When working with fluid handling systems, selecting the right tubing is essential for optimal flow and performance. Whether you're replacing existing tubing or setting up a new system, understanding how to measure tubing and identifying other critical parameters will help you make the best choice. By accurately measuring the tubing’s dimensions and considering your application’s requirements, you can confidently choose the right tubing for your project.
Understanding Tubing Dimensions
When determining the right tubing, dimensions are a primary consideration. Tubing is measured with three key dimensions:
Inner Diameter (ID): The distance across the inside of the tubing where the tubing flows, which determines the flow capacity. This is critical for ensuring the tubing can handle the volume of liquid, gas, or material that needs to pass through. A larger ID allows for greater flow rates, but it may also reduce precision in some applications. Compatibility with hose barb fittings depends on the ID.
Outer Diameter (OD): The distance across the outside of the tubing, including the wall thickness. This is important when the tubing needs to fit into specific system pathways or operate in tight spaces. Compatibility with compression fittings and clamps often depends on the OD.
Wall Thickness: The material difference between the ID and OD. This affects the tubing’s strength, flexibility, and durability. Thicker walls generally provide higher pressure resistance but may reduce flexibility, while thinner walls enhance flexibility but may compromise strength under pressure.
These dimensions can affect the tubing’s flow capacity, bend radius, and pressure rating. Understanding these dimensions in detail is essential for selecting the right tubing for your specific application. Whether you're working on fluid handling applications such as bioprocessing, food and beverage transfer, or solvent transport, the tubing's dimensions directly impact its functionality, efficiency, and safety.
How to Measure Tubing
Accurate measurement of tubing ensures proper fit and functionality. Here are four reliable methods:
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Printable Size Guide: To make measuring tubing easier, Cole-Parmer has created a downloadable PDF featuring cross-sections of over 20 common tubing sizes. You can print the guide at 100% scale and either hold up your tubing to the cross-section or cut out the size templates. [Download the Sizing Made Simple PDF]
Use a Caliper: A caliper provides precise measurements of the inner and outer diameters. Place the external, or lower caliper jaws around the outside of the tubing to measure the OD. Place the internal, or upper caliper jaws inside the tubing to measure the ID. If you are using vernier calipers, once you have the caliper jaws in the right position, read the fixed, or main scale measurement by finding the nearest mark to the left of the 0, or exactly on it, like you would read a ruler. Then read the measurement from the vernier, or movable scale the same way and add these values together for your final measurement.
Measure the Circumference for OD: Wrap a flexible tape measure around the outside of the tubing to get the circumference. Divide the circumference by Pi (3.1415) to get the OD of the tubing. If the wall thickness is known, subtract twice the wall thickness from the OD to find the inner diameter. If the wall thickness is unknown, use a micrometer to measure it directly on a section of tubing.
Wall Thickness = (OD - ID) / 2: If two of the three dimensions are known, use this formula to determine the remaining dimension. The flexibility makes the formula a versatile tool for ensuring precise measurements and selecting tubing that meets system and performance requirements.
Important Tubing Specifications to Consider
Beyond size, other factors play a significant role in tubing selection. Consider these additional factors to ensure the tubing meets your application’s needs:
Flexible vs. Rigid Tubing
Flexible Tubing can bend without cracking or losing integrity and is suitable for use with peristaltic pumps or in confined spaces. Flexibility is essential for applications requiring repeated motion or routing around obstacles. Softer, more flexible tubing typically has a lower durometer value with Shore A designation.
Ridgid Tubing maintains its shape and is best suited for applications requiring structural stability and for use in extreme environments. Typically made from hard plastics, rigid tubing provides superior strength and resistance to high pressure or impact but is more prone to cracking under flexing or bending stresses. This tubing has a higher durometer with Shore D value, reflecting its stiffness and hardness.
Material Compatibility: Choosing the best tubing material plays a critical role in the success of your fluid management system. Incompatible materials can result in chemical degradation, contamination, equipment damage, or even safety hazards. The wrong material may also produce hazardous byproducts or fail catastrophically, posing risks to personnel and equipment. The Cole-Parmer Chemical Compatibility Database is an invaluable tool for ensuring you select the best tubing material for your specific application.
Pressure and Temperature Ratings: These parameters are critical when selecting tubing because they determine the conditions the tubing can safely withstand without failure. Tubing exposed to temperatures or pressures beyond its rated capacity may weaken, crack, or burst, leading to equipment damage or safety hazards. Some chemicals become more aggressive under high temperatures or pressures, potentially causing accelerated corrosion or degradation of the tubing material. Choosing tubing with appropriate ratings ensures durability, chemical compatibility, and safe operation under the intended conditions.
Compliance Standards: Verify that the tubing meets relevant industry standards, such as FDA, USP, or ISO certifications, depending on your application requirements. Learn more about these compliance standards in our blog post.
Cole-Parmer’s Tubing Offering
Cole-Parmer offers an extensive selection of tubing materials and formulations to meet diverse application needs, including chemical transfer, upstream and downstream bioprocessing, and laboratory use. This selection features high-performance brands such as Tygon® and DuPont™ Liveo™, renowned for their flexibility and chemical resistance, as well as Viton®, ideal for handling aggressive chemicals and high temperatures. Additional materials include Cole-Parmer Silicone tubing, prized for its purity and temperature tolerance, and PVC tubing, designed for peristaltic pump applications requiring long service life.
Cole-Parmer's tubing portfolio also includes specialty formulations tailored to unique requirements, such as fuel and lubricant tubing for hydrocarbon-resistance and Food, Milk, and Dairy tubing , which ensures a sanitary fluid path for the food and beverage industry. Whether you need to maintain sterility in a critical bioprocess, transfer corrosive chemicals in an industrial setting, or ensure reliable operation in laboratory equipment, Cole-Parmer provides the right tubing to meet your specifications.
Now that you’ve measured, find the right tubing for your application—browse our full range of tubing and hose now.
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