[Esr-users] Hall C SHMS high 4K return pressure investigation

[Steve Lassiter]

Hi Dave, 

Thank you for your work on the Anaconda He return high pressure investigation. Your ability to pull resources together in a short time and pro-active involvement was greatly appreciated in completing this task. 

Sincerely 
Steven 

----- Original Message -----

From: "Dave Kashy" <kashy at jlab.org> 
To: "Stephen A. Wood" <saw at jlab.org>, "Cynthia Keppel" <keppel at jlab.org> 
Cc: "esr-users" <esr-users at jlab.org>, "Jerry Nines" <jnines at jlab.org>, "Walter Kellner" <kellner at jlab.org>, "Larry Carraway" <larryc at jlab.org>, "Morgan Cook" <mcookiv at jlab.org> 
Sent: Friday, May 18, 2018 1:07:30 PM 
Subject: [Esr-users] Hall C SHMS high 4K return pressure investigation 

All, 
This week we completed the investigation of the Hall C SHMS high return pressure. A full report will follow, but I want to let you know what we found and I want to thank those who helped. 

The team included 
Eric Sun 
Steve Lassiter 
Walter Kellner 
Jerry Nines 
Larry Carraway 
Denny Insley 
Morgan Cook 
Me 

We took advantage of the warm up of the Hall and the loss of LN2 due to bad vacuums in the transferlines which allowed us to pull U-tubes while warm and at low pressure. 
We started out by pulling both the supply and return u-tubes of the "Anaconda" from the "A can" to "Can 1". 
We set up flow measuring hardware borrowed from Hall B and pressure measurment instruments from Halls B and C. 
We flow tested both 4K circuits of the Anaconda as well as a third U-tube (used for G Zero) using GN2 from K-bottles 
We measured the inside diameters of the the 4K U-tubes as deep as 8 ft from the end of the male bayonets. 
We purged the U-tubes, and reinstalled them this morning, to allow the SHMS to get its LN2 cooling re-established. 

Results: 
>From the flow tests: At the same pressure drop the SHMS supply passed approximately 15% more flow than the SHMS return. The G Zero passed the most at 130% of the SHMS return. This would seem to be an obvious choice to use the G Zero line. But, the G Zero line does not have a shield and is not cooled by the supply helium so the actual DP for normal operations (5K helium return) is not predicted to be better than the SHMS u-tube and the total heat load will be higher ( bad for ESR and everyone). Note: the G Zero U-tube was tried during the last run and found not to be any better. 

Eric and I did flow calculations and found that our calculations matched fairly well the measured pressure drops. Then we fine tuned our friction factors and spread sheets and changed the properties to helium and got results similar to that which was seen during SHMS operation. This proves that there was no plug, neither contamination or physical plug such as rag or other debris, in the return circuit. 

To be sure we understood the geometry we sucked in plastic spheres of 7/8", 3/4" and 5/8" from each end of the male bayonets of the anaconda. The 7/8" only went in ~3 ft, this is the length of the male bayonet inner line. The 3/4" went in ~6ft" this is where the first section of corrugated flex hose starts. The 5/8" diameter sphere went in over 7ft proving that the 3/4" ID flex hose as called out on the drawing was correct. I decided not to go further with the sphere and risk the retrieval line getting cut. This decision was based on knowing that the flows through the supply and return circuits had similar DP for the same flow rate and that the calculations showed that the supply should have a lower pressure drop which was confirmed by the previous days testing. 

So in summary the issue of high DP in the return line is due to geometry of the hardware. Calculations show that about 2/3 of the differential pressure is from the two sections of 3/4" ID hose. My recommendation is to replace both sections of 3/4" ID hose with sections of 1.25" diameter hose as time a budget allow. 

Thanks again to all who helped. 

Dave 
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