In my career with McWane Ductile, I've sold my fair share of polywrap, but the one thing that I haven't really thought about when selling polywrap is the tape needed to complete the installation. I'm not sure why this is. Maybe the biggest reason is I wasn't sure how much tape was required for each roll of polywrap I sold. Therefore, I wanted to take a deep dive into this subject to make it easier for people to know when ordering polywrap how much tape they need to purchase as well.
What is Polywrap?
First, you may ask, what is Polywrap? Polywrap is a dielectric film that reduces corrosion of metal products by reducing the potential for electric currents to travel from the metal surface through an electrolyte (soil) and return to a metal surface. The most recent development of polyethylene encasement is V-Bio® Enhanced Polyethylene Encasement (V-Bio).
It consists of three layers of co-extruded linear low-density polyethylene (LLDPE) film fused into one. The inside surface is infused with a proprietary blend of anti-microbial additives to mitigate microbiologically influenced corrosion (MIC) and a volatile corrosion inhibitor (VCI) to control galvanic corrosion.
How Do You Install Polywrap with Ductile Iron Pipe?
Before you determine how much tape you need, you need to know how to install Polywrap. Installation Methods are described by the Ductile Iron Pipe Research Association (DIPRA), ANSI AWWA C105 Polyethylene Encasement For Ductile-Iron Pipe Systems, and ANSI/AWWA C600 Installation Guide For Ductile-Iron Mains And Their Appurtenances. The installation method will dictate the amount of polyethylene tape to be used.
Method A – is where one length of polyethylene tube overlapped at the joints is used for each length of pipe. Please see our blog on Eight Steps for Installing B-Bio Polywrap, demonstrating this method.
Modified Method A – is a modification of Method A, which uses one length of polyethylene tube for each length of pipe. In this modified method, one end of the tube is secured to the spigot prior to making the joint. The 12-inch overlap is achieved when bringing the remaining film over the joint from the previous length of pipe.
Method B – a length of polyethylene tube is used for the barrel of the pipe, and separate lengths of polyethylene tube or sheets are used for the joints.
Method C – is where each section of pipe is completely wrapped with a flat polyethylene sheet.
Important Note: when installing polyethylene, be sure to repair all small rips, tears, or other tube damage with polyethylene tape.
What Tape Should You Use?
What tape to use? The most common tape to use when installing V-Bio Polywrap is Pipe Wrap or Poly Tape, and it is IAPMO/UPC certified for AWWA and Plumbing Applications. It is ten mils thick and comes in a 2-inch x 100-foot roll. We stock it and will be glad to send it with the polywrap. There are a variety of manufacturers out there.
How Many Rolls of Tape Should You Use?
To make it easy for you, we’ve used our resources and calculated how many tape rolls you will need for each roll of polywrap you purchase. Calculations are based on Method A Installation. Additional consideration should be given when installing Method B or Modified Method A for wet trench conditions. The number of rolls of tape are MINIMUM quantities.
|Pipe Size||Roll Length||Lay Flat Width||Tape Rolls per Roll|
|Number of Pipe per 100-foot of Polywrap Tape||56||56||44||36||34||26||22||20||18||16||14||11||9|
Beyond Standard Pipe Installations
Additional installations common to the pipe installer are:
- Odd-shaped Appurtenances
- Air Valves
- Connections to alternate materials
Placing a quantitative value on every possible combination would be a book in itself. This is one of many scenarios where an experienced crew can demonstrate why they are more valuable than a greener crew or someone new to the industry.
Odd-shaped appurtenances such as valves, hydrant connections, blowoffs, and air valves vary in size and shape. The key to protecting such appurtenances is to ensure the entire body (below ground level) is covered. The polyethylene must be cut to suit and taped accordingly. The best example of securing the polyethylene is to compare it to wrapping a Christmas present. If you wrap like I do, tape is your friend.
What About Joints?
Joints may vary as well. Mechanical Joints (MJ) are the most common fittings used during construction. The OD must be considered as the OD of the fitting is greater than the pipe. There is a potential for sharp edges on the retainer glands and bolts to puncture the polyethylene encasement. Damage to the polyethylene must be repaired. Obviously, the more experienced crew with less damage equals fewer repairs and less tape. A solid 12-inch fitting installation will require a minimum of 92 inches of tape. One wrap on each side of the fitting and a couple of 6-inch tabs to secure the fold in the middle.
What About Service Taps?
There are two suggested methods when installing service taps.
- The first is to wrap two to three layers of poly tape around the pipe and install the tap through the polyethylene encasement and tape. For example, 12-inch pipe has a 41-inch circumference, to wrap the pipe 3 times will require 123 inches of polyethylene per tap.
- The second method is to cut an "X" in the polyethylene, fold back the tabs, install the tap, close the tabs, and secure them with polyethylene tape. The amount of polyethylene tape is, therefore, significantly reduced.
Tape is a small but critical part of the installation of polywrap, and as you can see, there are a lot of variables that determine how much tape you will need for your project.
- First, look at the method you intend to use for your polywrap installation and the number of rolls you will need based on how many rolls of polywrap you are purchasing.
- Then you will need to factor in other items such as odd-shaped appurtenances, joints, branches, blowoffs, air release valves, taps, and connections to get exactly how much tape you want to purchase with your Polywrap.
There isn't a perfect science here, but we wanted to provide you with a starting point and some useful information that will allow you to determine how much tape you need with your next ploywrap project. I hope you find this Iron Strong Blog informative and if you have any further questions or need assistance with your water or wastewater project, please contact your local McWane Ductile representative.
We have team members who've managed small and large water utility systems, served in engineering consulting firms, and bring decades of experience in solving field issues involving pipeline construction and operation. From design to submittal, to installation, we strive to provide education and assistance to water professionals throughout the water and wastewater industry.
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