Here is everything you need to know about rubber tubing and its use.
You will learn:
Rubber tubing, sometimes referred to as rubber hose or piping, is crafted from both natural and synthetic rubber. It serves a variety of purposes in transporting and circulating liquids and gases in both domestic and industrial settings. The use of these rubber materials imparts exceptional flexibility, durability, and reliability, making rubber tubing ideal for applications in hydraulic and pneumatic systems, as well as in food processing and medical fields.
Rubber tubing comes in a diverse range of diameters and wall thicknesses, offering significant versatility. This adaptability makes it suitable for numerous specialized and unique industrial applications.
Unlike other types of tubing, rubber tubing stands out due to its elastomeric properties, which provide high strength, durability, and the ability to stretch and deform without permanent damage. This is attributed to its flexibility, tear resistance, resilience, and thermal stability.
Rubber tubing is manufactured using two primary methods. The first involves wrapping rubber strips around a mandrel and heating them. The second method is extrusion, where rubber is pushed through a die to form the tubing.
In the mandrel process for producing rubber tubing, the rubber is supplied in rolls of strips. The wall thickness of the tubing is dictated by the thickness of these rubber sheets. The color of the tubing depends on the color of the rubber roll used. While color is not essential for the tubing's function, it often serves as a means of classification and for determining its final application.
To prepare the rubber for processing, it is passed through a mill where it is heated. This softens and smooths the rubber strips, ensuring a consistent texture throughout.
The softened and pliable rubber is then transferred to a cutting machine, which slices it into strips of uniform width. These strips are sized to match the desired dimensions of the rubber tubing.
Once cut, the rubber strips are fed onto a mandrel. Before the strips are applied, the mandrel is coated with a lubricant. The mandrel's diameter matches the internal dimensions of the tubing. As the mandrel rotates, the rubber strips are evenly and consistently wound around it.
The wrapping process can be repeated multiple times to achieve the desired thickness of the rubber tubing.
Once the tubing reaches the desired thickness, a reinforcement layer is applied, which consists of a high-strength synthetic material coated with rubber. The choice of reinforcement depends on the pressure requirements of the tubing. For added durability, wire may be included in the reinforcement layer in certain applications.
The outermost layer of the rubber tubing is its exterior covering.
After applying all the layers of rubber strips, the entire length of the tubing is wrapped in wet nylon tape. This tape, upon drying, shrinks and compresses the layers together, creating a textured finish on the outer diameter (OD) of the tubing. This textured surface is advantageous for certain applications where enhanced grip or additional functional properties are required.
Once the tubing is wrapped around the mandrel, it is placed in an autoclave where steam is introduced under high pressure. This process of steam and heat triggers vulcanization, a chemical reaction that cures the rubber, giving it its elastic properties.
To facilitate the removal of the rubber tubing from the mandrel, one end of the tubing is securely sealed to build up pressure. A hole is then created in the tubing to allow water to be pumped in. This separates the rubber tubing from the mandrel, allowing it to be easily slid off. The tubing is then trimmed at both ends and cut to the specified lengths.
During the extrusion process, rubber is pushed through a disc-shaped die to form tubing. This method uses a soft, unvulcanized rubber compound, resulting in tubing that remains soft and flexible. After extrusion, the tubing is then subjected to a vulcanization process to achieve its final, durable properties.
The extrusion process starts with feeding the rubber compound into the extruder.
The rubber compound gradually exits the feeder and is conveyed by the screw towards the die.
As the rubber material is advanced by the screw, it is pushed through a die that shapes it to the specified diameter and thickness of the tubing. As the rubber approaches the die, the temperature and pressure increase, causing the material to expand based on the compound's type and hardness.
Since the rubber used in extrusion is unvulcanized, it must be subjected to a vulcanization process after exiting the extruder. While sulfur was historically the primary vulcanizing agent, modern methods include microwave treatments, salt baths, and other heating techniques. This process is essential to shrink and harden the final product.
The vulcanization or curing process is illustrated in the diagram below.
The decision to use the extrusion method is guided by its rapid processing capabilities and effectiveness, along with its flexibility in creating various sizes, colors, and shapes of tubing.
