RE: !!! RE: about surge

From: <Erik>
Date: Mon Jan 24 2005 - 03:36:00 EST

It is not so much the frequency but the magnitude who is of importance in waterhammer.
There is a fundamental relation, called Jukowsky's equation, between pressure wave dH ,change of velocity of flow dV, and wave speed a.

         dH=dV*a/9.81

Typical values for qa pipe containing water are:

PVC a= 30 m/s, steel a= 1100 m/s

Erik

Van: Firman Tuakia [mailto:engineer@lmbsp.ms.itb.ac.id] Verzonden: zondag 23 januari 2005 14:44
Aan: PipingDesign@yahoogroups.com
Onderwerp: RE: !!! RE: [PipingDesign] about surge

thanks for ur respons..

1.im talking abt instant closure of the valve.. i already figure it abt

    the 2L/a freq., but what i want to make it sure, is it true the     frequency of oscillation only depend on L and a ..?

    Because what i understand: 2L/a = first mode of frequency of sound wave     (the same as freq. for closed end pipe).

    If the 2L/a freq. is an accurate estimation, so if we have a quite long     L,the frequency will be very high.
    Then I imagine abt the reflection, isn't the longer L the longer period     of time needed --> the longer the period the shorter/smaller freq.

2. if i modelled the damping for the oscillation head only by friction 

     (viscous damping equivalency) then it means i ignore the energy
     disspation at pounding/hammering that converted into heat & sound.
     is my model still accepted ?

Thank you for you all..

Regards,

Firman Tuakia

On Sun, 23 Jan 2005, Erik Scheir wrote:

