[Dsg-rtpc] Questions about the gas systems

Wed Jun 27 15:00:19 EDT 2018

Hi all, 

after Howard email, I've been checking the numbers running in the previous emails and the numbers in George's scheme. I checked the MKS GE50A data sheet and I found that this MFC can operate as low as 10 psid in the flow range indicated in the gas supply scheme (0-200 sccm). Please, find attached a screenshot of the data sheet. 

Perhaps I'm wrong due to my inexperience in these systems and I misinterpret some concepts.

Cheers

-Carlos

----- Original Message -----
From: "Howard Fenker" <hcf at jlab.org>
To: dsg-rtpc at jlab.org, "George Jacobs" <jacobsg at jlab.org>, "William Crahen" <wcrahen at jlab.org>
Cc: "Bob Miller" <rmiller at jlab.org>
Sent: Wednesday, June 27, 2018 12:36:41 PM
Subject: Re: [Dsg-rtpc] Questions about the gas systems

Carlos- 

If the MFC you have really requires 30 psi to operate, please consider purchasing 
new MFC's that work at a lower differential pressure. The MKS 1179 series controllers 
work as low as 10 psi (between the input and the output), for example. 

The reason for running at the lowest funtional pressure is to have a system 
pressure that remains below the 15psig limit for pressure-system exemption. 

Howard 

On 6/27/18 11:15 AM, George Jacobs wrote: 

Hi All, 

The 25 psi relief valve setpoint is too low. The MFC require 30 psi to operate. The 25 psi relief was chosen for use when the system used a rotometer. This was an earlier design. 

Please consider the 75 psi setpoint relief valve to be a place holder with a reasonable setpoint. You can choose any relief valve you prefer. 

The orifice selected is a standard precise orifice, O'Keefe Controls, we use these in many gas cylinder supply setups of this type. You can also consider it, a place holder and choose one of your own preference. 

There is a short write up I did on this system a couple weeks ago located on the jlab O: drive. I am out of the office today, perhaps Brian or Mark can send you a copy of it. 

George 

From: "William Crahen" <wcrahen at jlab.org> 
To: "Brian Eng" <beng at jlab.org> , dsg-rtpc at jlab.org 
Cc: "Bob Miller" <rmiller at jlab.org> 
Sent: Tuesday, June 26, 2018 5:24:43 PM 
Subject: Re: [Dsg-rtpc] Questions about the gas systems 

So this valve has a minimum crack pressure of 25 psig, which would be 
okay, it just means that all piping going from the gas shed to the mass 
flow controller must be per ASME B31.3, or perhaps B31.9 (We used 31.9 
for the hall D FDC, and Tim Whitlatch is on the pressure system 
committee, so I don't see a reason we can't use for the CO2/Helium 
stuff). I see what appears to be an orifice disc on the high pressure 
side of the supply regulator-do we have the cut sheet on that? that is 
typically the design limiter for un-controlled flow- you assume the 
regulator fails at full gas bottle pressure (3500 psi?) and calculate 
what flow can occur- that sizes your relief valve. 

On 6/26/2018 4:47 PM, Brian Eng wrote: 
> Not sure if it's on hand or not, but here's some information on that ASME relief valve from their site: http://www.cdivalve.com/products/valves/air-compressor-valves/asme-code-safety-valves 
> 
> Specs: http://www.cdivalve.com/images/uploads/ST.png 
> Drawing: http://www.cdivalve.com/files/upload/23/st25.pdf 
> Flow Chart: http://www.cdivalve.com/files/upload/23/flow_charts_st.pdf 
> 
> Hope that helps. 
> 
>> On Jun 26, 2018, at 4:34 PM, Carlos Ayerbe <gayoso at jlab.org> wrote: 
>> 
>> FYI 
>> 
>> Goerge already has it. 
>> 
>> -Carlos 
>> 
>> ----- Forwarded Message ----- 
>> From: "William Crahen" <wcrahen at jlab.org> 
>> To: "George Jacobs" <jacobsg at jlab.org> , "Carlos Ayerbe Gayoso" <gayoso at jlab.org> 
>> Cc: "Bob Miller" <rmiller at jlab.org> 
>> Sent: Tuesday, June 26, 2018 4:30:48 PM 
>> Subject: Questions about the gas systems 
>> 
>> Hi guys- Carlos provided me with some documentation on the parts you are 
>> planning to use- I see a parts list showing a relief valve RV1 = STLMO 
>> model ST25-1/4", set to crack at 75 psi, presumably accommodating 74 
>> scfm at some higher pressure. Do you plan to use this? If so, I need to 
>> see a cut sheet on it with flow curves, etc. Alternately, is this 
>> replaced by the CONRADER valve I find elsewhere in this documentation? 

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-- 
George Jacobs 
Physics Detector Support Group 
Jefferson Lab 
12000 Jefferson Ave. 
STE 12 
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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