Polypropylene Growing in Popularity for Chiller Engineers

By its very nature, the engineering profession is based on the constant search for new and better ways of accomplishing a task; however, there also is a well-known human tendency to “do things the way we’ve always done them.”

Engineers who design and specify chiller systems find themselves squarely in the center of these two worlds. Chiller system engineers may be well-versed on the latest advances in chiller and cooling tower technology but may be unaware of the best options for their customers when it comes to another critical element of the system — the piping. A tendency to specify steel or copper by rote is understandable, as (despite their shortcomings) those are the piping systems that have been used in chiller systems for generations. But there is another option.

Popular choice for chiller engineers/designers:

Chiller Applications for PP
In the Field
Other Considerations
Labor Savings from Fabrication
Compliance and Resources
Conclusion

Thermoplastic polypropylene (PP) pipe — and its variants poly-propylene-random (PP-R) and polypropylene raised crystallization temperature (PP-RCT) — is often viewed as “new” or perhaps even as a novelty. However, it has been used around the world for nearly 40 years on thousands of projects and in a huge range of mechanical, plumbing, and industrial applications in North America for roughly a dozen years. It is highly engineered to offer benefits for mechanical applications that other piping systems can’t.

Chiller Applications for PP

PP pipe is hydrophobic and chemically inert. This makes it ideal for use in chiller systems. PP material resists any form of change to the material wall, such as scaling or corrosion, which guarantees a consistent flow rate throughout its long life. In addition, chillers operate at temperatures well within the range suitable for PP pipe.

In a chiller system, PP pipe can be used to transport heated water, chilled water, or condensate. Depending on the wall thickness of the pipe (expressed in SDR, or standard dimension ratio, which is a ratio of the wall thickness to the overall diameter of the pipe), many PP piping systems can handle fluids at 100 psi up to 180°F as well as extremely low operating temperatures. Typically, the PP piping includes a fiberglass reinforcement layer that significantly reduces thermal expansion and contraction, keeping it comparable to metal piping traditionally used in these systems. This is also true for low-temp chiller applications, where the temperature differential from start-up to operating conditions can be significant.

Chillers are tough and durable pieces of equipment and so is PP pipe — with an anticipated life span of 50 years or more.

PP also is versatile and lends itself well to “real-world” chiller installations. For example, on a recent chiller replacement at an historic 27-story skyscraper in downtown Akron, Ohio, PP piping’s light weight was a bonus inside a tight mechanical chase. The installers were able to stay on one floor and lower the piping in 60- to 80-foot sections without having to move.

“PP piping is so light you can use just a few guys to install two fittings and a full [13-foot] stick,” said Jeremy Bejger, project manager for the Akron project’s piping contractor, Harner Plumbing, Mantua, Ohio. “With steel you need a hoist and chain falls.”

Figure 1. Polypropylene pipe is clean, lightweight, and easy to work with. Specialized tools ensure virtually leak-free heat fusion connections on every job.

Added Kevin Kindbom, vice president and co-owner of Bandwen Williams Kindbom, Akron, Ohio: “PP piping makes less impact on a building structure because it’s lighter, which also makes it easier to lift or monkey into small existing spaces. We hadn’t thought about [PP] in the past but certainly will in the future.”

In addition, as chiller systems become more complex in an era of changing refrigerant regulations and increasing efficiency standards, PP pipe can be used to transport a secondary coolant or refrigerant such as glycol or brine.

In the Field

Even the most excellent chiller system design relies on a contractor’s installation team to see it through. Installation personnel are crucial to the proper functioning of the system, and many have come to genuinely appreciate working with polypropylene pipe.

“You’re not moving stuff as heavy so the guys can be more productive all day long,” said Ryan Pepper, piping project manager at T.H. Martin Inc., after the company installed PP pipe as part of a high-rise office-to-apartment conversion in Cleveland.

And when speed is important in a project (and when isn’t it?), PP pipe offers a huge advantage.

Dave Allemand, associate director of plant services, Southern Adventist University, Collegedale, Tennessee, recently oversaw chiller and piping upgrades at the university.

“We were able to install [the PP pipe] in two weeks,” Allemand said. “It would have taken an additional three weeks if we had used steel. We eliminated all of that hassle and downtime by using PP.”

Allemand’s lead plumber, Tim Mitchell, noted that rather than welding steel, PP pipe is joined by using reliable heat fusion.

“It takes me five minutes to do two 3-inch connections at a 90-degree joint with PP,” Mitchell said. “That would take me an hour and a half to weld with steel.”

Heat fusion is a strong and reliable form of joining piping systems, and heat-fused pipe can be used almost immediately. Heat fusion can be more reliable, quicker, and more cost-effective than most mechanical forms of bonding, and it does not introduce any foreign materials into the system.

Other benefits of heat fusion include virtually leak-free connections. When properly executed, heat fusion joints create a bond that is as strong as the pipe itself with no leak paths.

