2019 Philadelphia refinery explosion

In the early morning of June 21, 2019, a fire and multiple explosions occurred at the Philadelphia Energy Solutions (PES) refinery in Philadelphia, Pennsylvania. A release of hydrocarbons and hydrofluoric acid in the refinery's alkylation unit caused a ground-hugging vapor cloud which rapidly ignited, leading to three separate explosions minutes apart from each other. The largest explosion, a BLEVE, sent a vessel fragment flying 2,000 feet across the Schuylkill River. Five employees sustained minor injuries, but there were ultimately no fatalities. The refinery announced it would shut down operations the same month, and filed for bankruptcy a month later.

Background
The Philadelphia Energy Solutions refinery was an oil refinery complex in Philadelphia, Pennsylvania. The site resulted from the integration of two previously separate refineries, Girard Point and Point Breeze refineries.

Fire, explosions, and emergency response
On the morning of June 21, 2019, the refinery's alkylation unit, which produced high-quality gasoline, was functioning normally. However, shortly after 4:00 am, a leak of liquefied hydrocarbon gas (mostly propane) containing about 2.5% hydrofluoric acid (HF) developed from a ruptured pipe elbow at the discharge of a pump. At the time, three field operators were working in the alkylation unit. At 4:01 am, one of the operators reported seeing a ground-hugging vapor cloud, estimated by another to be 10 feet high. At 4:02 am, the vapor cloud ignited in the unit, causing a massive fire. The field operators in the alkylation unit were able to flee the area and avoid injury.

At 4:03 am, a remote control room operator activated the refinery's rapid acid deinventory (RAD) system, routing approximately 339,000 lb of hydrofluoric acid into an isolated drum for sequestration and safety. At 4:12 am, the control room operator attempted to activate the water cannons which were designed to reduce airborne HF through vapor suppression, but the system failed to respond. In fact, the associated control system had failed at 4:02 am, and its backup uninterruptible power supply failed 9 seconds afterwards. One field operator attempted to walk to the water pumps to manually activate them but reported they were too hot at the time to approach.

At 4:15 am, the first explosion occurred in the alkylation unit, followed by a second explosion at 4:19 am. Then, at 4:22 am, a vessel containing flammable hydrocarbons (primarily butylene, isobutane, and n-butane) ruptured and caused the largest blast, a boiling liquid expanding vapor explosion (BLEVE). Fragments of the vessel, one weighing approximately 38,000 lb and two other fragments weighing approximately 15,500 lb and 23,000 lb, were sent flying; the largest fragment was propelled 2,000 feet across the Schuylkill River.

At 4:39 am, the alkylation unit shift supervisor entered the alkylation unit in firefighting protective bunker gear and manually activated the water pumps to help suppress the release of hydrofluoric acid from the alkylation unit.

Residents who lived east of the plant were ordered to shelter in place. The fire burned for over 24 hours before it was extinguished at approximately 8:30 am on June 22, 2019, and the shelter-in-place order was lifted.

Investigation and shutdown
The U.S. Chemical Safety Board released its final report on the incident on October 11, 2022. The report stated that a corroded elbow pipe, installed in 1973, ruptured and caused the initial leak. PES announced it would halt operations completely on June 26, 2019, and filed for bankruptcy on July 22. The shutdown reduced US refining capacity by about 2%. As of 2022, developers were looking into redeveloping the site of the refinery.