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Product category: Simulation, modelling and validation software
News Release from: Rebis | Subject: Autoplant 97 3D modeling software
Edited by the Engineeringtalk Editorial Team on 23 July 2001

Plant problem solved thanks to versatile
software

Transfering a 3D plant model directly to a flow analysis program allowed 4 Front Engineering to quickly determine that scale build-up was causing a cooling water imbalance at a polymer manufacturer

The ability to transfer a 3D plant model directly to a flow analysis program allowed 4 Front Engineering to quickly determine that scale build-up was causing a cooling water imbalance at a major polymer manufacturing facility The project took only eight weeks, which included taking digital photos of the chemical plant, accurately gathering dimensions and piping information from the photographs, building a 3D computer model, running multiple flow analyses, and preparing a report with color coded 3D model view drawings

Considering the traditional method of gathering field dimensions and piping component data and solving flow and pressure calculations, it is unlikely the engineering work could have been justified based on cost and accuracy and that the cause of the flow and pressure imbalance ever have been found.

Plant operators would have attempted to solve the problem by randomly throttling manual valves effecting exchanger heat transfer fouling and process production rates.

Instead, they received a comprehensive analysis from 4 Front Engineering indicating the reduced effective diameters of the fouled piping and exchangers which were plugged with scale as well as a prioritized schedule for replacing piping and cleaning heat exchangers in the most efficient and cost-effective order.

The same integrated method was used for an application at a major refinery to predict the effects on a cooling water circuit and corresponding heat exchangers for a process debottleneck project which was to introduce an additional heat exchanger within the loop.

The project took only 6 weeks and results of the analysis predicted the impact and effects on all of the existing exchangers.

Flow rates, pressures, velocities, and skin temperatures were predicted using the network node analysis and presented using an interactive 3D graphical representation of the piping system.

4 Front Engineering provides computer aided engineering services and 3D modeling for the petroleum refining and chemical processing industries.

The company offers the 4D technological method for constructing models of existing plants using close range digital photogrammetry and Rebis' Autoplant 97 3D modeling software.

4 Front Engineering's technology has proven to be cost-effective in modular construction and skid design with limited spatial constraints and in applications where piping and steel interferences are critical.

With its linked engineering-design method, 4 Front Engineering's multi-discipline team has displayed the ability to provide cost-effective 3D wireframe and rendered models for the smallest scale projects.

The company supplies electronic drawings in any version of MicroStation or Autocad, mechanical and construction design lists, and 3D model presentations for client review on compact disks and VHS video using customized Rebis Explorer software and proprietary software programs.

4 Front Engineering is committed to operating at the leading edge of technology and optimizing productivity by utilizing an integrated information system, high-speed linked PCs, and proprietary technology that allows for concurrent performance of engineering disciplines.

The polymer manufacturing plant that contacted 4 Front Engineering about the problem with its cooling water system had discovered that too much cooling water was going to some heat exchangers and not enough was going to others.

This was a relatively large facility with 190 segments of pipe and 65 heat exchangers.

One option for determining the cause of the imbalance was to take pressure and flow readings at various locations and use the data in spreadsheet calculations to try to determine flows at various locations.

A low flow value might have indicated a problem somewhere in the general vicinity of the reading but would not have pinpointed it precisely due to limited availability of pressure tap sources and inaccuracies in external flow measurements.

Workers would have then replaced piping in the area in hopes of solving the problem, but there was no guarantee that they would replace the right piping segments and that this solution would work.

The polymer manufacturing plant hired 4 Front Engineering to discover the exact nature of the cooling water imbalance and present an effective solution.

Supplied with limited and outdated piping drawings of the plant, 4 Front Engineering's first step was to take digital photos and use digital photogrammetry software to accurately and expeditiously gather field dimensions and piping component information.

It took about a week to take all the photos but this was much faster than the alternative, taking measurements by hand and hiring a survey crew, which would have taken closer to two months.

The company took the digital photos rather than working exclusively from existing drawings because the drawings would not reflect changes that had been made since the plant was built.

The photos provided centerlines and dimensional data, accurate to within one inch.

This information was used along with existing drawings to create the 3D model.

The CAD software used to create the model was Autoplant 97, from Rebis, Walnut Creek, California.

This program runs as an add-on to Autocad, which is one reason why 4 Front Engineering selected it.

Their engineers and designers were experienced with AutoCAD, so learning the Autoplant software was an easy transition.

The program was cost-effective per seat, especially compared to other plant design systems that run on Unix workstations.

Autoplant was also chosen because of its tight integration with the analysis software, Plantflow, also from Rebis.

