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Hi Mauri,<br>
<br>
FYI, 65 sccm is the minimum flow rate for the MFC. So, further
reduction of flow can only be obtained by using the supply solenoid
valve to limit detector pressure. Currently, the solenoid valve is
programmed to shut, isolate the gas supply, at 2.020"wc. This should
minimize gas loss due to overfilling the detector. Once we see how
the detector works with beam, this value may be further optimized to
insure proper detector operation. The dead band is set at 0.020"wc
for now, we may need to further optimize this value. This is an
iterative process. The strip charts will illustrate how it
functions.<br>
<br>
The theoretical gas usage obtained from the N2 testing does not take
into account losses due to atmospheric pressure changes. When the
ambient pressure drops outside the LTCC, some gas will bubble out
due to the increase in differential pressure. This gas loss is in
addition to the 20 liter per day leak rate the detector volume had
with N2 gas.<br>
<br>
When the ambient pressure outside of the LTCC increases, the
differential pressure decreases. Gas flows into the detector volume
to make up for the gas lost due to leakage and what was lost when
the ambient pressure goes low. We are currently in this cycle. See
below strip chart;<br>
<br>
Please refer to the strip chart below.<br>
<br>
Blue Line - Output of Pressure Transducer located at the detector
gas inlet, this is located at the lowest point of the detector
volume. <br>
Brown Line - Output of the Pressure transducer connected to the
pressure protection bubbler. (was the S4 transducer)<br>
Green Line - Ambient Pressure in Hall B<br>
<br>
The 2 blue step function lines resulted from when I programmed the
solenoid setpoint and dead band on the omega controller.<br>
<br>
One can see from the below strip chart where the detector
differential pressure is limited to 2.1"wc by the bubblers. The
solenoid isolation valve is now set to limit the pressure increase
due to gas flow to 2.020"wc. This should be clearly visible on
future strip charts whether it is working as desired.<br>
<br>
As is indicated by the green line, ambient pressure is slowly
increasing. This results in a lower differential pressure indicated
by the blue and brown lines. The blue and brown lines, detector
differential pressure react to the changing ambient pressure and gas
flow. These strip charts are essential tools in the optimization
process.<br>
<br>
<br>
<img moz-do-not-send="false"
src="cid:part1.8396A644.C26CB543@jlab.org" alt="" height="1000"
width="1924"><br>
<br>
<br>
<br>
<div class="moz-cite-prefix">On 1/31/2018 9:13 AM, Maurizio Ungaro
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:1453741206.5404213.1517408010469.JavaMail.zimbra@jlab.org">
<pre wrap="">Hi Brian, George,
a 0.065 l / minute flow is still 93 liters / day, which is about 1 1KG / day. George please correct me if I'm wrong.
The expected losses may be less than that. I'm worried about forcing flow and losing gas this way.
Thanks,
Mauri
----- Original Message -----
From: <a class="moz-txt-link-abbreviated" href="mailto:beng@jlab.org">beng@jlab.org</a>
To: <a class="moz-txt-link-abbreviated" href="mailto:dsg-ltcc@jlab.org">dsg-ltcc@jlab.org</a>
Sent: Monday, January 29, 2018 1:30:04 PM
Subject: [Dsg-ltcc] [New Logentry] S5 Flow Rate
S5 Flow Rate
Lognumber 3523300 . Submitted by beng on Mon, 01/29/2018 - 13:28. Logbooks: HBLOG LTCC
References: 3523143 - Follow-up Re: Follow-up Re: Began filling LTCC S5 with C4F10 gas @ 0.500 slm
The flow has been reduced another 0.1 slm from 0.4 slm to 0.3 slm.
The plan is to reduce the flow every hour or so by 0.1 slm until we get to 0.1 slm (or the pressure starts to drop) and hold it there for the night.
If 0.1 slm holds the flow will be set to 0.065 slm, which is slightly above the minimum flow value of 0.063 slm that the MFC can control.
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</pre>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
George Jacobs
Jefferson Lab (TJNAF)
STE 12
12000 Jefferson Ave.
Newport News, VA 23606
(office) 757-269-7115
(cell) 757-876-0480
(email) <a class="moz-txt-link-abbreviated" href="mailto:jacobsg@jlab.org">jacobsg@jlab.org</a>
(website) <a class="moz-txt-link-freetext" href="https://userweb.jlab.org/~jacobsg">https://userweb.jlab.org/~jacobsg</a></pre>
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