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<div class="moz-cite-prefix">Greetings<br>
<br>
There are two issues with SHMS dipole ( and other shms magnets)
that we have identified that we can certainly address now.<br>
<br>
First :<br>
<br>
The warm return valve fast open settings were just too
conservative. Too slow and not enough valve stroke to be
effective.<br>
We choose these settings to try to minimize system disruptions.<br>
We will revisit and revise.<br>
<br>
Second:<br>
<br>
The lead flow interlocks are just way too sensitive.<br>
All the Hall C magnets enjoy having burn out resistant current
leads and we are not taking advantage of this fact.<br>
Lead flow interlocks really should be on slow discharge instead of
fast discharge and the thresholds should be reexamined and
adjusted for more transient tolerance.<br>
<br>
The final problem that needs some testing is the function of the
dipole mechanical relief valve.<br>
This is the only mechanical relief on SHMS to ever open ( just
once) during magnet training.<br>
It alone enjoys a one time demonstration that it can limit the
pressure at 4 atm.<br>
There is nothing in the pressure rise curve from yesterday to
suggest that the pressure rise was too fast or conditions too
severe for the mechanical relief have been able to handle it.<br>
Indeed, the warm return valve should have been able to cope.<br>
The event yesterday was a "normal" fast dump based on temperature
and pressure profiles.<br>
The pressure curve looks like the mechanical valve did not open.<br>
The valve was warm and dry when we entered the hall while the
rupture disc and its line were heavily frosted and still venting.<br>
We did find evidence in Hall C that the mechanical valve may have
opened even though there is no evidence in the pressure curve that
was recorded or its temperature or appearance.<br>
<br>
I would like to remove the valve and test its function as soon as
possible.<br>
<br>
WE started a very slow ~ 1 gm/sec purge using He gas at about 240
K last night back thru the warm return to try to measure
contamination in the dipole.<br>
The dipole is 35-40 degrees and very slowly warming.<br>
The magnet exhaust temperature is about 80K in the dipole warm
return line so if we have significant N2 contamination it should
show up unless it is too dilute to measure.<br>
We will need a Hall access today to trouble shoot the warm up
system.<br>
We could not get LN2 into the Cool down/warm up system after 12
hours.<br>
That is why the flow thru the dipole was kept very small.<br>
<br>
Cheers<br>
<br>
<br>
Paul Brindza<br>
<br>
<br>
On 12/12/2017 3:10 AM, Rolf Ent wrote:<br>
</div>
<blockquote type="cite"
cite="mid:1017571458.6062009.1513066215544.JavaMail.zimbra@jlab.org">
<div style="font-family: arial, helvetica, sans-serif; font-size:
12pt; color: #000000">
<div>Hi Steve,<br>
</div>
<div><br data-mce-bogus="1">
</div>
<div>Seems the issue is really why both the warm return and
primary relief
<div style="" data-mce-style="">did not act as supposed at
this fast discharge, and the pressure in the</div>
<div style="" data-mce-style="">magnet kept building towards a
rupture disk doing its job.<br style="" data-mce-style="">
</div>
<div style="" data-mce-style=""><br data-mce-bogus="1">
</div>
<div style="" data-mce-style="">Was good that we were only at
relatively low SHMS momentum settings,<br data-mce-bogus="1">
</div>
<div style="" data-mce-style="">so not much power stored in
the system.<br data-mce-bogus="1">
</div>
<div style="" data-mce-style=""><br data-mce-bogus="1">
</div>
<div style="" data-mce-style="">Good luck!<br
data-mce-bogus="1">
</div>
<br data-mce-bogus="1">
</div>
<div>Best regards, Rolf<br>
</div>
<div><br data-mce-bogus="1">
</div>
<hr id="zwchr" data-marker="__DIVIDER__">
<div data-marker="__HEADERS__"><b>From: </b>"Steve Lassiter"
<a class="moz-txt-link-rfc2396E" href="mailto:lassiter@jlab.org"><lassiter@jlab.org></a><br>
<b>To: </b>"Dave Kashy" <a class="moz-txt-link-rfc2396E" href="mailto:kashy@jlab.org"><kashy@jlab.org></a><br>
<b>Cc: </b>"Cryo" <a class="moz-txt-link-rfc2396E" href="mailto:esr-users@jlab.org"><esr-users@jlab.org></a>, "Thia Keppel"
<a class="moz-txt-link-rfc2396E" href="mailto:keppel@jlab.org"><keppel@jlab.org></a>, "Rolf Ent" <a class="moz-txt-link-rfc2396E" href="mailto:ent@jlab.org"><ent@jlab.org></a>,
"Javier Gomez" <a class="moz-txt-link-rfc2396E" href="mailto:gomez@jlab.org"><gomez@jlab.org></a>, <a class="moz-txt-link-abbreviated" href="mailto:cperry@jlab.org">cperry@jlab.org</a><br>
<b>Sent: </b>Monday, December 11, 2017 9:26:43 PM<br>
<b>Subject: </b>Hall C dipole shms magnet<br>
</div>
<br>
<div data-marker="__QUOTED_TEXT__">Hi<br>
<br>
The Hall C SHMS dipole magnet tripped off this afternoon at
about 4 PM.<br>
The dipole trip caused the rest of the SHMS magnets to trip
one after the other probably due to lead flow interlocks.<br>
<br>
The dipole on line data evidence shows that this was a normal
fast discharge.<br>
A fast discharge of this magnet causes some coil heating due
to eddy currents and this results in pressure and temperature
rise in the coil.<br>
Helium is usually vented by opening the warm return to keep
Helium out of Hall C.<br>
The warm return did not open fast enough and the pressure rose
in the magnet reaching finally 5 atm.<br>
The primary relief appears not to have opened at all or if it
did open, it did not open far enough or long enough to limit
the pressure.<br>
The rupture disc worked as expected and vented the magnet and
limited the pressure to 5 Atm.<br>
When we entered the hall and inspected the SHMS dipole magnet
the rupture disc was heavily frosted and still venting at a
low rate while the mechanical relief valve was warm to the
touch and dry.<br>
<br>
The SHMS dipole was completely isolated and the rupture disc
replaced.<br>
We have set up a low rate ie. few grams per sec. ~ 80 K Helium
purge thru the SHMS dipole to measure contamination levels
overnight.<br>
<br>
Cheers<br>
<br>
Paul<br>
</div>
</div>
<br>
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