Effective Winterization Programs Can Prevent Process Accidents

Winter is here. As temperatures continue to drop, it’s important for chemical plants to be prepared for the unique safety challenges of subfreezing weather. Since 2001, the CSB has investigated two major accidents that resulted from water freezing inside process pipes.

Both accidents involved what are known as “dead legs.”

Dead legs are sections of piping without any flow of liquid. They are often created when existing processes are reconfigured. Dead legs are particularly vulnerable to the hazards of freezing.

Most recently, a massive fire occurred at a refinery near the town of Dumas in the Texas panhandle. The fire seriously burned three people, shut down the refinery for two months, and contributed to gasoline shortages hundreds of miles away. The fire occurred in a unit that used large amounts of high-pressure liquid propane. Years earlier, the unit had been reconfigured, creating a dead leg. The dead leg was blocked on one side by a valve that was later found to leaking Over time, small amounts of water, which were contained in the liquid propane, sank past the leaking valve and accumulated in the piping below.

On February 15, 2007, the temperature fell to six degrees Fahrenheit. The water froze, expanded, and cracked the pipe. The following day, the weather warmed up, the ice melted, and propane began jetting from the broken pipe. Fire engulfed the area, injuring workers and causing more than 50 million dollars in damage.

In February 2001, a similar accident occurred at a steel mill in Chesterton, Indiana.

This accident actually had its origins nine years earlier, when the mill disconnected a furnace that was fueled by coke oven gas. The 25-foot vertical pipe that once supplied gas to the furnace was left in place, with a closed, ten-inch valve at the bottom. It was a dead leg.

In the winter of 2001, water accumulated inside the dead leg and froze, cracking the valve. As a crew later began work to replace the valve, they were sprayed with flammable liquid gas condensate, which ignited. The fire killed 2 workers, and injured 4 others.

Both the water and the flammable liquid had condensed from the coke oven gas. The accumulation of liquids had accelerated because insulation had been removed from piping, and the drain lines in the gas system had become blocked with ice. These two serious accidents illustrate the importance of effective winterization programs at refineries, chemical plants, and other facilities that handle hazardous materials.

Dead legs need to be surveyed. Ideally they should be removed, or else permanently and effectively isolated from hazardous process streams. Piping that is susceptible to freezing needs to be identified and properly winterized. That can include insulation, or heat tracing.

Winterization is a simple concept. But the lack of winterization has caused serious accidents that have cost lives and inflicted huge property losses. Companies should establish formal, written winterization programs, and they should apply appropriate management of change techniques when piping or equipment is taken out of service.

Maintain Process Safety During the Recession

By John S. Bresland

As the holidays approach, Americans are getting some much-needed relief at the gas pump where prices have been dropping. While that’s good news for drivers, the economic downturn will likely reduce margins at the nation’s oil refineries. As refining margins fall, the pressure will always be there to trim operating expenses – perhaps by delaying a needed repair project or cutting operator positions. During this period of economic uncertainty for refineries, management and workers alike need to remain focused on process safety. Oil company managers, executives, and boards of directors should ensure that fluctuating oil prices do not impact needed preventive maintenance and investment in the nation’s refineries. Unfortunately, around the country, refinery accidents continue to be a concern. On November 20th, during seemingly routine operations, flammable hydrocarbons were suddenly released, causing an explosion and fire at a refinery in Tyler, Texas.

Two workers at the refinery were fatally burned. The explosion also damaged a manned room located near the perimeter of the unit. The company has announced that the refinery will remain shut down until the middle of next year. In February 2008, a refinery in Big Spring, Texas, experienced a major explosion that caused damage both on-site and off-site. And just the month before, a veteran employee was killed in a process-related explosion at a refinery in Texas City, Texas. That’s the same refinery where 15 workers died – and 180 others were injured – in a devastating blast on March 23, 2005.

The Chemical Safety Board found that corporate spending decisions in the 1990s – when oil prices were low – played into the tragedy. Our investigation noted that preventive maintenance, training, and control room staffing were cut in an effort to economize. Managers deferred the installation of modern flare systems to control hydrocarbon releases. The accident, years later, not only caused untold human suffering but also cost the company billions of dollars – a far heavier price than the safety equipment and management systems that could have prevented the disaster. My safety message for oil and chemical companies is clear: even during economic downturns, spending for needed process safety measures must be maintained. Downturns and recessions can actually be a good time to take care of deferred maintenance. In fact, as noted process safety expert Trevor Kletz has observed, downturns and recessions can actually be a good time to take care of deferred maintenance. That’s because there’s less financial impact from temporarily shutting down a process during periods when sales are depressed. Today, as gasoline prices remain low, companies should weigh each decision to make sure that the safety of plant workers, contractors, and communities is protected. In the long run, companies that continue to invest in safety will reap benefits far into the future.