ISO 7231 Polymeric Materials, Cellular, Flexible - Determination of Airflow Value at Constant Pressure Drop

The ISO 7231 standard, “Polymeric materials, cellular, flexible - Determination of airflow value at constant pressure drop,” published by the International Organization for Standardization (ISO), describes two methods for determining the airflow value of flexible cellular polymeric materials:

• Method A is for traditional flexible cellular polymeric material types.
• Method B is for all types of flexible cellular polymeric materials, but especially for materials with low air permeability. Two standard methods are specified for Method B:
  • Method B1: Manual measurement
  • B2 method: With automatic measurement

Airflow values ​​can be used as an indicator of the effects of formulation and production variables on cellular structure.

In this standard, the term "conventional flexible cellular polymeric material type" refers to types unsuitable for sealing purposes.

For the purposes of this standard, the airflow value refers to the volumetric flow rate required to maintain a constant pressure difference in a flexible foam test piece.

ISO 7231 is an international standard that specifies a method for determining the resistance of rubber and plastic hoses and hose assemblies to kinking under pressure or vacuum conditions. This standard plays a crucial role in evaluating how hoses behave when subjected to kinking in real-world service environments.

Hoses used in industries such as oil and gas, automotive, and manufacturing are often subjected to constant kinking, vibration, and pressure fluctuations. The ISO 7231 standard was developed for these purposes:

• To assess flexibility and durability.
• Identifying potential failure points under bending stress.
• To ensure that the hoses maintain their structural integrity during operation.
• Supporting quality control and product development.

The ISO 7231 standard applies to the following:

• rubber hoses
• Thermoplastic hoses
• Hose assemblies with connectors

This standard is commonly used in the following sectors:

• Hydraulic systems
• Fuel and oil transfer
• Industrial fluid processing
• Pneumatic systems

The ISO 7231 standard test method evaluates how a hose performs when bent to a specific radius under pressure or vacuum. Generally, this method follows these steps:

• Sample preparation: A hose or hose assembly is cut to a specific length.
• Pressurization: The hose is filled with fluid and subjected to a defined internal pressure (or vacuum).
• Bending process: The hose is bent to a predetermined radius or angle.
• Observation: The result is examined in terms of cracks, leaks, bending, and structural deformation.
• The key parameters measured are as follows:
  • Minimum bending radius
  • Change in internal diameter
  • Resistance to bending
  • Sealing under tension
  • Visual damage or deformation

The importance of the ISO 7231 standard is based on a simple fact: hoses rarely operate in straight, static conditions. In real-world applications, they are constantly bent, stretched, and subjected to pressure. This standard ensures that hoses can withstand these conditions. Here are the main reasons why this standard is important:

• It prevents real-world malfunctions: During service, hoses are exposed to the following:
  • Repeated bending
  • Narrow assembly areas
  • Internal pressure or vacuum

Without proper verification, bending can lead to the following:

• Curling (flow restriction)
• Cracking
• Leakage or rupture

This standard simulates these conditions, allowing for the identification of weak points before the hose is put into use.

• It ensures safety: Many hoses carry hazardous or high-energy environments, such as those listed below:
  • Hydraulic oil (high pressure)
  • Fuel or gas (combustible)
  • Chemicals (corrosive or toxic)

Failure during bending can lead to the following:

• Equipment damage
• Fire or explosion
• Environmental pollution

This standard helps significantly reduce these risks by verifying bending performance.

• It verifies the minimum bending radius: Every hose has a minimum bending radius, which is the tightest curve it can safely withstand. This standard,
  • The manufacturer confirms the claims.
  • Prevents incorrect installation.
  • It helps engineers design safer systems.

Ignoring this can significantly shorten hose life or cause sudden failure.

• It improves product quality and durability: Manufacturers use the standard for the following purposes:
  • Optimizing hose structure (reinforcement layers, materials)
  • Comparing product designs
  • To ensure consistent production quality.

This results in hoses that last longer and perform reliably under stress.

• It supports international acceptance: This standard,
  • It provides a globally recognized testing method.
  • It allows for fair comparison between products.
  • It facilitates international trade and certification.
• It complements other performance tests: Bending is only a failure mode. This standard works in conjunction with the following standards:
  • ISO 1402 (pressure and strength testing)
  • ISO 6803 (fatigue under compression cycles)

Together, these standards ensure that a hose is robust against combined mechanical and compressive stresses.

• It reduces maintenance and downtime: Hose failures often cause the following:
  • Unexpected stops
  • Costly repairs
  • Production losses

This standard helps ensure that hoses can withstand bending stresses, thereby:

• It extends service life.
• Reduces maintenance frequency.
• It increases operational reliability.

In short, these standard tests ensure system reliability by demonstrating that the hose can withstand kinking without collapsing, leaking, or cracking.

In conclusion, the ISO 7231 standard is a vital testing standard for ensuring the mechanical reliability and flexibility of hoses under real-world conditions. By simulating kinking under pressure, it helps manufacturers design safer and more durable hose systems, giving end-users confidence in their performance.

For many years, our organization, with its competent and experienced staff, has been understanding the needs of its clients, providing the advanced testing services they require, and assisting them in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services compliant with the ISO 7231 standard.