>
> Are you talking about a pumptrip or closing a valve at the end of the
> pipeline?
> The response time of a pressure wave is 2l/a where L = pipelength and a=
> wavespeed.
> The demping time is depending on the pipe roughness.
> In case of a pumptrip if the rotational inertia of the centrifugal pump
and
> motor continue to rotate the pump for a while after power failure, water
> hammer pressure transients may be reduced.
>
> Erik
>
>
>
>
>
> _____
>
> Van: Firman Tuakia [mailto:engineer@lmbsp.ms.itb.ac.id]
> Verzonden: zaterdag 22 januari 2005 17:52
> Aan: PipingDesign@yahoogroups.com
> Onderwerp: !!! RE: [PipingDesign] about surge
>
>
>
>
> anybody please help me: how to plot the oscillating head/pressure
> increase (when water hammer occur) at any point we want.
> especially how to:
> 1. calculate the frequency of the oscillation
> 2. estimating the damping tt causing the oscillated head/pressure become
> stabil again (such as the respon of step function)
>
>
> Thanks before..
> Regards,
>
> Firman Tuakia
>
>
>
>
> On Thu, 20 Jan 2005, Erik Scheir wrote:
>
>>
>> Measurement of Pressure.
>>
>> Lets keep it simple:
>>
>> Perfect vacuum cannot exist on the surface of the earth, but it
> nevertheless
>> makes a convenient datum for the measurement of pressure.
>>
>> Barometric pressure is the levelof atmospheric pressure above perfect
>> vacuum.
>>
>> "Standard" atmospheric pressure is 1.0325 bar (19.6959 lbf/in2) or 760
>> millimeters of mercury.
>>
>> Gauge pressure is measured above atmospheric pressure,while absolute
>> pressure always refers to perfect cvacuum as a base.
>>
>> Vacuum is the depression of pressure below the atmospheric level.
> Reference
>> to vacuum conditions is often made byexpressing the absolute pressure in
>> terms of the height of a column of mercury or of water.
>>
>> At least that's the way we define pressure in Europe.
>> If it is still not clear, its always possible to graphically illustrate
> the
>> relationsship between gauge and absolute pressures.
>>
>> Erik
>>
>>
>>
>>
>>
>>
>> _____
>>
>> Van: Steve McKenzie [mailto:mechproj@xtra.co.nz]
>> Verzonden: woensdag 19 januari 2005 23:06
>> Aan: PipingDesign@yahoogroups.com
>> Onderwerp: RE: [PipingDesign] about surge
>>
>>
>> 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: PipingDesign@yahoogroups.com
>> Cc: aluser2; mechproj@xtra.co.nz
>> 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: PipingDesign@yahoogroups.com
>>> 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: PipingDesign@yahoogroups.com
>>> 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: PipingDesign@yahoogroups.com
>>> 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: PipingDesign@yahoogroups.com
>>> 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: PipingDesign@yahoogroups.com
>>> CC: mechproj@xtra.co.nz; erik.scheir@pandora.be
>>> 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: http://www.pipingdesign.com
>>>
>>> Yahoo! Groups Links
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> =========================================
>>> PipingOffice - Excel Spreadsheets for Piping
>>> Calculations
>>> http://www.pipingoffice.us/ =========================================
>>> Main site: http://www.pipingdesign.com
>>>
>>>
>>>
>>>
>>> ---------------------------------
>>> Yahoo! Groups Links
>>>
>>> To visit your group on the web, go to:
>>> http://groups.yahoo.com/group/PipingDesign/
>>>
>>> To unsubscribe from this group, send an email to:
>>> PipingDesign-unsubscribe@yahoogroups.com
>>>
>>> Your use of Yahoo! Groups is subject to the Yahoo!
>>> Terms of Service.
>>>
>>>
>>> ______________________________________________________________________
>>> __
>>> Yahoo! India Matrimony: Find your life partner online
>>> Go to: http://yahoo.shaadi.com/india-matrimony
>>>
>>>
>>>
>>>
>>>
>>> =========================================
>>> PipingOffice - Excel Spreadsheets for Piping Calculations
>>> http://www.pipingoffice.us/ =========================================
>>> Main site: http://www.pipingdesign.com
>>>
>>>
>>>
>>>
>>> _____
>>>
>>> Yahoo! Groups Links
>>>
>>>
>>> * To visit your group on the web, go to:
>>> http://groups.yahoo.com/group/PipingDesign/
>>>
>>>
>>> * To unsubscribe from this group, send an email to:
>>> PipingDesign-unsubscribe@yahoogroups.com
>>> <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: http://www.pipingdesign.com
>>>
>>> Yahoo! Groups Links
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> =========================================
>>> PipingOffice - Excel Spreadsheets for Piping Calculations
>>> http://www.pipingoffice.us/ =========================================
>>> Main site: http://www.pipingdesign.com
>>>
>>>
>>>
>>>
>>> _____
>>>
>>> Yahoo! Groups Links
>>>
>>>
>>> * To visit your group on the web, go to:
>>> http://groups.yahoo.com/group/PipingDesign/
>>>
>>>
>>> * To unsubscribe from this group, send an email to:
>>> PipingDesign-unsubscribe@yahoogroups.com
>>> <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: http://www.pipingdesign.com
>>>
>>> Yahoo! Groups Links
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> =========================================
>>> PipingOffice - Excel Spreadsheets for Piping Calculations
>>> http://www.pipingoffice.us/
>>> =========================================
>>> Main site: http://www.pipingdesign.com
>>>
>>> Yahoo! Groups Links
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>>
>> =========================================
>> PipingOffice - Excel Spreadsheets for Piping Calculations
>> http://www.pipingoffice.us/
>> =========================================
>> Main site: http://www.pipingdesign.com
>>
>> Yahoo! Groups Links
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> =========================================
>> PipingOffice - Excel Spreadsheets for Piping Calculations
>> http://www.pipingoffice.us/
>> =========================================
>> Main site: http://www.pipingdesign.com
>>
>>
>>
>>
>> _____
>>
>> Yahoo! Groups Links
>>
>>
>> * To visit your group on the web, go to:
>> http://groups.yahoo.com/group/PipingDesign/
>>
>>
>> * To unsubscribe from this group, send an email to:
>> PipingDesign-unsubscribe@yahoogroups.com
>> <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: http://www.pipingdesign.com
>>
>> Yahoo! Groups Links
>>
>>
>>
>>
>>
>>
>>
>
>
>
>
>
> =========================================
> PipingOffice - Excel Spreadsheets for Piping Calculations
> http://www.pipingoffice.us/
> =========================================
> Main site: http://www.pipingdesign.com
>
>
>
>
> _____
>
> Yahoo! Groups Links
>
>
> * To visit your group on the web, go to:
> http://groups.yahoo.com/group/PipingDesign/
>
>
> * To unsubscribe from this group, send an email to:
> PipingDesign-unsubscribe@yahoogroups.com
> <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: http://www.pipingdesign.com
>
> Yahoo! Groups Links
>
>
>
>
>
>
>


PipingOffice - Excel Spreadsheets for Piping Calculations http://www.pipingoffice.us/

Main site: http://www.pipingdesign.com

Yahoo! Groups Links

[Non-text portions of this message have been removed] Received on Mon Jan 24 03:36:00 2005

This archive was generated by hypermail 2.1.8 : Mon Oct 27 2008 - 20:24:06 EDT