Figure 2. Versatility is a hallmark of polypropylene pipe. It can be worked on overhead or in tight spaces that would make welding difficult or impossible

In addition, PP presents several significant safety benefits over steel pipe on a job site — a number of safety concerns that usually accompany steel installations don’t apply when heat fusing PP. There is no open flame, no need for a fire watch, and no hot work permit required. For direct-buried applications, the faster fusion time of PP pipe means hazardous open trenches are able to be closed more quickly. PP also is well-suited for directional boring, which eliminates the trench work and added cost of digging trenches across existing parking lots, roads, etc. The lighter weight of PP pipe reduces strains and the risk of back injuries, and no grinding of metal means no airborne metal particles and a reduction in the risk of eye injuries.

Other Considerations

There are additional reasons to consider specifying PP that may be unrelated to an actual chiller project but are important considerations in the real world. The first is the uncertainty of metal pipe prices in an era of tariffs. Price is always going to be a factor for building owners and managers who are making the purchasing decisions when it comes to their chiller system, and unlike metal pipe, PP offers stable, predictable pricing.

The second is that unlike copper tubing and steel pipe, PP pipe has no value to thieves, thus eliminating the risk of job site theft. In addition, PP materials are 100 percent recyclable.

Although there is a learning curve to working with PP, pipefitters and those already familiar with heat fusion are usually able to run with it very quickly. A factory training typically prepares even the most inexperienced crews to perform heat fusion and can lead to labor savings of 25-30 percent compared to traditional materials. Pipefitter union locals are now incorporating PP fusion into their apprentice programs directly, which may not replace the required training by the pipe manufacturer but does provide an introduction to upcoming apprentices in the industry.

Jamie Hassett, owner of Demand Mechanical, Nashville, Tennessee, has used PP pipe on a number of chiller projects and has made PP his “go-to” pipe. Over the years Hassett said he has consistently found PP to be a more reliable and cost-effective solution than copper.

For example, Hassett estimates that PP pipe is at least 10 percent faster to install. That helps keep labor costs down, especially on projects such as a renovation at the Embassy Suites – Nashville Airport, which was awarded to his firm based on a competitive bid. But most important is the long service life of an anticipated 50 years or more that PP provides.

“We know it is a good product as far as longevity,” said Hassett.

Labor Savings from Fabrication

Unlike metal pipe, PP pipe’s light weight and versatile orientations that are available through the fusion process make it easy to fabricate custom spools either on the job site or remotely. Some manufacturers of PP systems offer design and fabrication services and have BIM files available for their products.

At the Akron skyscraper project, the contractor received some spools fabricated by a major PP pipe manufacturer but opted to fabricate most of the closed-loop piping system at the job site. Beginning in mid-January 2016, the installers fabricated 180-foot piping runs on the building’s fifth floor. Then, before the cooling tower was installed, they used a crane to lift the pipe assemblies onto a section of roof outside the eighth floor. The installers then simply slid the assemblies into place.

These labor savings of fabrication can be significant. In most cases, the vast majority of fixtures and spools can be fabricated off-site and shipped directly to the job site. Thanks to the pipe’s light weight, the fabricated assemblies arrive ready to hang.

Compliance and Resources

Most PP pressure pipe currently available in North America is compliant with the International Plumbing Code; International Mechanical Code; Uniform Plumbing Code; Uniform Mechanical Code; and Uniform Solar, Hydronic, and Geothermal Code for physical properties and temperature and pressure ratings. Check with the manufacturer of the pipe or contact the Plastics Pipe Institute (PPI) before specifying a particular brand. PPI is a trade association representing all segments of the plastics piping industry. The association and its members work together for education, standards development, code updates, and other initiatives to advance the adoption of plastic piping systems.

Figure 3. Polypropylene pipe is available in a variety of sizes, making it suitable for virtually any chiller project.

In late 2017, PPI’s Building & Construction Division formed the Polypropylene Pressure Pipe Steering Committee to reflect the rapid growth and continuing acceptance of PP pressure pipe in the North American market.

PPI offers many resources to engineers interested in specifying plastic pipe. A webpage dedicated to PP piping systems, https://plasticpipe.org/building-construction/bcd-pp.html, contains technical information, links to product standards, advantages and applications, and links to member firms that produce PP systems.

In addition, the PPI Plastic Pressure Pipe Design Calculator is a free online tool that performs calculations for pressure and head loss, thermal expansion and contraction, surge pressures, and pipe weight and volume for plastic piping materials. It is relevant to plumbing, water service, hydronic heating and cooling, snow and ice melting, fire protection, and geothermal applications. It can be accessed at www.plasticpipecalculator.com.

According to Tony Radoszewski, CAE, president, PPI, “PPI has been a strong advocate and technical resource for many types of plastic pipe systems since its formation in 1950, including new materials as they develop. While not new in Europe, polypropylene pressure pipes are relatively new in North America, and PPI can serve members by helping to grow this market in a technically correct and responsible manner. Pipe producers see the value in this industry collaboration. In fact, the number of polypropylene producer members at PPI has tripled since this steering committee was initiated.”

In addition, PPI’s Hydrostatic Stress Board (HSB) is developing policies for listing long-term pressure ratings of polypropylene pressure pipes, similar to its listing programs for materials such as PVC, CPVC, HDPE, and PEX.

Conclusion

Engineers who design and specify chiller systems are responsible for one of the largest investments a building owner or manager will make. Chillers and their components have experienced a host of innovations and advancements in the past several years, and your customers will be well-served to know all their options when it comes to piping, which is an integral part of their chiller system.