Concrete pipe producers like Vince Bussio often have a difficult time documenting quality for customers since the applicable standards, ASTM C 969 and ASTM C 1103, measure joint integrity with low-pressure air or water only after contractor installation. When the pipe fails to meet these field standards, the contractor often points to the producer, claiming the pipe fit was poor. Many times, poor field workmanship causes a failure, and the producer must rely on written records of in-plant measurements to verify product quality.
Bussio's company, Geneva Pipe Co., Orem, Utah, is trying to prevent such confrontations by using a third-party verification of its product's quality. A non-contact laser-line scanner now automatically measures each pipe's spigot and enters the data into a special computer software program that compares the measurement to the pipe's design criteria. "The laser scanner is an answer to the engineering community's request for a better joint," says Bussio, Geneva's vice president.
"The scanning system not only provides some labor savings in our quality control program, but has become a marketing tool," says Bussio. Geneva's contractors know that each pipe is measured with the laser, and field complaints have been reduced to almost zero.
Traditionally, quality-control technicians have used handwritten records of hand-held micrometers and go- /no-go gages that verify quality checks of bells and spigots. But this new laser tool transforms a tedious manual effort into an automated process that increases reliability.
The process, Pipetech, was developed by a Danish scientist and recently introduced in the United States. "Our goal was to develop a documentation system that eliminates the need for manual measurements," says Preben Hjoernet, president of Controlled Vision Systems (CVS). Involved in Danish concrete pipe production for many years, Hjoernet has seen an increased emphasis on the documentation of concrete pipe quality, especially in sanitary sewer pipe.
Hjoernet developed Pipetech to give the producer the flexibility to focus quality efforts on either spigots or bells. A third option, a double scanner setup, determines the pipe's exact length and straightness.
Pipetech uses a Class A laser (which presents no danger to humans) that replaces hand-held micrometers or gauges. A scanner head containing a mirror and a video camera rotates around the pipe's spigot or bell.
As the scanner circles the pipe's end, a special diode laser emits a visible light, forming a narrow beam of visible light on the spigot's or bell's surface. The video camera detects the light's path, creating a sequence of 1,000 to 1,500 separate measuring points. This data is stored in a computer, and special software uses digital image processing to create a three-dimensional image of the pipe's actual surface. The software compares the image to the pipe's design drawing to determine whether the finished product meets design tolerances. Technicians store the data from each pipe's image on a computer disk for future verification.
Plant efficiency increased
Pipetech offers quality control benefits in addition to efficient record keeping. Increased sample frequency provides data that allows managers to monitor production activity by quality rather than quantity. When the pipes are not within dimension tolerances, the system can provide accurate records of the pipes' production date and lot number. Managers can then focus on what might have caused the failure. Other quality control factors, such as aggregate moisture content, aggregate gradation or mix-design modifications, easily correlate to the production date or lot.
At Geneva, every piece of pipe from 12-inch-diameter to 48-inch-diameter is scanned. The scanning process takes about 35 seconds per pipe. "I can sleep well each night, knowing that the yard man hasn't made a mistake or missed a piece of pipe," says Fred Klug, Geneva's plant manager.
Producers also use the laser setup to reduce culls created by worn-out equipment, says Hjoernet. "The laser can detect premature wear on bell pallets and set rings." Producers can then remove worn forms before the pipe goes out of tolerance.
Quality means market share
Producers have traditionally marketed concrete pipe as the highest crush-resistance pipe material at the lowest cost. Now, the American Concrete Pipe Association (ACPA) specifically promotes the industry's "quality-driven manufacturing process" as one attribute of the "new" concrete pipe.
The ACPA promotion comes at a time when large-diameter concrete pipe sales are expected to increase 2% from 1996 levels over the next four years. According to a 1996 estimate by the Freedonia Group, Cleveland, concrete pipe accounts for about 72% of the sanitary sewer market. The Aberdeen Group's Construction Marketing Institute estimates that concrete pipe sales will reach $1.7 billion in 1997.
While concrete pipe is the leader in most pipe-style categories, the promotion is geared to position concrete pipe to gain an even larger share of the U.S. $5.82 billion large-diameter-pipe market (1996 estimate by the Freedonia Group). The closest competitor, especially in the smaller diameters, is plastic pipe, which has 25% of the market.
"The challenge of being the leader is that all alternative pipe products are gunning for you," says Vince Bussio, chairman of ACPA's Quality Committee. Concrete pipe production methods are much different today than they were 50 or even 15 years ago. Pipe machines, batch plants and mix designs have allowed pipes to reach new performance levels, Bussio notes. "With these performance improvements and ACPA's new bedding specifications, owners and specifiers can feel confident that the concrete pipe system is a proven structure that will provide service for many years."
KEYWORDS: pipe production