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.

While research staff were working in a lab, a staff member opened the primary valve to a 0.2" (1500 psi) hydrogen gas line connected to a manifold supplying instruments in the lab. Upon opening the valve, the hydrogen gas line failed at a fitting on the switching manifold, releasing a small amount of hydrogen gas. The staff member closed the valve immediately, then inspected the gas line and found the front ferrule (of the compression-style fitting) to be missing. There were no injuries or damage to equipment.

In the follow-on discussion with research staff, it was learned that approximately one month earlier, a similar condition (front ferrule missing from a fitting) was found while performing a modification to a similar manifold. Following a critique, management expressed view more

A demolition technician noted an elevated combustible gas lower explosive limit (LEL) on a pipe that was being tested prior to cutting (No. 2 pipe). The No. 2 pipe was one of four pipes being tested. The other three pipes tested less than detectable for combustible hydrogen gas. Testing involves tapping the pipe and connecting the pipe to an Explosive Gas Detector via a tube. When an elevated LEL is identified, the pipe is allowed to vent and then retested prior to cutting. After tapping the No. 2 pipe, the work crew left the pipe open to vent and departed the area for the end of shift.

At approximately 7"45 PM on the same day, a crew was on overtime to support roofing activities. Since additional workers were available, the craft supervisor decided to re-enter the viewing view more

During inspection of a hydrogen make-up compressor, it was discovered that a 1/4” stainless steel screw and nut that mounted a temperature gauge to a stainless steel pipe was resting against the side of a schedule 160 high-pressure hydrogen pipe. Constant vibration of the process equipment had caused the bolt to rub a hole in the high-pressure suction piping, resulting in the release of make-up hydrogen. The pipe was out of sight, and the problem was identified by an employee who heard the whistling sound of escaping hydrogen. The compressor was taken offline and depressurized.

A subcontractor employee was using a band saw to cut a 1" metal pipe when a flash fire occurred on the third floor hydrogen fluoride area. Subcontractor employees were removing all piping associated with the Anhydrous Hydrofluoric Acid (AHF) system. These lines were being removed during plant decontamination and demolition (D&D). The subcontractor employee was attempting to cut a 90-degree elbow located at the highest elevation on the 1" line, but the lowest elevation of the overall piping run. Since hydrogen is lighter than air, it is speculated that a minute amount of hydrogen gas had accumulated in the elbow.

Even though Safe Shutdown personnel had previously opened the system and placed it in a safe configuration, residual hydrogen fluoride could have still view more

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

Description of Circumstances
An incident occurred in late 2001, while a boiling water reactor (BWR) unit was operating at rated power. The utility was performing a periodic surveillance of the high-pressure coolant-injection (HPCI) system. Immediately after the test began, the HPCI system automatically isolated and the reactor building fire detectors actuated. The unit was then manually shut down. An examination of the residual heat removal (RHR) system revealed that a pipe elbow had ruptured near the high point in the RHR branch steam supply line leading to one of the two RHR heat exchangers (steam condensing mode line) in the reactor building. Fragments from the piping rupture caused some damage to equipment in the general area, but no significant damage to any safety-related view more

A facility experienced a major fire in its Resid Hydrotreater Unit (RHU) that caused millions of dollars in property damage. One employee sustained a minor injury during the emergency unit shutdown and there were no fatalities.

The RHU incident investigation determined that an 8-inch diameter carbon steel elbow inadvertently installed in a high-pressure, high-temperature hydrogen line ruptured after operating for only 3 months. The escaping hydrogen gas from the ruptured elbow quickly ignited.

This incident occurred after a maintenance contractor accidentally replaced an alloy steel elbow with a carbon steel elbow during a scheduled heat exchanger overhaul. The alloy steel elbow was resistant to high-temperature hydrogen attack (HTHA), but the carbon steel elbow was not. view more

A power plant reported a hydrogen leak inside an auxiliary building. The given plant was in cold shutdown at the time of the event. The discovery of this problem was as a result of an unassociated event involving the activation of a chlorine monitor in the control building. When additional samples indicated no chlorine gas, the shift supervisor ordered further investigation into other plant areas. Because there was no installed detection equipment, portable survey instruments were used to determine gaseous mixtures. Hydrogen was detected in the auxiliary building at 20 to 30 percent of the lower flammability limit (LFL) for hydrogen. A level of about 30 percent of LFL corresponds to about 1.2 percent hydrogen by volume.

When hydrogen was discovered in the auxiliary building, the view more

An offgas system mishap involved two explosions occurring within an interval of about 3 ½ hours. The first offgas explosion was reportedly caused by a welding operation on an air line adjacent to a hydrogen sensor line containing off gas. The welding arc initiated a detonation within the offgas piping. The detonation was contained by the piping system but blew out the water seal at the base of the vent stack.The second hydrogen explosion in this incident occurred in the stack base area. Hydrogen accumulated in the enclosed base area after the water seal had been blown in the first explosion. The stack base metal door was blown off its hinges from the second explosion, and the reinforced concrete stack was also damaged. A plant employee walking by the stack at the time of the explosion view more

A large, hydrogen-cooled generator is driven by steam turbines at a power station. During maintenance shutdowns, the hydrogen cooling loop in the generator is purged with carbon dioxide. After CO2 concentrations are measured with a densitometer to verify the complete removal of hydrogen, the generator is purged with air and the maintenance is performed.

This purging procedure was used prior to the explosion. The CO2 reading was reported to be 100 percent CO2 at the top of the generator. The cooling system was then purged with air and a 1/2 inch pipe in the cooling loop was cut to install some new instrumentation. When the pipe was cut, pressurized gas was emitted at the opening. Workers assumed the gas was either carbon dioxide or air and proceeded with the new instrument view more