CEN/TC 69/WG 10 - Safety devices against excessive pressure

This document specifies the sizing of safety valves and bursting discs for gas/liquid two-phase flow in pressurized systems such as reactors, storage tanks, columns, heat exchangers, piping systems or transportation tanks/containers, see Figure 2. The possible fluid states at the safety device inlet that can result in two-phase flow are given in Table 1.
NOTE          The pressures used in this document are absolute pressures, not gauge pressures.

This document specifies only the requirements for a product assembled from the in-series combination of safety valves or CSPRS (controlled safety pressure relief systems) according to ISO 4126‑1, ISO 4126‑4 and ISO 4126‑5, and bursting disc safety devices, according to ISO 4126‑2, installed upstream of the valve within five pipe diameters of the valve inlet. It specifies the design, application and marking requirements for such products, composed of the bursting disc safety device, a safety valve or CSPRS and, where applicable, a connecting pipe or spool piece. In addition, it gives a method for establishing the combination discharge factor used in sizing combinations.

This document specifies the requirements for bursting disc safety devices.
It includes the requirements for the design, manufacture, inspection, testing, certification, marking, and packaging.

ISO 4126-6:2014 gives guidance on the application, selection and installation of bursting disc safety devices used to protect pressure equipment from excessive pressure and/or excessive vacuum.

ISO 4126-5:2013 specifies the requirements for controlled safety pressure relief systems (CSPRS) irrespective of the fluid for which they are designed.
It is applicable for main valves having a flow diameter of 4 mm and above which are for use at pressures of 0,1 bar gauge and above. No limitation is placed on temperature.
ISO 4126-5:2013 is a product standard and is not applicable to applications.

ISO 4126-1:2013 specifies general requirements for safety valves irrespective of the fluid for which they are designed.
It is applicable to safety valves having a flow diameter of 4 mm and above which are for use at set pressures of 0,1 bar gauge and above. No limitation is placed on temperature.
ISO 4126-1:2013 is a product standard and is not applicable to applications of safety valves.

ISO 4126-4:2013 specifies general requirements for pilot operated safety valves, irrespective of the fluid for which they are designed. In all cases, the operation is carried out by the fluid in the system to be protected.
It is applicable to pilot operated safety valves having a valve flow diameter of 4 mm and above which are for use at set pressures of 0,1 bar gauge and above. No limitation is placed on temperature.
ISO 4126-4:2013 is a product standard and it is not applicable to applications of pilot operated safety valves.

ISO 4126-7:2013 specifies requirements for safety valves. It contains information which is common to ISO 4126-1 to ISO 4126-6 to avoid unnecessary repetition.

Definition of the operative testing procedure to be applied for the determination of functional characteristics and exhaust capability of direct loaded and pilot operated safety valves and bursting discs working with compressible or uncompressible non-vaporizing fluids, under atmospheric and back pressure conditions (built up or superimposed).

ISO 4126-3:2006 specifies the requirements for a product assembled from the in-series combination of safety valves or CSPRS (controlled safety pressure relief systems) according to ISO 4126-1, ISO 4126-4 and ISO 4126-5, and bursting disc safety devices according to ISO 4126-2 installed within no more than five pipe diameters from the valve inlet. It specifies the design, application and marking requirements for such products, which are used to protect pressure vessels, piping or other enclosures from excessive pressure, and which comprise the bursting disc safety device, a safety valve or CSPRS and, where applicable, a short length of connecting pipe or spool piece. In addition, it gives a method for establishing the combination discharge factor used in sizing combinations.

TC - Modification to Table ZA.1

ISO 4126-2:2003 specifies the requirements for bursting disc safety devices.
ISO 4126-2:2003 includes the requirements for the design, manufacture, inspection, testing, certification, marking, and packaging.
The requirements for the application, selection and installation of bursting disc safety devices are given in ISO 4126-6.

AFNOR/DIN - Modification to subclause 3.30 (translation error)

ISO 4126-6:2003 gives guidance on the application, selection and installation of bursting disc safety devices used to protect pressure equipment from excessive pressure and/or excessive vacuum.

TC - Modifications in Subclause 3.
CMC - Correction on the French title.

CMC - Replace Figures 1b) and 1c) (editorial error)

ISO 4126-5:2004 specifies the requirements for controlled safety pressure relief systems, irrespective of the fluid for which they are designed. It is applicable to main valves having a flow diameter of 6 mm and above for use at pressures of 0,1 bar (= 0,01 MPa) gauge and above. No limitation is placed on temperature.This is a product standard and is not concerned with applications.

ISO 4126-1:2004 specifies general requirements for safety valves irrespective of the fluid for which they are designed. It is applicable to safety valves having a flow diameter of 6 mm and above which are for use at set pressures of 0,1 bar gauge and above. No limitation is placed on temperature. This is a product standard and is not concerned with applications for safety valves.

ISO 4126-4:2003 specifies general requirements for pilot operated safety valves, other than those covered in ISO 4126-1, irrespective of the fluid for which they are designed. In all cases, the operation is carried out by the fluid in the system to be protected.
ISO 4126-4:2003 is applicable to pilot operated safety valves having a valve flow diameter of 6 mm and above which are for use at set pressures of 0,1 bar gauge and above. No limitation is placed on temperature.
This is a product standard and it is not concerned with applications for pilot operated safety valves.

ISO 4126-7:2004 contains data common to other parts of ISO 4126, thus avoiding unnecessary repetition, and is referenced in those other parts as appropriate.