[Dsg-ltcc] LTCC gas system

[David Anderson]

As Marc discovered, the problem was the set point was at 0 for sector 1.
There was an Ethernet cable that was not seated totally and when it was re-seated the "MFC" lost it's set point data and reset to zero.

Thanks Marc...
David 

----- Original Message -----
From: "George Jacobs" <jacobsg at jlab.org>
To: "David Anderson" <dla at jlab.org>, "Brian Eng" <beng at jlab.org>
Cc: "Douglas Tilles" <tilles at jlab.org>, "Bob Miller" <rmiller at jlab.org>, "Marc McMullen" <mcmullen at jlab.org>, "dsg-ltcc" <dsg-ltcc at jlab.org>
Sent: Wednesday, December 7, 2016 9:13:16 AM
Subject: Re: [Dsg-ltcc] LTCC gas system

OK, I will explain how the controls are working without the PID pressure control system installed. This info is also included in the operators manual and is the same as it was during CLAS 6 ops. 

First of all, N2 gas flows from the N2 manifold and supplies the MFC. The MFC will try to flow at the setpoint unless the gas supply solenoid safety valve is closed. 

The gas supply solenoid safety valve closes when pressure in the detector reaches 2.0 inches wc. This is an active protection to prevent window failure. This is active until the pressure decreases to 1.9 inches water column ("wc), due to the programmed 0.100"wc deadband. So, gas will not flow if the pressure does not decrease enough to reset the relay and open the valve. 

So, how do you flow gas to leak check if the gas pressure is too high? You must first lower the pressure in the sector you are checking. The easiest and most direct method to do this is to remove the 1" cap from the exhaust manifold and open the exhaust valve to lower pressure for the sector you want to flow gas to. Another method is to remove one of the 1" lines from that sector on the LTCC valve panel. Once the pressure is lower, the solenoid relay will reset and you can once again flow gas. Please note that if you do not shut the valve, pressure will decrease to 0.000"wc. 

The pressure protection bubblers are a passive mode of protection. Currently, not all bubblers are set at the proper oil height to bubble at 2.5"wc. Some currently bubble at 2.0"wc . This task is on the to do list along with several others to be completed during the KPP setup. 

George 

On 12/7/2016 8:17 AM, David Anderson wrote: 



Gentlemen,
 For some reason I have lost all flow to sector 1, can I get some assistance with this?
I am still tracing down leaks in the system and can't troubleshoot with zero flow available.
Also, can we verify the flow rates/set points for the other sectors? 
There are several bubblers that are venting due to some variations in the set points and in the bubbler levels.

Thanks,
David  

----- Original Message -----
From: "David Anderson" <dla at jlab.org> To: "Brian Eng" <beng at jlab.org> Cc: "Douglas Tilles" <tilles at jlab.org> , "Bob Miller" <rmiller at jlab.org> , "George Jacobs" <jacobsg at jlab.org> , "Marc McMullen" <mcmullen at jlab.org> Sent: Monday, December 5, 2016 9:04:11 AM
Subject: Re: [Dsg-ltcc] LTCC gas system

OK guys I found some 1" line and tied the supply and return together at sector 6.
It appears the gas circuit is leak free and the #6 chamber is leaking.
I am planning to leak check that chamber by pressurizing and injecting 134a so I can leak check just the chamber as soon as I am able to. 
Due to drift chamber work ongoing getting manlift time to do so is difficult.
Also, as George pointed out the bubbler levels need to be tweaked as well.

Thanks,
David

----- Original Message -----
From: "David Anderson" <dla at jlab.org> To: "Brian Eng" <beng at jlab.org> Cc: "dsg-ltcc" <dsg-ltcc at jlab.org> , "Douglas Tilles" <tilles at jlab.org> , "Bob Miller" <rmiller at jlab.org> Sent: Monday, December 5, 2016 6:47:56 AM
Subject: Re: [Dsg-ltcc] LTCC gas system

Ok thanks Brian, leak checking will continue this morning.
George and I were discussing Friday about isolating the gas circuit from the chambers.
By connecting the supply and return together at the chamber I can quickly tell if the leak is in the gas circuit of the chamber itself.
That may save a lot of time....I'll need a 12' section of 1" tubing that terminates with a male fitting on each end.
Any help rounding that up would be helpful.

Thanks,
David 

----- Original Message -----
From: "Brian Eng" <beng at jlab.org> To: dsg-ltcc at jlab.org Cc: dla at jlab.org Sent: Friday, December 2, 2016 4:59:33 PM
Subject: Re: [Dsg-ltcc] LTCC gas system

So I finally saw the S4 flow turn on for the first time; also S1 has turned on as well so it is still leaking, albeit much improved. I still haven't seen S5 turn on yet.

So currently the LTCC leak rates look like the following (from worst [biggest leak] to best):

S2 > S6 > S3 > S1 > S4 > S5

--
Brian Eng
Detector Support Group
757-269-6018 

BQ_BEGIN

On Dec 2, 2016, at 2:51 PM, Brian Eng <beng at jlab.org> wrote:

Hi David,

All the flows were reduced to 0.5 LPM except for S2 & S6 (5 LPM & 3 LPM respectively). Those were set to ~1 LPM higher than when the flow as on 100% of the time, so figure the leak rate is somewhere between those numbers.

The leak on S1 is much improved if not completely fixed as I haven't seen the flow kick on recently.

S3 still has a leak as I see the flow (at 0.5 LPM) turn on periodically. 



BQ_END

-- 
George Jacobs
Jefferson Lab (TJNAF)
STE 12
12000 Jefferson Ave.
Newport News, VA 23606

(office) 757-269-7115

(cell)   757-876-0480

(email) jacobsg at jlab.org (website) https://userweb.jlab.org/~jacobsg