ISO 8659:2020 pdf download Thermoplastics valves — Fatigue strength — Test method
1 Scope
This document specifies the endurance test necessary to confirm the ability of hand-operated plastics valves to withstand prolonged use, with repeated opening and closure. It does not specify the ability of valves to withstand adverse conditions, in particular those of chemically aggressive fluid media and/or environments, or excessive fluid velocities and cavitation. NOTE Concerning the chemical aggression of the materials, a classification table is reported in ISO/TR 10358 [1] . This document includes values of the parameters necessary for the proper performance of the endurance test, with the reservation that the parameters are different in particular product standards (see 5.1).
2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document.
For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 161-1, Thermoplastics pipes for the conveyance of fluids — Nominal outside diameters and nominal pressures — Part 1: Metric series
ISO 16135, Industrial valves — Ball valves of thermoplastics materials
ISO 16136, Industrial valves — Butterfly valves of thermoplastics materials
ISO 16138, Industrial valves — Diaphragm valves of thermoplastics materials
ISO 16139, Industrial valves — Gate valves of thermoplastics materials
ISO 21787, Industrial valves — Globe valves of thermoplastics materials
3? Terms? and? definitions
For the purposes of this document, the terms and definitions given in ISO 161-1 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
nominal pressure
PN
alphanumerical designation of pressure, used for reference purposes, which is related to the mechanical strength of the valve
Note 1 to entry: Usually nominal pressure (PN), measured in bar, corresponds to water pressure at 20 °C water temperature. See also ISO 161-1.
3.2
closing torque
torque exerted over the full closing operation to achieve full tightness of the valve at nominal pressure
3.3
opening torque
torque exerted initially to open the valve from fully closed or over the full opening operation
3.4
fluid velocity
velocity of a fluid in a pipe connected to a valve of nominal size equivalent to the nominal diameter ofthe pipe
3.5
nominal sizeDN
alphanumeric designation of size for components of a pipework system, which is used for referencepurposes,comprising the letters DN followed by a dimensionless whole number which is indirectlyrelated to the physical size, in millimetres, of the bore or outside diameter of the end connections
[SOURCE:ISO 6708:1995]
3.6
nominal outside diameterdn
specified outside diameter, assigned to a nominal size DN
Note 1 to entry: The nominal outside diameter d. of pipes is given in ISO 161-1 and of flange adapters and loosebacking flanges in lSo 96243].
4 Apparatus
Test apparatus, capable of testing the whole valve assembly with its obturator mechanism.Furthermore,it shall include appropriate devices to perform each step separately, or continuously and automatically.The apparatus, when clamping the valve assembly, shall not apply to the valve ends any axial force, norradial force to the valve stem.
The test apparatus shall include appropriate means to discontinue the test cycle during the pressureperiod and to maintain the pressure in the closed position.
Pressure gauges shall be accurate to within ±1 % of the full-scale reading.Temperature sensors shall be accurate to within ±2°C.
Attention is drawn to the need for adequate safety precautions when using compressed air or gas forthis test.
5Procedure
5.1Test requirements to be taken from product standards
The following specifications shall be taken from the particular product standard.
a) any tests which shall be performed before the endurance test, and those which shall be repeated
after completion of the endurance test;ISO 8659:2020 pdf download