ISO 6358-2:2013 specifies a discharge test and a charge test as alternative methods for testing pneumatic fluid power components that use compressible fluids, i.e. gases, and that have internal flow passages that can be either fixed or variable in size to determine their flow-rate characteristics. However, ISO 6358-2:2013 does not apply to components whose flow coefficient is unstable during use, i.e. components that exhibit remarkable hysteretic behaviour (because they can contain flexible parts that deform under the flow) or that have an internal feedback phenomenon (such as regulators), or components that have a cracking pressure such as non-return (check) valves and quick-exhaust valves. In addition, it does not apply to components that exchange energy with the fluid during flow-rate measurement, e.g. cylinders, accumulators, etc.
ISO 6358-2:2013 does not provide a method to determine if a component has hysteretic behaviour; ISO 6358-1 does provide such a method.
The charge test cannot be performed on components that do not have downstream port connections.
ISO 6358-2:2013 specifies requirements for the test installation, the test procedure, and the presentation of results.
Annexes provide the following:
- evaluation of measurement uncertainties;
- requirements for a method to test the volume of an isothermal tank;
- guidance on the isothermal tank;
- requirements for a method to test isothermal performance;
- guidance on the equation for calculating characteristics;
- guidance on calculating flow-rate characteristics.