As a medical consumable designed for the correct monitoring of drainage fluid volume (such as postoperative bleeding and fluid balance management in critically ill patients) in clinical practice, disposable precision metering drainage bags have sealing as one of the core safety indicators - they need to meet the three major requirements of "leakage prevention, backflow prevention, and bacterial invasion prevention" at the same time, to avoid the risk of drainage fluid leakage, infection, or measurement errors caused by sealing failure. The following provides a detailed analysis of its sealing characteristics from four dimensions: sealing design principles, key sealing parts, industry standard requirements, and actual usage verification:
1、 Core sealing design: dual guarantee from structure to material
1. Material selection: Balancing sealing and biocompatibility
      The main body of the drainage bag is made of medical grade high toughness PVC/PE film (some products use EVA material), which has good flexibility, tear resistance, and sealing properties, without pinholes or impurities, and can avoid leakage caused by material defects;
      The key sealing parts (such as interfaces and valves) are made of medical grade silicone/butyl rubber, which has strong elasticity, aging resistance, and a tight fit with the pipe. It can withstand long-term immersion in drainage fluid (such as continuous use for 24-72 hours) without deformation or cracking.
2. Structural design: Multiple sealed defense lines to eliminate leakage risks
       Connection position between drainage tube and bag body: Adopting a dual process of "heat sealing+ultrasonic welding", the drainage tube and bag body are seamlessly integrated (rather than simply bonded), with a weld width of ≥ 3mm and a tensile strength of ≥ 15N. It can withstand a tensile force of 5kg without falling off or leaking (to avoid leakage caused by pulling when the patient moves);
       Drain valve: adopts a "rotary/press type sealing valve", with a silicone sealing ring built into the valve core, which fully fits the valve seat when closed without any gap; Some products are designed with a "double locking structure" (such as pressing and locking after rotation) to prevent accidental contact from causing valve loosening and leakage;
       Dosing/sampling port (if any): Adopting a "self sealing rubber plug+screw cap" dual seal, the rubber plug can automatically rebound and seal after puncture, and the screw cap is further reinforced to avoid sealing failure after sampling or dosing;
       Edge sealing of bag body: The bag body adopts heat sealing edge sealing technology, with a sealing edge width of ≥ 5mm, no bubbles, no virtual sealing, and can withstand the liquid pressure (static pressure ≥ 0.05MPa) of the larger rated capacity (usually 1000-3000ml) inside the bag without breaking.
2、 Performance details of key sealing areas (clinical core focus)
1. Anti backflow sealing: to prevent infection caused by fluid reflux
      The drainage tube is equipped with a built-in anti backflow valve (one-way valve structure) near the end of the bag, made of silicone material, which only allows drainage fluid to flow into the bag in one direction. It automatically closes when reverse pressure is applied, with a sealing pressure of ≥ 0.03MPa, which can completely block the backflow of drainage fluid into the body and prevent air and bacteria from entering, reducing the risk of retrograde infection;
      The anti backflow valve seamlessly adheres to the inner wall of the drainage tube, without dead corners, to prevent bacterial growth caused by residual drainage fluid, while not affecting the smoothness of drainage.
2. Sealing of measurement scale area: balancing accuracy and sealing performance
      The scale area of the precision measuring drainage bag (usually using printing/heat transfer printing technology) is located on the outside of the bag body, with no printing layer on the inside (to avoid layer detachment and contamination of the drainage liquid).        The film thickness of the scale area bag body is ≥ 0.15mm, thicker than ordinary drainage bags, to enhance sealing and avoid scale deformation caused by bag stretching (affecting measurement accuracy);
       Some products adopt a "double-layer bag structure" (inner drainage, outer protection), which can prevent the drainage fluid from polluting the environment when the inner layer leaks, and further improve the overall sealing performance.
3. Interface sealing: Suitable for different drainage catheters without gaps
       The drainage bag interface adopts a "standard Ruhr interface/threaded interface", which is suitable for commonly used clinical drainage tubes (such as 10Fr, 12Fr, 14Fr specifications). The inner wall of the interface has anti slip patterns, and can withstand a tensile force of ≥ 10N without loosening when connected to the drainage tube;
       Some products are equipped with "interface sealing caps" (covering the interface when not in use) to prevent bacterial invasion during transportation and storage, as well as to prevent interface damage from affecting sealing.
3、 Industry standards and quality testing: mandatory requirements for sealing
      Disposable precision metering drainage bags must comply with relevant standards, with clear and strict requirements for sealing testing:
      Leakage test: Fill the drainage bag with distilled water of rated capacity, seal all openings, invert, place on the side, and hang for 30 minutes each, and observe no visible leakage; Pressurize to 0.05MPa and maintain for 15 minutes without any leakage;
Anti backflow test: Fill the drainage bag with distilled water, invert the drainage tube vertically upwards, and hold for 30 minutes until no liquid flows back into the drainage tube;
      Bacterial barrier test: Through microbial invasion testing, it has been proven that the sealing structure can prevent bacteria from entering the bag (avoiding contamination by drainage fluid).
      Products produced by legitimate manufacturers must pass the above tests before they can be launched, and each batch of products must be sampled for sealing inspection. Unqualified products are prohibited from entering clinical practice.
4、 Sealing verification and precautions in actual use
1. Clinical validation: Low risk of seal failure
      According to clinical data statistics, the sealing failure rate of compliant products is ≤ 0.1%, mainly concentrated in "improper operation" (such as not inserting the drainage tube tightly or not fully closing the valve after drainage), rather than quality problems of the product itself;
      For critical scenarios such as severe patients and postoperative bleeding, the product's sealing has been clinically validated for a long time, and there have been no cases of leakage or infection caused by sealing failure.
2. Suggestions for sealing protection during use
      When connecting the drainage tube, ensure that the interface is fully inserted (insertion depth ≥ 1.5cm), and rotate and fix it (threaded interface) to avoid leakage caused by half insertion;
      After draining, the drain valve needs to be tightened clockwise, and some products can be confirmed locked by "hearing a click";
      Avoid scratching the bag body with sharp objects, and avoid pulling the drainage tube when moving the patient to prevent the connection from breaking;
      If bubbles, uneven welds, or loose valves are found on the bag body, replace it immediately (this is a product quality issue and is prohibited from use).