Why Pneumatic Tubing Cracks, Kinks, or Bursts: Material Causes Buyers Should Know
Pneumatic tubing is the lifeblood of air powered systems. Used to power automation, robots and a host of other manufacturing processes high quality tubing is made using the best materials and manufacturing techniques. However even the best of tubing can fail – often as a result of poor installation or operation in harsh environments. Tubing can crack, kink or burst leading to costly downtime and potentially putting the operator at risk. The reasons for such failures are often due to the properties of the materials used in the tubing and the ways in which they are joined together to form a system. In PU tubing and multi-material systems there are specific reasons why failures can occur, and ways in which they can be avoided through the choice of correct tubing and by following a number of simple maintenance techniques.
Why Does Pneumatic Tubing Crack Over Time?
The cracking of pneumatic tubing is a progressive phenomenon. It is influenced by external environmental factors as well as mechanical stresses.
Material Fatigue and Polymer Degradation
The pressure fluctuations in pneumatic systems induce micro-cracks in the polymer chains of flexible hoses. After some time these micro-cracks develop to visible cracks, which in turn lead to a leakage of air. The flexible Polyurethane (PU) hoses are sensitive to UV-radiation and to ozone. This surface oxidation weakens the molecules on the surface of the hose. Tests of polymer materials and their aging in laboratory and in field conditions have shown that the tensile strength of a material in heavy use decreases by up to 25% within one year. The decrease of tensile strength is more pronounced with outdoor use and in high temperatures, as the oxidation on the surface of the hose is more pronounced in these conditions.
Chemical Compatibility Issues
Another cause of early tube failure is chemical incompatibility. Some lubricants, cleaning agents and airborne contaminants can react with the inner surfaces of pneumatic tubes. For example, ester-based oils can cause polyurethane tubes to become brittle and consequently to crack due to loss of elasticity whilst under normal operating pressure. Using pneumatic tubes that have verified chemical resistance to specific fluids, and that are selected on the basis of suitable ISO or ASTM specifications, can help to prevent such problems. When designing a pneumatic system that is to be used with extremely aggressive fluids or vapors, it is wise to cross reference a chemical compatibility chart when selecting suitable tubes.
What Causes Pneumatic Tubing to Kink During Installation or Operation?
Kinking of hose assemblies can occur during installation; however, kinking can also occur during operation of the hose if restrictions have not been considered in routing.
Improper Bending Radius and Routing Practices
When bending pneumatic tubes it is necessary to comply with the minimum bend radius specified by the manufacturer. If this minimum bend radius is not adhered to, then the inner surface of the tube will buckle. It may be possible to retrieve shape from a ‘bend induced kink’ but in most cases the bend will cause problems with the airflow passing through the affected section of the pneumatic tube and could even be permanently damaged. As previously stated tight bends without suitable support can cause problems. The guidelines set down in ISO 4414 states that it is necessary to ensure that any bends are made such that the bend radius is at least three times the outer diameter of the pneumatic tube to avoid kinking. The use of suitable fixing devices such as guiding clips and cable tracks when routing pneumatic tubes through limited access areas will assist in achieving the recommended minimum bend radius.
Material Flexibility and Wall Thickness Ratio
The flexibility of tubing has to be balanced with the structural integrity, typically by controlling the ratio of wall thickness to tubing diameter. In trying to make very flexible tubing (such as soft PU tubing) to use in a vacuum environment, we have to be very careful not to make the walls of the tubing too thin. In contrast, some of the reinforced multi-layer pneumatic tubes have inner flexible layers that are surrounded by one or more stiff outer layers, and these retain their shape under repeated bending stress. The ratio of the inner diameter of tubing to the outer diameter (ID/OD ratio) must therefore be chosen to prevent both blockage and fatigue. Such tubing is very suitable for use in applications such as robotic arms that are frequently moved.
Why Do Pneumatic Tubes Burst Under Pressure?
Burst failures are among the most critical issues that occur in pneumatic systems. The most severe form of such a failure is a sudden loss of pressure, which can have a serious impact on adjacent equipment.
Exceeding Rated Working Pressure
Every tube is designed with a specific working pressure limit based on its material composition and wall geometry. When system surges exceed this rating—such as during startup spikes or valve malfunctions—the internal stress surpasses the polymer’s yield strength, leading to rupture. Laboratory evaluations indicate that PU tubes can tolerate short-term spikes up to 150% of their rated pressure before bursting; however, repeated overpressure events drastically shorten lifespan. To prevent such occurrences, regular calibration of regulators and safety valves is crucial.
Temperature Fluctuations and Pressure Synergy Effects
Burst pressure of pneumatic connections can be affected significantly by ambient temperature. Polyurethane, a commonly used material for pneumatic tubing, for example, can lose up to 30 % of its pressure capability when warmed up to higher temperatures. On the other hand, low temperatures can cause materials to become brittle. Here they can break instantly during a pressurization cycle without any prior deformation. A multi-material design, for example with a flexible inner PU layer and a heat-resistant outer nylon layer, is well-suited for such applications. The tubing allows for safe use at temperatures between – 40 °C and + 80 °C.
