We have arrived! It’s time to put all of these highly coordinated design elements to work for us and start fabricating from our design model. To do this, we will need to provide the fabrication shop with the information they need to build our designs and the pipe fitters the information they need to install our designs. To do this, we need to create fabrication drawings of our model content that include all the crucial details that will make fabrication and installation possible. Fabrication drawings are different from design drawings in that they convey only the physical information required to build the elements and leave out information like flow and notes to adhere to local code jurisdictions. Fabrication drawings can be vastly different from one building element to another and from one client or fab shop to another. They adhere somewhat to a set of standards but are typically tailored over time to a specific process that is defined by specific industries and fab shops. For the bulk of this topic, I’m going to stick to what I know again and use piping as the basis for my explanation.
I’m going to stress trade collaboration here again. We’ve already discussed the importance of early P&ID review to identify part manufacturers, complex connections and overall constructability considerations. This is where all of those considerations come to light and are examined under a magnifying glass. Every valve, fitting, pipe length, and field weld location are identified in detail so that the fabricator and installer know exactly what is require. To accomplish this level of detail, your information needs to be conveyed in a way that your trade partners are familiar with, to a point. We are in the midst of a sea change in the piping industry and in many other industries as well. Pipers are used to receiving information a certain way and they have been receiving it that way for decades. Now, we have turned the process on its head and are giving them documents that have an entirely different look and feel than they are used to. Its human nature to reject change and we need to be sensitive to that. It is extremely important to sit down with the detailers you will be working with and set some ground roles for the content and appearance of you drawings. I have experienced this process getting side stepped or not receiving the detailed examination that it deserves and I can tell you that it is not fun to go back and rework hundreds of spools because the information you provided is not sufficient to build from. Present sample sets to your trade partners to baseline what you plan to provide. Request sample sets of what they typically produce so that you can incorporate some of their shop specific information. Do whatever you can to provide as much of the information that they ask for because at the end of the day, if they say they need it, they need it. That being said, there are some limitations in Revit that just cannot be avoided without taking a great risk. Overriding dimensions for example. In AutoCAD, that’s an easy task and comes with little risk in that your spool drawing content probably isn’t directly tied to your design content, or maybe it is. One off instances are a bit more cumbersome in Revit as well. You may need to deal with them by way of creating another family type or possibly a separate family all together. Teach your design team about these limitations ahead of time so that they understand them and why they should not be circumvented. Nothing is worse than getting a call from a contractor saying that the spool you provided doesn’t fit, opening that spool to investigate and finding a piece of opaque text on top of a dimension or callout to override the actual content. It can happen, don’t think it won’t.
Creating spool drawings in Revit is actually quite easy thanks to a concept that was developed by our former BIM manager turned API Jedi. For those of you who took his session back in 2013, this may look fairly familiar. As a side note, there are a variety of add-ons at this point that were not available or fully functional when we initially set out to create fabrication drawings entirely in Revit. Revit 2016 also introduced the fabrication parts feature which I haven’t had the opportunity to break yet, but from what I’ve seen it doesn’t quite do everything we need it to at this point either. It also reminds me way too much of my days using AutoCAD MEP to take it seriously. Plus, the underlying concept that I’m presenting on is that all of this is possible using native Revit functionality only and regardless of the fact that fabrication parts is an out of the box feature, it’s still an add on in my opinion.
