Geo Week News

October 21, 2008

Taylor & Hill Scans Navajo ROSE Unit for Dismantling and Reassembly

Editor’s note: This is a story we’ve wanted to tell for some time, as it highlights yet another value of laser scanning technology for refinery operations. It is no secret that the oil and gas refining sector is stressed-from demand, changing regulations and shock from hurricanes and other storm events. Scanning can help to document the existing conditions of many plant components at different times and serve as a tool in the transaction of purchased or sold units by oil and gas companies. – Lieca N. Hohner

Holly Corporation’s Navajo Refining Company purchased a ROSE (residual oil supercritical extraction) unit from a decommissioned refinery in El Dorado, Kan., in early 2005. The unit was disassembled and shipped 700 miles away to the Artesia, N.M., refinery, where it was reassembled and installed. Navajo decided at the outset that 3D laser scanning was the only way to document the unit’s existing conditions quickly enough to meet the disassembly schedule and completely and accurately enough to confidently support reassembly.

A ROSE unit is a solvent de-asphalting device for extracting the last recoverable bits of gas oil, the substance from which gasoline is refined. According to the Navajo Refinery’s Web site, it “has a crude oil capacity of 83,000 BPSD [Barrels Per Stream Day] and has the ability to process sour crude oils into high value light products (such as gasoline, diesel fuel and jet fuel).” The refinery distributes products to markets in Arizona, New Mexico and west Texas.

Navajo Project Manager Bill Romine says the work scope for the disassembly specified that the unit be laser scanned beforehand with the model turned over to Navajo. And although Navajo had never before used laser scanning, Romine says the company knew the experiences of others who had, and management was “pretty adamant” that the requirement for scanning be part of the RFP.

Navajo awarded the disassembly contract to maintenance, construction and turnaround services company Repcon Inc., of Corpus Christi, Texas, which selected Taylor & Hill Inc. (T&H), a Houston-based petrochemical engineering services company, to provide laser scanning and modeling services. The primary objective of the scanning project was to document all equipment-pumps, exchangers, tanks, towers-and related piping more than 3 inches in diameter in order to aid reassembly at the new site. Documenting the structural steel was not part of the scope.

Scanning Team Captures Site in Five Days

Using a Leica HDS3000 laser scanner in conjunction with a Leica TPS1100 Series total station, the scanning team, including T&H CAD Manager Rito Morales and Greenscan 3D (Cumming, Ga.) President Scott Pool, scanned the site in five days. Glen Kearns, then T&H’s laser scanning project manager (now with Hi-CAD, part of the Intertek group), notes that collecting data in a manual walkdown would have taken several weeks-time the project schedule did not allow. The target area occupied a footprint of 200 feet by 180 feet; the tallest furnace-stack structures extended upward of 100 feet above grade. Collecting all needed data required 20 scan positions throughout the unit. Some 4 Gb of scan data was collected in all.

Georeferencing the point clouds to the existing plant coordinate system was critical. The total station was used to record the location of all scan targets and known plant features. At the end of each day onsite, the team reviewed all scans, then registered them using cloud-to-cloud registration. Cyclone software was used for both scanner control and point cloud registration. Once registered, the scans were aligned with real-world coordinates from the total station data. AutoCAD, running with T&H’s internally developed AEMS (Advanced Electronic Measuring System) software, was used to export plant coordinates, which were then imported into Cyclone for georeferencing.

Post-processing: Cyclone to AutoCAD DWG

Once back at T&H’s home office in Houston, Kearns and Morales commenced modeling using Cyclone. Aided by such tools in the software as limit boxes and temporary model spaces, the process of generating the equipment and piping went fairly quickly. Each was assigned his own sections of the unit to avoid duplication of work. Another request of the contract was to identify and label the points where the piping was to be cut during removal and disassembly of the ROSE unit; Kearns and Morales say that Cyclone’s Annotation tool was the perfect solution for this. The resulting model could be dynamically viewed from any perspective with the cutpoint annotations floating in unison with the moving model.

Each line and piece of equipment was placed on individual layers and assigned colors in Cyclone. The final deliverable was an 8 Mb AutoCAD DWG file of the entire 3D model. The use of Leica’s COE (Cyclone Object Exchange) utilities permitted T&H to export the model to AutoCAD while retaining solids and properties without data loss. [This project was completed in early 2005. In late 2006, Leica Geosystems unveiled TruView, its free 3D viewer for point cloud data, which T&H subsequently used to create a model of the unit – Ed.]

Schedule, Safety Benefits

Repcon was impressed with the technology. “Laser scanning was fast!” says Gary Byrd, vice president of construction with Repcon. “Those guys got in, did their work and were out of there inside a week. Then it took a month to process the raw data into models. To have had engineers out there measuring manually, then trying to create as-builts or a CAD model, would have taken a lot longer.”

The biggest benefit of laser scanning, according to Kearns and Morales, is that T&H was able to accommodate the project schedule by compressing data-capture time from weeks to days. “They had already started taking the unit apart when we were called in,” Kearns says. “They stopped so we could record the geometry. They wanted us in and out of there within a couple of weeks, and we were able to do that.” T&H assembled its scan team, mobilized to the site, spent five days scanning, and then, Kearns says, “the day after we left, they restarted disassembly.”

Another advantage, they say, is the portability of the equipment. Wet and icy conditions developed during part of the scanning work, but the light precipitation-including some sleet-did not halt data collection. The HDS3000’s range allowed T&H to continue scanning by shooting from inside a mechanical room across the street from the target area. In addition, said Morales, “there were a couple of days when it was raining in the morning, and we couldn’t find a shelter to set up in. But it didn’t matter, because we could scan into the night-in pitch dark-and still get good data.”

Finally, the safety advantages were highly valuable. “If we had to do it conventionally, even with total stations, there would have been climbing and laddering,” Morales says, whereas laser scanning allowed data to be safely captured from both ground and elevated vantage points without scaffolding or ladders. “And there may have been contaminants onsite that we would have had to be careful not to touch. But with laser scanning, you don’t have to worry about getting right up on the objects you’re measuring.”

The Navajo Refinery Company ROSE unit began operation in December 2005.

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