The extensive application of rubber tubing has resulted in various types designed for specific and specialized uses. While there are numerous rubber varieties available, they generally fall into two categories: natural and synthetic.
Different types of rubber come with distinct advantages and limitations, which are influenced by the properties of the selected polymer. Choosing the right material depends on factors such as the operating temperature, exposure to chemicals, abrasion resistance, compression levels, and load-bearing requirements, among others.
Fluoroelastomer rubber tubing is designed for high-temperature applications and offers excellent resistance to chemicals, oils, and heat, withstanding temperatures exceeding 200°C. FKM types are categorized based on their fluorine content, which varies from 66% to 70%. Tubing with higher fluorine levels provides enhanced resistance to various fluids.
Butyl rubber tubing is ideal for transferring air and carbon dioxide. It features thick walls, excellent shock absorption, and strong resistance to oxygen degradation, operating effectively within a temperature range of -30°F to +275°F. This type of rubber is composed of a blend of isobutylene and isoprene.
CSM (Chlorosulfonated Polyethylene) is produced by chemically treating polyethylene with chlorine gas and sulfur dioxide. This process converts the polyethylene into a flexible, vulcanized rubber with enhanced flame and oil resistance due to the chlorine treatment.
Known commercially as Hypalon by DuPont, CSM offers excellent resistance to oxygen, ozone, and severe weather conditions. It is particularly suited for environments involving corrosive chemicals, acids, oil, and grease. Hypalon performs well across a temperature range of -34°C to 93°C, maintaining its tensile strength over extended periods.
Natural rubber is derived from the sap of rubber trees and boasts outstanding mechanical attributes, including high impact resistance, tensile strength, and durability against abrasion and tearing. It is ideal for applications that demand superior physical performance but is unsuitable for environments where exposure to chemicals, fuels, oils, or solvents is a concern.
Produced from the latex extracted from rubber trees, natural or latex rubber is known for its durability and flexibility. It is particularly valuable in settings that require exceptional strength, elongation, and resistance to tearing. However, despite its many advantages, natural rubber is not recommended for outdoor use due to its susceptibility to damage from UV radiation and ozone.
Neoprene rubber is a synthetic material derived from coal, salt, and limestone. It is well-suited for environments requiring resistance to petroleum products, sunlight, ozone, and high temperatures. Its durability makes it ideal for outdoor applications where it must endure significant temperature fluctuations. However, neoprene rubber has a drawback in its electrical conductivity, which makes it unsuitable for use in environments with electrical currents.
Nitrile rubber, a copolymer of acrylonitrile and butadiene, offers outstanding resistance to water, petroleum-based products, and fuels. It maintains its flexibility and resilience even after prolonged contact with petroleum substances, making it highly durable and less prone to brittleness over time.
Styrene-Butadiene Rubber (SBR), a blend of styrene and butadiene, shares many properties with natural rubber, including its resistance to solvents and petroleum-based substances. However, SBR offers superior water resistance compared to natural rubber. Its notable features include excellent abrasion resistance and cost-effectiveness, making it a popular choice for manufacturing applications.
Silicone rubber, which is reinforced with silica, is known for its versatility across various environments, from extremely cold to very high temperatures. It is flame-resistant and features a smooth, flexible, and elastic texture. Silicone tubing offers excellent water resistance and pliability, making it suitable for a wide range of applications.
Thermoplastic elastomers (TPE) are employed in settings where durability against harsh chemicals and a broad range of acids is essential. Their ability to withstand continuous bending and movement makes them ideal for applications in robotics and pumping systems. TPEs can be stretched and deformed extensively yet return to their original form without noticeable wear, offering a long-lasting and reliable performance.
Ethylene Propylene Diene Monomer (EPDM) is a terpolymer composed of ethylene, propylene, and a diene component, which allows it to be vulcanized using sulfur. Known for its excellent resistance to heat, ultraviolet light, and ozone, EPDM is particularly suited for outdoor applications. It can endure temperatures as low as -40°C, making it durable for extended use in various environmental conditions. During manufacturing, additives such as black carbon, calcium carbonate, and plasticizers are incorporated to enhance its rubber-like properties.
