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<td><a href="https://misportal.jlab.org/ll/index.jsf?function=view&lessonId=1173">Discovery of Overpressure Condition on Liquid Nitrogen Dewar in LCLS Hutch 2.2 - SLAC National Accelerator Laboratory (SLAC)</a></td>
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<h2 style="white-space:nowrap">Statement of Lessons Learned</h2>
<pre>This Lesson Learned is taken from a preliminary occurrence report. At the time of this writing the event was still under investigation.
On March 25, 2022, a Science and Engineering Associate worker discovered a liquid nitrogen dewar with its pressure gauge pegged at the maximum reading of 15 psig. The dewar was located in Hutch 2.2 of the Near Experimental Hall (B950). The associate immediately opened a manual vent valve on the dewar to allow gas phase nitrogen to release in order to lower the internal pressure. It took 4 minutes of venting before the pressure gauge reading began to drop below the 15 psig maximum reading. It was later determined the pressure relief valve (PRV) on the dewar was stuck closed and would not actuate the PRV with the valve's "pop-off' mechanism. The Area Manager was notified and ultimately determined that the dewar was depressurized and in a safe state. There were no impacts to environment, safety, or health.
</pre>
<h2 style="white-space:nowrap">Discussion of Activities</h2>
<pre>The dewar involved supplied liquid nitrogen (LN2) to two cryopumps located on an experimental setup. The dewar was initially fitted with a 5 psig PRV. Both dewar and PRV were obtained from a reputable vendor.
After the dewar was installed staff determined that the LN2 was not adequately transferring from the dewar to the cryo systems to meet the needs of the experimental equipment. The vendor was consulted and approved changing the working pressure of the system from 5 psig to 7 psig.
On the afternoon of March 24, 2022, the associate replaced the 5 psig PRV with a 7 psig PRV obtained from the vendor. No problems were noted with the system for the rest of that day.
On March 25, 2022, late in the afternoon, the associate discovered that the gauge installed near the PRV was "pegged" at the maximum reading of 15 psig, which was well above the pressure at which the 7 psig PRV should have actuated. The associate immediately opened the manual vent valve to release gas phase nitrogen to lower the dewar's internal pressure. The associate also tried, but was unable, to open the "pop-off' mechanism of the PRV.
</pre>
<h2 style="white-space:nowrap">Analysis</h2>
<pre>No operational checks were performed (or considered required) to verify the operability of the newly installed 7 psig PRV.
It is estimated that the dewar could potentially have been in an over-pressurized condition for a maximum of approximately 18-24 hours before the problem was discovered.
It was determined that during replacement the 7 psig PRV was tightened with a wrench causing deformation of the PRV threaded pipe body as it threaded into the receiving pipe fitting. The clearance between the movable, internal poppet assembly and the pipe body was very small; and the deformation was enough to lock the spring-loaded poppet mechanism into the closed position.
Follow up review showed that
1. There was no secondary mechanism on the dewar to relieve pressure (for example, a burst disk).
2. The dewar had no markings or stamps indicating maximum pressure rating or associated standards.
</pre>
<h2 style="white-space:nowrap">Recommended Actions</h2>
<pre>1. The dewar was secured in a safe state and will be permanently taken out of service.
2. An Extent of Condition review is to be performed on all other dewar system configurations to verify that
a. Redundant, appropriately rated pressure relief devices are in place,
b. dewars/vessels are properly marked with pressure ratings and standards,
c. There is a process to periodically check the readings of dewar system pressures.
3. An evaluation will be performed on existing processes to ensure adequate design, procurement, installation, and operation of pressure systems.
4. Training modules, dealing with pressure systems, will be re-evaluated to ensure content is adequate and appropriate.
</pre>
<h2 style="white-space:nowrap">JLab Preventive Measures</h2>
<pre></pre>
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<h2>Comments</h2>
<h5 style="white-space:nowrap">4/7/2022 8:09:44 AM by Bailey, Mary Jo</h5>
<pre>Submitted to those current in:
SAF130A: Pressure Systems Safety Awareness
SAF130B: Pressure Systems Safety Design Authority
SAF130kd: PRESSURE SYSTEMS QUALITY PROCEDURE
SAF130AU: Pressure Systems Safety Awareness for Users
SAF130C: Pressure Systems Owner Training</pre>
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</td>
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<div class="yui-u" id="lesson_info">
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<legend>Summary</legend>
<table>
<tr class="row">
<td class="label" nowrap>Lesson ID:</td>
<td class="dataval">1173</td>
</tr>
<tr class="row">
<td class="label" nowrap>Status:</td>
<td class="dataval">OK</td>
</tr>
<tr class="row">
<td class="label" nowrap>Doc ID:</td>
<td class="dataval">2022-JLAB-1173</td>
</tr>
<tr class="row">
<td class="label" nowrap>Priority:</td>
<td class="dataval">Caution</td>
</tr>
<tr class="row">
<td class="label" nowrap>Safety Related:</td>
<td class="dataval">NO</td>
</tr>
<tr class="row">
<td class="label" nowrap>Originator:</td>
<td class="dataval">Bailey, Mary Jo</td>
</tr>
<tr class="row">
<td class="label" nowrap>Issued:</td>
<td class="dataval">4/6/2022 3:03:58 PM</td>
</tr>
<tr class="row">
<td class="label" nowrap>Approved By:</td>
<td class="dataval">Bailey, Mary Jo</td>
</tr>
<tr class="row">
<td class="label" nowrap>Approved On:</td>
<td class="dataval">4/7/2022 8:09:44 AM</td>
</tr>
<tr class="row">
<td class="label">Source:</td>
<td class="dataval">
DOECRD
</td>
</tr>
<tr class="row">
<td class="label" nowrap>Location:</td>
<td class="dataval">SLAC</td>
</tr>
<tr class="row">
<td class="label" nowrap>Cost Savings:</td>
<td class="dataval"></td>
</tr>
<tr class="row">
<td class="label" nowrap>Contact:</td>
<td class="dataval">Marc Clay, SLAC Director Mission Assurance, (650) 926-2086 </td>
</tr>
<tr class="row">
<td class="label" nowrap>Queued Emails:</td>
<td class="dataval">412</td>
</tr>
<tr class="row">
<td class="label" nowrap>Sent Emails:</td>
<td class="dataval">0</td>
</tr>
<tr class="row">
<td class="label" nowrap>Viewings:</td>
<td class="dataval">2 times</td>
</tr>
</table>
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<legend>Attachments</legend>
<a name="attachments"></a>
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<li><a target="_blank" href="https://misportal.jlab.org/ll/downloadAttachment?attachmentId=6386">ORPS-SLAC Pressure Vessel.pdf</a></li>
</ul>
<hr>
</fieldset>
<fieldset>
<legend>Hazard Issues</legend>
<ul class="lesson_attribute_listing">
<li>Cryogenic Material - Gas or Liquid</li>
<li>Gas Cylinders</li>
<li>Pressure Systems</li>
<li>Pressurized Tanks, Containers, and Vacuum Vessels</li>
</ul>
</fieldset>
<fieldset>
<legend>Skills</legend>
<ul class="lesson_attribute_listing">
<li>SAF130A: Pressure Systems Safety Awareness</li>
<li>SAF130B: Pressure Systems Safety Design Authority</li>
<li>SAF130kd: PRESSURE SYSTEMS QUALITY PROCEDURE</li>
<li>SAF130AU: Pressure Systems Safety Awareness for Users</li>
<li>SAF130C: Pressure Systems Owner Training</li>
</ul>
</fieldset>
<fieldset>
<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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