Creating the Fabrication Drawings
Back to creating fabrication drawings in Revit. The basic idea is to populate shared parameters and use them to create a series of view and schedule filters to isolate the contents of the assembly and associated spools. You will need to create, at the very least, two shared parameters, one for the assembly and one for the spool. You can include as many as makes sense to isolate your information and schedule it accordingly. For example, you may add a higher level parameter for system mapping so that you can easily create an overall system map showing multiple assemblies and how they tie together. You will also want to include an item number parameter to identify the elements in your spool and tie them to a BOM. I would steer clear of going too crazy with the amount of shared parameters you use since these will be instance based parameters and require a certain level of maintenance depending on what phase in design development you start cutting spools. As a side note, one of the biggest advantage of doing this directly from the design model is that you can start fabrication drawing development as early in the design process as makes sense because model adjustments will be capture in the spool drawings without having to re-export anything. In our most recent project, we actually started kicking out assemblies at the 60% review milestone and were issuing IFF drawings parallel to IFC drawings. So, understandably, maintaining those shared parameters while the design was still in development was not an easy task, so by limiting the total quantity of parameters we avoided a lot of tedious busy work and potential exclusions. Once you have your parameters established and applied to your project, the next step is to populate the elements you wish to isolate. In this example, I’ll be using piping, naturally, and our unique parameter will be represented by…anyone…anyone? Remember when I talked about line numbers and using them to connect the dots across documents? This is exactly what our parameter value is going to be. By using the line number you will have connected your P&ID to your model geometry to your fabrication drawings.
Once that value is populated in the piping, we can create an isometric view with a filter using the line number value to isolate the assembly content. We now have a clean isometric showing only the content of our assembly.
In terms of dimensions, it is very critical which dimensions you give the shop and how you present those dimensions. For pipe lengths, most shops prefer hard cut lengths rather than theoretical dimensions like center to center that require the shop to do calculations and back checking before they make a single cut. Other shops prefer to have the cut lengths and the center to center dimensions for reference. On our projects, we were only able to provide center to center dimensions at the time. Although we had the capability to provide pipe cut lengths, we were not able to anticipate the material manufacturer that the shop was going to use at the time of conception due to pricing. We identified this as a risk at the beginning of the project so that the shop was aware and could include the added time for dimensional calculations in their estimates. If you do decide to include dimensions on your fabrication drawings, you will need to utilize reference planes to do so. All dimensions in Revit require a reference plane to be hosted to. This is easily done in plans and sections because the plane of the view serve as the host for the dimension. This is not the case in a 3D view. Start by creating reference planes parallel to the center of the pipe you wish to dimension, one vertically and one horizontally. You will need to do this in a plan and section, so it is a good idea to set up plan and section views of your work area that you can move around as you work through your system. Be sure to name your reference planes as you are creating them so that you can find them once you are in your isometric view. I use the line number followed by either -X or –Y for the reference plan names so that I know what spool the plane is for and the orientation of it.
Once you have your reference planes placed and named you can go back to your isometric view, and set your current reference plane using the pick option and pull down to the plane you need. Now you can add your dimensions. Be sure to include a reference that states what you are dimensioning to. For example center to center (C-C), center to end (C-E), or face to face (F-F) for flanges. There are quite a few more, and center to cent is typically implied unless otherwise noted. It’s also important to mention that you will need to lock the orientation of your view so that you can add any text or tags.
Provide bottom of pipe or center of pipe from an established reference point. Finished floor works as a great reference point unless the finish floor isn’t uniform due to sloping or incorrect pouring. Ideally, a reference elevation will be established in the field. This will be a common elevation above a point on the finished floor that is marked with a laser and referenced by all disciplines. This provides a uniform reference elevation so that all elements are installed at the correct elevation. In Revit, your floor will be uniform, so include a note stating that all elevations are X feet above or below the project level elevations. This may require creating additional levels in Revit and moving the reference level of the elements to the added levels. I also suggest creating a new level type with a symbol that is different than your project levels to clearly identify their difference.
The location on the pipe that you provide the elevation to matters as well. Depending on who you are working with, they may prefer center of pipe instead of bottom of pipe. If you are working with piping that is sloped, it is best to provide work points for reference elevations at each of end of the pipe run.
Rolling offsets can be especially challenging to convey correctly and I could probably do half of a presentation on them alone. This is definitely something to bottom out on with your trades up front. How they typically present the information to their shop and pipe fitters can be critical. The traditional and most straight forward way is to use the offset triangle to identify that there is roll and in which direction. Then dimension the triangle. Roll angles can be provided for additional clarity, but not always necessary.
