Better Design Is No Pipe Dream

The benefits of using pipeline simulation tools at the piping and instrumentation diagram (P&ID) level, rather than running simulations just on the process flow diagram, can often be overlooked.

By Mike Spear, editor at large

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“Fluid flow is the forgotten science in the chemical industry,” says Todd Willman, director of development and engineering with engineering software company EPCON International, Houston, Texas. By not understanding what is going on in a plant’s piping systems, engineers are in danger of “forgetting half the possibility of where you can make your process better,” he warns.

As Willman has highlighted before, the benefits of using pipeline simulation tools at the piping and instrumentation diagram (P&ID) level, rather than running simulations just on the process flow diagram, can often be overlooked. The problem, he says, is that chemical engineers “typically have significantly less ‘schooling’ in fluid mechanics principles” than their mechanical engineering counterparts, who tend to take charge of fluid flow analyses in other industries.

Leigh Gillard, Asia channels manager with Flowmaster International, Towcester, U.K. and Skokie, Ill., makes a similar point. Speaking of an application of his company’s pipe modeling software at BP’s complex at Hull, U.K., he says BP’s view was that many chemical engineers are “classically trained in production,” and so tend  to ignore  the mechanical effects of simply getting fluid from point A to point B — events such as valve slamming or pressure surges, for instance. “You can’t just specify a pipe and hope you get a flow down it. You have to take into account many other factors,” he notes.

That BP application involved a complete redesign of the utility services at the site, where steam, water, air and nitrogen pipe networks serve a variety of process plants producing a number of basic chemicals from acetic acid to oxygenated solvents. With Flowmaster in use there since 1993 (initially for transient surge analysis of incompressible fluids), BP’s engineers were well versed in how to build accurate design models of all the networks, models which are now continually in use to analyze the impact of prospective changes in the service requirements of each plant.

Flowmaster Version 6.5 was released in October 2005  with several enhancements to the basic one-dimensional package that was originally designed to analyze the fluid dynamic effects of fast-acting pressure transients (such as pressure surge and water hammer) in complex pipe networks. The main drivers behind its use in the chemical industry, according to Gillard, are basically asset management — “knowing which pipes are going where” — and simulation of flare and pressure-relief systems.

Tailored to chemical engineers

EPCON’s SiNET 7 software, which is part of the company’s Engineer’s Aide Toolbox suite, recently celebrated its 25th anniversary with a new edition that, says Willman, “fully completes the metamorphosis of taking a traditional mechanical engineering task to the ‘mainstream’ for chemical engineers in the chemical process industries (CPI).”

“If you use this technology right,” Willman notes, “you can find out all sorts of problems. We’re not trying to force a hydraulic, mechanical engineering view onto chemical engineers. We’re basically helping them to do the right calculations from their point of view.”

With options including access to AIChE’s DIPPR physical properties database of more than  2,000 components and EPCON’s own two-phase flash models, SiNET is said to be good for general-purpose pipeline network analysis and process equipment sizing and troubleshooting.

For its fluid-flow modeling modules, Applied Flow Technology, Woodland Park, Colo., offers the 700-component-strong Chempak database licensed from Madison Technical Software of Westwood, Mass. The basic module is AFT Fathom for incompressible-flow pipe network analysis and system modeling, complemented by AFT Arrow for studies of compressible fluids, AFT Mercury and Titan for incompressible- and compressible-flow system optimizations, respectively, and AFT Impulse for water-hammer/surge-transients analysis.

Noting that the software is used in just about every industry that has piping or ducting systems, Tom Glassen, AFT’s vice president, operations, finds it somewhat surprising that application of pipe flow network analysis in the chemical industry is “still at a relatively early stage, not nearly as extensive as, say, the use of pipe stress analysis tools.” Many engineers, he believes, are still using “relatively crude tools based on spreadsheets,” although he is now seeing steady growth in the adoption of piping flow analysis software. “Companies that take it up,” he says, “soon appreciate the benefits of better design and fewer problems later on in operation…”

This gradual uptake is also recognized by Michael Blondin, sales and marketing manager of Engineered Software, Lacey, Wash. Its flagship product is Pipe-Flo, which started out life more than 20 years ago as a tool primarily for engineering design firms. Blondin says the current customer split has now swung around to being nearer 40% operators and 60% design firms. “We’ve seen a shift in probably the past 10 years,” he notes, “as we’ve moved to sophisticated Windows-based solutions and graphical interfaces, P&IDs and so on, trying to make the program as easy to use as possible. In many cases we work both with the design firm and then also with the end user, so that the Pipe-Flo model will apply throughout the life of the system.”

One end user can thank Pipe-Flo for a $40,000/year saving in energy costs. Bill Kane, manufacturing technologist at the Monsanto plant in Luling, La., used the software to optimize the plant’s compressed air system. “You wouldn’t have time or the expertise to do this type of analysis without Pipe-Flo,” he says. “These types of projects get more complicated as you get more people involved, so using the working model in Pipe-Flo made communication easier.”

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