A hydrogen alarm sounded when hydrogen buildup occurred in an unmanned switching room containing backup lead acid batteries after the exhaust ventilation fans failed to start at the 1% hydrogen trigger level. Failure of the ventilation fans to vent the normal off-gassing hydrogen from the lead acid batteries resulted in the hydrogen concentration in the room increasing to 2%, which triggered the hydrogen alarm. The alarm was automatically sent to an alarm-monitoring company that alerted the local fire department as well as company personnel of the condition. The fire department was dispatched to the scene and, along with company personnel, provided secondary ventilation to lower the hydrogen concentration to normal conditions. Hydrogen leakage from lead acid batteries is normal, and view more
The malfunctioning of the non-return valve of the hydrogen compressor caused the pressure between the hydrogen bottle and the compressor to rise up to the maximum allowed pressure of 275 barg. As a consequence, as foreseen by the safety system, the rupture disk of the safety valve broke and the hydrogen content of the gas bottle and the pipe section involved was released on top of the building. The flame was seen for a very short period by a guard, and could have been caused by the following series of events:
Expansion of hydrogen at the end of the exhaust pipe.
Consequent mixing of hydrogen and air up to a near-stoichiometric mixture and increase of gas temperature.
Mixture ignition due to sparks from static electricity generated by gas molecule friction against view more
Liquid Waste Disposition Projects (LWDP) has experienced repetitive events involving Hydrogen Monitor/LFL Analyzer degradations over the last year. There have been 12 reportables in the last two years. As a result, a determination was made to issue a recurring occurrence report referencing management concern as its reporting criteria.
Engineering has recently made significant progress in further defining issues and potential corrective actions necessary to address the lower flammability limit (LFL) failures. The engineering path forward to resolution of this issue addresses potential failure contributors, among these are: Drift - This phenomenon is being closely assessed. Initial tests indicate the monitor power supply may be a significant contributor to instability resulting 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
A control room received a tank lower flammability limit (LFL) analyzer low sample flow alarm. The control room operator initiated the appropriate alarm response procedure and the facility entered limiting conditions of operation. At the time of the alarm, the facility was experiencing severe weather and the field operator was unable to investigate the alarm in the field. After the severe weather cleared, the field operator investigated the alarm and found the sample flow to be low and out-of-limits.
At the given facility, composite lower flammability limit (CLFL) monitors are used to detect the presence of hydrogen and other flammable gases in waste tank vapor spaces. Maintaining the concentration of flammable vapors in tank vapor spaces below CLFL levels maintains tank view more
A deficiency was discovered in the application of a hydrogen sensor in the Rotary Mode Core Sampling (RMCS) portable exhauster. The sensor is installed in the flow stream of the exhauster designed to be used with a RMCS truck for core sampling of watch list tanks, and is part of the flammable gas detector system. During the previous week, a quarterly calibration of the sensor, per maintenance procedure, was attempted by Characterization Project Operations (CPO) technicians. Ambient temperatures during the sensor calibration were approximately 20 to 30 degrees F. Inconsistencies in calibration results and the failure of the sensor to meet the response-time calibration requirement lead to the conclusion that the unit could not reliably perform its safety function at low ambient view more
As a prerequisite to a storage tank slurry pump run, a tank operator identified a Lower Flammability Limit (LFL) Analyzer surveillance reading to the control room that was out of limits low. The reading was a negative zero % LFL indication (-0 % LFL). The tank operator roundsheet limits are 0 to 10% LFL. The "null" value (value read on analyzer when air with 0% LFL is drawn through the analyzer) as directed by the LFL Analyzer loop calibration procedure is set between 0 and 4% LFL.
To alert personnel to the buildup of potentially dangerous levels of explosive gases in the tank, a Combustible Gas Detection System is used to monitor and analyze sample air drawn from the tank vapor space. This system consists of a sensing element, a 4-20 milliAmp direct current (mADC) view more
A waste pretreatment tank operator was performing surveillance rounds on a tank and found the Composite Lower Flammability Limit (CLFL) Analyzer sample flow reading 1.4 cubic feet per hour (CFH). The Operational Safety Requirements (OSR) document required flow range is 1.5 CFH to 2.5 CFH. The Limiting Condition for Operation was immediately entered and the tank operator adjusted the flow into the required surveillance range.
The hydrogen and CLFL monitors are used to detect the presence of flammable gases in waste tanks vapor space. Maintaining the concentration of flammable vapors in the tank vapor space below flammability limits maintains tank integrity by preventing the possibility of tank deflagrations. The hydrogen monitors provide an automatic means to monitor flammable view more
A hydrogen gas detector on the ground floor of a building registered the release of a small amount of hydrogen gas and actuated automatic alarms both at the fire department and in one of its buildings. Additionally, interlocks connected to the gas detector completely shut down the experiment. Upon hearing the alarm, all occupants (about 6) promptly left the building. Fire department personnel are housed in the trailer next to a building and responded within one minute. They tested the atmosphere within the building, reset the gas detector, and secured the alarm at 9:15. The alarm was actuated when an experimenter assigned to the experiment was evacuating lines using a vacuum pump.
The speed of evacuation was controlled by a commercially manufactured flow meter. It is believed view more