Our standard stocked product is made from a full 10 to 1 safely factor, polyester warp fabric in both Grade I and Grade II
CWP provides belting in most standard widths and plies. We stock Grade I belts in 3 ply and above, as well as our single ply straight warp products. We stock Grade II belts for our 2 ply products. We can supply many combinations of cover and fabric types per request. Belting is available cut to order, by the roll or in container quantities.
CWP K-Flex single ply straight warp belting is exceptional for heavy impact and abusive areas under crushers and belts conveying large sized rock.
This is a K-Flex belt working in a heavy and abusive application. This customer was getting 30 days out of a standard belt. This 440 single ply ¼” top cover belting has been running for 3 months with 24” material dropping on it!
There is often confusion in comparing belting products from various suppliers. The most common terms noted when selecting belt in the US is RMA Grade I or Grade II. These terms are from the Rubber Manufacturers Association (RMA). They only apply to belt covers and not fabric. They also specify only two requirements. Grade I belt must have a minimum cover elongation at break of 400% and minimum tensile strength at break of 2,500 psi. Grade II belt must have a minimum cover elongation at break of 400% and minimum tensile strength at break of 2,000 psi. CWP belt grades cover additional specifications that are important when evaluating conveyor belt. An overview of these specifications follows:
The piw units used in the US are based on working strength. A typical fabric used is 110 piw. The safety factor determines breaking strength. CWP belt fabric is a 10 to 1 safety factor. Therefore the breaking strength on a 110 piw working strength fabric would be 1,100 lbs. Some manufacturers and suppliers use a lower safety factor so a less expensive fabric can be used but still be called a 110 piw fabric. RMA specifications do not cover fabric.
For the aggregate industry it is desirable that the fabric in the length direction (warp) have minimal elongation or stretch. If the belt stretches beyond the amount of take-up designed for a given conveyor the belt will need to be re-spliced. There are two elongation specifications we consider. Elongation at 10% of breaking strength (typical working strength), and elongation at break (100% of breaking strength). Elongation at 10% of breaking strength is an indication of how much the belt will stretch under normal use. A full 10 to 1 safety factor fabric will stretch less than a lower safety factor fabric. All CWP belt uses 10 to 1 safety factor fabric. Nylon fibers have good strength characteristics but stretch considerably more than Polyester fibers stretch so we require a polyester fabric in the warp. The weft fibers do not see much of a load so we accept weft fibers made from both polyester and nylon. Again RMA specifications do not cover fabric.
Cover elongation at break:
The more the rubber cover will stretch before it breaks the better the cover will perform. The RMA grade 1 and 2 specifications are a minimum of 400% elongation before breaking. A higher elongation at break rubber will take more abuse and be able to wrap around pulleys and conform to troughers over a longer time period. CWP meets or exceeds the RMA 400% specification requirement.
Cover tensile strength:
The higher the cover tensile strength the stronger the cover will be. A stronger cover will better resist cutting and gouging better and will hold up better under impact. CWP belt grades meet or exceed RMA specifications.
Cover abrasion resistance:
A cover with higher abrasion resistance will wear longer. The standard abrasion resistance test used for measuring the abrasion resistance of rubber is from a German specification. The test utilizes an abrasive wheel turning at a specified speed and imparting a specified force for a specified time. The volume of material removed is then measured in mm³. The lower the amount of material removed the more abrasion resistant the cover is. Cover abrasion resistance is included in the German specifications but is not covered by RMA. I have heard that a new organization called the Association for Rubber Products Manufactures (ARPM) will be replacing RMA for conveyor belt specifications. They may include abrasion resistance in future specifications but RMA does not. We specify a minimum 150 mm³ abrasion resistance for our Grade I belt and 200 mm³ for our Grade II belt.
Cover to ply adhesions:
This specification is a measurement of the force it takes to pull the fabric away from the covers and the skim coats between the plies in N/mm. A force of 5 N/mm for the top cover, bottom cover, and the skim coats between the plies are typical. Test measurements are typically much higher than the spec. Our CWP specifications require a minimum adhesion of 5 N/mm.
Many suppliers state that their belt meets RMA grade specifications. RMA only defines the tensile strength and elongation at break of the belt cover. It does not define the abrasion resistance of the cover nor the strength or material of the fabric. CWP belts not only meet or exceed RMA grade specifications, they meet the additional specifications described above to insure you know what you are buying.
Our standard stocked product is made from a full 10 to 1 safely factor, polyester warp fabric in both Grade I and Grade II. We stock Grade I belt in 3 ply and above as well as our single ply straight warp products. We stock Grade II belt for our 2 ply products. We can supply many combinations of cover and fabric types per request.