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<td><a href="https://misportal.jlab.org/ll/index.jsf?function=view&lessonId=933">Unexpected Toxic Gas Release - Oak Ridge National Laboratory</a></td>
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<h2 style="white-space:nowrap">Statement of Lessons Learned</h2>
<pre>Design of a nitrogen dioxide (NO2) gas delivery system did not take into account the potential of corrosive liquid condensing in the system tubing and components. Engineered controls and safeguards did not take into account all potential deviations to the process parameters, whether expected or not.</pre>
<h2 style="white-space:nowrap">Discussion of Activities</h2>
<pre>On October 2, 2015, an NO2 sensor alarmed in a laboratory indicating the presence of high levels of highly toxic NO2 gas. The NO2 was sourced from a gas cylinder containing liquid NO2 and dinitrogen tetroxide (N2O4) in equilibrium. Two workers were in the area and they evacuated immediately. The ORNL Hazardous Material (Hazmat) Spill Response Team responded to the alarm and performed a planned entry into the lab using fully-encapsulated, supplied-air Level A personal protective equipment. Readings taken within the room indicated abnormally high levels of NO2. Hazmat team members isolated the gas cylinder and manually closed the cylinder valve. Shortly thereafter the NO2 levels in the lab returned to below the alarm set point. The NO2 alarm and notification system worked as designed and no workers were injured.</pre>
<h2 style="white-space:nowrap">Analysis</h2>
<pre>An engineering review of the event found:
* Liquid NO2 and N2O4, which is more corrosive than gaseous NO2 was being delivered in a system intended for gas phase only. This resulted in condensation, swelling, and corrosion of the autovalve and other components, and ultimately a ( <30 psi) pressured leak in the system sufficient to cause gas to exit the gas cabinet.
* Because of damage to the system, the automatic isolation valve, intended to shut off the gas supply in the event of an alarm, did not function properly.
* Work in the lab involved the use of relatively large quantities of highly toxic gases. Several layers of engineered controls were in place to mitigate the hazard including:
(1) Multiple layers of containment using an approved, ventilated gas cabinet and hood as well as double-contained process lines that run outside of ventilated containment;
(2) Alarming gas sensors located at multiple locations in the lab, in the ventilation ductwork and attic spaces above the lab; and
(3) An alarm controller system that automatically activates local alarms, activates the isolating autovalve, and notifies the ORNL Laboratory Shift Superintendent and Fire Department in the event of a toxic gas release.
* The design of the gas delivery system did not take into account the potential for corrosive liquid condensing in the system. Therefore, the construction material (including the autovalve) was not compatible with the actual contents. Typical polymer valve seals corrode or swell in liquid N 2 O 4 . The corrosion and/or swelling caused the leaks, and, in this case, the autovalve failure.
* The remaining layers of engineered controls and safeguards functioned and ensured that the leak was quickly detected. The alarm notified personnel to evacuate, and emergency response personnel were notified.
* The gas delivery system was designed for gaseous NO x (NO and NO 2 ) only. It was not designed to tolerate the much more corrosive liquid N 2 O 4 . The gas bottle was equipped with a heater blanket to vaporize the NO 2 and it was believed that the increased temperature (up to 125°F) would be adequate to ensure a gaseous phase throughout the system. </pre>
<h2 style="white-space:nowrap">Recommended Actions</h2>
<pre>Below are the consequences of the above event. They are provided for information and discussion purposes only.
Design reviews are to take into account all potential deviations to process parameters, expected or not. Structured System Safety Analysis, such as a Hazard and Operability Study (HazOp) or What-If Analysis, are to be performed a ensure all deviations to process parameters, expected or not, are evaluated for potential causes and consequences.
Managers and supervisors are to provide this Lessons Learned in pre-job briefings, reviews, safety meetings.
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<h2 style="white-space:nowrap">JLab Preventive Measures</h2>
<pre>Jefferson Lab's Subject Matter Expert has read and provided the following:
In the Pressure and Vacuum Systems Safety Supplement, Part 2 Pressure System Construction, Section 7 Materials, the Jefferson Lab Design Authority is directed to carefully consider the choice of materials for all pressure components (equipment vessels and piping). The selected materials shall be compatible with the fluid service, system fluids, and the engineering design.
A listing of material selection considerations is provided for the Design Authority, the first being "Fluid compatibility" which includes gaseous versus liquid states and corrosion, rust, scale, etc. In addition, in Part 8 Operation and Maintenance, System Owners and operators are responsible for regularly checking their pressure system including pressure relief valves, gages, rupture disks, system components and piping for leaks, degradation, corrosion and blockage.
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<h2>Comments</h2>
<h5 style="white-space:nowrap">2/23/2016 9:15:05 AM by Bailey, Mary Jo</h5>
<pre>The following was provided to those with
SAF129: R&D Chem Room Safety
SAF130A: PRESSURE SYSTEMS SAFETY AWARENESS</pre>
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<legend>Summary</legend>
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<td class="label" nowrap>Lesson ID:</td>
<td class="dataval">933</td>
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<tr class="row">
<td class="label" nowrap>Status:</td>
<td class="dataval">OK</td>
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<td class="label" nowrap>Doc ID:</td>
<td class="dataval"></td>
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<td class="label" nowrap>Priority:</td>
<td class="dataval">Info</td>
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<td class="label" nowrap>Safety Related:</td>
<td class="dataval">YES</td>
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<td class="label" nowrap>Originator:</td>
<td class="dataval">Bailey, Mary Jo</td>
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<tr class="row">
<td class="label" nowrap>Issued:</td>
<td class="dataval">2/23/2016 9:11:18 AM</td>
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<tr class="row">
<td class="label" nowrap>Approved By:</td>
<td class="dataval">Bailey, Mary Jo</td>
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<tr class="row">
<td class="label" nowrap>Approved On:</td>
<td class="dataval">2/23/2016 9:15:05 AM</td>
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<tr class="row">
<td class="label">Source:</td>
<td class="dataval">
DOECRD
</td>
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<td class="label" nowrap>Location:</td>
<td class="dataval">ORNL</td>
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<td class="label" nowrap>Cost Savings:</td>
<td class="dataval"></td>
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<td class="label" nowrap>Contact:</td>
<td class="dataval">Teresa Cochran - 865-241-9670</td>
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<tr class="row">
<td class="label" nowrap>Queued Emails:</td>
<td class="dataval">0</td>
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<td class="label" nowrap>Sent Emails:</td>
<td class="dataval">0</td>
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<td class="label" nowrap>Viewings:</td>
<td class="dataval">2 times</td>
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<legend>Attachments</legend>
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<li><a target="_blank" href="https://misportal.jlab.org/ll/downloadAttachment?attachmentId=4323">DOE - NO2 System.pdf</a></li>
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<legend>Hazard Issues</legend>
<ul class="lesson_attribute_listing">
<li>Chemicals</li>
<li>Pressure Systems</li>
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<legend>Skills</legend>
<ul class="lesson_attribute_listing">
<li>SAF129: R&D Chem Room Safety</li>
<li>SAF130A: PRESSURE SYSTEMS SAFETY AWARENESS</li>
</ul>
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<legend>Distribution/Notification</legend>
<ul class="lesson_attribute_listing">
<li>*Division Safety Officers (DSOs)</li>
<li>*Safety Wardens</li>
<li>*DOE Notification</li>
<li>*ESH&Q Liaisons</li>
</ul>
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Do you have a lesson learned you would like to contribute? Contact the <a href="mailto:mbailey@jlab.org,sjsmith@jlab.org,cjohnson@jlab.org">Lesson Learned Coordinator</a>.