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Thread: How to calculate pipe sizes in hydraulics.

  1. #1
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    Question How to calculate pipe sizes in hydraulics.

    Hi,

    I have used ductulator (in HVAC) for a pre tender project and where we have a tentative design that helps in finding the amount of duct required. I am curious do we have anything similar to that in hydraulics? Coz I have to calculate the amount of pipe that is required for hot and cold water supply tend to use in the system.

    Just wondering do we have anything similar to that to calculate the pipe sizes in hydraulics?

    Thanks for your help. Cheers

  2. #2
    Forum Addict tzframpton's Avatar
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    I believe you're referring to hydronics rather than hydraulics. And yes, the calculator is named "Duct/Pipe Sizing" respectively. As long as your hydronic system's Calculations are set to All in Type Properties, you should be able to successfully use the Pipe Sizing calculator the size of pipe, not the amount of pipe, as you previously mentioned. Calculating the amount of pipe would involve a simple schedule.

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    Junior Member noss's Avatar
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    Plumbing is known as hydraulics in Australia and New Zealand. Not sure about other regions, but hot and cold water is indeed 'hydraulics' here. Hydronics (space heating using circulated water) is uncommon in Australia I guess due to our climate. I've only ever seen it used in Melbourne in one older building.

    As is pointed out though, if you're just wanting the quantity of pipe, that is a simple schedule, you just need to sort and filter it to get the results you're looking for.

    To perform pipe sizing for a plumbing system, you need to have either flow rates or fixture unit ratings on connected plumbing fixtures for both the hot and cold water connectors. If you're using OOTB Revit families, check the loading units (called fixture units in Revit) match what is expected in your region. Another alternative that I have used is rather than model all plumbing fixtures, I will have an isolation valve box family where I fill out the fixture units of the fixtures it is serving that I've manually input into the family.

    You may have to tinker with settings a little to get the results that you're after, but start by setting your maximum velocity to 3.0m/s (AS/NZS 3500) and go from there. I've seen people try and target 1.8m/s by using it as the maximum value but Revit will automatically try and stay under your maximum velocity, so 3.0m/s should be fine.

    I've put together a bit of an example, I just cobbled together some basic shapes to use as fixtures and a hot water unit. The plumbing fixture (large boxes) connectors are set to 'in' and the hot water unit (cylinder) has the cold water set to in and the hot water set to out. The small box is to cap off the end, it is set to out as it is essentially the water connection to the site.

    Note that my example is in 2013, only reason is it's because that is the version of the project I'm working in at the moment, the basics of sizing work the same in later versions.

    I've drawn everything in at 32 dia, everything connected. You should make sure that there are no open ends. Each of the plumbing fixtures have a loading unit of 1 for both hot and cold water.
    You then select everything, in the ribbon you'll see 'duct/pipe sizing'
    I've set the maximum velocity to 3.0m/s and the sizing to match the connector size - The reason I have done this is that size the last run to the individual fixture to be 15 dia (AS/NZS 3500) as long as you have the connector sized accordingly
    Now you've now got sized pipework

    I also highly recommend setting up a view with a piping legend on it (analyze -> colour fill panel -> piping legend) and setting it up to show pipework velocity, my example above looks like this:



    The green pipework (10m/s) is acceptable because of that last 3m of pipework at 15 dia rule.
    Last edited by noss; March 4th, 2015 at 05:07 AM.

  4. #4
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    Yes Noss, that's what I mean. The project that I'm working is using hot water to heat the room temps during winter. I know my velocity as 3.5 m/s which is not noisy (audible) in quite rooms and I rely on auto sizing function in revit. Later I can round off to the closest available size that we get in the market. Again thanks for your time and detail explanation. I can't give you more than one like otherwise I would definitely do that.

    Last edited by Shan1512; March 4th, 2015 at 09:51 AM.

  5. #5
    Junior Member noss's Avatar
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    Is the system a combination of plumbing fixtures and heating elements, or is it just heating elements? If you only have heating elements on the loop, use hydronic supply and return as was suggested earlier. I probably got a bit carried away on the AS/NZS inclusion in my example, but just things that are in my head all the time.

    Jeremy Tammik has a good document on his site that I referred to a lot in my early days:

    http://thebuildingcoder.typepad.com/...ep_content.pdf

    The document has a diagram of how to do a chilled water loop with inline pumps, if you don't have any plumbing fixtures attached to the loop you can use the same methods to create a hot water loop.

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