Example of Standard Rolling Offset
Compound rolling offsets add another level of challenge. These offsets will require two triangles to properly convey the two offsets that are occurring. Here is an example of a compound offset as it would appear on a spool drawing.
Example of Compound Rolling Offset
I would suggest building a parametric family to tackle the task of showing the triangles. What you are seeing in this example is just that. It’s a box with several triangles with visibility parameters to toggle them on and off. This particular one will actually do the angle and length calculations for us and can be tagged to add that information to the sheet. I wish I could take credit for this one, but someone much smarter than me built it.
In addition to dimensioning the content of the spool you will need to include a bill of materials for the shop to do takeoffs and ensure that they are building to exactly what you are specifying. Unfortunately, if you wish to include size, and I would strongly encourage you to do so, you will not be able to use a common multi-category schedule for you BOM. You will need to make three individual schedules in Revit: A pipe schedule, a fitting schedule, and an accessory schedule. The schedules will also need to be isolated down to only the contents of your spool drawing. You can do this by applying a similar technique used for the spool view. Start by creating a pipe schedule. For pipes, we are interested in size, length and description. The description of your pipes should be the line class information and at the very least include material, schedule and pressure class. It is a good idea to include manufacturer as well when possible.
Pipe BOM Initial Setup
Include those fields and also your assembly, spool and figure number parameters. Filter the schedule down to only include the elements that match the assembly parameter, and then once again to the spool parameter. This will ensure that no erroneous elements sneak through. Sort the schedule based on description then size then length. You can leave sorting by length out so long as you check “Itemize every instance” under the sorting and grouping tab to ensure each pipe gets its own row and not collapse and give you total lengths by size.
Schedule Filter Settings
Schedule Sorting/Grouping Settings
Once the schedule is created, hide the assembly and spool parameter columns since we don’t need to see those on our spool sheet. Populate the figure number column in sequential order. By doing this, you are also populating the parameter in model elements in your spool. Repeat this concept for a pipe fitting schedule and a pipe accessory schedule, except in these schedules you will replace length with quantity. It is not necessary to sort by quantity or check “Itemize every instance” in this case because I want all 4” butterfly valves to have the same figure number or example. Now, with the combination of those three schedules, you have your spool BOM.
Now that you have an annotated and dimensioned isometric view and your BOM schedules, you can create a spool sheet. The name of the spool sheet should match the line number of the spool. Drop the view and schedules onto the sheet, adjust as needed, and voila! Native Revit fabrication drawing.
If you are venturing into creating fabrication drawings for the first time, another recommendation that I will press on you is to have a senior level detailer or installer on your team to help guide your decisions and keep your fabrication drawings in adherence with industry standards as much as possible. You can only lean on trade partners so much and you will want to have most of the process established prior to meeting with them so that you are only making minor tweaks to help cater to their shop’s needs. It’s amazing to me how little of the information included on fabrication drawings are governed by ISO, ANSI or other standards and practices organizations. The information is quite literally passed down from generation to generation of piping detailers and fitters. It may vary from one company to the next, but ultimately, tribal knowledge reigns supreme. So my advice is to capture and implement as much of that tribal knowledge as possible by including senior detailers and fitters in your process.
The need for having seasoned veterans of the trade within your company extends beyond setting up standards and procedures, they should also be the ones performing the QA process on your fabrication drawings prior to issuing to the fab shop. These are people that have been detailing, reviewing and installing pipe for most of their career. They know what shops and pipe fitters expect to see and the information they need to do their jobs. They will add an immeasurable amount of quality and value to your project.
