Tulsa is on the cusp of something incredibly special on its Arkansas River waterfront. The George Kaiser Family Foundation is developing a $400 million park, the result of a public-private partnership that has set a record as the largest private gift to a public park in our country’s history.
A Gathering Place for Tulsa is transforming 100 acres of urban land into a natural setting for the public to enjoy with numerous amenities including a five-acre playground, boathouse, nature trails, sport courts, bike and skate parks, and much more. Set to open by the late spring or summer of 2018, the park was designed by the renowned landscaping architect, Michael Van Valkenburgh Associates, who is behind the award-winning Brooklyn Bridge Park.
There are significant infrastructure needs to serve the million visitors that are expected to visit each year especially in the area of water, storm water, sanitary sewer lines and irrigation. More than 5,700 trees are being planted that represent more than 118 different species from all over the U.S. Over a million shrubs, bushes and flowers will be planted and park goers will be able to recreate on beautiful, sprawling lawns.
To deliver a reliable water source for this huge and important investment, a fusible high-density polyethylene (HDPE) piping system was selected.
WHY FUSIBLE HDPE PIPE?
HDPE is a pipe material used in the water distribution and transmission industry that is growing in acceptance. The benefits include the fact that it doesn’t corrode or rust which greatly extends its lifespan for up to 100 years. It’s also a flexible material that withstands ground shifting, pressure surges and extreme temperature fluctuations.
Equally important is the way that HDPE is joined through leak-free heat fusion, commonly referred to as butt fusion. This works by heating the pipe ends and joining them together with pressure. This allows the flow and mixing of melted materials which changes the molecular structure from a crystalline to an amorphous state. Once the pipe cools, the molecules return to their original state to create a monolithic pipe system.
While other joining methods have an allowable leakage rate that can be 10 to 30 percent or even more, fusible piping systems are considered to be out of compliance if they leak at all. This boosts water conservation efforts and lowers costs associated with the ongoing maintenance of metallic pipe to prevent corrosion. HDPE can also prevent water contamination since leaky joints can pollute potable water lines.
Butt fusion machines are designed for pipe as small as ½” CTS up to 2000mm OD. The smaller manual machines can usually be carried from joint to joint with separate heater and facing components. The larger machine carriages can be mounted on wheeled or self-propelled, tracked vehicles. The tracked fusion machines are self-contained with everything needed on-board including the generator. Both manual and track-mounted machines were used at A Gathering Place to fuse pipe as small as 3” up to 14”.
While pressure is applied by hand with manual machines, the larger, hydraulic machines deliver a specified gauge pressure that is based on a mathematical formula that takes into consideration the kind of machine, specification, pipe size, wall thickness, interfacial pressure and drag pressure, which is the frictional resistance that occurs when the carriage is moving.
Operators should check the pipe manufacturer’s specific recommendations for interfacial pressure based on pipe diameter and wall thickness which can be determined by dividing the outer diameter (OD) by the dimensional ratio (DR). The theoretical fusion pressure for use in McElroy fusion machines is easily summed up by using an online or mobile fusion calculator. See mcelroy.com/mccalc.
Meanwhile, there are several key steps in the fusion process to create a quality joint:
CLAMPING THE PIPE
The pipe ends are placed into each side of the machine where they are held in place by serrated jaws that clamp the pipe into place. A balanced force system places the centerline of the pipe clamping jaws on the same plane as the pipe’s centerline. This allows for an equal distribution of force around the pipe’s diameter to form a quality joint.
ALIGNING & FACING
Before the pipe ends can be fused, they are cut with powerful, electrical facer blades for a square face-off perpendicular to the centerline of each pipe. This exposes fresh pipe material which is necessary for a successful fusion. One complete revolution around each pipe end is recommended to accomplish this. Once the ends are faced, it is critical for the operator to remove all of the pipe shaving debris and wipe away dirt or any other contamination on the pipe end surfaces with a clean, lint free, non-synthetic cloth.
A two-sided heater is placed between the pipe ends as they are brought against each side of the heater for the melt process. The pipe ends will form a melted bead on each side of the heater. Depending on the size of the pipe, the fusion parameters and jobsite setup, the heating time takes about 1 ½ to 2 minutes per inch of the pipe diameter. The operator should always check the pipe manufacture’s recommendations for heating time and as well as for the correct temperature. The temperature should be measured with a pyrometer or data logging device periodically.
FUSING & COOLING
Once the heater is removed, the melt patterns of the pipe ends are joined together and held immobile under a specified amount of force that is sufficient to mix the pipe material together and form a homogeneous joint. As it cools for the proper amount of time with the jaw clamps still in place, the molten material forms a bead or joint that is strong or stronger than the pipe itself.
Trained fusion operators who understand their machine and know how to operate it are a crucial part of producing reliable and leak-free joints and successful piping systems. Proper training and knowledge of and adherence to the applicable ASTM and ISO fusion standards helps operators stand out from the crowd with a greater level of expertise and professionalism. Trained operators know how to stage their jobsites effectively and they can operate fusion machines safely and efficiently.
McElroy, the maker of the most complete line of fusion machines, has offered advanced, certified training at its facilities in Tulsa, Okla., for more than 35 years. They also provide onsite training at the customer’s location. Students are given the opportunity to learn more about the specific machines that they will be operating on their jobs whether it is for small-, medium- or large-diameter pipe. Classes include Operator Qualification, Troubleshooting and Rebuild and Inspector Training. Each class includes an appropriate mix of classroom and hands-on time followed by testing after each class to insure that students understand the proper concepts and procedures. Learn more at mcelroy.com/university.
The longevity of fusion machines is increased with preventative maintenance and rebuild techniques that keep the hydraulics, electrical and other systems running properly. Since the malfunction of the machine is sometimes simply the result of operator error, a skilled operator with the ability to identify a potential problem helps make sure that machines spend more time in the field than the repair shop. Good maintenance is the best way to help protect a machine owner’s investment.
A Gathering Place has been under construction since September 2014. Like many projects, the weather has sometimes slowed them down, but leaders say it will be well worth the wait. The beauty and operation of the park wouldn’t be possible without a good, underlying infrastructure system and that takes time.
The jobsite is brimming with construction activity and Crossland Construction Co. has multiple sub-contractors working side-by-side. With the great variety of work in close proximity, they have often worked together closely to stagger their jobs to stay out of each other’s way when it was necessary. Approximately 300 men and women are working long hours each day performing a variety of work.
Water distribution plays a significant role among the many infrastructure needs at the park that include the construction of new roads, land bridges, lighting, pond construction and a lot more. Once the park opens with running water, a reliable sewer and storm water system and irrigated landscaping, there may not be much thought given to what kind of piping system made it all possible. While it serves its important purpose quietly underground for decades, visitors to the park will simply be enjoying their quality of life.