Schematic Diagram of Hydroentang Lement Process

The formed web (usually air-laid or wet-laid, but sometimes spun bond or melt-blown, etc.) is first compacted and prewetted to eliminate air pockets and then water-needled. The water pressure generally increases from the first to the last injectors. Pressures as high as 2200 psi are used to direct the water jets onto the web. This pressure is sufficient for most nonwoven fibers, although higher pressures are used in specialized applications. It has been argued that 10 rows of injectors (five from each side of the fabric) should achieve complete fabric bonding.

Injector hole diameters range from 100-120 mm and the holes are arranged in rows with 3-5 mm spacing, with one row containing 30-80 holes per 25 mm . The impinging of the water jets on the web causes the entanglement of fibers. The jets exhaust most of the kinetic energy primarily in rearranging fibers within the web and, secondly, in rebounding against the substrates, dissipating energy to the fibers. A vacuum within the roll removes used water from the product, preventing flooding of the product and reduction in the effectiveness of the jets to move the fibers and cause entanglement.