Forces at Pipe Elbows

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fawagy Active Contributor Join Date: May 2009 Location: Dubai Posts: 13	Forces at Pipe Elbows 05/12/2011 4:38 AM
	We are in process of installing a water fire monitor. In brief, the monitor will be installed on top of 90 degree elbow (flanged connection) which in turn is connected to a 4-way breaching inlet (welded connection). Water supply will be through hoses. Expected flow is 1,000 gpm at 10 bar pressure. The elbow will be anchored to a newly constructed concrete foundation through trunnion support. The query is as follows: Given that the monitor jet would result in the entire monitor/elbow tendancy to tilt/turn, what would the turning force be which the concrete foundation would have to overcome? The following was calculated: Resultant force due to flow and pressure at the elbow is 12.3kN (8.17kN in x and y direction). Jet reaction force of the nozzle is 2.8kN. Direction of water entry through breacing inlet and direction of water jet from the monitor are at a max of 45 deg (both horizontal and vertical). Thanks ....
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Doorman Guru Join Date: Apr 2009 Location: Yellowstone Valley, in Big Sky Country Posts: 7425 Good Answers: 295	#1 Re: Forces at Pipe Elbows 05/12/2011 10:19 AM
	There are a few more variables involved. This site has information and formulae that should answer your query. __________________ Semper Ubi Sub Ubi
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ChaoticIntellect Guru Join Date: Aug 2010 Posts: 714 Good Answers: 38	#2 Re: Forces at Pipe Elbows 05/12/2011 10:20 AM
	It appears you have a statics problem. Just sketch the arrangement with appropriate dimensions, the vectors for the forces you've calculated and reactions, and sum the forces and moments to 0. If you need a little further explanation, see wiki... http://en.wikipedia.org/wiki/Statics __________________ Sometimes my thoughts are in a degree of order so high even I don't get it...
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nick name Guru Join Date: Mar 2007 Location: City of Light Posts: 3943 Good Answers: 183	#3 Re: Forces at Pipe Elbows 05/12/2011 11:38 AM
	To compute the force one needs the massic flow (flow*specific mass) and fluid velocity at in and out-let. With only the flow it is not possible to compute any force. Give the elbow section and make as mentioned a sketch to show if inlet vertical or horizontal.
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nairck Associate Join Date: Apr 2011 Location: Located in INDIA.Kerala state,kottayam Dt,pala. Posts: 42	#4 Re: Forces at Pipe Elbows 05/12/2011 1:02 PM
	A60 lps discharge at right angle through 4 inch DIA pipe willhave avelocity of Q/A.The momentum of water at TEE junction will be MV.This much will be the force to be met by concrete block anchor.If rigid pipe is used water hammer too has to be met. Whic is the total fiow weight velocity.Adangerous valu. __________________ Lalithambika
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Lehman57 Guru Join Date: Sep 2009 Location: Louisville, OH Posts: 1925 Good Answers: 36	#5 Re: Forces at Pipe Elbows 05/12/2011 11:38 PM
	In the replies I see the shear/thrust/nozzle reaction mentioned, but not the overturning moment, which you seem to expect by mentioning "turning force." __________________ Lehman57
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ajwinemaker Power-User Join Date: Dec 2008 Location: Australia Posts: 143 Good Answers: 24	#6 Re: Forces at Pipe Elbows 05/13/2011 1:00 AM
	The force on the support is due to the change in momentum due to the changing direction (90 deg elbow). There will be a force, but your flow is relatively small and provided the operational velocity is within normal range (under 3.0 m/s, ideally 1 - 1.5 m/s), the force on the support should be minor (virtually insignificant). What you need to consider is the water hammer, which can send a pressure spike up and down the line. There are many websites to assist you in this (assume you can use google). If you really want to go into the nuts and bolts, Perry's chemical Engineering Handbook is a good place to start, and the Crane Handbook for fluid flow and pressure loss. Without knowing the details of your installation it is hard to comment, but assuming your flow velocity is less than 3.0 m/s and the line diameter is less than 6 inches - I'm confident your system will be fine.
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fawagy Active Contributor Join Date: May 2009 Location: Dubai Posts: 13	#7 Re: Forces at Pipe Elbows 05/15/2011 5:31 AM
	Thank you for your time and reply guys. I agree with Lehman57 regarding the requirement of a turning force/overturning momentum. Regarding the pipe hammer, I do not foresee any problem with that. Please refer to attached sketch and photo. The photo is of something similar that we are going to install. Regarding the comments for the momentum, massic flow.... (i.e. dynamic forces), another question would be is the turning force mainly due to dynamic forces? If yes, then I believe we do not have a major problem. If no and pressure forces do play a role, can we simply add the dynamic, pressure and jet reaction forces and simply uses statics, as referred to by ChaoticIntellect? Meanwhile, I have attached the sketch and a photo of the monitor. In addition, the calculated dynamic forces was around 0.5kN. Just to remind, the main aim is to design a civil foundation that is capable of standing the overturnning forces. Regards,
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