Table of Contents

How to Keep Plastic Tubing from Kinking

how to keep plastic tubing from kinking

Importance of good fluid flow


IV tubing made of polyvinyl chloride (PVC) connects the IV fluid bottle or bag to the patient’s vein. It thus serves as a conduit where fluid flows from the IV fluid bottle into the patient’s circulatory system. When the medical staff hooks the patient to an IV set, it transfers the fluid and the medicines mixed into it. When the IV tubing kinks, the fluid, and the medication are prevented from reaching the patient, thus preventing the patient from receiving the benefits of the IV therapy. It is, therefore, essential to keep the patency of the IV tubing at all times when the medical staff administers the IV therapy.

Strategies for preventing kinks along the IV tubing

Choose the suitable polymer for your work application

Understanding the intricate interplay between the polymeric material used in producing the IV tubing or IV set and its specific application occupies the highest consideration to prevent tubular kinking. If the material used in the IV tubing is not the right one, then kinking will take place. Based on Table 1, the use of PVC in the production of IV tubing is the right one.

MATERIALUSESCHEMICAL COMPATIBILITYAPPLICATION
Polyvinyl Chloride (PVC) General fluid transferGood with water, weak acids, alkalisWater supply, irrigation, industrial fluids 
Polyethylene (PE) General fluid transferExcellent with water, many chemicals Water, food, non-corrosive liquids 
Polypropylene (PP) General fluid transferExcellent with water, acids, alkalis Water, chemicals, industrial fluids 
Thermoplastic Elastomers (TPE) Flexible and durable tubing Good with water, mild chemicals Medical tubing, laboratory fluid handling 
Polyurethane (PU) Flexible and kink-resistant Good with water, oils, some solvents Pneumatic systems, robotics, automotive 
Fluoropolymers (e.g., PTFE, FEP, PFA) Corrosive chemicals and high temperatures Excellent with most chemicals, high temperatures Corrosive chemical handling, biopharmaceuticals 
Silicone Biocompatible and temperature-resistant Biocompatible and temperature-resistant Biopharmaceuticals, medical applications
Table 1

Use material dimensions compatible with performance specifications


Bend radius

The bend radius is the minimum radius of curvature that a tube can bend without kinking. Material scientists consider the minimum bend radius (MBR) to determine the tube flexibility. The smaller the MBR, the higher the tube flexibility will be. If the MBR is high, flexing the tube too far can cause kinking or permanent deformation. Thus, depending on the nature of the work application, a particular MBR of a tube needs to be followed or used

Wall thickness

Tubes with more thickness are better able to resist kinking when bent than their thinner counterparts.3 Based on Plot 1, as the wall thickness increases, the average bend radius decreases, and therefore, it can sustain more bending. In the test samples, material researchers found that tubing could bend around smaller mandrels without kinking as the wall thickness and outer diameters (ODs) increased. This observation indicates that larger silicone tubing with ODs greater than 0.5 inches requires a substantial wall thickness to resist kinking effectively. Thus, depending again on the nature of the work application, a particular thickness of the tube needs to be used to prevent kinking.

Tube diameter

The flexibility of a tube is inversely proportional to its bend radius. It means that as the flexibility increases, the bend radius decreases. Hence, manufacturing engineers must use a more flexible tube in a work application that requires a smaller bend radius. In this connection, the bend radii can also be reduced—thus increasing the flexibility—by using a smaller or shorter diameter tube for as long as it is compatible with the work application. In the study, material scientists found out that silicone tubes with larger inner diameters (IDs) are more likely to kink than those with smaller IDs.

Based on Plot 1, as the outer diameter (OD) increases, brought about by increasing the thickness, the average bend radii decreases, and the flexibility increases.

External forces

External forces act on the IV tubing. These are the weight of the transported fluid, the tube’s mass, changes in the flow rates during operation, and sharp bends or junctions where the tube must flex. The performance specifications of the IV tubing need to be compatible with these external forces.

Correctly install the IV tubing

Proper installation of the IV tubing and its subsequent management plays a significant role in preventing kinks along the tube. When the IV tubing kinks, not only will there be a disruption of fluid flow, but it will also compromise the integrity of the tubing. The kinking will lead to possible leaks. Plant managers must follow these techniques:

  • Use smooth, gradual bends that meet tubing recommendations;
  • Use elbow fittings to change the tubing route, avoiding sudden and drastic bends and safeguarding tubing integrity;
  • Avoid excessive stretching or twisting to prevent stress points and potential kinks;
  • Allow adequate slack without sagging, securing with clamps or brackets as needed;
  • Ensure careful routing and secure fastening to avoid compression or damage;
  • Regularly inspect tubing for wear, kinks, or damage; promptly replace compromised tubing.

Use reinforcements as needed

Increasing the flexibility of the IV tubing may lead to a decrease in structural rigidity. For this reason, kinking of the IV tubing may occur. To prevent the kinking or collapse from happening, material scientists incorporate reinforcement into the tube’s design, which is now called reinforced tubing.

Reinforced tubing is a type of flexible tubing that includes additional layers or materials to enhance its structural integrity, strength, and resistance to specific forces like pressure, kinking, and collapse. The material engineers add the reinforcement to the tubing during the manufacturing process and said reinforcement could come from various materials, such as braided fibers, spiral wire, or textile materials.

Typically, the reinforced tube consists of three layers: the core, the braid, and the jacket. The core and the jacket can be the same or different materials, depending on its final use. In braided reinforcement, braided fibers, commonly coming from materials like nylon, polyester, or aramid, are embedded within the tubing wall. In spiral reinforcement, a wire helix is embedded within the tubing’s structure, providing enhanced flexibility, collapse resistance, and protection from crushing.

Final words on the generation of kinking in IV tubings

The IV set, or IV tubing, consists primarily of a tube. When material engineers notice a kink, or kinks, along the tube, observers could conclude that the tube is incompatible with the work application.

Incompatibility of the tube and the work application occurs with the following possible causes:

  • The polymer used in the production of the IV tubing or IV set was not appropriate for the requirements of the work application;
  • The structural dimensions and parameters, such as thickness, diameters (inner and outer), and bend radii, of the tube could not cope with the requirements of the work application;
  • Medical staff failed to install the IV tubing or IV set appropriately.
  • The IV tubing or IV set lacks structural rigidity, which external forces require, so reinforcement needs to be incorporated into the tube.

The work application dictates the nature and properties of the tube. Hence, the tube needs to be designed and produced according to the needs of the work application.

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