This program is used to design and analyze gas or liquid piping networks and was necessary in this project to find the cause of the flow imbalance.

Plantflow can import Autoplant geometry without any data translation, making the analysis software an integral tool in the engineering process.

It took about five weeks to create the Autoplant model using the dimensional information from the digital photos and existing plant drawings.

One benefit of building the model in Autoplant rather than plain Autocad was that, rather than simply being geometric representations, the 3D objects within the model had intelligence associated with them.

Objects in Autoplant are called "reboids" and can be linked to external databases containing additional information such as performance and material specifications.

When a user clicks on a particular pipe in an Autoplant model, for example, information such as the line size, line number, and material of the pipe is immediately available.

That information might have been entered by the user but much of it is already available within the Autoplant component library.

As a user builds the 3D plant model, he picks components from the library.

Not only does this make the modeling go quickly, it also ensures that intelligence is incorporated into the model.

Having an intelligent 3D model was helpful in this project because certain information required for the flow analysis was already available in the model and did not have to be re-entered.

For example, pump discharge pressures were one of the inputs required for the analysis.

This information was available from pump curves that were part of the pump specifications already contained in the 3D model.

After the 3D geometry was transferred to Plantflow, engineers ran a preliminary flow analysis to determine the theoretical pressures, flows, and velocities at the polymer manufacturing plant.

Plantflow made the results easy to interpret by generating 3D drawings that were colored-coded according to flows.

Flows of 0-20,000 gallons per minute were shown in one color, 20,000 to 30,000 gallons per minute in another, and so on.

It was also possible to interrogate the results graphically.

The user simply picked a point in the model and the software presented the pressure, temperature, flow, velocity, and pipe size at that point.

The preliminary analysis was based on clean piping and the results did not agree with field data.

Actual flows were lower and actual pressures were higher than what the analysis model predicted.

The next step was to run additional sensitivity analyses simulating different scenarios to determine why the model results differed from actual operating conditions.

For example, one analysis was completed to evaluate whether the pumps were working correctly, which was one possible cause of the water flow imbalance.

PlantFLOW enables the user to tell if a pump is not working correctly by predicting the pump's theoretical performance according to actual flow rates obtained with physical measurements.

If the analysis results did not concur with the pump's operating curve, it was possible that the pump impeller was worn out or pump efficiency had been decreased.

This analysis showed that the pumps were operating properly, however, so 4 Front Engineering had to look for another cause for the flow imbalance.

4Front then decided to correct the model for dirty conditions by changing resistance coefficients.

The calculated results agreed closely with field data.

From these results, 4 Front Engineering determined that scale had formed in the pipes.

The results were confirmed with chemical analyses performed by the facility's water treatment company and their knowledge of a history of solids present in the cooling water.

Using color-coded flow diagrams they could then determine which sections were plugged.

When the polymer manufacturing plant's workers cut cross-sections in those areas, they saw that scale had reduced the pipe diameter by as much as 50% in some places.

4 Front Engineering prepared a report in which they prioritized which pieces of pipe needed to be replaced in the order that would have largest benefit on production.

Because 4 Front Engineering was able to complete this project so quickly, the polymer manufacturing plant was able to get the cooling water system back to optimal operation much sooner than if they had tried to fix it by randomly replacing pipes and reworking pump internals.

4 Front Engineering completed a similar project at a refinery that wanted to add a heat exchanger to its system.

This refinery wanted the consulting firm to show them how an additional heat exchanger would affect overall cooling system circulation.

4 Front Engineering built a 3D model from digital photos exclusively since there were no accurate drawings available for this facility.

Then they added a heat exchanger and performed a flow analysis in Plantflow to determine how its share of water would affect flow to all the other exchangers.

This problem would have been impossible to solve by hand because of the complexity of this refinery.

The analysis results showed that if the refinery added the heat exchanger, several heat exchangers would not get enough water while others would get too much.

The client then asked 4 Front Engineering to balance the system with the new heat exchanger in place.

After several iterations of modifying the piping layout and valve locations and then repeating the flow analysis, they had optimized the cooling system so that just enough water passed by each heat exchanger.

When the refinery implements these changes, the result should be an increase in production since temperatures will be better controlled.

For 4 Front Engineering, having plant flow analysis that is so tightly coupled to the 3D plant model makes it possible to offer a level of service that few other companies have.

Not only can they present the client with an intelligent 3D model of a facility accurate to within one inch, they can show detailed flow analysis results in a color-coded format that everyone can understand.

Thanks to the use of advanced technology, 4 Front Engineering has become the company to call when a plant has a flow problem that needs to be solved quickly.

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