[Hallb-engineering] Engineering Meeting Tomorrow -- Apr. 20

Dave Kashy kashy at jlab.org
Fri Apr 20 07:14:19 EDT 2012

When I setup pid loops in epics one critical parameter is the valve minimum position
For liquid levels I always set it up so the flow is just enough to keep the u-tube etc cold.

So even on a loss of signal the u-tube maintains flow. The level will slowly fall but this will give some time to respond and allow much easier and smoother re-establishment of operation

I was not asked to look at the controls but suggest that someone implement this change.

There.may be more to it and I can go over it with someone if they call me on my cell phone 

Sent from my iPhone

On Apr 19, 2012, at 2:09 PM, Saptarshi Mandal <mandal at jlab.org> wrote:

> Hi All,
> We will have an engineering meeting at the regular time tomorrow. People familiar with the control systems used in the hall should be present. Please read the email from Andy below.
> Saptarshi
> -------- Original Message --------
> Subject: Eng mtg tomorrow-re epics failure and IBC magnet quench
> Date: Thu, 19 Apr 2012 12:31:03 -0400
> From: A.M.  Sandorfi<sandorfi at jlab.org>
> To:<miller at jlab.org>
> CC: Krister Bruhwel<bruhwel at jlab.org>, burkert<burkert at jlab.org>,
>    David Kashy<kashy at jlab.org>, Christopher Bass<cbass at jlab.org>,
>     "mlowry at jlab.org"  <mlowry at jlab.org>
> Hi Bob,
> I gather Dave is away tomorrow and in such circumstances the Engineering
> meeting is often cancelled. Volker has asked that we hold at least a
> mini-meeting, particularly with the people familiar with the control systems
> used in the hall, to discuss what can be done to avoid another event like
> last night when the epics signals froze and the helium supply was cut to the
> IBC. A brief history of last night's event is below.
> I've copied Krister; please pass this on to whomever is appropriate.
> Thanks,...Andy
> _______________
>  at about 17:25 EPICS communications stopped;
> - epics alarm on alarm handler eventually went off, but probably not until
> epics came back.
> - the supply valve on the buffer dewar, EV8215, regulates LHe flow to
> the IBC by looking at the liquid level in the cryostat. The last good value
> read by epics happened to be high, so it began to close EV8215. Since the
> level value remained constant, it continued to close until 18:45 when epics
> signals returned.
> - while the supply valve was closing, the level in the IBC LHe bath was
> dropping, although the apparent epics value was a flat line at the last
> 17:25 value.
> - at 18:45 epics signals came alive again, the IBC LHe bath level
> registered only 38%, and the EV8215 valve immediately opened. Since the
> transfer line from the buffer dewar to the IBC had by now warmed, the LHe
> flow from the opening of EV8215 boiled in the transfer line and the
> expanding gas blew the IBC bath level down further, reaching 30% at 18:58.
> - when epics came alive, the nose temperature was 5K and rising.
> - by this time the solenoid magnet in the IBC nose, which was at 0.9 tesla
> and 46 amps, was completely uncovered and no longer cooled. This caused a
> quench, at about 18:55.
> - mix1 =>  spiked to about 3 K
> - polarizations dropped by about 40% !
> <mandal.vcf>
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