Understanding CIPP Tube Thickness & Design Thickness Relationship

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There is confusion when it comes to tube thickness and design thickness. This article will help you understand the relationship between design thickness and the thickness of the tube. First things first understanding tube and what it brings to the table in the CIPP process.

Tube is the vehicle used to hold the resin into place until it is cured.

Unreinforced, the tube provides no strength to the finished product. In fact, unreinforced tube reduces the strength of the resin used. When tested by itself, neat resin will always offer more strength when tested to ASTM D638 and ASTM D790, unless reinforced fibers are used in the tube. Reinforced fiber tube used with resin is called FRP (fiber reinforced polymer) and provides a stronger the composite than the neat resin by itself. To determine design thickness, the resin and tube combination must be calculated by applying testing using the two ASTM standards mentioned above. So, the more fibers that are unreinforced that are part of the composite meaning the less resin used to “wet out” the tube, the lower the strength of the composite. ASTM F-1216 Standard Practice for CIPP Inversion prescribes a minimum standard of 250,000 psi flexural modulus as tested against ASTM D790, a minimum flexural strength of 4,500 psi per ASTM D790, and a minimum tensile strength of 3,000 psi per ASTM D638. While neat (pure) resin may deliver numbers much higher than this, the minimum listed here takes in to account the tube factor reduction.

When we make tube, we consider a couple of things. If you’ve ever seen a felt needling process, batting material is processed through a machine that fluffs it up and carries it along a belt where it passes through thousands of needles that punch the fibers into felt. The more it’s needled the denser the number of fibers become in a thinner and thinner layer. Put another way, we could needle the same amount of fiber to make sheets of felt 8mm thick or 3mm thick or anywhere in between. There is a point where I can make it to thick that it won’t hold my resin as there aren’t enough fibers to keep it from running and conversely, I can needle it so much that I can’t get enough resin in the tube to meet the minimum standards mentioned earlier. Our challenge is to provide you a material that will hold the resin and still meet the minimum standards.

We make some materials with a tight needling that carry enough resin to meet the minimums, but we also provide you with materials that are fluffier that are designed to dampen wrinkling in turns and bends but can still carry the same amount of resin needed for the job. For example, we make several materials that are 4.5mm thick instead of 3mm thick. They are fluffier, but you will notice that we still call for calibrating the thickness using a 7mm bar. By “wetting out” for a higher thickness you could take this same material and calibrate it using a 10mm bar, giving a finished 4.5mm thick composite.

To help you with calculating your resin demand for these tubes we’ve developed a resin demand calculator that you can provide the tube diameter you are using, the thickness you are shooting for in mm, the pipe length you are lining, and the add in for waste material. It calculates the amount of resin you will need to prepare.  Please CONTACT US if you want a copy of our CALCULATOR

Pipe Lining Supply Events

Interested in a DEMO Day??
Pipe Lining Supply will be at the 3rd Annual DEMO DAY
FREE Lunch and Drinks for All!!  Watch LIVE Outside Demonstrations of the Latest Technology, Machines, & Tools of Our Trade!
Demo Day Flyer
Where: 6390 Columbus St. Riverside, CA 92504
When: Friday 9 a.m. to 5 p.m. Nov. 30th, 2018
The WWETT Show is speeding toward us quickly. If you are attending, be sure to register. John Heisler will be presenting this year the AIPPR coating process as the standard set by IAPMO in the UPC. Booth 6722

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