Developing a System Diagram: A Few Organizational Tips

In the previous post, I had taken the first step in developing my system diagram for the Pacific Energy Center ice storage system by picking the evaporator of the chiller as a starting point and putting a square, labeled as such, on my note pad.  I also included the piping connections and butterfly type service valves.

In this post, I am going to share a few organizational tips and tools that I have found to be useful over the years for developing drawings of this type.  In the next post, I will show you have I move forward from my starting point.

Incidentally, those of you who follow my posts, I discovered that I accidentally published the previous post in a half finished state.  So if you looked at it yesterday evening, you may want to review it because there have been some additions and improvements made to clarify the discussion.

Preparing for the Field Effort

Even though the over-all goal of the system diagram effort is to develop an organized representation of the system, developing the final draft is something that I find is best accomplished in my office where I have flat surfaces to sketch on and these days, a drawing program on my computer. But for that effort to be successful, I need to take an organized approach to gathering the information I need.

Part of that involves going out into the field with the right tools for the job.  For me, to develop a system diagram, I don’t really need to have much with me.  Here is what I find myself using at a minimum, some of which is probably obvious.

  • Paper;  I personally like graph paper, but that’s something that may or may not matter to you. The key is to have something to write on.
  • Pens, pencils, or markers:  Personal preference will probably matter a lot here, but I think the critical parameters are:
  1. Something that is water proof;  out in the field, you are frequently subject to water from a number of sources and it can ruin your day if your notes become a blurry mess as a result of on encounter with a leaky pipe or a rain or snow shower.
  2. Something that is renewable;  if all you have is a good old #2 wooden pencil, you are out of luck if the point breaks.
  3. Something that feels good to your hand;  this is a personal preference thing and maybe something that dates me, but the quality of my sketches and writing is very much a function of the writing instrument.  My field sketches are pretty rough, but they still need to be legible.  How the writing implement feels in my hand has a lot to do with that in my case.

I personally prefer a 0.9 mm mechanical pencil with HB lead and a twist out eraser.  As long as I keep spare leads in the barrel, I have to break the point a lot of times before I am out of luck.  The 0.9mm HP lead (its not really lead any more) resists breaking and makes a strong line that is as water resistant as the paper is.  The twist out eraser means that it can be renewed and I can erase with out triggering the mechanism that extends the lead which is how a lot of mechanical pencils work (you push the eraser to extend the lead) (and yes, I can be annal retentive).

I find the latter to be annoying because my pattern was to erase something, which extended the lead.  But since I wasn’t thinking about that, I would flip the pencil over to resume drawing only to have the over-extended lead break off.  (See, I told you the writing implement thing was very personal.)  (And that I can be annal.)

  • A clip board:  Having a firm writing surface is important for most people.  I carry a small (8″ x 5″ sheet size) very pretty laminated wood clip board that Kathy gave me.  The small size is a good compromise for me when I pack and fits in much better than a fill size board.  I also have a full size one that is made of aluminum and includes a compartment for storing documents, which is a nice feature too, but bulkier to pack.
  • A  camera:  Taking pictures of things as you develop your system diagram is a really good habit to get into.  For one thing, the pictures serve as memory joggers.  For another, they area fast way to document the details so you can focus your valuable field time on developing the basic diagram and add the details back at the office.  I’ve even done things like count the bricks or blocks  or ceiling tiles in a picture of something to get a feel for the dimensions of something.
  • A flashlight: Any time you are out in the field, a flashlight is a handy tool to have.  So handy that I usually have more than one.  A while back, I found a small LED/AAA battery flashlight that slips in with my cell phone so I just about always have that with me.  And for years, I have carried a Mini-mag light in my tool pouch.  Recently, I found a LED upgrade kit for it and made the conversion, which seems to provide just as much light but a much longer battery life.

Finally, a picture is an excellent way to find out what something is by asking someone who might know.  Contrast saying …

… well, it was this thing in the pipe that was sort of round and black with a flange on the top and a bolt sticking through it …

with …

… it looked like this …

… (its a swing check valve).

