Re: about surge

tsk tsk.

math sleight of hand steve. U switched from local atmos pressure in absolute to saying it was the gauge reading (barg)

  "Gauge pressure is defined as Pabs - Patm = 0bara - 2bar(a)     not= -2barg. not QED"
ie your Patm is not -2barg.

your gauge pressure is PAbs- Patm = 0bara- 2bara (as defined in your first line>ie. not 0barg-2barg)
so the gauge pressure on the tube would be -2bara = -1barg (i'm in NA and years since i used bar , but i recall1 bar absolute is 101kpa=14.7psia. and 1bar gauge is 14.7psig (relative to atmos ie on top of earths 14.7pisa
so (-2bara not -2barg). ie you wouldnt read this on a gauge.

so the gauge would read -1bar (ie complete vacuum) (relative to the ambient bell pressure) which is possible as you say with a vacuum gauge. the riddle missed the sealed ends of the pipe which we assumed was what you meant.

Practical problem - since a normal gauge measures relative to the surroundings you would have to be sure the gauge was able/calibrated to handle the bell submersed (environmental ambient pressure -32feet ). do i sense a troll?
.
----- Original Message -----
From: "Steve McKenzie" <mechproj@xtra.co.nz> To: <PipingDesign@yahoogroups.com> Sent: Tuesday, January 18, 2005 7:32 PM
Subject: RE: [PipingDesign] about surge

>
> Hi Erik
>
> Local air atmospheric pressure inside air bell is P atm = 1 barg + 1
> bara = 2 bara
> .
> Pressure inside pipe is P abs = 0 bara.
>
> Gauge pressure is defined as Pabs - Patm = 0 - 2 = -2barg. QED. However
> you will probably have to use a DP gauge to measure.
>
> I think most engineers can design a pipe (or a bell) which will stand a
> vacuum by designing to stay below the critical buckling pressure.
>
> Either run the pipe through the sides of the air bell (sealed at the
> intersections) or run the pipe up into and down out of the air bell, or
> have the pipe sealed at both ends.
>
> We engineers can do anything!
>
> Cheers
>
> Steve
>
>
>
> -----Original Message-----
> From: Erik Scheir [mailto:erik.scheir@pandora.be]
> Sent: Tuesday, January 18, 2005 8:12 AM
> To: <a href="/group/PipingDesign/post?postID=VxSETeG2gvC0nAqn4VTS0z0r-yKqVuFm-5DpGrdZ4wSqv6kTjK0DodnV7cZYlQuNfFYBw__1ywbdaRsqaxhLOJrxkfo">PipingDesign@yahoogroups.com</a>
> Subject: RE: [PipingDesign] about surge
>
>
>
> If the pressure above the waterlevel is atmospheric, then the pressure
> 10.3 m below the waterlevel is 1 barg (gauge) and an air bel with a 100%
> vacuum will collapse.
>
> How can you run a pipe through an air bell?
>
> Cheers,
>
> Erik
>
>
>
> _____
>
> Van: Steve McKenzie [mailto:mechproj@xtra.co.nz]
> Verzonden: zondag 16 januari 2005 19:46
> Aan: <a href="/group/PipingDesign/post?postID=VxSETeG2gvC0nAqn4VTS0z0r-yKqVuFm-5DpGrdZ4wSqv6kTjK0DodnV7cZYlQuNfFYBw__1ywbdaRsqaxhLOJrxkfo">PipingDesign@yahoogroups.com</a>
> Onderwerp: RE: [PipingDesign] about surge
>
>
> I am normally not one to split hairs, but couldn't resist this one:
> Consider an air bell 10.3m below water level, with a (perfect) vacuum
> pipe passing through it. Inside the air bell is a pressure gauge
> connected to the pipe. What is the gauge pressure?
>
> Cheers
>
> Steve
> -----Original Message-----
> From: Erik Scheir [mailto:erik.scheir@pandora.be]
> Sent: Sunday, January 16, 2005 11:45 PM
> To: <a href="/group/PipingDesign/post?postID=VxSETeG2gvC0nAqn4VTS0z0r-yKqVuFm-5DpGrdZ4wSqv6kTjK0DodnV7cZYlQuNfFYBw__1ywbdaRsqaxhLOJrxkfo">PipingDesign@yahoogroups.com</a>
> Subject: RE: [PipingDesign] about surge
>
>
>
> I used this sofware perhaps even before you were born, but what has that
> to do with te fact that -2 bar does nor exist on the earth. Try to use
> Flowmaster its even better then impulse from AFT and you will never see
> results with pressure nodes below 0 bar.
>
> Erik
>
>
>
>
> _____
>
> Van: gautam wayse [mailto:captain_wayse@yahoo.co.in]
> Verzonden: zaterdag 15 januari 2005 9:30
> Aan: <a href="/group/PipingDesign/post?postID=VxSETeG2gvC0nAqn4VTS0z0r-yKqVuFm-5DpGrdZ4wSqv6kTjK0DodnV7cZYlQuNfFYBw__1ywbdaRsqaxhLOJrxkfo">PipingDesign@yahoogroups.com</a>
> Onderwerp: RE: [PipingDesign] about surge
>
>
>
> hi
> friend
> better to go for impulse software for surge analysis
> .from applied flow technology,.
> use --- Erik Scheir <erik.scheir@pandora.be> wrote:
>
> ---------------------------------
> What do you mean with - 2 bar? Is it barg?
> The absolute vacum is - 1 barg or 0 bara, so - 2bar
> doesn't exsist.
>
> erik
>
>
>
>
>
> -----Oorspronkelijk bericht-----
> Van: Omid Hamlehdar [mailto:omid_7_ae@yahoo.com]
> Verzonden: dinsdag 11 januari 2005 7:19
> Aan: <a href="/group/PipingDesign/post?postID=VxSETeG2gvC0nAqn4VTS0z0r-yKqVuFm-5DpGrdZ4wSqv6kTjK0DodnV7cZYlQuNfFYBw__1ywbdaRsqaxhLOJrxkfo">PipingDesign@yahoogroups.com</a>
> CC: mechproj@xtra.co.nz; <a href="/group/PipingDesign/post?postID=0Sa60Yz-z3D7N6-8YknXV1QRHY9dXHhTr0ihHLzfdpoceBbZdMpnROx0kp9UCGP0G1KZZx4uu3WmXb1NELQYfg">erik.scheir@pandora.be</a>
> Onderwerp: [PipingDesign] about surge
>
>
>
> Hi all
>
>
>
> I have a project for water handling, a pipeline with
> 100 km length, I am
> studying about surge in it according to a probable
> rapture in pipe and I am
> going to close two valves surrounding rapture point to
> avoid wasting water
> and to find out about surge cause by closing valves.
>
> Any body has experience in this regards? How shall we
> protect our system?
>
> I have heard from Erhard valve, they recommend a valve
> called "pipe burst
> control valve" to avoid wasting water when there is a
> rapture, this valve
> will be closed in around 2 min and this will cause
> surge in system, in some
> point we have -2 bar minimum pressure. I know that you
> may need to know
> about the profile but generally I would like to know
> how shall we suppress
> this surge?
>
>
>
> Best regards
>
>
>
> Omid
>
>
>
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Received on Wed Jan 19 14:15:00 2005