6 replies to this topic

[sanchez]

Hi.

 

What are the differences between a process engineer and a process control engineer?

 

What do they really do (daily task) in a chemical plant?

[Steve Hall]

Books are written that address this question, so it's not easy to summarize in a Post. The daily tasks are highly dependent on the the engineer's role, his skill level, the skills of his colleagues, the industry, the environment (e.g., operating plant, engineering office, etc.), and many other factors. That said, consider these possible descriptions:

A process engineer is responsible for design, procurement, installation, operation, and maintenance of chemical process equipment and systems. He/she prepares flow diagrams, P&IDs, and equipment specifications. He/she sizes equipment, makes material balances, selects technology, chooses materials of construction, prepares equipment data sheets and specifications, and might be considered the overall 'architect' of the chemical plant. From the controls viewpoint, the process engineer determines what must be controlled (e.g., temperature, pressure, flow, level), and often determines the measuring points and final control elements. He/she might develop the initial control loops (on the P&ID).

A process controls engineer is responsible for the determining the controls details. Before distributed control, this function was called 'instrument engineer'. On a micro level, the controls engineer designs the control loops, decides whether advanced control strategies such as cascades are required, and selects the sensors, transmitters, controllers, and final control devices. He/she is responsible for sizing control valves and orifices, determining tuning parameters, and matching control signals. On a macro level, he/she writes Functional Design Specifications and Detailed Design Specifications, and (depending on the person's exact function) might do the actual configuration and programming of the controllers. These days, the controllers are likely to be in a distributed system which may consist of localized PLCs, a centralized control system, or a combination system. The controls engineer helps determine acceptable process ranges, alarm limits, and calibration tolerances.

In summary, adding 'controls' to the job title results in a completely different set of responsibilities. Both jobs are typically filled with a chemical engineer. But the skill sets quickly diverge.

[kkala]

In an old local fertilizer plant (~1978) they were not "pure" process and process control engineers. The process activity was covered by chemical engineers in Operations (quite fruitful); control of the units by an electrical/instrument engineer and relevant technicians of Maintenance Dept, also responsible for the new control installations of the units. Important modifications or new units were designed out of the plant, but we had to carry out the start ups, even under some designer's "guidance".
Big modern plants have their own engineering Depts, but they usually do not undertake full engineering design. In a local refinery of such an organization, Process Dept deals with plant improvements and new projects, not usually intervening in Operations. Instrumentation Dept deals with same activities but from the Instrumentation view point, which includes controls. Design for new projects is usually elaborated by external engineering companies.
Such external engineering company has Instrumentation Dept, having to be familiar with the process of an undertaken project, but from their own view point. Its process Dept has to describe the controls using words and simple symbols in PIDs, Instrumentation has to present controls in more formal and complicated symbols. Hardware is responsibility of Instrumentation, also checking vendors' offered material and elaborating bid tabulations. Process offers only clarifications on operation, if requested. These are mentioned here because engineering Dept of other plants may be strong enough for such activities.
I have not mentioned "process control engineer", since it has not been met here so far; it may exist in more industrially developed countries, probably in engineering companies. Even instrument engineers were not widely known here before (say) 1980, activity was covered by electrical engineers. At present instrument engineers officially cover all control activities, but process should "describe" them initially (as said). But I have seen brilliant exceptions on this.
What has not been heard of here is instrument/control design using Bode or Nyquist diagrams, differential equations, Laplace transforms (except one case of sugar plant design). Probably the "process control engineer" deals with more control activities like these and has deeper understanding of process than an ordinary instrument engineer, which is very important. But hopefully somebody else will clarify the role of "process control engineer' based on experience.

Editing note: Post no 2 (by Steve Hall), not detected during writing, clarifies that instrument engineer is same as "process control engineer" nowadays.

Edited by kkala, 19 February 2013 - 08:15 AM.

[sanchez]

Thank you so much for those explanations. These help me a lot. I'm actually taking advanced process control for this semester in my university, and still wondering how the process control engineer really works in a plant. Thanks.

[sanchez]

is there any experienced process control engineer here? what is your opinion regarding this topic?

[kkala]

Probably it is useful to briefly tell contents of your course on Advanced Process Control, then members clarify whether these can have application in industrial practice. Are you also interested in engineering companies' practice? 

[timcenta]

My experience has been that process engineers tend to have a bit more "product" responsibility than a controls engineer. Controls engineering tend to have more "system and infrastructure" responsibility. There is lots of overlap based on the industry segment and the convention of the unique businesses.