Hybrid Modeling for Quick Economical Plant Modifications

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"Measure then model" has long been the standard approach for designing plant modifications. Nestle Group Engineering was ready to do just that after a modification to an ammonia (NH3) refrigeration unit led to trapped ammonia inside a compressor, creating a potentially dangerous situation.

However, Vernon Jensen of Construction Management and Design Services (CMDS) and Brighton Engineering knew a better way. Compared to conventional methods, CMDS knew that "hybrid modeling" would instead save Nestle both time AND money. So Vernon teamed with Danny Lazear, 3D modeler with Archway Systems, Inc., to create this "hybrid model," a combination of point cloud and solid geometry. As a result, they saved Nestle four weeks off the schedule and $24,000 in construction costs.

Hybrid modeling is gaining more and more traction as new software and hardware are capable of responsively handling larger and larger point clouds. Traditionally, the approach has been to use the cloud as a guide with the intent to model everything into solids. This is a long and laborious process to do manually, and it is almost just as laborious to go back and edit the solids created from software that claim to have automatic processes.

As systems are now able to handle larger amounts of scan data, sometimes in excess of 1 billion points for a single point cloud, it is apparent that modeling the entire facility is no longer the most practical or efficient method. The portions of the cloud that represent the proposed modifications can be modeled while the remainder of the facility can be left as a point cloud for contextual reference. The ability to model in a realworld environment has many economic advantages, including fewer changeorders and less on-site modifications.

Bentley Pointools V8i software converts point clouds from any LiDAR format to the highly compressed and very efficient POD file format. Bentley Pointools can then be used to clean up scan noise, classify the points and create a walkthrough of the facility. It has long been the industry leader in handling large datasets from a wide variety of sources.

Likewise, Bentley Descartes is a product specifically designed to handle point clouds on top of Bentley’s solid modeling software (MicroStation and AECOsim Building Designer). Descartes can be used to semi-automatically convert groups of points to planes or cylinders. If a solid model is what you are after, Bentley AECOsim Building Designer can then be used to convert the point cloud into solid 3D models with building or plant components. AECOsim Building Designer is Bentley’s BIM software suite. To show how this software can be used in a hybrid modeling workflow, let’s take a look at how it helped solve Nestle’s trapped ammonia problem quickly and effectively (Figure 1).

The goal for CMDS and Brighton Engineering was to address the problem traps of the High Stage Suction (HSS) and Booster Discharge (BD) Header after the installation of a new vertical intercooler. The existing NH3 refrigeration system had horizontal intercoolers. The connection points of the new vertical intercooler are much higher in elevation than the existing High Stage Suction (HSS) and Booster Discharge (BD) Headers. Consequently, this issue causes a problem with the possibility of trapping liquid ammonia in the High Stage Suction (HSS) and Booster Discharge (BD) Headers that could get to the High Stage Suction (HSS) and Booster Discharge (BD) Compressors.

Liquid NH3 in a compressor is an extreme safety hazard that puts operation personnel in danger and could also cause the destruction of plant property. The potential result of this system damage could cause a plant shutdown and loss of marketable product. Both Nestle and IIAR Refrigeration Specifications have strict guidelines for this kind of trap issue.

The solution CMDS came up with was to use 2 FARO Focus3D Laser Scanners to create an as-built of the current conditions of the refrigeration system. After they had scanned the entire facility, CMDS registered the scans using FARO SCENE 3D and then exported a POD file for use inside Bentley Pointools V8i.

Using the editing tools in Bentley Pointools V8i, the point cloud was classified so that each piping system was separated according to its purpose, such as High Stage Suction (HSS), Booster Discharge (BD) and each of the compressors. Utilizing the POD file’s ability to handle classifications, CMDS created a point cloud that could then be used as contextual reference in Bentley Descartes and AECOsim Building Designer. Descartes handled the editing of the classified point cloud while AECOsim Building Designer was used to create the new piping model.

Jensen of CMDS had worked closely with Danny Lazear, of Archway Systems, to create the POD file, so he brought Lazear on board to model the new piping system. They were able to eliminate the liquid ammonia traps by modeling the modifications in AECOsim Building Designer. Once modeled, each of the pipe segments were exported to .obj files for import back into Bentley Pointools V8i.

Bentley Pointools was then used for presentation to the client for conceptual review and clash detection with neighboring equipment in Nestle’s facility. Once the conceptual design was accepted, CMDS produced engineering drawings in AECOsim Building Designer for a Request for Quote (RFQ) to various refrigeration contractors for the actual construction of the new piping system (Figure 2).

This project was originally identified by Nestle to address the issue of potential hazard to life and property at their Chatsworth plant. When it comes to the possibility of loss of life and property cost is not the major issue, but the team was still trying to produce a cost effective solution. A conventional method of creating an as-built model of this facility would have taken five weeks at a cost of $30,000. By understanding both the hardware and software side of point clouds, CMDS was able to reduce the project schedule down to just one week at a cost of $6,000. Nestle saved four weeks and $24,000 of guaranteed expenditures while also avoiding the potential hazard of a plant shutdown or injury to plant personnel.

The hybrid modeling workflow that CMDS employed shows how economical point cloud technology can be when used in the right way. Many companies try to fit laser scanning into their current as-built workflows without thinking about why they actually need a solid 3D model as a deliverable. However, if the solid model is going to be used just as a reference for later projects, why spend valuable resources to go through the conventional methods when you can have an accurate, digital representation of your project in a fraction of the time?

Vernon Jensen is the President, CEO and a Project Manager for CMDS, Inc., a full service AEC firm. His 20+ years in the food and beverage processing industry makes him a coveted construction manager in all types of plant facilities.
Danny Lazear is an Application Engineer and 3D Modeler for Archway Systems, Inc., a Bentley channel partner and engineering services firm. He has consulted on many point cloud and 3D modeling projects for various Southern California companies.

A 1.971Mb PDF of this article as it appeared in the magazine complete with images is available by clicking HERE