Synthetic textile yarns are used in low to medium pressure hose applications up to 300 psi as reinforcement. Circular Knitting and Spiral Wrapping are often used to integrate the reinforcing yarn into the garden hose, air hose, agricultural hose, industrial hose, automotive hose, etc. This article discusses these two methods and some tips that can improve processing for hose manufacturers using cone wound yarn for hose reinforcement.
Hose Knitting Process
The knitting process forms a “sock” around the inner hose liner using a combination of a circular rotating deck feeding the yarn and needles that produce the loops or stitches. A tight sock with high picks per inch or courses will help control expansion of the hose while the burst strength is more affected by yarn fiber type, denier size and the amount of yarn that is used. Knitting with intricate precision stitching generally processes at rates of 30-60 feet per minute.
Spiral Winding Hose
Spiral hose winders consist of two counter-rotating decks of yarn that lay a specific wrap pattern over the inner liner. The spacing of the wrap is adjusted to provide the yarn coverage desired. As with knitting, burst strength is directly affected by the type and size of the yarn used and the spacing between the yarns. Due to the high throughput speeds of up to 300 feet per minute, precision wound yarn packages travel at a high rotational velocity and are subject to high centripetal forces.
Process Setup Tips and Items to Check
Proper package installation
- Cones should be locked down properly so that there is no unwanted movement
- Foam pads should be placed at the base of each cone to fill any gaps between the bottom of the yarn traverse and the machine plate. The pads will help to prevent yarn from getting caught underneath the base of the package and causing yarn breaks. Pads should make firm contact with the entirety of the package based. Foam pads do wear over time due to the forces generated by the equipment and should be replaced on a regular basis.
Eyelets and Tensioning devices
- Any ceramic or metal guides/eyelets should be inspected regularly for cracks, buildup, and broken or missing guides and replaced as needed
- External tensioning devices such as alligator-style tensioners or disc tensioners should be inspected to ensure they are functioning properly and are not deforming due to centripetal forces. Improper tension can cause defects in the yarn reinforcement being applied.
- Canisters are often used to control the balloon of the yarn and prevent the yarn from one package from making contact with yarn from another package. This becomes especially important as the yarn size increases, as the weight of the heavier yarn will throw out a larger yarn balloon. Increasing deck speeds can also contribute to larger yarn balloons.
- Inspect any centering guides for defects and make sure there are no damaged surfaces inside the canister where the yarn comes into contact.
Package Size, Density and Deck Speed
Not all spiral machines or knitters are alike and just because you can run one type of machine at a high deck RPM does not mean they will all run the same way. The distance of the yarn package to the center is critical in determining the amount of force being applied to the yarn package during deck rotation. Just like a child’s merry-go-round, the further you are away from the center of rotation, the more centripetal force is applied to the yarn package. This means that while a heavier package may be able to be used in smaller deck diameters, larger decks running the same speeds will require smaller packages to reduce the amount of force and the chances of catastrophic package deformation or yarn breaks.
Regardless of how well a yarn package is constructed, the centripetal forces applied to the material during production will affect the yarn package integrity. It is critical to use as dense of a package as possible to reduce the amount of deformation. It is also important to note that once yarn packages are partially run or are removed from the machine and reloaded onto the deck at a later time, you may not be able to achieve the same speeds due to already weakened package integrity.
For additional detailed information on how your equipment speeds relate to the yarn package densities being used, please see our previous article on Increasing Production Line Speeds. If you need processing help or selecting the best material for your hose reinforcement application, contact Service Thread for expert assistance.