Hi Al
much as I enjoy deception, it was not used intentionally in this case.
My Patm is 2bara being the sum of sealevel air pressure of 1bara plus
the submergence of 10.2m or 1 bar. As you go deeper the pressure in the
bell gets higher. It is my Pgauge that is -2. This condition could
conveivably occur in a subsea line under water hammer conditions. Eriks
contention is that you cannot go less that -1 barg while I maintain it
depends what value you put on Patm.
A bourdon tube pressure gauge measures the pressure differential between
the inside and outside of the tube. With 2 bara on the outside and 0bara
on the inside it would try to read -2, scale and mechanicals permitting.
If you enclose an unconnected pressure gauge in a vacuum chamber, the
needle should rise to about 1 bar, as there is no external pressure
pushing the needle back to 0bar (must try this).
The grey area it whether or not the pressure in the bell can be called
Patm.
Its easy to do in practical terms; just use a DP gauge with the HP leg
disconnected and the LP leg to the pipe.
I hope you remember to remove the vent plug when you install a pressure gauge, otherwise your Patm becomes the pressure inside the gauge casing instead of the surroundings. In hot places, with a well sealed case the difference could be considerable.
Cheers
Steve
-----Original Message-----
From: aluser2 [mailto:alwynk@shaw.ca]
Sent: Thursday, January 20, 2005 8:15 AM
To: <a href="/group/PipingDesign/post?postID=tWwWSDSuwSt_369T0_kLwoXbYAwCx49vFbyYB8UFdPbOiw-CGNlU5iYiZpPXvhfoWsk4H8u4iflyvq29JYWc9IFAjM0p">PipingDesign@yahoogroups.com</a>
Cc: aluser2; <a href="/group/PipingDesign/post?postID=y-PmTesLncEdcOKyYbhRkqdCvl3Cj45VebPbYOchQJ4N3Y0Q-oNyygg1kUEJKGVaiaWzHKeH21hq">mechproj@xtra.co.nz</a>
Subject: Re: [PipingDesign] 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=tWwWSDSuwSt_369T0_kLwoXbYAwCx49vFbyYB8UFdPbOiw-CGNlU5iYiZpPXvhfoWsk4H8u4iflyvq29JYWc9IFAjM0p">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=tWwWSDSuwSt_369T0_kLwoXbYAwCx49vFbyYB8UFdPbOiw-CGNlU5iYiZpPXvhfoWsk4H8u4iflyvq29JYWc9IFAjM0p">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=tWwWSDSuwSt_369T0_kLwoXbYAwCx49vFbyYB8UFdPbOiw-CGNlU5iYiZpPXvhfoWsk4H8u4iflyvq29JYWc9IFAjM0p">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=tWwWSDSuwSt_369T0_kLwoXbYAwCx49vFbyYB8UFdPbOiw-CGNlU5iYiZpPXvhfoWsk4H8u4iflyvq29JYWc9IFAjM0p">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=tWwWSDSuwSt_369T0_kLwoXbYAwCx49vFbyYB8UFdPbOiw-CGNlU5iYiZpPXvhfoWsk4H8u4iflyvq29JYWc9IFAjM0p">PipingDesign@yahoogroups.com</a>
> CC: mechproj@xtra.co.nz; <a href="/group/PipingDesign/post?postID=dxuOQxXr19L0WyRh7zKV4kv6628-z4YzGxClqXms0NJW2GlemtGi7Z2AAgNFVefRsphE-m_HnslZGueN">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
>
>
>
> ---------------------------------
> Do you Yahoo!?
> The all-new My Yahoo! - What will yours do?