Sometimes, I think digital cameras are one of the greatest field engineering tools ever invented because the make capturing and sharing field information so easy.  And they allow you to make sure you actually captured the picture you wanted before you leave the site.  More than once, when using a conventional camera in the field, I was disappointed to find that some of the pictures I thought I had taken were no good after I got them back from the developer.  Usually they were the ones I really needed too.

Those are the basics.  I also find it handy to have my little tool pouch with me, in case I want to open an access panel.  Having my 4-in-1 HVAC tool is also handy in case I want to document an operating condition.  And, a digital tape recorder is a handy way to gather nameplate data instead of writing it down, perhaps supplemented by a picture (don’t forget to put the camera in “Macro” mode if you do this, otherwise the picture will be out of focus).

One of those micro cassette tape recorders will serve the same purpose too, but the digital recorders are nice because you can off load the file to your computer and simply listen to it when you need to instead of transcribing it.  I have even used the digital files as a way to ask someone if something sounded like it was working right;  sort of an audio version of “what is this?”

Organizing the Field Effort

That said, when I first started going out in the field and developing my system diagrams, I actually would agonize over where to start.  Part of the indecision was related to picking a place in the system to start, as discussed previously.   But part of it was related to where, exactly to put that first square on my piece of paper.

Since I didn’t know what the final drawing was going to look like, I would find myself wondering if I should start in the middle of the sheet or the corner of the sheet and if the sheet should be horizontal or vertical.   I finally came to realize that none of that mattered;  I just needed to make the square and move on from there.

For one thing, I was taking notes, not doing the final drafting.  Until I knew more about the system, it would be virtually impossible to figure out what the final arrangement of the diagram would look like.   The reality is that most of my system diagrams take several drafts to work out into their final configuration.

Frequently, as I transcribe my notes into my first organized arrangement, I realize that if I just shift part “A” to point “B”, things will be clearer, at least to me.  So out comes another piece of scratch paper to start a different draft.

Back in the days before computers and AutoCAD (yes there was a point in time when we drew with these things called pencils and pens on mylar, tracing paper, or even linen) I quickly learned that it was best to make a couple rough sketches to figure out the arrangement before committing to paper.  Otherwise, I would have eraser marks all over the sheet and waste a lot of time and effort.

Drawing programs like AutoCAD, and Visio are a real blessing when you are developing system diagrams because you can quickly and easily move things around as you gain insight into the best arrangement.  And the ability to snap things to a grid makes it easy to keep things parallel, perpendicular, and professional looking.  There is even an open source drawing program from Open Office called Draw that provides this sort of utility and will let you do a small diagram (I think you are limited to a page that is about 12 inches square).

Its also possible (but a bit cumbersome) to develop system diagrams with the drawing tools in Microsoft Office.  That said, I still typically start out with a paper sketch or two before breaking out the computer screen, mouse, and drawing package.

If you look closely at the screen shot of my note pad paper, you will notice that I have included some information at the top of the sheet; specifically, the date, where I was when I drew it, what I was drawing, the page number, and my initials.  This is a really good habit to get into.  You would be amazed how field notes from project “A” can look just like the field notes from project “B” a couple of months down the road.

Systems on the same project can start to look pretty similar too.   Writing down the date, system and location solves that problem.  Page numbers are handy because they help you remember the order in which you took the notes. And, they will clue you in on the fact that something is missing at a later date.

Putting your initials on the page help someone else who may be referring to your notes.  For one thing, if they have a question, they know who to ask.  And, knowing who made the notes can give you some guidance if you have to interpret something that is not clear or doesn’t seem right when the person who took them is not around to ask.  For instance, if my notes showed an unusual connection and you recognized my initials, you might think …

… that’s an unusual connection, but David’s been doing this a long time and I suspect he thought it was too and made sure his notes were right; I’m going to assume it really is piped that way …

or

… that’s an unusual connection, and David’s starting to get up there in years;  I wonder if the”lights were on” when he did this;  better check it out before I use it …

Hopefully, I’m not quite to the point alluded to in the latter example, but you get the idea.  But just to be sure, I better move on to the next post and get on with explaining how I go about doing a system diagram before I completely loose my marbles.


David Sellers
Senior Engineer – Facility Dynamics Engineering

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