Family Details
Last and certainly not least, let’s back track a little bit and talk about families. I’m not going to try to squeeze a family building lesson into this presentation, but I do want to talk about two things with regards to families: timing and content. These will be your two biggest hurdles as you start down the road of building a fabrication ready family library. They will in a sense define your entire process because there will constantly be the question of how elaborate does the family need to be and how much time do we have to build it. You can, of course, always go the route of downloading manufacturer content or subscribe to a content library provider, but these can be hit or miss and if you need content that they don’t have, you can be left in the lurch and have to build it yourself anyway. If you have the capability in place to develop your own library, I highly suggest you do so almost exclusively. You will be able to control your own family standards, quality, consistency, parameters and appearance. Besides, you know how you need the family to function, therefore you know best what content to include. This will allow you to leave out all the content you don’t necessarily need and save yourself a lot of time and performance eating geometry when it comes to deployment. As a general rule, we maintain our own library and admittedly it has its own set of challenges, but we know where the families are coming from, we know what to expect them to act like, and we know who to go to if we need an update or fix.
By building our own family library, we are constantly presented with the question of what to build and when to build it. We tend to live on the edge a little and not build families until we need them. There are so many families that could be built and no sure way of knowing which ones we’ll need first or at all. As we execute more and more projects we progressively have more and more of the families we need on hand, but we have found that the most efficient way of building our library is to employ a just in time approach to reduce a lot of overhead. Again, we are living on the edge a little so it may be important to identify which family categories you will use the most and develop family templates and standard testing procedures so that you can reduce build and QA times.
This process also leans heavily on the early contractor P&ID review that I mentioned quite a few times already. By reviewing the P&IDs with the contractor prior to the modeling process you will be able to identify the manufacturer that the contractor intends to use and therefore better identify which families need to be built. You can then take the list of families that need to be built and compare them to the design schedule to identify priority. For example, I may need a high point vent and a 12” butterfly valve family. I know that I’m probably going to lock down the 12” pipe and its inline components like butterfly valves before I start modeling high point vents, so it stands to reason that the butterfly valve should get built first.
Given that we will be providing detailed shop drawings from our modeled content, it’s a given that our families need to be of the utmost accuracy. But how accurate and in what regards. The level of accuracy required to install a part is not the same as the accuracy required to manufacture that part. We can agree on that, right? So how do we decide which details to include and which details to exclude? Well, what information do we need to get out of the family for construction? In regards to pipe, if I want an accurate pipe BOM, then the location of the connectors in my fitting and valve families need to be accurate. Do I need to include all the stiffening webs that might be on a valve body? Unless they are very large webs and space constraints are an issue, then probably not. I’m not casting the actual valve body, so I really don’t need that level of detail. However, we don’t want to leave out so much detail that it isn’t spatially accurate or we can’t identify it just by looking at it. For example, I could make all of my MEP fittings out of cubes using the overall dimensions of the fitting as constraints. No discernible geometry, just blocks with connectors. Well, why not? If the connector locations gave me an accurate pipe BOM and there were data parameters that provided manufacturer, cost, size, material, and any other important information, then why add all that flashy aesthetic detail.
Suction Diffuser with no Discernible Geometry
For one reason, we are professionals and we want to be taken seriously. But mostly because this is a digital representation of what is going to be built. We need to provide clarity in design and intent. So provide enough detail that the family is both technically accurate and aesthetically accurate, but no so much that you could manufacture it yourself.
Suction Diffuser with Clear but Minimal Geometry
Conclusion
Whew, that’s a lot to take in in one sitting. Let’s do a quick recap. A joint venture between the A/E and GC offers the opportunity to pull construction forward into design and foster cross discipline coordination not only between design teams but between trades as well. Take full advantage of Revit shared parameters to manage scope demarcations and Revit schedules to generate material takeoffs and project metrics. Develop process workflows for your project and identify how and where the team’s roles and responsibilities fit into it. Carefully consider the extent in which you will use existing conditions for retrofits and whether or not it’s worth modelling or working directly from the point scans. This is VDC and with any luck, design for fabrication, so model everything means model everything. Have confidence in your fabrication drawings by providing the right information and using accurate families. Hopefully all of this will give you a good starting point for you next VDC project. Remember that collaboration and transparency are key and keeping an open dialog between the entire team is the best way to maintain it.