Creating a reducing pipe elbow

[Anonymous]

Is it even possible to create a elbow that reduces within the elbow fitting?  So I'd have a 4" pipe, then a 90 degree elbow that's 4" on one end and 2" on the other end, then a 2" pipe.  Rather than a 4" pipe, a 4" elbow, a 4">2" reducer, then a 2" pipe.

I can't find anything online, and have started playing around a bit with the fittings families but I'm concerned with how the sweep will work with two different radii parameters, and don't want to spend too much time on it if it's ultimately not going to work. 

Any thoughts?  Has anyone seen this or know where I can find such a fitting?  Do you think it's possible or should I just stick to using a reducer?  Thanks!

[rudi.roux]

Hi @Anonymous, 

Hope you are well. 

Personally, I would stick to using reducers. "Reducing pipe bends" isn't a default family in Revit or in the MEP Fabrication Library. This being said, it comes down to what would happen on site. It's "unpractical fittings", so when you model "unpractically", then it would most lightly not be used on site.

So keep in mind when creating families or modeling systems for that matter that it should be able to be constructed/implemented on site conforming to actual manufacturable fittings etc. Also, cost, contractors might opt to install a normal reducer and bend, which might end up costing less for the two fittings opposed to one reducing bend. (Due to the manufacturing costs).

You're looking for something to this effect? 

I personally haven't built such a family for reasons outlined above. 

I hope this helps! 

[Anonymous]

Rudi,

Thank you for your response.  Yes, the example you gave is exactly what I was trying to accomplish.  I've spent a few hours trying to create a new family but I don't think it's going to work.  You're correct that using a separate reducer should be fine - I was tasked with trying to create this, with the understanding that it might not be possible.  Your response reinforces my opinion.  I'm going recommend just using separate reducers.  Thanks again!

[RobDraw]

While I agree with what has been said about modeling the way it will be built and was actually going to respond in a similar fashion, I hesitated because reducing elbows do exist and thought there might be an actual need for them.

With that being said, I've built a couple of complex pipe fitting families that were type driven, not pipe size driven. It can be done, if there is a real need. After all, how many different sizes could you need?

[Anonymous]

Rob,

Thanks for your response.  You're right, it's important to note that such fittings do exist in the field - the engineer that requested the family is using such fittings.

Did you just make a different fitting for each possible size combination?  I could definitely do that.  The problem is she wants it to be smart like the standard elbows, and automatically make each end the correct size for whatever pipes were being used.  I got stumped trying to get the sweep to read the radii of both connection points, and ultimately gave up.  I'll suggest making individual fittings for each size, but I think for the amount of time that will take we're better off just using a reducer, and maybe call it out in the specs so they use the correct fittings in the field. 

[RobDraw]

I'm sure it could be made "smart" so that the pipe sizes determined the fitting type but that's beyond my skill set at this time.

The "fittings" that I made required the user to select the size by selecting a type. As long as the pipes connected to it were sized correctly, no other fittings were added by Revit. If the wrong type was selected, reducers were added between the fitting and the pipes. More like a pipe accessory, than a fitting. If I remember correctly, when the fitting size and pipe sizes were set correctly any reducers that were automatically added by Revit were deleted.

It comes down to what the project requires. If you are on the fabrication side, your going to have to come up with a way to make the family. It can be done. If the project is spec driven, there are alternatives.

[fabiosato]

Hello,

I have done families like that, they adjust their end sizes depending on the pipe size connected to each end, it can be a normal bend or a reducing bend, instead of using a sweep to create the extrusion, use a swept blend, the main difference is that you will need two nominal diameter parameters and outside diameter parameters, also the lookup table must support both types.

[pkolarik]

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@fabiosato wrote:

Hello,

I have done families like that, they adjust their end sizes depending on the pipe size connected to each end, it can be a normal bend or a reducing bend, instead of using a sweep to create the extrusion, use a swept blend, the main difference is that you will need two nominal diameter parameters and outside diameter parameters, also the lookup table must support both types.

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Do you have an example of how this would be created? Something like this is wayyyy beyond my capabilities at the moment, but it's something I'll need to be using very soon.

As for those who've said an elbow and reducer is the better way to go because it's more practical. You're overlooking the very real and very common need for these reducing elbows where there's space constraints. The single most practical reason for using a reducing elbow instead of an elbow and a reducer is because there simply isn't room for two fittings when one can easily solve the issue.

Reducing bends are very widely used in the water / wastewater fields, and the fact that Revit doesn't come with them out of the box is another testament to just how lacking Revit is in the piping disciplines even today.

[RobDraw]

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@pkolarik wrote:

the fact that Revit doesn't come with them out of the box is another testament to just how lacking Revit is in the piping disciplines even today.

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I totally disagree with that deduction. OOTB content is not meant to cover all the bases by any stretch of the imagination. I already said that i had to look it up because I wasn't even sure if they existed. I've never had a need for a reducing elbow and I've done some pretty tight CoGen plants..

[pkolarik]

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@RobDraw wrote:

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@pkolarik wrote:

the fact that Revit doesn't come with them out of the box is another testament to just how lacking Revit is in the piping disciplines even today.

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I totally disagree with that deduction. OOTB content is not meant to cover all the bases by any stretch of the imagination. I already said that i had to look it up because I wasn't even sure if they existed. I've never had a need for a reducing elbow and I've done some pretty tight CoGen plants..

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That's fine, you don't have to agree. And I never said OOTB content is supposed to cover all the bases. However, reducing elbows (and reducing tees, and reducing laterals, etc) are insanely common in everyday usage. A 42" pipe that needs to not only take a hard 90 degree bend, but also get down to 36" is going to take up a ridiculous amount of lay length. We literally use reducing elbows on every project of any decent size. I'm surprised you haven't ever heard of them before. They've been around for ages.

(edit: To add to my point are the numerous examples of fittings families that are simply broken OOTB and in need of fixing to work correctly)

[RobDraw]

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@pkolarik wrote:

I'm surprised you haven't ever heard of them before. They've been around for ages.

(edit: To add to my point are the numerous examples of fittings families that are simply broken OOTB and in need of fixing to work correctly)

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In my world, if someone mentions 36" pipe, eyebrows go up. I totally get how they are necessary in some niche fields that use those larger pipe sizes. Also, in my world, where seeing 12" pipes doesn't happen very often, a design that requires a reducing elbow would be scrutinized for another option. As to the rest of the world where residential and small to medium commercial applications are, well I'm sure you see where I'm going with this. Expecting Revit OOTB content to be ready for prime time, no matter what the application is akin to getting everything spoon fed to you. There are people out there that are much smarter than you and I put together that would poo poo any hint of using OOTB content and tell us we are crazy for not creating our own. Saying a platform is lacking because the OOTB content doesn't suit your needs, especially in your field, is just inane.

With that being said. Since I started Revit back in 2009, the main source for content has been from manufacturers, not Autodesk. Have you approached any of your vendors that you buy fittings from to see if they have the content? That is were you should be looking for content and not expecting it to come with Revit.

That's the problem with Revit bashers. They don't know where to get what they need or learn how to make the program work. They expect Revit to suit there idea of a perfect modeling environment when if you consider all of the potential uses of Revit, that is really a unfathomable expectation.

[fabiosato]

Hello,

I can share the attached family, but it is in metric, you will need to edit the lookup table to support imperial.

Unfortunately I am busy now to change it for you.

I made a course for Pluralsight about how to create fittings for Revit, it may help you to understand the basics.