Explosion from a Hydrogen Transportation Trailer, in a Storage Area
Two explosions rocked the industrial area of Santa Clara afternoon June 1st 2019, sparking a smoky fire at a chemical, gas storage and transportation facility of Air Products and Chemicals Inc. near the 1500 block of Norman Avenue, Santa Clara, the San Francisco Bay Area, California. No injuries were reported, according to fire officials.The first explosions came just before 4:30 p.m., Saturday. The blasts were felt five miles away and the area was quickly evacuated as firefighters worked to get the upper hand on this dangerous blaze. A person working across the street from the Air Products plant heard and felt the explosions. He captured images with his cell phone of flames shooting over the fence.According to the Santa Clara Fire Department, a hydrogen tanker truck CT450 was being fuelled. The tanker truck CT450 started leaking and there was a large hissing noise. When the shutdown of the tanker truck that was being fuelled occurred, an explosion resulted. That is when the initial explosion went off. The explosion damaged the emergency shut off panel and valve near the tanker. At least 4 workers at the Air Products plant were on site during the explosion. Workers were able to shut off two valves but could not shut off the valve near the original tanker truck. According to firefighters those workers were lucky to be alive since they stayed the proper distance away from their truck during the fuelling process. The tanker caught on fire, which spread to other tankers nearby. Only some tankers in the fuelling area were affected and the fire did not spread beyond that area.Nobody was injured. Multiple vehicles were damaged by the explosion and Air Products has temporarily suspended deliveries from its CT-450 and CT-500 fleets while the incident is being investigated. Air Products said in a statement, There was significant damage to the distribution trailer directly involved in the incident, as well as to multiple other distribution trailers at the site.
Event Date
June 1, 2019
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Cause Comments
According to the H2 Safety Panel report, the release of high-pressure hydrogen at the transfer facility has been caused by a miscommunication between the senior driver/trainer and the driver/trainee. The former had disassembled the piping supplying hydrogen to the trailer cylinders trying to repair a leaking valve, without being authorized to do so. The latter actuated the flow to the open pipe section when he inadvertently opened the trailer valves that had an ambiguous control label. A flammable hydrogen-air mixture rapidly formed in and around the trailer front module and an explosion occurred when the mixture was ignited. Because of lack of adequate venting of the open top of the module, a deflagration occurred that subsequently damaged the module and pressured components such as PRDs and high-pressure seals. A domino effect followed triggering the pending of other PRDs, producing jet fires directed to trailer cab and the adjacent trailers, diesel fuel fires and tire fires.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
CT-450 hydrogen distribution trailers
Storage/Process Medium
Storage/Process Quantity
450
Design Pressure
500
Location Type
Location description
Industrial Area
Operational Condition
Pre-event Summary
The affected facility transfer liquid hydrogen from an stationary storage tank to high-pressure tube trailer. This process implies the pressurization of the liquid hydrogen, its warming up to ambient temperature and the transfer into the tubes.
Currency
Lessons Learned
Lessons Learned
MEASURES ADOPTED:Based on their root cause analysis, the company implemented the following measures. Improved Training and Retraining of Drivers Improved Trailer Filling Procedures Equipment Evaluations and ModificationsRECOMMENDATIONSThe following is a summary and simplification of the recommendations issued by the H2 Safety Panel: 1. NFPA should consider providing additional guidance on hydrogen system repairs on requirements for training all personnel. 2. Standards organizations should explore improvements in their standards for PRDs intended to actuate and relieve cylinder pressures during fire exposure. Improvements are needed to specify direct fire exposure requirements and vent line. 3. In-depth examination on fire protection of compressed pressure hydrogen cylinders and the requirements for PRDs, aiming at improved quantitative risk assessment comparing risks of cylinder use with and without PRDs. 4. NFPA should consider including recommendations or requirements for hydrogen process and transfer controls.5. The role played by walls or bulkheads on hydrogen trailers should be clarified in case of release/ignition. Walls can trap hydrogen but walls can also exclude hydrogen accumulating from different sources. 6. The use of flow-limiting devices for inadvertently opened piping during hydrogen transfers and refuelling should be encouraged 7. Guidance on improved fire protection for trailer/tanker transfer stations should be provided in NFPA 2.
Event Nature
Emergency Action
16:30 - The fire was reported. The fire-fighters found multiple hydrogen tanker trucks on fire in the facility yard. The fire department ordered an evacuation radius of ca. 450 m, (affecting an industrial area and few people working there at that time). Once it was confirmed that no one was injured and the area was evacuated, the fire-fighters switched to defensive operations with multiple ladder trucks flowing water from aerial master streams, to cool the liquid hydrogen tank and surrounding equipment exposed to the residual fires. 17:40 - The fire was extinguished. It took firefighters an hour and at least three aerial water streams to put out the fire. Later firefighters made access to tanker valve and shut down while master streams flowed to cool the tanks and trucks previously impinged with Fire.Firefighters used thermal imaging cameras from different vantage points to make sure that the hydrogen was not burning even after it appeared that it was shut down.
Emergency Evaluation
An internal accident investigation performed by Air Products is performed: "A hydrogen leak was detected during the trailer fill process. Per our fill procedures, the fill should have been stopped and the vehicle placed out of service for maintenance to be performed by trained technicians at one of our maintenance locations. Instead, an employee attempted to perform maintenance on the process equipment without authorization. This resulted in a release of high pressure hydrogen and the subsequent fire. We have inspected all trailers and leak checked the entire fleet, which resulted in the replacement of one o-ring."
Release Type
Release Substance
Hydrogen Release Concentration (%)
100.00
Release Rate (kg/s)
4.30
Release Amount (kg)
250.00
Release Pressure (bar)
50.00
Ignition Source
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
US Hydrogen Safety Panel Report
https://h2tools.org/sites/default/files/2021-06/AP_Santa_Clara_Incident…
(accessed May 2023)
246_Hydrogen Gas Explosion and Fire at Air ...ucts-and-chemicals-inc-in-santa-clara_.pdf