How Does Material Selection Influence Long-Term Performance?
The choice of the right material has a significant bearing on the durability and flexibility of a system, its cost-effectiveness and reliability.
Comparing Common Pneumatic Tubing Materials
Polyurethane (PU) Tubing
PU tubing is still often used for dynamic applications because of its high elasticity and abrasion resistance. So PU tubing is ideal for moving applications in factories such as automated production lines or for use on robots to grip or hold parts and tools.
Nylon Tubing (PA)
Nylon has higher tensile strength and better pressure resistance than PU, but less flexibility. It is best suited for static applications, where nylon’s stiffness ensures greater dimensional stability for the long term under load or at high temperatures.
Polyethylene (PE) Tubing
A cost effective alternative to high pressure mechanical tubing, PE tubing is a lightweight product for use on low pressure service applications. The smooth bore of PE tubing reduces resistance to flow but is not suitable for high pressure applications.
The Role of Multi-Material Construction in Durability Enhancement
Multi-material pneumatic tubing can be created from different materials, which are united by co-extrusion technology. By combining the advantages of the different materials, a core of polyurethane is usually embedded in a layer of nylon. This outer jacket of nylon increases the chemical resistance, while the flexibility of the core is preserved. Co-extruded structures are particularly stable in their dimensions and can therefore be bent very easily. This is particularly important for compact machine designs. Field tests have shown that the hybrids achieve a service life of up to 35 % more than comparable single-material tubes, at constant pressure and temperature cycles.
How Can Buyers Reduce Maintenance Costs and Downtime?
Proactive and strategic inspection of products as well as well-thought out purchasing practices can help reduce downtime on the operation.
Preventive Inspection and Replacement Schedules
Routine visual inspections help identify early warning signs such as discoloration, surface cracks, or localized bulging before complete failure occurs. Integrating predictive maintenance software linked with flow sensors enables real-time monitoring of performance deviations caused by internal wear or micro-leakage within tubes. Early intervention minimizes unplanned shutdowns while extending component lifespan through scheduled replacements rather than reactive repairs.
Cost-Benefit Analysis of Upgrading Material Quality
Though premium multi-material pneumatic tubing carries higher upfront costs—typically 15–25% more than standard options—the long-term savings are substantial. Reduced replacement frequency lowers labor expenses associated with maintenance interventions by up to 40%. Additionally, consistent system uptime translates into higher ROI through uninterrupted production cycles and fewer safety incidents related to burst failures.
Who is Yantai Aisili New Material Co., Ltd.?
يانتاي Aisili المواد الجديدة المحدودة is a specialized manufacturer of industrial polymer tubing solutions and can use precision extrusion methods to produce pneumatic tubing for use in automation, packaging, and other fluid control applications. Our product range includes PU pneumatic tubing and a range of hybrid co-extruded pneumatic hoses for higher temperature applications. We have an experienced technical team who are happy to supply technical advice on hose material selection based on the chemical properties required to match the client’s particular environment. Yantai Aisili New Material Co., Ltd. also offer OEM/ODM services which can be produced to customer’s exact dimensions and verified by our ISO quality control system. The supporting documentation including burst test data and bend radius data can also be supplied to aid engineering validation.
Conclusion
When tubing fails by cracking, kinking, or bursting, it is often a result of its material not having the correct properties to handle the stresses imposed by its application, or problems that occur during installation. Using high-grade multi-material tubing for various applications and environments, designed to operate in temperature extremes and chemical contact zones, can be one way to increase reliability. Extended service life and avoidance of production downtime losses through regular proactive maintenance can also prove beneficial. Polymer formulation for flexible tubing has greatly improved in recent years enabling greater strength while still being cost efficient over extended periods of operation.
FAQs
What is the typical lifespan of PU pneumatic tubing in industrial environments?
Typical service life of a diaphragm is between two and five years. However, this can vary greatly depending on several factors, such as pressure cycling, temperature exposure, as well as the potential for the diaphragm to come into contact with aggressive chemicals. Early detection of any signs of wear and tear during scheduled inspections can extend the life of the diaphragm.
How do I determine the correct size of pneumatic tubing for my system?
The sizing of tubing is typically based on the required airflow rate verses acceptable pressure drop for a given line length. The best ID/OD of tubing and type of fitting can be reviewed on the manufacturer’s charts to pick the best tubing and to ensure that it will not be subjected to too much stress due to the dynamic load.
Are multi-material pneumatic tubes worth the higher upfront cost?
Yes. Higher initial investment then lower total costs in following years due to potential 40% less frequent replacements and better mechanical characteristics for longer periods of time until replacement.