Kerotest Designs High-Quality Natural Gas Valves with FEA

	The Kerotest POLYBALL™ product line includes ½” to 12” standard- and full-port valves made from medium- and high-density polyethylene.
	Richard Adams and Richard Conley (left to right) designed the POLYBALL™ valve shown here.
	Kerotest engineers modeled the POLYBALL™ valve in Pro/ENGINEER and used ALGOR linear static stress analysis results to optimize parameters such as the wall thickness, the shape of the transition into the piping and the inside shape of the valve through which the gas flows.
	Kerotest engineer Richard Adams used ALGOR’s Report Wizard to automatically generate reports that were used to communicate FEA results and facilitate design optimization.
	POLYBALL™ production is based at Kerotest’s Mansura, Louisiana facility, where Kerotest invested $4.5 million USD in new equipment.
	A construction worker installs a Kerotest POLYBALL™ valve into a new piping system. Photo courtesy of Memphis Light, Gas and Water Division.
	Kerotest engineer Richard Adams built the CAD models of the POLYBALL™ valves and performed the ALGOR FEA analyses.

At a time when many manufacturing jobs are being shipped overseas, Pittsburgh-based Kerotest Manufacturing Corporation set out to make their POLYBALL™ polyethylene ball valves competitive in the global marketplace. “We are employee-owned and our products are American-made, which allows Kerotest to offer a stable, long-term relationship to our customers,” said Kerotest President, Robert Visalli. Kerotest determined that they could remain competitive only by implementing new design and manufacturing technology.

An important component in their new, high-technology design and manufacturing process was FEA software from ALGOR, Inc. to optimize their valve designs. “We invested in ALGOR FEA software to evaluate our POLYBALL™ valve in more detail than we had with previous products and to create a valve that offered more features at a lower cost,” said Chief Engineer Richard W. Conley. “We chose ALGOR software because it is easy to learn and use and would be effective in providing significant insight into our design.”

Creating More Than Just a Great Design

For nearly a century, Kerotest has been specializing in valves that help companies like New England Gas Company, New York State Electric & Gas Corporation, The Philadelphia Gas Works and Sierra Pacific Power Company distribute natural gas to our homes and businesses. In response to a growing industry trend toward corrosion- and maintenance-free valves, Kerotest set out to design the POLYBALL™ product line that includes ½” to 12” standard- and full-port valves made from medium- and high-density polyethylene.

“Our goal was to make a polyethylene valve that outperforms the competition and offers more features at a lower price point,” said Conley. Because public safety is critical in the natural gas industry, the valves also had to meet or exceed ASME B16.40, ASTM D-2513 and the U.S. Code of Federal Regulations (CFR), Part 192 standards.

Their high-technology design and manufacturing process is what Kerotest credits with giving the POLYBALL™ its edge in the marketplace. “From the beginning, we believed that if we designed the right product and produced it with the right manufacturing process, we could be competitive with anyone in the world without exporting jobs,” explained Conley. “Everyone pays about the same price for raw material, so success is based on how you transform raw material into a final product. We wanted to be successful based on a robust design and high-technology manufacturing.” Kerotest turned to ALGOR FEA software to help trim excess material from their valve design while maintaining consistent structural integrity throughout the product.

Designing the POLYBALL™ with FEA

Conley developed an initial design based on his experience with valves in the natural gas industry. “The outside diameter at the valve ends never changes because it must match standard pipe diameters,” said Conley. “However, the inner and outer diameters of the valve center section have to be optimized in order to find a wall thickness that will withstand the necessary pressures. Our goal was to design the valves to withstand higher pressures than the current industry standard – up to 125 PSI – because of emerging trends in the gas industry.” After Conley developed a working design and sizing specifications, he forwarded this information to fellow engineer, Richard Adams, Senior Design Engineer, to build the CAD model and perform the FEA analyses.

