Segment Of Process Flow Diagram
Figure 1. A unit engineer should be able to sketch an adequate and accurate process flow diagram.
These questions are good indicators of plant knowledge. Both outside troubleshooters and plant supervisors can use them to check how much the engineer or superintendent knows.
A unit engineer should be able to sketch the unit from memory — and include on that sketch all the major equipment with numbers, names and service descriptions. Details about major equipment should be generically correct — for example, the engineer should know which fluid is on the shell-side versus the tube-side of every heat exchanger.
This is the basic level of knowledge needed from a plant support engineer assigned to a unit. Failure to provide an adequate and accurate sketch means either the engineer hasn’t been assigned to the unit long, doesn’t understand the importance of these details, or just isn’t doing the required job. Lack of this basic knowledge makes any information offered suspect because the engineer doesn’t know the context. It also indicates the person is unlikely to be able to solve major problems on the unit.
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PFDs summarize the most important unit knowledge. They show the major possible interactions among equipment. They may include the most crucial control loops as well. PFDs may be complex but nothing beats getting everything most important about a unit on one page or, when absolutely necessary, on two to three pages. (A 20-pp. set of PFDs I got on a recent case certainly made seeing the unit as a whole difficult and time-consuming.) If PFDs don’t exist, it’s likely that many people who think they understand the unit actually don’t.
Free-hand sketching isn’t my strong suit. So, I use CAD software. Figure 1 shows an example segment from a one-page PFD of a unit. It took a while for the importance of one-page PFDs to sink in, but I’ve never regretted the time spent on them. Today, my collection includes PFDs on more than 130 individual units plus hundreds of variants looking at different operating, revamp and modification options.
The final three questions focus on how often the engineer or supervisor gets into the field. Going to the unit is critical for understanding layout, piping configuration, elevations, measurement and sampling locations as well as for building trust with operating personnel. Today, many engineers spend too much time looking at a computer screen in their office. While computers and data analysis software are powerful, base knowledge of unit configuration and operation still counts, often even more than data easily accessible in the computer.
