What is Lessons Learned?

What is H2LL?

This database is supported by the U.S. Department of Energy. The safety event records have been contributed by a variety of global sources, including industrial, government and academic facilities.

H2LL is a database-driven website intended to facilitate the sharing of lessons learned and other relevant information gained from actual experiences using and working with hydrogen. The database also serves as a voluntary reporting tool for capturing records of events involving either hydrogen or hydrogen-related technologies.

The focus of the database is on characterization of hydrogen-related incidents and near-misses, and ensuing lessons learned from those events. All identifying information, including names of companies or organizations, locations, and the like, is removed to ensure confidentiality and to encourage the unconstrained future reporting of events as they occur.

The intended audience for this website is anyone who is involved in any aspect of hydrogen use. The existing safety event records are mainly focused on laboratory settings that offer valuable insights into the safe use of hydrogen in energy applications and R&D. It is hoped that users will come to this website both to learn valuable lessons from the experiences of others as well as to share information from their own experiences. Improved safety awareness benefits all.

Development of the database has been primarily supported by the U.S. Department of Energy. While every effort is made to verify the accuracy of information contained herein, no guarantee is expressed or implied with respect to the completeness, causal attribution, or suggested remedial measures for avoiding future events of a similar nature. The contents of this database are presented for informational purposes only. Design of any energy system should always be developed in close consultation with safety experts familiar with the particulars of the specific application.

We encourage you to browse through the safety event records on the website and send us your comments and suggestions. We will continue to add new records as they become available.

How does H2LL work?

If you have an incident you would like to include in the H2LL database, please click the "Submit an Incident" button at the top of the page. You will be asked for a wide range of information on your incident. Please enter as much of the information as possible. In order to protect your and your employer's identities, information that may distinguish an incident (your contact information, your company's name, the location of the incident, etc.) will not be displayed in the incident reports on H2LL.

Lessons Learned Corner

Visit the Lessons Learned Corner Archives.

Key themes from the H2Incidents database will be presented in the Lessons Learned Corner. Safety event records will be highlighted to illustrate the relevant lessons learned. Please let us know what you think and what themes you would like to see highlighted in this safety knowledge corner. You can find all the previous topics in the archives.

Summary

A hydrogen generation plant experienced a fire and significant damage due to a concussive combustion event that started in a high-pressure hydrogen feed pipe.

System Description

A certain hydrogen plant is designed to continuously produce hydrogen at a purity of 99.75% and at a rate of 510 m3 per day. Hydrogen is produced in two banks of cells filled with a strong solution of caustic soda. Current is passed through the cells to produce hydrogen and oxygen. The oxygen is vented directly to the atmosphere, while the hydrogen is piped to the gasholder. The gasholder is a low-pressure storage vessel capable of storing 28 m3 of gas. It is constructed in two parts. The bottom section is a large round tank. The upper section is an inverted tank or bell that is view more

A water treatment plant used an electrolytic process to generate sodium hypochlorite (NaOCl) from sodium chloride (NaCl). The strategy of using liquid sodium hypochlorite for disinfecting water instead of gaseous chlorine (CL2) is popular because the liquid is generally safer and falls under fewer OSHA and EPA standards. The further idea of generating the liquid sodium hypochlorite on an as-needed basis and in limited quantities also has certain obvious safety advantages.

One of the disadvantages of the electrolytic process is that hydrogen gas is also created as a byproduct. The hydrogen is supposed to be vented, by design, to the atmosphere before the liquid sodium hypochlorite passes into a holding tank.

For various reasons, in this instance it is believed that the view more

One afternoon, a hydrogen-monitoring system alarm sounded. The system isolated the building hydrogen gas distribution system from the source and purged the distribution piping with argon. Activities were terminated and personnel were immediately evacuated.

Prior to re-entry, the hydrogen system was walked down to ensure that it was in a safe state and that the remote indicator showed no hydrogen present in the facility. Normal operations were suspended until the cause of the alarm could be determined.

