[Dsg-rich] [Rich] rich air flow
Tyler Lemon
tlemon at jlab.org
Mon Oct 15 09:32:46 EDT 2018
Hello,
>From the compressor manual, the web interface Brian mentioned seems to give us the same information as if we were standing right in front of the compressor. There is a communication module that we could buy that would give us Modbus communication to the compressor. I will contact Atlas Copco to get a quote on the module and to see what other features and capabilities the communication module would give us.
In regards to Sandro's email, what he said is correct. The behavior of the pressure and airflows from October 11 to October 13 is what you see if you don't allow the buffer tank to build up pressure when starting the system. It could be that the ambient pressure change was great enough to force the buffer tank pressure below a value that allows steady operation. However, like Brian said, that is just a guess.
I do know we are running the compressor at it maximum capabilities. It's output pressure regulation is set to regulate between 104 psi and 113 psi. 113 psi is the maximum output pressure the compressor is capable of. A 9 psi differential is the the minimum recommended differential between high and low. Adjusting the airflow to a lower value that still maintains low enough temperatures may help the system run more stably. We would have to take the time to methodically lower the airflow and study the resulting temperature increase, though.
Best regards,
Tyler
From: "Tomassini Sandro" <sandro.tomassini at lnf.infn.it>
To: "Brian Eng" <beng at jlab.org>
Cc: "dsg-rich" <dsg-rich at jlab.org>, "Mirazita Marco" <marco.mirazita at lnf.infn.it>
Sent: Sunday, October 14, 2018 3:19:12 PM
Subject: Re: [Dsg-rich] [Rich] rich air flow
Hi all,
I remember the same behavior when we started the system the first time. In other words I try to explain: if the air flow rate is set to the nominal value (the gate valve is open) and the air tank is empty, when the compressor is switched on then the pressure vs time in the tank assumes exactly the same behavior you have posted so far and this behavior remains stable in time.
If the air flow rate to the rich is set to zero (gate valve is off), when the compressor is switched on and you wait until the pressure in the tank reaches the max value before opening the flow to the rich than the pressure behavior vs time is stable.
Why this behavior? I think there is an instability in the system that shows up when the tank pressure drops below a certain value. Someone should study the stability of the system (poles and zeros) to find out the limit parameters! I know it is not so easy!
Hope it is clear.
Sandro
Inviato da BlueMail
Il giorno 14 ott 2018, alle ore 19:16, Brian Eng < beng at jlab.org > ha scritto:
Unfortunately we don't currently have any way of independently monitoring the compressor status. From what I remember from initial testing the information that the web page contained was quite limited, but we should at least look again to see if it has when it is on/off. If not, maybe there is funding to get the communications module? I believe Tyler has already looked into that?
So it could just be that the compressor was on the whole time trying to build pressure vs cycling on/off. It wasn't just the pressure that wasn't cycling the flows were pretty flat too. In any event, we're all just making guesses at this point though.
I still think interlocking (and to a lesser extent the alarms) on the flows and especially the pressure when the temperatures are okay seems overly aggressive, especially with the values being so tight.
----- Original Message -----
BQ_BEGIN
From: "Valery Kubarovsky" <vpk at jlab.org>
To: "Brian Eng" <beng at jlab.org>
Cc: "Tyler Lemon" <tlemon at jlab.org>, rich at jlab.org, "dsg-rich" <dsg-rich at jlab.org>, "Marco Mirazita"
<Marco.Mirazita at lnf.infn.it>
Sent: Sunday, October 14, 2018 12:17:34 PM
Subject: Re: [Dsg-rich] [Rich] rich air flow
BQ_BEGIN
Brian,
I think that if you switch off the compressor the pressure will drop very
rapidly (several minutes) independently of ambient pressure. Take a look to the
pictures. It may be a problem with pressure sensor or something connected with
that.
vk
BQ_BEGIN
On Oct 14, 2018, at 12:05, Brian Eng <beng at jlab.org> wrote:
Valery,
It's actually the opposite, this cycling behavior is actually how it previously
used to look (see overview plot). The "flat" flow/pressure is a relatively new
phenomenon and it looks to be caused by the remnants of the hurricane coming
through; lower ambient pressure causes higher differential pressure in the
various gas volumes. Normally this shows up as the compressor cycling on/off
less (see pre storm plots). Since the drop was so large it manifested as not
even turning on.
The compressor used to get the tank to 120 psi, now it's only going to 110 psi,
which is why the bottom part of the "spike" is lower.
However, the flow is basically the same as it was before: this points to the
alarm and especially interlock values being to conservative or in many cases
counter-productive as they'll shut off the detector and could result in a junk
run prematurely.
Personally I would remove quite a few interlocks and loosen many of the alarms,
but that decision should come from the detector exports.
----- Original Message -----
BQ_BEGIN
From: "Valery Kubarovsky" <vpk at jlab.org>
To: "Tyler Lemon" <tlemon at jlab.org>
Cc: rich at jlab.org, "dsg-rich" <dsg-rich at jlab.org>, "Marco Mirazita"
<Marco.Mirazita at lnf.infn.it>
Sent: Sunday, October 14, 2018 11:02:15 AM
Subject: Re: [Dsg-rich] [Rich] rich air flow
BQ_END
BQ_BEGIN
Hi Tyler,
Look at zoom picture. Do you understand this behaviour?
I mean this sharp drop of the pressure.
Valery
From: "Tyler Lemon" <tlemon at jlab.org>
To: "Valery Kubarovsky" <vpk at jlab.org>
Cc: "Marco Mirazita" <Marco.Mirazita at lnf.infn.it>, rich at jlab.org, "dsg-rich"
<dsg-rich at jlab.org>
Sent: Sunday, October 14, 2018 10:28:51 AM
Subject: Re: [Rich] [Dsg-rich] rich air flow
Hi Valery,
I agree, the plot looks normal after 18:40 on October 13.
Attached is the same plot you shared, but with annotations showing the pressure
measurement any time the value looked to be under 40 psi. The lowest it seems
to have gotten was ~36 psi.
Also, the archiver doesn't ever show that the hardware interlock for the air
pressure ever tripped. It's low limit is set to 35 psi.
Best regards,
Tyler
From: "Valery Kubarovsky" <vpk at jlab.org>
To: "Tyler Lemon" <tlemon at jlab.org>
Cc: "Mirazita Marco" <Marco.Mirazita at lnf.infn.it>, rich at jlab.org, "dsg-rich"
<dsg-rich at jlab.org>
Sent: Sunday, October 14, 2018 10:15:03 AM
Subject: Re: [Rich] [Dsg-rich] rich air flow
Hi All,
I got several calls yesterday evening and today night from CLAS12 shift about
AIRPR1 alarm (currently minimum set to 35). See attached plot. I changed this
limit to 30 for a moment. The plot looks not normal before Oct.13 18:40 in my
view.
Regards,
Valery
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<post-storm.png>
<pre-storm.png>
<overview.png>
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