Hytrel® rubber tubing is engineered for applications requiring distinct functionalities from the inner and outer linings. It is produced through a co-extrusion process, where the Hytrel® layer is extruded first, followed by a layer of PVC. This construction allows the tubing to withstand demanding and challenging conditions effectively.
The manufacturing of rubber tubing focuses on creating products suited for specific conditions. Although a range of materials can be used, the choice of grade and type is tailored to meet particular requirements, resulting in various specialized tubing types.
In the food industry, ensuring that tools are safe and free from contaminants is crucial. Tubing used in this sector must adhere to stringent guidelines set by the Food and Drug Administration (FDA), which outlines the acceptable materials for food contact applications. Like other industrial applications, food handling equipment must be capable of withstanding high pressures, temperatures, and exposure to acids and chemicals used in food processing.
Similar to food-grade rubber tubing, medical-grade rubber tubing is subject to rigorous standards concerning its design and construction. These standards ensure the tubing's ability to resist contaminants, withstand chemical degradation, endure thermal damage, and maintain biocompatibility. The primary goal of these regulations is to ensure patient safety.
Silicone is the most commonly used type of medical rubber tubing due to its compliance with FDA regulations outlined in 21CFR177.2600. Medical rubber tubing comes in various grades, hardness levels, and sizes to suit different medical applications.
Conductive rubber tubing is employed to manage static electricity in applications involving electromagnetic interference (EMI) or radio frequency interference (RFI) shielding. This type of tubing, made from natural or silicone rubber, achieves its conductive properties through the inclusion of carbon or other conductive particles during the manufacturing process.
Static electricity can attract dust, which poses a risk of sparks. By minimizing friction, conductive rubber tubing helps mitigate this risk. While it does not conduct electricity itself, it is designed to transport gases and liquids near electrically sensitive equipment without generating static.
Microbore tubing is specifically crafted for medical applications and features extremely small diameters. To ensure safety and effectiveness in patient care, it must comply with FDA standards for sterility and material quality. This tubing is used for intravenous lines and insertion into veins and arteries, offering robust wall construction to facilitate the smooth flow of liquids like blood or medications. It is designed to be ultra-smooth, inert, and sterile, meeting USP Class VI biocompatibility requirements for medical use.
Air tubing is utilized to channel pressurized air to actuators, valves, and various tools. It can be produced using extrusion or mandrel techniques. The tubing features an inner layer reinforced with fibers or a protective coating. The outer diameter (OD) of the air rubber tubing determines its pressure tolerance; smaller ODs may restrict airflow.
Chemical rubber tubing is engineered for transporting hydraulic fluids, acids, and hazardous substances. It is co-extruded to include both an inner and an outer layer. The primary attributes of chemical tubing are its flexibility, resistance to absorption, and smooth internal surface.
Heat shrink tubing is employed for insulating, protecting, and repairing wires to enhance their lifespan. The rubbers used are resistant to abrasion, chemicals, oil, and acids, and can withstand temperatures ranging from -90°F to 390°F. It has a dielectric strength of 500 to 800 V/mil, indicating its capability to endure electrical, thermal, or signal disruptions without degradation.
Fabric, cloth, or textile reinforced tubing consists of three main components: the reinforcing material, the tube, and the cover. The tube is made from synthetic rubber, often NBR, which resists abrasion, corrosion, and oils. The reinforcing material comprises multiple synthetic layers, providing a strong and sturdy structure. A second layer of synthetic rubber, with properties similar to the first, covers the fabric. This construction ensures the tubing is highly durable and resilient.
Non-reinforced rubber tubing is suitable for low-pressure uses, such as in pneumatic machinery and the food industry. It is highly flexible, lightweight, and durable, and can be used as lay-flat tubing. This type of tubing can be customized to various sizes with different IDs and ODs and is available in multiple colors. The smooth, consistent inner surface enhances flow and minimizes buildup.
To enhance strength and stability, non-reinforced rubber tubing may be reinforced with one or more layers of cloth, such as polyester, nylon, or cotton. This additional reinforcement makes the tubing suitable for applications involving oils, caustic substances, and hydrocarbons.
