Aug-2013

Refinery power failures: causes, costs and solutions

Power outages typically lead to damaging costs for refiners. Strategies are needed to minimise them.

Patrick J Christensen, William H Graf and Thomas W Yeung
Hydrocarbon Publishing Company

Article Summary

About 90 seconds into the second half of the 2013 Super Bowl, the American football championship game, half of the stadium lost power — a 34-minute delay caused by a malfunction in a faulty electrical relay that was supposed to monitor the electrical load. This event not only caused much frustration between the teams, fans and workers trying to fix the problem but also cost the broadcast network advertising revenue. The point is that we all take electricity for granted until the lights go out. For most of us, we just endure until the power comes back on. For refineries, however, there are more serious consequences that occur when power is lost. This article is the first of a two-part series examining technology-driven strategies to mitigate refinery power failures and minimise impacts on company earnings. Part 1 discusses the causes and financial costs when a refinery suffers a power disruption. Part 2 focuses on mitigation technologies available to refiners for minimising power disruptions and unplanned shutdowns as well as overall strategies to reduce financial impacts.

Refinery shutdowns happen on a daily basis
Hydrocarbon Publishing Company collected data from reports published by the US Department of Energy’s Energy Assurance Daily. The information analysed focused on power failures and disruptions at US refineries.

From 2009 to 2012, there were over 1700 refinery shutdowns, which equates to an average of 1.2 shutdowns per day. As Figure 1 shows, 46% of the shutdowns were due to mechanical breakdowns, 19% were caused by electrical disruptions and power failures, 23% were the result of maintenance, and the last 12% were because of other causes, mostly fires that occurred at the refinery. While some incidences last only a couple of hours, many last multiple days and even weeks. About 92% of maintenance-related shutdowns were unplanned, many due to leaks in piping and different units.

Major causes of power disruptions
As Figure 3 shows, 17.6% of refinery power disruptions were the result of electrical equipment failures or refinery processing units having electrical problems. This includes transformers malfunctioning or the FCC unit suffering an electrical failure. Some 16.4% of causes were due to weather events. This includes hurricanes, lightning strikes and wind causing power lines to fall or units to be knocked out of service. While accidents due to weather cannot be avoided, proper maintenance of processing units and electrical equipment can help avoid breakdowns.

Unfortunately, over 60% of the causes of electrical disruptions are not specified. Most of the unspecified power failures were listed as “a power failure occurred at the refinery and caused flaring” or similar statements. There are multiple reasons why the reports were so vague: the refiner did not know the reason at the time of the report, there are confidentiality policies that prevented the refinery from reporting the causes, or the refinery for whatever reason did not want to be very specific in its report. The fact that so many are unspecified makes it difficult to minimise power disruptions. Therefore, any prevention and protection strategies deployed by a refinery should include detailed bookkeeping of failed equipment so that statistical analyses or predictive analytics can be performed in identifying exact causes to reduce future incidents, as discussed in part 2 of this article.

In Figure 4, 56.1% of the failing units were electrical equipment such as circuit breakers, switchgears, transformers and substations. Some 24.6% of power disruptions were caused by refinery processing units such as the FCC unit having electrical issues. About 7% of problems were the result of rotary equipment such as motors and compressors having electrical problems. About 12% did not specify the unit or equipment that was having problems.

From 2009 through 2012, there were about 320 power disruptions at refineries in the US. In this section, some of their experiences are reviewed. All of these disruption events were gathered from the US Department of Energy’s Energy Assurance Daily publication. We chose events that provided a clear picture of the causes and impacts from power disruptions.

Weather problems
The most common weather event that causes power failures is a thunderstorm. High winds, lightning strikes, heavy rain and flooding can all cause problems. Power lines can be knocked down, lightning strikes can disrupt units, and rain can interfere with the steam supply. These are a few of the examples that show how weather can cause a refinery shutdown.

In February 2010, Valero’s Ardmore, Oklahoma, refinery experienced thunderstorms that caused temporary power outages at several units, reducing runs. Valero reported that it was restoring full production at the plant the next day. On 1 December 2011, a wind storm caused a power outage and forced several units offline at Chevron’s El Segundo, California, refinery, halting production until 7 December. Among the affected units was a CDU that caught on fire in the aftermath of the electrical failure. Flaring occurred as a result of the incident and during the subsequent restart process. Fire damage to the CDU, six days of inactivity and flaring all adversely affected the refinery’s bottom line.

In March 2009, Motiva’s Port Arthur, Texas, facility experienced lightning that led to a power outage and also stated a fire. The lightning caused a crude unit, two hydrotreaters and a delayed coker to shut down. Unlike Motiva’s experience, in July 2009, Pasadena Refining’s Pasadena, Texas, complex experienced a lightning strike that disabled all power to the Red Bluff Tank farm, which resulted in loss of feed to the refinery’s crude unit. The feed was restored with a backup generator, and the refinery was able to run using backup power and keep operations online despite the loss of power to the tank farm. In April 2012, Valero’s Norco, Los Angeles, facility experienced a power surge caused by lightning, which caused the hydrocracking unit to trip. Emissions of sulphur dioxide and hydrogen sulphide were released during the flaring caused by the shutdown.

Although high wind and debris are the most commonly cited causes of hurricane damage, for Gulf Coast refineries in the US, where hurricanes hit most often and hardest, the greatest hurricane damage is the result of flooding. Hurricane Isaac, which touched down in Louisiana 28-29 August 2012, caused extensive flooding, forcing nine Louisiana oil refineries with a collective capacity of 2.2 million b/d to shutter about 42% of that capacity by 29 August due to power outages. Backup generators are typically only used for refineries’ most important units.