The cause of the alarm was not escaping hydrogen gas, but drift in one of the eight monitoring system sensors. The sensor was recalibrated and the monitoring system determined to be functioning properly. The gas distribution system was recharged with hydrogen and verified as view more

The bulkhead between a liquid hydrogen tank and a liquid oxygen tank failed due to a series of events. Air services to the building were shut down for repairs and the facility had switched to an emergency nitrogen supply. Failure to switch back to service air when it became available, led to the mishap.

The emergency supply became depleted and two valves in the normal nitrogen purge system failed in the open position, releasing the high-pressure nitrogen gas from the manifold into the liquid hydrogen tank. The gas flow raised the liquid hydrogen tank pressure to 4.5 psig. That was sufficient to rupture the bulkhead wall.

Overview
A solution of potassium carbonate was being drawn off to an inventory tank for a turnaround/shutdown maintenance activity at a refinery's hydrogen production unit. On the day of the incident, the solution level in the tower wasn't checked as it should have been, which resulted in hydrogen gas flowing back into the tank until the increased pressure caused the tank to explode. The direct cause of the incident was the workers neglecting to check the solution level in the tower. It is not known whether the potential for backflow of hydrogen gas into the inventory tank was understood beforehand or not.

Incident Synopsis
An explosion occurred due to unexpected backflow of hydrogen gas while a solution of potassium carbonate was being drawn off to an view more

A laboratory technician died and three others were injured when hydrogen gas being used in experiments leaked and ignited a flash fire.

The incident occurred in a 5,700-square-foot, single-story building of unprotected non-combustible construction. The building was not equipped with automatic gas detection or fire suppression systems.

Employees in the laboratory were conducting high-pressure, high-temperature experiments with animal and vegetable oils in a catalytic cracker under a gas blanket. They were using a liquefied petroleum gas burner to supply heat in the process.

Investigators believe that a large volume of hydrogen leaked into the room through a pump seal or a pipe union, spread throughout the laboratory, and ignited after coming into contact with the view more

An employee at a soap manufacturing plant died in a flash fire outside the facility's hydrogenation building. Responding personnel encountered a fire at the base of the plant's hydrogen storage towers, and they found the victim, who was burned over 90 percent of his body, some 50 feet away.

Officials determined that a pipe connection failed and that hydrogen, pressurized at 1,800 psi, ignited when it was released into the atmosphere, killing the plant operator.

According to reports, the pipe connection failure stemmed from pressures higher than design tolerance, which in turn were the result of over tightening that occurred during routine maintenance replacement. The new bolts were stronger than those they replaced, and the threads of the nuts had been partially view more

Overview
During start-up operation of a high-temperature, high-pressure plant using hydrogen, hydrogen gas leaked from the flange of a heat exchanger and a fire occurred. The leakage occurred for two reasons:

Insufficient tightening torque control was carried out during hot-bolting and an unbalanced force was generated across the bolts.
A temperature rise was induced across the heat exchanger as a result of a revamping activity, during a turnaround shutdown.

Background
Hot-bolting: In equipment and piping that operate at high temperatures, as the temperatures rise, the tightening force decreases, thus re-tightening of bolts is necessary. This work is called hot-bolting. The design conditions of the evaporator where the fire occurred were 2.4 MPaG, view more

On a given day personnel were removing a blind hub that had been used to temporarily isolate a portion of a gaseous hydrogen system. As a result of a sudden release of 2,800 psig gaseous nitrogen, sand and debris kicked up from the concrete pad and caused minor injury to two technicians.

During the investigation, it was found that:

The temporary configuration change to the gaseous hydrogen system was initiated on multiple work orders and by different individuals. There was no single document that documented the temporary system configuration.
The procedure for performing the work was written using a drawing that had not been updated to show the actual system configuration. Verbal field direction was given when it was discovered the system was not configured per view more

Hydrogen was released near the ground when the vent line from a 13,000-gallon liquid hydrogen storage vessel suffered damage from unusually high winds. The toppled vent line did not shear or tear, but sustained a kink that restricted hydrogen flow and created a back pressure on the vessel relief system.

Repair efforts were hampered by the potential for cold hydrogen gas, a flammability hazard, in the work area. Shut off or redirection of the hydrogen was not possible, and variable breezes made set up of safe zones uncertain. A protocol had not been prepared for this scenario.