01 February 2003
Breaking new ground with functional diagrams
By Ellen Fussell
Fossil fuels are hot again, especially in the standards world, where ISA's SP77 committee is igniting a new series of standards to address functional diagrams in this booming industry.
Headed by Dan Lee, manager of the control application group at ABB Automation in Wickliffe, Ohio, the ISA SP77.40 committee hopes to expand on the illustration and use of function block symbols and functions and to prepare examples to develop them. The committee will help introduce International Electrotechnical Commission (IEC) standards on functional diagrams into similar U.S. standards.
The document will be ISA-TR77.40.01, but the SP77.40 committee is made up of a series of fossil fuel standards such as boiler controls, combustion controls, and feed water. They all use functional diagrams, so the new technical report encompasses all of them, Lee said.
Lee's committee now has 15 to 20 people from multiple industries internationally. One of the interesting aspects of this standards- writing effort is that it'll be done entirely via the Internet. "We have only five people in the U.S. and only three in the power industry," Lee said. While Lee said he might schedule a meeting for ISA EXPO 2003 in October in Houston, he'll mostly explore online, real-time collaboration to minimize the time it takes to get the document on the street.
The SP77.40 committee will rush to get the document out, but it's not the only group working on a document about functional diagrams. The SP5.1 subcommittee has been working for some time on a similar standard on symbols and symbol identifications. Although the SP77 committee had tried to form the new subcommittee a while ago, it fell through because the Standards and Practices board considered the subject matter to fall under the scope of the existing SP5.1. Yet the work in that committee is taking a lot longer than the SP77 committee is willing to wait—10 years in the making, said Lee, who also serves on the SP5.1 subcommittee.
There are also some discrepancies in what the scope and purpose of each document should contain. The IEC documents are based on the International Organization for Stan dard i zation (ISO) symbols, whereas ISA's documents are based on the Scientific Apparatus Makers Association (SAMA) symbols, Lee said. (SAMA is now known as the Measurement Control & Automation Asso cia tion.) In the new document, Lee would like to publish a table that shows a comparison between the ISA/SAMA symbols and the ISO symbolsthe SP5.1 committee isn't planning to do. Jim Carew, SP5.1 chairman, was not immediately available for comment.
In its rewrite, the SP77.40 subcommittee is taking all the examples out of the old revision and putting them in its technical report. Now serving as a liaison between the two committees, Lee said his task is "to get the SAMA PMC 22.1 [which also has examples in it] into 5.1, making sure the symbols, identifications, examples, and illustrations are documented in future ISA documents and revisions," he said. "We had agreed to include SAMA 22.1 into the next revision of 5.1. But since we're not making progress in 5.1, the SP77 committee said we'd take it on ourselves. Then when 5.1 makes further progress, we'll renumber our document as 5 whatever."
Lee said the new technical report will include the examples and illustrations from the SAMA standards. "That will cover explanations on how we do functional diagrams in the 77.40 series documents," he said.
"We talk about ISA being an international society, but it doesn't happen," Lee said. "I want to make an attempt to get something done in that area. If there's ever going to be collaboration between the two societies, then we need to understand the difference between the existing symbols." IT
MORE NEW FOSSIL FUEL COMMITTEES
The SP77.70 committee, led by Goray Mookerjee at Detroit Edison, needs volunteers to help revise the existing standard, ANSI/ISA-77.70-1994, Fossil Fuel Power Plant Instrument Piping Installation. This standard covers the mechanical design, engineering, fabrication, installation, testing, and protection of fossil power plant instrumentation sensing and control lines. The boundaries of the standard span the process tap root valve to the instrument connection. This standard applies to all fluid media (liquid, gas, or vapor).
The SP77.82 committee, led by Cyrus Taft at the Electric Power Research Institute, is working on a standard about selective catalytic reduction (SCR) controls. This standard will address the control functions associated with the SCR systems on fossil-fired steam boilers greater than 200,000 pounds per hour and combustion turbines greater than 25 megawatts. This includes the outlet NOx control using ammonia flow control, start-up and shutdown logic, bypass/ isolation logic, dilution air system control, ammonia storage and delivery system control, and catalyst cleaning systems.