An engineer with 30 years of experience designing products for Kerotest, Adams had little exposure to FEA and no formal training before using ALGOR software. “Much of my work involves upgrading and adapting existing products, where I can make those changes based on experience,” said Adams. “My preparation for using the ALGOR software involved seeing it in action in a sales demonstration and viewing the ‘Getting Started’ instructional Webcast included with the software. That was all I needed to work with our Pro/ENGINEER models, set up and perform analyses, view the results and automatically generate HTML reports containing my findings.”

Adams began by modeling POLYBALL™ valves of various sizes in Pro/ENGINEER. In addition to creating a full assembly for each valve, he created a simplified model representing only the parts that were of engineering interest and added sections of pipe to each end to simulate how the valve would be attached to a piping system. He then used ALGOR’s InCAD technology to directly capture the geometry. “InCAD technology makes it very convenient to work with Pro/ENGINEER models,” said Adams. “I was impressed that there was no extra work required to obtain geometry for FEA analysis.” Adams then created a 3-D solid finite element mesh. “ALGOR’s meshing tools produced a high-quality mesh on the first pass,” commented Adams. “I later verified that the default mesh was sufficient by analyzing a model with a finer mesh, and there was no appreciable difference between the results of the two models.”

Radial pressure loads were applied to the inside surface of the valves and tensile loads were applied to the ends of the pipes. To facilitate the application of tensile loads, Adams modeled the ends of the pipes as if they were closed. Adams then applied material properties obtained from the resin manufacturer. “In this project,” Conley notes, “we learned that much of the analysis and results depend on obtaining accurate material properties.”

Adams performed a linear static stress analysis and viewed the stress results within ALGOR FEMPRO’s Superview IV Results environment. “I like the range of results evaluation and presentation tools ALGOR provides,” said Adams. “The Report Wizard, in particular, saved me time in preparing reports to communicate with others on the projects.”

Adams followed this same process on models of various valve sizes. He then reviewed the findings with Conley and together they optimized parameters such as the wall thickness, the shape of the transition into the piping and the inside shape of the valve through which the gas flows. The changes they made reduced excess material and high stresses.

Kerotest performed extensive prototype tests to ensure that the valves met the safety codes required for the natural gas components. “The POLYBALL™ valves are manufactured from polyethylene, which requires the production of molds,” said Adams. “If the prototype isn’t right the first time, you’ve wasted a lot of time and a lot of money producing the molds. FEA enabled us to create a robust design that passed the prototype testing on the first attempt.” An independent polyethylene piping consultant, Volgstadt & Associates, Inc., verified the performance and ease of operation of the POLYBALL™ valves. The consultant performed their own independent analysis and a detailed review of test procedures and results and then concluded that the valves had been designed and tested according to industry-standard codes.

POLYBALL™ valves were released to the market in April 2003, backed by a 5-year warranty. Production is based at Kerotest’s Mansura, Louisiana facility, where Kerotest invested $4.5 million USD in equipment to support this new product line.

Kerotest to Further Integrate FEA

Now that the Kerotest design team has initial experience with FEA, they plan to use ALGOR software for other designs. “In future projects, I will be confident about using these tools and basing design changes on the results,” said Conley. “We are investigating additional techniques and training to further integrate FEA into our design process.”

Although the current line of POLYBALL™ valves was designed to be used primarily in the natural gas industry, it has also been used in general industry applications and the water utility industry. As the market for POLYBALL™ valves grows, Conley expects that Kerotest will use FEA to re-evaluate the design according to water industry standards, which has different pressure needs and safety factors. “Although the water utilities operate at higher pressures than the gas industry, the safety factors are not as stringent, so the same pipe sizes are often used in both markets,” explains Conley. “However, we would want to re-evaluate the POLYBALL™ valves to ensure that the mechanism within the valve withstands the higher pressure.”

Whatever the future may bring, Conley and Adams consider the integration of FEA into their design process to be a success. Not only were they able to produce a high-quality product, but they were able to get answers quickly. “Adams and I would discuss what needed to be done in the ALGOR software and in a few hours, he was done,” said Conley. “We are designers who are responsible for getting real product development done on time. We could not spend months learning FEA software and performing analyses. ALGOR has a reputation for being easy to learn and use and, in fact, we were able to get results with it quickly.”