[Dsg-rich] MVT exhaust fan in EEL 124

Wed Oct 18 15:15:41 EDT 2017

hello everyone, 
in my opinion, fans will not help much. 
further, it is going to be a bear to put it together. 

    1. the length of the tubing has to be increased dramatically to exit the air beyond the FTOF 
    2. the fan has to be located somewhere. 
    3. the whole system has be be wired and installed in time. 

this is a "no-can-do" for DSG, as DSG does not have the manpower or the time. 
perhaps some one else (or group) can procure the fans and install it in time. 

my suggestions for the interim are: 

    1. redo the cabling so that it does not block the air-flow apertures. 
        1. measure the temperatures. (my guess is, it will be good. 250 watts is of the order of a powerful light) bulb. FPGAs typically work up to 85 C, no sweat! 
    2. increase the volume exchange of air, 
        1. by increasing the flow (flow can be increased to ~1000 l/m (500l/m per tube) 
        2. by increasing the size of the of the holes from 2 mm O.D. to 5 mm O.D. 
    3. if still unsatisfactory add a chiller (dew point for dry air is 70 C) 

amrit 

From: "Valery Kubarovsky" <vpk at jlab.org> 
To: "George Jacobs" <jacobsg at jlab.org> 
Cc: "dsg-rich" <dsg-rich at jlab.org> 
Sent: Wednesday, October 18, 2017 12:28:33 PM 
Subject: Re: [Dsg-rich] MVT exhaust fan in EEL 124 

Hi George, 

I want to notice that our electronic panel is not gas tight at all and has 6 exhaust pipes in addition. It is not so easy to significantly increase the pressure inside. Nevertheless we are going to test what happens with the pressure system in the clean room 

- with 6 pipes but with/without fans connected 
- with fans ON/OFF 

When we tested the cooling system we did not notice any increase pressure in the main Cherenkov volume (with N2 gas). 

The cooling of the epanel is in a critical condition for a moment. It is the reason that we consider fans to help keeping front-end electronic at safe temperature. Several groups in CLAS12 are using similar technics (Forward tagger, SVT). 

Regards, 
Valery 

From: "George Jacobs" <jacobsg at jlab.org> 
To: "Valery Kubarovsky" <vpk at jlab.org> 
Cc: "Tyler Lemon" <tlemon at jlab.org>, "dsg-rich" <dsg-rich at jlab.org> 
Sent: Wednesday, October 18, 2017 9:36:06 AM 
Subject: Re: [Dsg-rich] MVT exhaust fan in EEL 124 

BQ_BEGIN
Hi Valery, 

Have you looked at this scenario? Fan stops running during run. This would result in an increased pressure in the electronics box. The increased pressure increases the leak rate of cooling air into the RICH detector volume. Depending on the severity of the leak, pressure in the RICH gas volume may increase until the cooling system is turned off. The O2 concentration will increase until the cooling flow stops. The O2 contamination then absorbs the light until it is removed via N2 purge. 

There is, of course, a worse case scenario, depending on how high the pressure in the electronics box goes. Since final pressure is unknown, it may or may not be a realistic failure mode. 

So, perhaps a good question to answer would be; What are the advantages of using the fan vs consequences of fan failure. Is adding a fan a good solution to your problem or does it potentially create another problem? 

George 

On 10/17/2017 6:25 PM, Valery Kubarovsky wrote: 

BQ_BEGIN

Hi George, 
Thank you for looking to all these issues. I agree that we have to determine the exact location of these fans in the Hall-B and determine the change in the length of the exhaust tubes. 

And sure we will test the exhaust line pressure when the fans will be on and off. 

In any case the cRio interlock will monitor the temperature inside the electronic panel and will shut down the detecter in case of accident with exhaust fans. 

Thank you again, 
Valery 

BQ_BEGIN
From: "George Jacobs" <jacobsg at jlab.org> 
To: "Valery Kubarovsky" <vpk at jlab.org> 
Cc: "Tyler Lemon" <tlemon at jlab.org> , "dsg-rich" <dsg-rich at jlab.org> 
Sent: Tuesday, October 17, 2017 5:31:52 PM 
Subject: Re: [Dsg-rich] MVT exhaust fan in EEL 124 

BQ_END

BQ_BEGIN
Hi Valery, 

Have you taken into account the length of the hose or tubing that must be added in order to attach the fan to the detector? If the overall line length must be doubled or tripled to reach the fan, the flow restriction from the tubing will also double or triple. 

If the fan stops running, the fan blades will restrict the gas flow at some level. Flowing gas has velocity and momentum, fan blades will require the gas change direction, loosing momentum and velocity. 

So, there will be additional flow restriction and it will increase the cooling air pressure in the electronics box in the case of fan failure. The added restriction due to the additional lengths of tubing or hose can be calculated. The additional restriction created by the fan blades can be physically tested by turning off the fan and monitoring the change in the exhaust line pressure. 

George 

On 10/17/2017 4:27 PM, Valery Kubarovsky wrote: 

BQ_BEGIN

George, 

First we want to test it at the cleaning room to measure the effectiveness of these fans. 
And later on we will use it in the hall. 

The design of the cooling system was done without exhaust fans. In case of the power failure nothing will happen with the pressure system. The fan has much bigger diameter than our tubes and by this reason will not block the air flow. It is completely open. 

Regards, 
Valery 

BQ_BEGIN
From: "George Jacobs" <jacobsg at jlab.org> 
To: "Tyler Lemon" <tlemon at jlab.org> , "dsg-rich" <dsg-rich at jlab.org> 
Sent: Tuesday, October 17, 2017 1:20:12 PM 
Subject: Re: [Dsg-rich] MVT exhaust fan in EEL 124 

BQ_END

BQ_BEGIN
Would this setup be used only in the clean room for testing or would this be for use in the hall during normal operations? 

If the answer is the latter, what would happen to air cooling flow and pressure if the power to the fans tripped off during a run? 

George 

On 10/17/2017 11:56 AM, Tyler Lemon wrote: 

BQ_BEGIN

Hello Valery, 

Attached is the photo of the MVT exhaust fan in use in EEL 124. 

Would there be a possibility that RICH would use similar fans to pull out the hot air from the electronic panel? 

Best regards, 
Tyler 

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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 

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Dsg-rich mailing list 
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BQ_END

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 

BQ_END

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 

BQ_END

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