DCS Selection, Distributed Control Systems

Why would you choose one brand/model of DCS over another. At SPEC we have used, (for various reasons)

  • Emerson DeltaV, with and without S88 Batch
  • ABB 800XA, batch
  • Siemens PCS7, non-batch

(All the flagship products of leading companies)

They each have their advantages and disadvantages:

Price -

Due to the competitive nature of the industry, pricing varies widely. In the last project we bid, ~ 120 I/O points with 2 workstations. The budget pricing was $18,000 for PCS7 and $25,000 for DeltaV. (without I/O).

This may look like a big difference, but when a good configuration engineer cost 4K to 6K per week, the ease of use and speed of configuration becomes significantly more important than the initial cost of hardware and software licenses.

Ease of Use for Configuration Engineer-

By far, DeltaV is the easiest system to configure. There are fewer options, fewer menus and check boxes. One of the best features, is the control module templates.

A control module is a pre-set subroutine which is configured for a specific function. Examples of control modules:

  • Analog Input with scaling, alarming, and trending (historical collection)
  • Digital Input with alarming, latching, logging, and time delay.
  • PID Loop

With the control module setup, and engineer can setup a typical analog input point, define ranges, alarm levels, and historical collection (example: every 10 seconds).

Then whenever a new AI is required, this is dragged out of the library, just change name, assign I/O, reset alarm limits and you are done.

ABB has similar functions, and can even can wrap together the control code with the associated graphic object, but it is more difficult to do.

Siemens PCS7 has control module library, but CM’s are copy/paste, and not instantiated. To learn more about this “instantiation” see: http://www.specsoft-pfs.com/Brewery%20Automation%20Model.pdf

Ease of Use for Client-

As with ease for a configuration engineer, DeltaV has the fewest options and simplest menus. For a refinery, or very large plant with sophisticated operators, it probably won’t make a difference. SPEC sometimes installs the first control system a client has in their plant.