The versatility and resilience of rubber tubing have established it as a crucial element across various industries. Known for its durability and reliability, rubber tubing is well-suited for applications in domestic settings, such as transferring water and chemicals, as well as in industrial environments where it handles hydraulic fluids and chemical processes.
In the automotive sector, rubber tubing is commonly known as hoses and is used for various purposes, including fuel lines, radiator hoses, lubricant supply, and cooling systems. The efficient functioning of vehicles relies on the rubber tubing remaining in optimal condition. Given its longevity and proven reliability, rubber tubing is the preferred choice for fluid transfer in automobiles.
There are several varieties of rubber tubing used in agriculture. It is used to transfer grain, collect debris, and provide ventilation. Each application requires a specially designed tubing. Flexible tubing is used to move abrasive materials such as animal feed, grain, and manure. A major use for agricultural tubing is for ventilation to ensure proper airflow for livestock. Agriculture rubber tubing is required to be chemical resistant due to the wide variety of chemicals used for food production and feeding.
In the aerospace sector, rubber tubing must endure extreme weather, significant pressure variations, and substantial temperature fluctuations. Flexible hoses are crucial in aircraft to connect moving components with stationary parts in vibration-prone areas. Additionally, rubber tubing serves as a link between metal tubes.
To ensure the necessary strength, durability, and dependability for aerospace applications, synthetic rubbers such as neoprene, butyl, and EPDM are used in the production of aircraft tubing. The pressure ratings for aerospace rubber tubing typically range from 250 psi to 3000 psi.
In food processing, rubber tubing must adhere to strict FDA standards due to its critical role. Essential characteristics of food-grade rubber tubing include resistance to kinking and preventing the buildup of contaminants or sediments, which ensures smooth flow and easy cleaning. The tubing features thick walls to avoid kinking while maintaining a lightweight and flexible structure. Designed to handle the acids and chemicals present in food products, food-grade rubber tubing also resists alcohol and alkali. It is manufactured through a purity process to prevent the transfer of flavors and odors. This type of tubing is utilized for water, air, beverages, and dairy applications.
A diverse range of tubing and hoses are employed in marine applications, as illustrated in the diagram below. Water hoses are essential for circulating engine cooling water, flushing toilets, and cooling air conditioning systems. Drainage hoses, located in areas like the cockpit, sink, or shower, are designed to be kink-resistant and abrasion-resistant. Drinking water hoses adhere to FDA standards to ensure the water remains free of unpleasant tastes. Additionally, bilge pump and sanitation hoses are built to be durable for continuous use.
Medical and pharmaceutical grade rubber tubing is typically crafted from synthetic rubber, with silicone being the most prevalent, and involves minimal use of compounding agents. These tubes undergo rigorous testing, including implantation studies in both animals and humans, adhere to stringent FDA manufacturing guidelines, and are subject to high-quality control standards.
Applications for medical grade rubber tubing include feeding tubes, catheters, implants for both short-term and long-term use, and syringe pistons. The Center for Devices and Radiological Health (CDRH), operating under FDA regulations, oversees the standards for medical and pharmaceutical grade rubber tubing.
Essential characteristics of medical and pharmaceutical grade rubber tubing include being odorless, non-toxic, chemically inert, temperature stable, and highly resistant to chemicals. Compliance with FDA regulations largely depends on the choice of raw materials and the methods used for vulcanization or curing.
Rubber tubing is crucial for any industry involved in the transmission, movement, or transport of liquids or gases.
Despite its wide range of uses, rubber tubing requires proper care to maximize its lifespan and ensure reliability. Regular inspection and maintenance are essential to avoid issues such as leaks, cracks, odors, or deformation.
Rubber's inherent softness and flexibility make it prone to tearing and wear. Most rubber tubing comes with a protective coating or layer to enhance its durability, but this does not completely eliminate the risk of damage. It is crucial to store rubber tubing in a clean, uncluttered environment, away from debris, moisture, and potentially damaging items like metal tools or sharp objects.
