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Contractor Makes the Cut for Giant Resin Pipe Correction

Tue January 26, 2010 - Northeast Edition
Construction Equipment Guide

Upon discovering that a giant section of piping was too long to connect to a new stack at a West Virginia power station in April 2009, the general contractor at Fort Martin Power Station needed someone to modify the pipe, and quickly. When CSDA cutting contractor Accurate Pro-Cut, of Parkersburg, W.Va., was approached to cut the pipe to the required specifications, they knew of an ideal way to make this cut, with great precision and in only a few days.

Fort Martin Power Station is owned and operated by Allegheny Energy Supply Company, a subsidiary of electricity utility Allegheny Energy. The power station has a generating capacity of 1,107 megawatts of electricity and is located in Maidsville, W.Va. The generating facility operates 24 hours a day, using coal to generate electricity and deliver low-cost, reliable electric service to more than 1.5 million customers in Pennsylvania, West Virginia, Maryland and Virginia.

In order to turn coal into kilowatts, the coal must be placed into a grinder to produce a fine powder. This powder is then blown into a furnace area inside a large boiler, where the coal burns much like a gas. Purified water is circulated through steel tubing inside the boiler, which can be as tall as a 23-story building, and the intense heat of the furnace — approximately 1,000 degrees F — boils the water and turns it to steam. The steam is then piped at high pressures, around 3,600 psi, to a turbine, where it spins giant, fan-like blades connected to a shaft. The revolving shaft turns a generator, where magnets spinning inside a coil of wire produce the electricity.

The new stack at the power station needed to be connected to an existing 3-in. (7.6 cm)-thick fiberglass resin pipe, with an outside diameter of 25 ft. (7.6 m). However, the pipe was found to be too long to make the necessary connection to the stack. General contractor Washington Group International (WGI) was contracted to shorten the pipe by 4 ft. (1.22 m) to accommodate an existing custom-fit resin flange that would connect the pipe to the new stack.

“Because we had been on this work site the week before, core drilling 1,440 holes through the flanges of the pipe readying it for the connection,” said Nick Ledford, site supervisor for Accurate Pro-Cut, “we were in the right place at the right time to help Washington over their next hurdle. Our good working relationship with them probably did not hurt either.”

Hand sawing the pipe was considered, but with time and precision being extremely important factors, it was much more feasible to employ wire sawing. The general contractor also had considered the construction of a replacement pipe, but the time and associated costs involved with this alternative were far more expensive than having the existing pipe shortened. Accurate’s plan was to perform two cuts to shorten the pipe to the desired length so that it would fit into the stack.

Accurate had to set up its wire saw equipment on and around the pipe, working at approximately 165 ft. (50.2 m) in the air. Any breaks in the wire or any adjustments that would have to be made would require the team to navigate across a 10-ft. (3 m)-wide I-beam to gain access to the work area. Only one wire saw setup was required, so the cutting team did not have to worry about moving the saw during the course of the project. Special care was taken to make sure the operators were tied off at all times to prevent falls.

Getting the equipment to the work area was achieved by crane and this proved to be a job in itself, taking a 10-hour day to accomplish. In addition, on the first day of this project, the 4-ft. section of the pipe that would be cut and removed, was rigged by crane before the cutting commenced to alleviate pressure during the cutting process.

Operators had to ensure that enough wire was on hand given the wear that was anticipated when cutting dry. The wire would have to be carefully monitored for wear and correct tensioning.

The wire sawing set-up consisted of a Diamond Products WS25 wire saw, CBN65 hydraulic power unit and .4 in. (10-mm) electroplated wire. It was believed that 100 ft. (30.4 m) of wire would be sufficient to perform the cuts. Roller wheels were removed and mounted to a 12-in. (30.4 cm) I-beam with 0.5-in. (1.27 cm) bolts, c-clamps and ratchet straps for added security. The operators wrapped the wire around the pipe at the cut line using no additional wheels or brackets, and ran the wire counter clockwise, pulling the wire in their direction.

It took a 10-hour day to complete the first cut. On completion of the first cut, operators discovered that the lack of water had caused excessive wear to the wire and the diamonds, so an additional 100 ft. was shipped to site to be ready for the next day of cutting.

Equipped with additional diamond wire, the cutting team returned on the second day of the project to complete the second cut and demobilize. This time, the cutting and dismantling of the equipment took just eight hours. The remaining section of the pipe was secured in place with an existing frame and bolts.

Accurate did not go without water on the job site. The team had to deal with rain and high winds on their work platform at 165 ft., so took extra care to be properly tied off to prevent falls. The elements and the predetermined water restrictions were not the only challenges encountered by the Accurate operators.

The material being cut was fiberglass, not concrete. The dust and debris created when cutting fiberglass, although minimal in comparison to other materials, was a major concern and many steps were taken to ensure operator safety. The basis of textile-grade glass fibers is silica, a quartz crystalline material that can cause serious illness if it is inhaled and penetrates deep into the lungs. Exposure to silica dust can increase when dry cutting. All required Personal Protective Equipment (PPE) was provided, including harnesses and eye protection and masks.

In total, Accurate Pro-Cut wire sawed the entire 78.5-ft. (23.9 m) circumference of the fiberglass resin pipe over just two days of cutting. The job was completed on time and under budget. In fact, the whole process was so fast that the job was priced and awarded on a Wednesday and completed on Saturday. The sheer speed of wire sawing was a great advantage for this cutting contractor and proved that jobs can be completed not only with speed, but with great precision.

This story was reprinted with permission from Concrete Openings Magazine, Sept. 2009 issue.

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