Plasma Systems Useful For Pipeline Construction

It is early November and 6,000 feel up in the Wasatch Mountains near Ogden UT and wet snow has turned the already rough dirt road to halffrozen mud. Although gray skies are promising more snow. Kenny Glaze. member of Pipeliners' Union Local 798, was on his way to repair a porous weld bead on Associated Pipe Line Spread IB, part of the Ruby Pipeline project.

Construction on the Ruby began on July 31. 2010. The project included laying roughly 680 miles of 42-inch natural eas transmission pipeline on a right-of-way through parts of four states: Wyoming. Utah. Nevada, and Oregon. The pipeline is designed to transport 1.5 Bcfd of natural gas. Delays beyond the target completion date cost considerable time and money.

A 20- year pipeline veteran. Glaze has worked on numerous projects throughout the United Stales. This is the first one where he has used plasma to repair welds though. "Before plasma. I had io use a grinder to access the repair area. Thai generally look 45 minutes or more of hand grinding. But now that I'm using a Powermax45 plasma system. I can gouge down to the repair area in a third of the time."

Hypertlserm plasma systems, like the Powermax unit Glaze used can remove 6.2 pounds of melai per hour. Another time saving benefit is that the plasma leaves behind a weldable edge, and for Associated Pipe Line Contractors, hired lo build sections of the line, every minute saved helps keep the project on its tight schedule and under budget. For the welders though, time saved is just the beginning. Fatigue and safely come into play as well. The grinder is heavier and harder to hold than the plasma torch and grinding presents safety hazards, such as eye injuries, from living debris.

There are other options, but unfortunately, they aren't much better. For instance, carbon arc gouging presents a problem because the carbon winds up puddling on the pipe and must then be ground off. On the oilier hand, the plasma system Glaze is using is highly portable, light weight and can cut Vi-inch mild steel with case.

Once the palli for the pipeline has been cleared and prepared, sections of pipe ranging from 40-80 feet and varying in diameter and coaling thickness based on their specific location are laid out along the path in a process called "stringing the pipe" The pipes arc welded together, contoured coated inspected and tested. The inspection and testing phases may turn up defects in pipe welds that have to be repaired. For example, misalignment of the pipes can lead to inadequate weld penetration in a section of the weld seam. Another common problem is porosity in the weld. Porosity can b<¿ scattered cluster, or hollou-bead but all types are defects and must be repaired. While repairing weld defects adds time and cost to a project the consequences of not repairing them would be far more severe. In fact, inadequate penetration and high porosity in welds, along with other issues, are actually the suspected cause of the September 20 IO pipeline explosion in San Bruno. CA. Federal investigators say they found do/ens of substandard welds on the pipe, welds that could have been easily repaired with plasma.

Another advantage of using plasma is the increased visibility of the repair area. When making a repair, the goal is to remove the weld bead without touching the pipe section. "This is where plasma really pays off for the welder doing (he job," said Glaze. "The welder can see very precisely what he is doing." A wrong move while gouging or grinding can require the removal of a complete section of pipe at a cost of $60.000 or more. "WeYe here to fix things. not to create more problems." added Glaze.

Pipeline construction is a highly technical and regulated industry. Companies like Associated which has beenbuilding pipelines for more than 50 years, have to meet stringent quality demands. In addition. Associated specializes in working in difficult terrain. The company prides itself on its innovative approach and willingness to use new technology to meet these challenges. "New technology makes the industry much more efficient and works to eliminate ha/ards. such as those associated with the use of old hand grinders." said Sonny Weems. superintendent of Associated Pine Line Contractors.

Although gouging was the first application Associated found for plasma, they are finding other uses for the cutting method. One such use is for the actual cutting of pipe. The crew lias discovered that using another Hyperlherm product, the slightly larger PowermaseS. \vi!h a mechanized torch and a pipe bcveler, speeds up the process of cutting pipe for bends and preparing ends of pipe sections i'or fitting. With a recommended -%-inch cutting capacity, the system can run at full capacity off of a 15 k W engine-drive generator or at lower amperage off of a 12 k W engine drive.

These cuts were traditionaily done with oxyfuel. but the faster cut speeds of plasma reduce the amount of time the tie-in crews spend standing around waiting for the pipe to be prepped. Kevin Berryman. the tie-in foreman for Associated. has also found that the cut quality of plasma has reduced or eliminated the need for grinding the weld area after the cut - another time savings.

Better cut quality and smoother cuts result in easier "fit ups" of the pipe, which in turn result in better welds and fewer field repairs needed. "Plasma is all about time and efficiency in our line of work." said Berryman.

According to the provider of the plasma torch, in the past, pipe line builders needing to gouge out excess metal had to rely on hand grinding. The process was lengthy - typically taking at least 45 minutes for each small area- and dangerous with flying debris causing an average of one serious eye injury per day.

A good quality plasma system is capable of making smooth cuts. The plasma torch provider says the cut shown here was made by placing one of Hypertherm's new Duramax torches on a mechanized pipe cutter.

In addition to gouging out metal, Ruby workers used plasma to cut new sections of pipe prior to the tie-in process. Because the Hypertherm Powermax system used on the line came with several different torches, workers were able to use the same system for both handheld gouging and mechanized pipe cutting

Sumber : Flanders, Paula. "Plasma Systems Useful For Pipeline Construction". 30 Januari 2014. http://search.proquest.com/docview/902705451?accountid=31562