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bs en 806-3 pipesize

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leiadad

Gas Engineer
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I am currently doing a project at uni, on pipe sizing and can't understand why bs en 806-3 does not take account for elevation into pipe sizing. I understand that the loading units have been accounted for so probabe demand is not necessary and that head loss through pipework is taken care of but I can't understand that if u need to lift pipe 5 metres or 50 metres then there is no difference in pipe designed in this way.
 
I have also been asked to do 3 othter types of design and compare, of which I am using thomas box, bs 8338 and I can't think of another way to do it, if anybody can give me one more suggestion
 
If you're at uni, please try to improve your sentences, spelling and grammar. Student support may well have someone to help if you aredyslexic, and even if you are not. As it stands, you sound like a capable student and are asking interesting questions, but you simply will not get the marks you would deserve if you are not able to communicate these views such that a marker can, easily, see what you mean. Markers will not assume you know something - you need to state it, and you need to be clear.

My uni had a learning support team that would give free courses on various study skills. Not enough for everyone to be able to go - but most people don't go, so it was quite easy to get an appointment.

I'd like to help, but cannot quite work out what you are on about, especially in your second post. Possibly I don't have the knowledge, but as it is, I don't understand the question. Are you able to re-phrase please?
 
You are.:p:p:p:p

86F44B6D-CBFC-46A9-AE02-FDA705DBA728.jpeg
 
ha ha I didn't think I would be tested for grammer on here, anyway what I am trying to say is that on 806 a pipe can be selected using only flow rates as probable demand and has been accounted for within the flow rate. My question Is why is there nothing mentioned about the pressure that is within the pipe. The tabulation method does mention this pressure and will gain pressure on a vertical drop and lose pressure on a vertical rise which will effectively give a pipe size to suit the installation whereas 806 won't. 806 also only gives max lengths of pipe on any type of pipe up to 6 loading units which I am struggling to undersrand as well. Sorry if you couldn't understand in the earlier post.
 
The only other way I can put it would be, if I was planning for a building with 6 loading units and 25 metres height, with an initial pressure of 3 bar, then surely the 15mm pipe recommended in 806 would be no good due to the initial loss of head on vertical riser
 
Harvest Fields said:
You are.:p:p:p:p

View attachment 36780
Click to expand...
You will note I have not edited my original post since your reply. It does not read as you have quoted it. When I view it on my screen, I see the words 'if you aredyslexic'[sic.] . You are correct to note I have missed a space, for which I can only apologise, but that's not so bad as to miss a whole word. Are you deliberately mis-quoting me, or is there a technical imp at work?
 
leiadad said:
The only other way I can put it would be, if I was planning for a building with 6 loading units and 25 metres height, with an initial pressure of 3 bar, then surely the 15mm pipe recommended in 806 would be no good due to the initial loss of head on vertical riser
Click to expand...
I've been given a copy of 806. I haven't read it though, as I was given it as an electronic file and not on paper and I'm not really an e-person. I will try to have a look, as your question will make reading it all the more interesting... to try to see how 'they' have factored this in, if at all. As you say, it makes little sense to ignore the effect of elevation on available head.
 
Ric2013 said:
You will note I have not edited my original post since your reply. It does not read as you have quoted it. When I view it on my screen, I see the words 'if you aredyslexic'[sic.] . You are correct to note I have missed a space, for which I can only apologise, but that's not so bad as to miss a whole word. Are you deliberately mis-quoting me, or is there a technical imp at work?
Click to expand...
No mate. In the picture That I took of your post. You can clearly see that it says you and not you are. That is what I was pointing out.
 
Harvest Fields said:
Not to worry. I just found it funny that you had made a mistake after taking the p out of the OP. :p:p:p:D
Click to expand...
I wasn't taking the Sod. My point was that a lot of people who work in unis are lazy sods and probably couldn't be arsed to make the point I was making, and so I made it because it was better he hear it from me and be offended than not hear it at all and fail, especially if he is otherwise a good student. If there are extra services available, then it's worth making the most of... how much a year now?
 
Don't worry I wasn't offended, I am doing a building services course, not an English course so they are prob not as strict. In class my punctuation prob a little better anyway. you were right anyway, I wasn't getting my point accross at that time but hopefully you know what I'm talking about now
 
4.3 Sets the Pressure conditions for the use of this Simplified method doesn't it ?
i.e.
Static pressure at draw off point = max. 500 kPa (Exception: garden/garage taps max. 1 000 kPa);
Flow pressure at draw off point = min. 100 kPa.
"The difference between the static pressure at the lowest draw off point and the flow pressure at the hydraulic worst- case draw off point, reduced by the pressure losses (resulting from wall frictions and individual head losses), give the possible head of difference in elevation within a pressure section."
 
Yeah that explains a bit, the pressure loss/gain when elevated would be the same regardless of pipe size. the only difference is the fact that 6700 or 8338 gives the opportunity to work out the total head loss and 806 doesn't. I'm assuming that the pressure loss would then need to be worked out by the designer to produce a minimum of 1 bar dynamic pressure at any fittings.
 
so I am also assuming that because the simplified method (806) does not account for fittings or for losses through valves then the designer would have to take fittings as a percentage loss and valves as metres head lost when working out pressure loss within the pipework to make sure that the 1 bar pressure available at taps is achieved.
 
806:3 does what is say on the tin -
As far as I can see it simply provide a quick way of selecting pipe sizes for H&C systems against the appliance supplied from it, within a set pressure range.
Given that most modern systems are high pressure so pipe / fitting losses have such a small effect on the discharge would we need to alway calculate these ?

Do a couple of simple calc's using 6700, one high (say 3+ bar) one low (say 3 metre head) using the same fittings each time.
Then think about the advantage of using 806 in real life albeit with the limitations.
 
leiadad said:
The only other way I can put it would be, if I was planning for a building with 6 loading units and 25 metres height, with an initial pressure of 3 bar, then surely the 15mm pipe recommended in 806 would be no good due to the initial loss of head on vertical riser
Click to expand...
You need to think about it logically, and separate static heads from friction losses. It might help to have a talk with your tutor to get you started. If you're working on a heating system, and it sounds like you are, it's almost certainly a closed loop so there is no net static pump differential. But you still need to ensure there is positive pressure (ie above atmospheric) at the highest point. Maybe you're aware of that, hence reference to 25m height and 3bar.
 
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