Proper handling is essential while using rubber tubing. Always adhere to the manufacturer's recommended procedures and use the correct connectors when attaching the tubing to equipment. Avoid applying excessive force or stress, as this can compromise the tubing's integrity. When relocating tubing, use a cart to transport it rather than dragging it, which can damage the protective coating. Never crush, stand on, or sharply bend the tubing to stop the flow.
Each rubber tubing is engineered for specific applications, with particular flow rates and pressure limits. Surpassing these rated specifications can lead to the tubing bursting or failing. Understanding the materials used in the rubber tubing is crucial for maintaining proper usage levels. Different materials have varying responses to pressure, determined by their tensile strength, which indicates the maximum pressure they can endure. Introducing chemicals into a tube designed for watering purposes can compromise its integrity and may lead to leaching.
The cleaning frequency for rubber tubing varies based on its usage. For infrequent use, a cleaning schedule of every six months is typical, though more frequent inspections may be necessary. Manufacturers usually provide detailed care instructions, including guidelines on cleaning intervals and methods.
Before cleaning rubber tubing, check for any signs of leaks or damage, and address these issues before proceeding. Use lukewarm water and a mild soap solution for washing the tubing. Ensure all dirt, chemicals, and residues are thoroughly removed. Rinse the tubing well to eliminate any remaining cleaning agents and dry it gently with a soft cloth. Avoid drying rubber tubing in direct sunlight or using excessive heat sources.
The storage environment of rubber tubing can greatly affect its performance and longevity. Factors like temperature, exposure to ozone or UV light, and physical abrasions play crucial roles in determining the condition of rubber tubing while in storage.
Temperature: Rubber tubing is affected by both the temperature of the fluids it carries and the ambient temperatures where it is stored. Extreme temperatures, whether too hot or too cold, can compromise the tubing's effectiveness and longevity.
Ozone and UV: Exposure to sunlight and ozone can lead to significant damage such as cracking or dry rot in rubber tubing. It is essential to ensure that tubing designed for outdoor use is thoroughly tested to withstand these conditions.
Abrasion: Frequent handling or dragging of rubber tubing across rough surfaces can cause erosion or mechanical wear. Choosing tubing made from more robust materials can help mitigate such damage.
Rubber tubing must be specifically designed for chemical resistance to endure exposure to chemicals. Tubing that is likely to encounter toxic substances should be rated appropriately to handle such interactions safely.
Rubber tubing is available in numerous sizes, configurations, grades, and applications. It's crucial to choose the appropriate type to ensure it meets the specific requirements for durability and performance needed for its intended use.
Rubber tubing is subject to the standards set by the International Organization for Standardization (ISO). For applications related to food, medical, and pharmaceutical uses, it is also regulated by ISO standards, the Center for Devices and Radiological Health (CDRH) under the FDA, and the United States Pharmacopeia (USP).
ISO standards provide guidelines for hoses and hose assemblies. These regulations address:
The regulation numbers start with ISO 1307:2006 and ISO 1402:2009, extending to ISO 28702:2008 and ISO 30013:2001.
FDA 21CFR177.2600 pertains to materials that may come into contact with food but are not intended to be added to it. This regulation includes a detailed list of elastomers, vulcanization agents, accelerators, retarders, activators, antioxidants, plasticizers, fillers, and emulsifiers. It identifies materials that are generally recognized as safe (GRAS).
The regulation also outlines the proper extraction methods, defining the acceptable amount of milligrams per square inch. The list of approved rubber materials includes acrylonitrile-butadiene copolymer (Buna), silicone, polytetrafluoroethylene, and ethylene propylene diene monomer.
The sanitary standards extend to all equipment that may come into contact with food, such as tubing, hoses, gaskets, o-rings, and seals.
USP Class VI is the standard used to evaluate the biocompatibility of materials. Among the six USP classifications for biocompatible materials, Class VI is the most stringent. It ensures that the materials used are safe, non-toxic, and do not cause any harmful chemical leaching that could affect the body over time. The USP plays a key role in regulating the safety and quality of medical devices and food-related products.
The CDRH oversees the manufacturing processes and safety standards for medical devices. Additionally, it regulates non-medical devices that emit electromagnetic radiation, such as cell phones and microwave ovens.
The CDRH categorizes devices into three distinct classifications:
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