<html><body><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" <lassiter@jlab.org><br><b>To: </b>"Dave Kashy" <kashy@jlab.org><br><b>Cc: </b>"Cryo" <esr-users@jlab.org>, "Thia Keppel" <keppel@jlab.org>, "Rolf Ent" <ent@jlab.org>, "Javier Gomez" <gomez@jlab.org>, cperry@jlab.org<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></body></html>