Metal vs Plastic Belts

With more resources and R&D monies being spent on plastic materials and new design belt types including multiple collapse factors, lateral stiffness increases, plastic belts have been ahead of metal in this area.

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The use of metal belts on spirals have been around since 1967 and are a know factor for their abilities and limitations. The first plastic spiral belt was installed in 1987 so metal has more experience, although in straight running applications plastic belts have proven to outwear metal by a 3:1 factor. We feel this will also apply to plastic belts in a spiral.

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As of this writing, plastic belts carry a higher load rating factor than metal, but strengths of belts are not as important as radius weight factors and belt cycle life, either way plastic belts have an advantage over metal.

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In general plastic belts have an advantage because they weigh less than metal belts, and carry a lower friction, which has a running tension affect on a belt. Assuming no strength loss, plastics are better.

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Plastic belts do not have an expected cycle life as metal belts, so fatigue or work hardening of metal belts going through a spiral at expected life of 100,000 cycles are not
an issue with plastic belts. Plastic belts are expected to last > 1,000,000 cycles, given all else equal.

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Both plastic and metal belts have as small as a 1:1 to 1 ratio of belt width to inside radius collapse factor, so they are equal. This reduced radius gives you the ability for a smaller footprint spiral diameter, but must be evaluated in processing items as the height requirements increase for the same dwell times.

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The most open area metal belts (rod type) have more open area than the most open plastic belts. Metal belts are better here, given all else equal.

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The most open area metal belts (rod type) are easier to clean than the most open area plastic belts. Detailed documentation on cleaning comparisons between the 2 materials should be reviewed by the belt manufacture you are reviewing.

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The contact surface of plastic belts offers a more non stick surface than metal belts. Plastic belts are a better choice when the application calls for non stick surfaces.

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Plastic belts have the advantage as they can go up to 72” in width. Metal belts are limited to 54”. In all cases these widths are application dependent.

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Plastic belt manufacturers (all plastic belts with no protruding stainless rod connectors) are recommending running the belt edges against stainless steel vertical uprights, removing materials out of the spiral and increasing the drive capability of cage to belt. New plastic belts no longer need additional rail supports when retrofitting, so plastic belts are a better choice here. Consideration should also be given for running plastic belts directly on stainless steel belt supports, further increasing the sanitation of a system.

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Plastic belting has proven itself to be a better alternative when the application calls for higher belt speeds, as metal belts have generally been used only in applications where these speeds do not exceed 150 FPM. Plastic belts can go over 300FPM in a given application. 

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With less friction on plastic belts, and a higher drive ratio on the belt to cage interface, plastic belts normally do not require lubrication in areas where metal belts have before. This reduced friction gives plastic belts an advantage in this area, and allows for better sanitation.

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Since plastic belts have been in use over 20 years in spirals, we can now safely say that expected life is 3:1 times plastic over metal in a given application.

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Metal belts are the best choice here for applications requiring high heat, due to plastic material compositions and costing associated with high temperature materials. Oven belts are still best suited by metal belting, all infeeds and discharges are best suited by plastic. Check with your local belt manufacture for all applications over 250F to see if plastic is suitable.

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This area is probably the hardest to define as to which is better. Open area in a belt is always important as to air flows if the air comes from a vertical source application. If the air is horizontal in nature, then it has no substantial difference and does not apply. We can help you determine per installation.

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Metal belts have better thermal conductivity than plastic belts. We are finding that there is a 1 degree difference in temperatures when freezing a product on a 1 hour dwell time basis. We also encourage the belt manufactures to do a documented study on this in order to define the impact on plastic belts. 

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The standard plastic belts in the industry are made from various plastic materials and will normally burn. If you are using plastic it is imperative and your responsibility as a buyer to build in safety measures which prevent loss of property and personal injury. We have taken our many years of experience to come up with solutions in this area, contact us.

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Plastic belts have a greater drive surface contact area than metal, making them a better choice for lower tension systems.

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Metal belts can generate filings or metal particulates due to connector rod and belt link interface, or due to hold down rail to belt interface, all in selected applications. Plastic belts do not have this issue.

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Since plastic belts are modular in design, maintenance and repairs made in the filed are easier and quicker. No welding or grinding of metal I the area is required, so plastic are better.

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The least expensive metal belt is less expensive than the least expensive plastic belt. Metal belts have an advantage overall because they are not petroleum based, making belt prices per lineal foot less expensive in many cases. Costs vary daily so check with your belt supply for the best price of the day.

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The typical metal belt carries a 12 month warranty and does not include application warranties. Many plastic belt manufacturers offer multiple year warranties and cover application suitability warranties. Plastic is a better choice here.

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