<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head>
<title>Jefferson Lab Lessons Learned : Print Lesson</title>
<base href='https://misportal.jlab.org/ll/'>
<!--[if IE]>
<style type="text/css">
#page_content input[type=checkbox], #page_content input[type=radio] {
background-color: transparent;
border: 0;
}
</style>
<![endif]-->
</head>
<body>
<div id="doc3" class="yui-t7">
<div class='round' id='pageMessages'>
<!-- -->
</div>
<div id="lesson" class="yui-gc">
<style type="text/css">
pre {
white-space: -moz-pre-wrap;
white-space: -pre-wrap;
white-space: -o-pre-wrap;
white-space: pre-wrap;
word-wrap: break-word;
overflow: hidden;
margin-left: 10px;
}
</style>
<div id="topbar">
<div id="lesson_title">
<table width="100%">
<tr>
<td><a href="https://misportal.jlab.org/ll/index.jsf?function=view&lessonId=829">Premature Failure of Electro-Mechanical Switches due to Inadequate Installation - Brookhaven National Laboratory (BNL)</a></td>
</tr>
</table>
</div>
</div>
<table width="100%">
<tr>
<td valign="top" width="100%">
<div id="maintextcol" class="yui-u first">
<h2 style="white-space:nowrap">Statement of Lessons Learned</h2>
<pre>For a copy of the original report, see Attachments on Lessons Learned page.
Two Personnel Protection System (PPS) door switches failed simultaneously.
</pre>
<h2 style="white-space:nowrap">Discussion of Activities</h2>
<pre>Door switches are used throughout the accelerator community to prevent access to areas with high ionizing radiation sources. Door switches are part of the PPS and are interlocked to the radiation source. Unauthorized access through a door during interlock periods interrupts the electron beam preventing accidental exposure of staff.
When switches are in the closed position, the monitoring system detects the door is closed and locked. During a “Search and Secure Procedure,” two adjacent door switches were found in the “closed” position when they actually could have been opened, undetected by the system. (See attached.)
(Note: The locks, and a second set of switches, remained fully active. The safety of staff was maintained at all times.)
Investigation of the event revealed that the installation of the switches was inadequate and resulted in improper strike angles and interferences, which ultimately caused damage to the switch bodies and resulted in the premature failure of the switches.
</pre>
<h2 style="white-space:nowrap">Analysis</h2>
<pre>A "5 Whys" analysis was performed to assess the cause of the failure:
Why would two PPS Switches fail simultaneously? Either (a) the door struck the leading edge of the limit switch-body causing the internal components to be damaged or (b) the door struck the switch lever-arm while the arm was at a near-zero strike angle with respect to the door, which caused the internal components to be damaged.
Why wasn’t a thorough review of the mechanical elements of the PPS Door/Gate Interlock System conducted by an experienced mechanical engineer?
Why wasn’t the participation of a mechanical engineer considered in the scope of resources required to design and implement the PPS Interlock system. The PPS interlock system is mostly electrical in nature. The mechanical interaction between the door/gate, limit switches and "Mag Lock" appear to be straight forward but in actuality, there are many things to consider that would normally be reviewed by a mechanical engineer.
Why doesn’t the PPS design and installation practice include a review by a cross-cutting team?
</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.
A mechanical assessment of the switch installation was performed. This was extended to all door and gate switches in use. Several weaknesses in the installation of switches were discovered and have since been corrected. Weaknesses included:
• Inconsistent installation.
• -Varying strike angles.
• Interference between the switch body and the face of the door.
The current Design Review Process was reviewed to ensure all systems are reviewed by an appropriate team of engineers and/or technical staff. Now all installations are to be reviewed by a mechanical engineer or other qualified person.
All switch installations are to be periodically inspected to ensure proper clearance and strike angles are maintained.
</pre>
</div>
<div id="comments_div">
<a name="comments"></a>
<h2>Comments</h2>
<h5 style="white-space:nowrap">6/16/2014 9:24:18 AM by Bailey, Mary Jo</h5>
<pre>Submitted to those with current training:
•SAF141: PERSONNEL SAFETY SYSTEMS OPERATOR (PSSO)
•SAF142: Certified PSS Sweep QA Observer
</pre>
</div>
</td>
<td valign="top">
<div class="yui-u">
<fieldset>
<legend>Summary</legend>
<table>
<tr class="row">
<td class="label" nowrap>Lesson ID:</td>
<td class="dataval">829</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">2014-JLAB-829</td>
</tr>
<tr class="row">
<td class="label" nowrap>Priority:</td>
<td class="dataval">Best Practice</td>
</tr>
<tr class="row">
<td class="label" nowrap>Safety Related:</td>
<td class="dataval">YES</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">6/16/2014 9:20:58 AM</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">6/16/2014 9:24:18 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">BNL</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">Robert J. Lee, (631) 344-7936, blee@bnl.gov</td>
</tr>
<tr class="row">
<td class="label" nowrap>Queued Emails:</td>
<td class="dataval">0</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">4 times</td>
</tr>
</table>
</fieldset>
<fieldset>
<legend>Attachments</legend>
<a name="attachments"></a>
<ul class="lesson_attribute_listing">
<li><a target="_blank" href="https://misportal.jlab.org/ll/downloadAttachment?attachmentId=3120">M:\wcd\LessonsLearned\DOEOEC\DOE Lessons Learned - PSS1 pic.jpg</a></li>
</ul>
</fieldset>
<fieldset>
<legend>Hazard Issues</legend>
<ul class="lesson_attribute_listing">
<li>Other: Reporting Personnel Safety Systems (PSS)</li>
</ul>
</fieldset>
<fieldset>
<legend>Skills</legend>
<ul class="lesson_attribute_listing">
<li>SAF141: PERSONNEL SAFETY SYSTEMS OPERATOR (PSSO)</li>
<li>SAF142: Certified PSS Sweep QA Observer</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>
</fieldset>
<!--
<fieldset>
<legend>Applicable Orgs</legend>
<ul class="lesson_attribute_listing">
</ul>
</fieldset>
-->
</div>
</td>
</tr>
</table>
<script language="javascript">
var commentTextarea = document.getElementById("commentForm:commentText");
if (commentTextarea){
var validationErrorFound = commentTextarea.parentNode.innerHTML.indexOf("Validation Error: Value is required.") > -1;
if (validationErrorFound){
// add hash if necessary
if (window.location.hash == null || window.location.hash == "" || window.location.hash == "#"){
window.location.hash = "#comments";
}
}
else {
//JSF likes to hold on to the values entered into the form...so blank them out
commentTextarea.value = "";
commentTextarea.form.elements["commentForm:commentType"].selectedIndex = 0;
var numStars = commentTextarea.form.elements["commentForm:stars"].length;
for (var ii=0; ii<numStars; ii++){
commentTextarea.form.elements["commentForm:stars"][ii].checked = false;
}
}
}
</script>
</script>
</div>
<br>
<br>
</div>
</body>
</html>