Plant Design: Overcome a Site’s Lack of Drawings

Jan. 8, 2018
Follow a few pointers to efficiently produce essential diagrams

Drafting never was my favorite class in high school. The instructor considered me a lost cause because I am left-handed. Everything I write invariably is traced by the heal of my hand as I traverse left to right. I eventually learned to avoid pencil smears by using wax paper. Then came programs like AutoCAD that made being a southpaw irrelevant.


One unavoidable situation you’ll encounter in engineering design is working on a project for a facility that lacks drawings. How the plant ever got built without them remains a great mystery to me. I’m usually the one who must create drawings so the site can see what a mess they’ve caused.

To develop the process and instrumentation diagrams (P&IDs), first, prepare block flow diagrams (BFDs) of the processes. Forget about the details! You only want a birds-eye view of the plant. With a working set of BFDs, take on the P&IDs. I use photography and hand-sketched isometrics to complete this task. If a site prohibits photography, try negotiating: offer to surrender the camera’s memory card afterwards. If this doesn’t work, triple your price — you’re going to need the hours.

Assuming photographs are allowed, follow this procedure for each line going to and from tanks in the process: 1) draw a basic isometric from mover, i.e., pump or compressor, to destination; and 2) photograph from start to finish in sequence. Shoot from different angles to show things easily missed from one angle alone. Take identification point (IP) photos as needed so you don’t get lost in a sea of pictures.

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Don’t forget equipment nameplates. It’s a waste of time to copy information into a notebook or pad. Instead, take photos. However, because nameplates can be shinny or lighting may be poor, take pictures from different angles: a straight perpendicular shot usually won’t work because the light reflects straight back, over-exposing the picture. I usually find that 30° off perpendicular reduces over-exposure. Again, take IP pictures as you go, so you can remember which nameplate goes with which item.

Autofocus and zoom are absolute necessities for the camera. Give the zoom time to set up, especially in dim light. Zoom is useful for more than close-ups; I’ve successfully used it to read nametags or body stamps on distant equipment.

A camera zoom may not suffice, though. So, I usually bring a small pair of binoculars or rangefinder to see items out of range of the camera.

Another useful trick is to carry a pad of sticky notes and use them to create your own IPs. However, this approach can become cumbersome.

When you’re done, plug your camera’s memory card into a reader and edit the photos immediately. I mean immediately! Don’t be afraid of being redundant by labeling the same line several times with line size, etc. Use a photo editor to annotate a picture with important items you’ll want to remember later. Typically, I add: line sizes, identified from flanges, pipe stamps, check valves, body stamps and other labels (as a last resort, I’ve used Vernier calipers to determine a pipe size); flow direction and colored lines in pipe racks to discriminate a particular pipeline; and other identification information as well as comments.

Next, compare the photos to the isometric you drew while taking the photographs. Is anything unclear or missing? If so, take some more photographs. Ideally, your shots should reveal all mechanical details. The photos tell you what type of pipe is used and how valves are connected, e.g., flanged, threaded, socket-welded, etc. The isometric ties the photos together.

As for the editor, I use Picasa, a now-retired program. Fortunately, many other programs are available. Pick one that can reduce the size of picture files to allow easier export via email. My camera uses about 4–5 megabytes per photo. Picasa can decrease file size to about 200–300 kilobytes.

Once you’ve created a portfolio of pictures, organize them into equipment folders. To ease their use while drawing, I put the photos into a tablet that I can scroll through while drawing with AutoCAD. It’s amazing what you forget even after a few days. The portfolio also is useful during reviews because reviewers often can’t remember these details.

DIRK WILLARD is a Chemical Processing contributing editor. He recently won recognition for his Field Notes column from theASBPE. Chemical Processing is proud to have him on board. You can e-mail him at [email protected]
About the Author

Dirk Willard | Contributing Editor

DIRK WILLARD is a Chemical Processing Contributing Editor.

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