February 2010 Vol. 237 No. 2

Features

Faster And Safer As-Built Drawings Available

Piping systems have been around since the time of ancient Rome. Roman engineers developed pipe that was constructed of flat sheets of lead that was rolled and seamed. It was then connected into a system to provide water to the bath houses. Later in 16th and 17th century Europe, wooden water pipes were quite common. Pipes were constructed from hollowed logs or constructed from staves and hoops similar to a wooden barrel. Since the Industrial Revolution, pipe and piping systems have evolved to carry more than just water and other fluids. Technology has improved and a myriad of materials is now being used for manufactured pipe. These advancements have increased the allowable pressures and the types of products that the piping can convey.

For many years, gathering field data on existing piping systems remained basically unchanged. Even with the advent of CAD systems in the past few decades, a minimum of two field technicians wielding measuring tapes and sketch pads remained the best approach. When the piping systems were in accessible locations and squarely assembled, it was not extremely difficult for the technicians to hand sketch a field isometric diagram to be redrawn later back in the office.

As piping systems became more complex and more hazardous materials were being handled by them, the people collecting field data were often required to place themselves in potentially precarious situations to obtain the needed measurements. Further, the man hours required to obtain the field data could be very costly to the customer. The pitfalls of this method were many – missed dimensions, smudged or damaged sketches – all of which could stop the work in its tracks. Many times a return trip to the field was necessary to gather missed or erroneous data. Also, the exposure of personnel to hazardous locations or materials, coupled with a lack of access, greatly magnified the difficulty.

New Methods
Those were the old days. Now, in the 21st century, new methods of field-data collection have emerged. Hunt, Guillot & Associates (HGA), an engineering firm based in Ruston, LA has worked closely with COADE, Inc., a Houston-based provider of software for multiple plant design and engineering disciplines, in pioneering the use of the CADWorx® fieldPipe surveying system for the engineering services industry.

The new system integrates with the Leica Total Station surveying instrument that utilizes visible laser telemetry to make very accurate distance measurements. The system interfaces with a hardened laptop PC and fully integrates with the COADE CADWorx piping design software. Using the new system, the technician can quickly develop three dimensional as-built drawings from scratch while in the field. Complex piping system components can be modeled quickly and easily, from a minimum of set-up locations. In many cases, the technician can make all the necessary measurements from the ground or from another safely accessible location. Aside from the safety aspect, the system is extremely accurate. HGA tests have shown that an accuracy of plus or minus 1/8-inch at 300 feet is not uncommon.

Furthermore, the use of the system has almost eliminated the necessity of return field trips. These units are operated in the field, often by a single designer, obtaining the required data for as-built drawings. In addition to producing as-built drawings, HGA designers utilize the instrument to accurately place tie-in points directly into the 3-D model for retrofit work or modifications in existing plants.

The amount of time required in the office to interpret field data and to develop the finished drawing has been greatly minimized, resulting in cost savings to customers. HGA and one of its specialty chemical clients discovered the value on the very first job. After a brief two-day initial training session for the technicians, the CADWorx fieldPipe system was used to develop a set of field drawings for a customer. The job consisted of providing a 3-D model and detailed nozzle diagrams of six existing storage tanks at the customer’s plant site.

There was no easy access to the tops of the six tanks, and there were eight nozzles on top of each. There were also five more nozzles at ground level. The survey instrument was placed in a safe and stable location above a control room across the road from the tank farm. The field work took just two days to complete with another two days in the office to complete the drawing package.

The drawings were accurately completed without the technicians having to be near or on the tanks and no man lift was required. The result was an accurate set of drawings created safely and cost-effectively for the customer. Since that initial job, HGA has moved beyond this one system and has trained several of its designers in its application.

HGA is just beginning to scratch the surface in the application of this valuable tool in the natural gas and specialty chemicals industries and is continually finding new uses for it outside of piping. Other applications include the accurate measurement of steel-support structures, buildings, plant sites and equipment. The possibilities are endless and a long way from the days of “caveman CAD” using only a measuring tape, sketch pad and ladder.

Authors
Stephen K. Blackwelder, PE, services as engineer and business development manager for Hunt, Guillot & Associates, LLC (HGA), Ruston, LA. He can be reached at (318) 251-8952 or sblackwelder@hga-llc.com, www.hga-llc.com.

David Craig serves HGA as engineering manager.

Brian Michaud serves as HGA as piping designer.