>
> [Non-text portions of this message have been removed]
>
>
>
>
>
> =========================================
> PipingOffice - Excel Spreadsheets for Piping
> Calculations
> http://www.pipingoffice.us/ =========================================
> Main site: <a href="http://www.pipingdesign.com">http://www.pipingdesign.com</a>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>
>
>
>
>
> =========================================
> PipingOffice - Excel Spreadsheets for Piping
> Calculations
> http://www.pipingoffice.us/ =========================================
> Main site: <a href="http://www.pipingdesign.com">http://www.pipingdesign.com</a>
>
>
>
>
> ---------------------------------
> Yahoo! Groups Links
>
> To visit your group on the web, go to:
> <a href="http://groups.yahoo.com/group/PipingDesign/">http://groups.yahoo.com/group/PipingDesign/</a>
>
> To unsubscribe from this group, send an email to:
> <a href="/group/PipingDesign/post?postID=c3j1eFveRcr0I5KjGTJsL-pdQCbX5RiI0au5GwVLXgp_kT8D60cxhh09EF9Tol8UIcp-BUZ4q8ZfhCJoAr4d49KBQF3jHp8V1dveWrKEDw">PipingDesign-unsubscribe@yahoogroups.com</a>
>
> Your use of Yahoo! Groups is subject to the Yahoo!
> Terms of Service.
>
>
> ______________________________________________________________________
> __
> Yahoo! India Matrimony: Find your life partner online
> Go to: <a href="http://yahoo.shaadi.com/india-matrimony">http://yahoo.shaadi.com/india-matrimony</a>
>
>
>
>
>
> =========================================
> PipingOffice - Excel Spreadsheets for Piping Calculations
> http://www.pipingoffice.us/ =========================================
> Main site: <a href="http://www.pipingdesign.com">http://www.pipingdesign.com</a>
>
>
>
>
> _____
>
> Yahoo! Groups Links
>
>
> * To visit your group on the web, go to:
> <a href="http://groups.yahoo.com/group/PipingDesign/">http://groups.yahoo.com/group/PipingDesign/</a>
>
>
> * To unsubscribe from this group, send an email to:
> <a href="/group/PipingDesign/post?postID=c3j1eFveRcr0I5KjGTJsL-pdQCbX5RiI0au5GwVLXgp_kT8D60cxhh09EF9Tol8UIcp-BUZ4q8ZfhCJoAr4d49KBQF3jHp8V1dveWrKEDw">PipingDesign-unsubscribe@yahoogroups.com</a>
> <mailto:PipingDesign-unsubscribe@yahoogroups.com?subject=Unsubscribe>
>
>
> * Your use of Yahoo! Groups is subject to the Yahoo! Terms of
> Service
> <http://docs.yahoo.com/info/terms/> .
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
>
> =========================================
> PipingOffice - Excel Spreadsheets for Piping Calculations
> http://www.pipingoffice.us/ =========================================
> Main site: <a href="http://www.pipingdesign.com">http://www.pipingdesign.com</a>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>
>
>
> =========================================
> PipingOffice - Excel Spreadsheets for Piping Calculations
> http://www.pipingoffice.us/ =========================================
> Main site: <a href="http://www.pipingdesign.com">http://www.pipingdesign.com</a>
>
>
>
>
> _____
>
> Yahoo! Groups Links
>
>
> * To visit your group on the web, go to:
> <a href="http://groups.yahoo.com/group/PipingDesign/">http://groups.yahoo.com/group/PipingDesign/</a>
>
>
> * To unsubscribe from this group, send an email to:
> <a href="/group/PipingDesign/post?postID=c3j1eFveRcr0I5KjGTJsL-pdQCbX5RiI0au5GwVLXgp_kT8D60cxhh09EF9Tol8UIcp-BUZ4q8ZfhCJoAr4d49KBQF3jHp8V1dveWrKEDw">PipingDesign-unsubscribe@yahoogroups.com</a>
> <mailto:PipingDesign-unsubscribe@yahoogroups.com?subject=Unsubscribe>
>
>
> * Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service
> <http://docs.yahoo.com/info/terms/> .
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
>
> =========================================
> PipingOffice - Excel Spreadsheets for Piping Calculations
> http://www.pipingoffice.us/ =========================================
> Main site: <a href="http://www.pipingdesign.com">http://www.pipingdesign.com</a>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>
>
>
>
> =========================================
> PipingOffice - Excel Spreadsheets for Piping Calculations
> <a href="http://www.pipingoffice.us/">http://www.pipingoffice.us/</a>
> =========================================
> Main site: <a href="http://www.pipingdesign.com">http://www.pipingdesign.com</a>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>
>
Yahoo! Groups Links Received on Wed Jan 19 17:06:00 2005
This archive was generated by hypermail 2.1.8 : Tue Mar 04 2008 - 11:40:39 EST