3-PLY POLYURETHANE

3-Ply Polyurethane

Laminated, or 3-Ply hose is actually comprised of five layers; an inner PU tube, an adhesive tube, a reinforcement jacket, an adhesive tube, and an outer PU tube. Since the adhesive tubes melt during the manufacturing process, only three layers can be seen in the finished product; hence, the name “3-Ply.” The manufacturing process of 3-Ply starts by pulling a polyurethane (PU) tube through the inside of an adhesive tube; then, pulling these two tubes through the inside a woven reinforcement jacket. Steam is blown through the PU tube to melt the adhesive and bond the PU tube to the reinforcement jacket. The tube inside the jacket is then turned inside-out (“turning the inside tube out”) and the process is repeated with a second PU tube and a second adhesive tube. During this procedure, moisture builds up on the reinforcement jacket and numerous pin holes are made in the outer PU tube to permit this moisture to escape.

Users can buy 3-Ply hose for less than through-the-weave hose (TTW) for the simple reason that it costs less to manufacture 3-Ply PU covered hose than TTW PU hose. Also less TPU may be used in the manufacture of 3-Ply hose because of an incentive inherent in the manufacturing process to keep the hose tubes as thin as possible. This results from the necessary procedure of turning the inside tube out, which becomes very difficult if the tubes are too thick. While suppliers of 3-Ply hose will no doubt attribute a thinner wall to a manufacturing process finely tuned to using only the amount of material necessary to provide the desired outcome, the truth is that a thinner tube has been used to accommodate the manufacturing process.

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Some disadvantages of 3-Ply hose are:

  1. Just as the pin holes in the outer layer of 3-Ply hose allow steam used in the gluing process to escape, those same pin holes could allow moisture to reach the adhesive that binds the outer layer to the reinforcement jacket. While this should not cause the inner tube to leak per se, moisture would reduce the adhesive bond between both the outer and the inner PU tubes and the reinforcement jacket. Separation from the reinforcement jacket would mean a loss of integrity in the strength of the hose and in the worst case a rupture, the location and extent of which cannot be predicted.
  2. At working pressure, 3-Ply hose can reach an elongation rate as high as 10%. Such elongation results in “snaking” which causes the hose to move in an unpredictable manner and may lead to damage to the hose and the environment, as well as a reduced flow rate.
  3. In the process of “turning the inside tube out” manufacturers have to use a softer polyurethane material than that used in through-the-weave hose. As a consequence, 3-Ply hose is less resistant to abrasion and more prone to puncture than through-the-weave hose.

Mammoth’s mission is to supply the very best lay flat hose product available for water transfer in the oilfield. We believe that extruded-through-the-weave TPU hose is that product. Although the initial per foot cost of through-the-weave hose is higher than 3-Ply and Nitrile Rubber hoses of the same diameter, the superior performance and longer life of through-the-weave TPU hose should result in higher profitability over time.  Moreover, a leak or spill from the puncture of a Nitrile Rubber hose, or from delamination of a 3-Ply hose, could easily wipe out any savings realized by the purchase of the cheaper hose.