ's list of reportable quantities, the reportable quantity for SO2 is 500 pounds.
Sulfur Dioxide: 1,839.0 pounds
Hydrogen Sulfide: 19.0 pounds

Crude unit heat exchanger
Cause: At approximately 14:09 on 10/25/13, Valero experienced an unexpected release of crude oil when a stopple failed on a Crude Unit heat exchanger while a third party specialty contractor was working to install a bypass. A stopple is a device that isolates equipment for maintenance when a block valve is unavailable. The pressurized crude oil was released in an upward direction for approximately 15 minutes. Although most of the crude oil released remained on site, some of the resulting spray traveled offsite with the wind and was deposited on nearby East St. Bernard Highway and vehicles traveling on the highway. This spray continued in a southwesterly direction and left small spots of crude oil over the exposed sides of Valero buildings and vehicles in the nearby parking lot. Valero's dock facility and a moored ocean-going barge were also covered with a light spotting of small crude droplets. Valero also reported a sheen on the Mississippi River from this release which had largely dissipated by the time containment booms could be deployed. Light spotting has also been reported on some vehicles and structures in the Belle Chasse area. The root cause of the stopple failure was an undersized nose plate. The nose plate is a metal disc slightly smaller than the inside diameter of the pipe that is wedged into the pipe perpendicular to the flow. A gasket is attached to the nose plate that provides a seal along the inner walls of the pipe. In this case, the undersized nose plate did not provide enough support for the gasket and the gasket failed. The stopple fabrication and installation was performed by a third party specialty contractor with extensive expertise in performing this type of work. This contractor also conducted an investigation and determined that the nose plate had been modified in the field on a previous job, but no records of this modification existed. Consequently, this nose plate remained in circulation as a "standard" nose.

Followup: Yes

Notes: Valero immediately took steps to shut off the Crude charge pumps and all nearby unit heaters. The crude oil continued to leak at a much lower rate as the system depressurized, but shortly after the crude pumps were shutdown, oil was no longer spraying off site. A mixture of crude oil and water continued to leak out onto the ground at a reduced rate until all sources of pressure were isolated at 17:20. Valero quickly mobilized contractors to clean up the highway and the barge moored at the dock. The highway was re-opened at 18:21 on 10/25/13 and the barge sailed the next day. Inside the refinery, free oil has been removed by vacuum truck and recovered. Clean-up efforts are on-going in the refinery and south of St. Bernard highway. To date these activities have included: 1) Wiping up visible oil with absorbent materials, 2) Cutting grass spotted with oil and collecting the clippings for disposal, 3) Applying Micro-Blaze Emergency Liquid Spill Control bioremediation agent to affected areas on the ground, 4) Washing spotted vehicles at an offsite location. Valero has provided car washes to the public as well. Air monitoring was conducted on and off site. Valero personnel donned breathing protection (full face respirators) when working in the immediate area of the release. Benzene readings of 0.15 ppm were briefly detected offsite along Valero's property line. Valero has worked closely with the third party contractor to develop corrective actions to prevent a reoccurrence of this event. The third party contractor has committed to: 1) train all stopple set-up technicians to review the findings and reiterate procedures and best practices. 2) inspect all nose plates in use and remove from circulation those that are out of tolerance, 3) implement a receipt inspection requirement to flag field modifications and initiate repair, and 4) modify the Hot Tap Critical step checklist to require the field technician to sigh off on key stopple measurements. Note: During the time of flaring, a citizen complaint was submitted on account of sulfur odor (Incident #151864). According to the environmental engineers from Valero, the odors likely came from Valero's waste water treatment plant, which was operating normally at the time.
Crude Oil: 8,400.0 gallons
Benzene: 70.7 pounds

Pump at Tank 200-7
Cause: While collecting a sample from Tank 200-7, a laboratory technician observed 6-Oil under a pump and on the surrounding ground. He immediately notified Operations personnel who determined that the pump seal had failed. They proceeded to isolate the pump and stop the leak. It was determined that six barrels had spilled within the pump's concrete containment basin and another five barrels overflowed onto the surrounding grassy area. The root cause of this spill to be an improper pump seal flush design. Due to the improper design, variations in product density and low levels in Tank 200-7 may have reduced seal flush supply pressure and flow, allowing the seal to run dry and ultimately fail.

Followup: Yes

Notes: A vacuum truck was dispatched to remove as much of the 6-Oil as possible and shovels and a backhoe were used to remove the remaining material in the grassy area. Recovered liquids were transferred to the refinery for separation and treatment and the contaminated soil was moved to a roll off bin for off-site disposal. All soils and vegetation with visible contamination was removed for disposal at an offsite commercial landfill. Valero will modify the pump seal flush piping to allow for adequate seal flushing.
#6 Oil: 210.0 gallons

North Flare
Cause: On March 15, 2013 at approximately 08:40, Valero experienced excess emissions of Sulfur Dioxide at the North Flare during a planned shutdown of the Hydrocracker/Hydrotreater Unit. Valero was conducting a normal shutdown for a planned maintenance turnaround. During start ups and shut downs, H2S containing gases can pass through the Pre-fractionator stripper and accumulate in the Fractionator Overhead Receiver. The Fractionator Overhead Recveiver has no means of removing this gas, so Valero must vent it to the flare to prevent the pressure safety valve from lifting. The root cause of excess sulfur dioxide emissions from the Hydrocracker/hydrotreater during start ups and shutdowns has been identified from previous incidents to be inherent to the original design of the unit.

Followup: No

Notes: As a corrective action for previous incidents, Valero designed a vent line that will direct the gases vented from the Fractionator Overhead Receiver to the refinery's HiJet so that these gases will no longer need to be flared during startups and shutdowns. Valero will install this vent line during this maintenance turnaround. SO2 emissions from the North Flare occurred on 3/15/13 from 08:40 to 3/16/13 00:00 for a duration of 15.34 hours (15 hours and 20 minutes). Valero completed the shutdown of the Hydrocracker/Hydrotreater Unit according to procedure. Valero will install the vent line designed to prevent the Fractionator Overhead Receiver from being flared.
Sulfur Dioxide: 1,057.0 pounds
Hydrogen Sulfide: 12.0 pounds