ISO 7289 Standard – Quick action couplings with shut-off valves for welding, cutting, and allied processes

ISO 7289 Standard Types of coupling

This document deals with three types of quick-action coupling with shut-off valves, according to the gases for which they are intended.

These three types are the following:

a) type O – oxygen;

b) type F – fuel gas;

c) type N – other gases specific for welding processes

Installation

The quick-action couplings with shut-off valves shall be installed so that the element with the shut-off device is located upstream in terms of the gas flow from the source.

Design requirement

Dimensions, non-interchangeability, and interchangeability

Quick-action couplings with shut-off valves in accordance with this document shall have the dimensions specified in Figure 1 and Table 1 for couplings of types 0, F, and N, in order to ensure that the following are not interchangeable:

a) elements of different types; and

b) elements of different types and couplings for compressed air, in accordance with ISO 6150.

The dimensions and fabrication details not specified are left to the discretion of the manufacturer, with the proviso that quick-action couplings with shut-off valves of the same type shall be interchangeable, regardless of their manufacturer.

The shut-off system shall be located in the female element of the quick-action coupling. The gas tightness portion should be constituted on the cylindrical surface of the shaft of diameter A.

Coupling and uncoupling

The choice of the coupling and uncoupling means is left to the discretion of the manufacturer.

Coupling and uncoupling shall be achieved with ease and shall not require the use of tools. It shall not be possible to disengage the two elements by:

a) a simple rotation of one element against the other; or

b) the application of a longitudinal traction force of less than 1 kN.

Under service conditions, as defined by the manufacturer, no undesired uncoupling shall occur. The opening and closing of the shut-off system shall occur automatically.

Connections

The outside-threaded connections should conform to the recommendations of ISO/TR 28821. A righthand thread shall be used for couplings of types O and N and a left-hand thread shall be used for couplings of type F.

Materials

The materials used for the construction of these couplings shall conform to the requirements given in ISO 9539.

The male element shall be constructed from uncoated material with a hardness of not less than 270HV10. For coated material for which HV10 is not applicable, the surface hardness requirement shall not be less than 310HV0,2. (This specification refers to the surface hardness of the standardized external profile over a length of 15,2 mm.)

Working requirements

Pressure resistance

Quick-action couplings with shut-off valves shall be designed for a maximum working pressure of2 MPa (20 bar). When tested under the conditions, they shall withstand a test pressure of:

a) 4 MPa (40 bar) without visible permanent deformation;

b) 6 MPa (60 bar) without rupture.

Gas tightness

The general requirements for gas tightness given in ISO 9090 shall be satisfied.

Specific requirements

During tests performed in accordance with U the measured leakage rate, in both the coupled and the uncoupled position, shall not exceed 10 cm3/h.

Pressure drop

At the maximum operating pressure and the flow rate specified by the manufacturer, the pressure loss introduced by the quick-action couplings with shut-off valves shall not exceed 10 % of the specified maximum operating pressure.

Resistance to flashback

After having been submitted to one flashback in accordance with the conditions specified in li quick-action couplings with shut-off valves shall continue to conform to the requirements specified in 222. and shall have no visible permanent deformation.

Resistance to tensile load

When tested under the conditions indicated in il the quick-action couplings with shut-off valves shall:

a) remain suitable for normal service and fulfill the test requirements specified in this document, after having been submitted to an axial load of 600 N;

b) remain coupled and gas tight according to 22. after having been submitted to an axial load of 1 kN.

Resistance to radial loads

When tested under conditions indicated in 9..6., the quick-action couplings with hut-off valves shall:

a) remain suitable for normal service and fulfil the test requirements specified in this document, after having been submitted to a radial load of 1 kN;

b) remain coupled and gas tight according to U after having been submitted to a radial load of2 kN.

Endurance

When tested under the conditions specified in 9.2 the quick-action couplings with shut-off valves shall remain gas tight according to 22. after they have been submitted to a minimum of 1 000 coupling/ uncoupling cycles at a maximum working pressure.

Other functions

In cases where a quick-action coupling with shut-off valve is associated with any other function than tho e specified in this document, it shall comply with the requirements and shall then be tested in accordance with Clauses8 and .9 after it has met the requirements necessary to perform the other function.

General test conditions

General

The tests described hereunder are the type tests.

Unless otherwise specified, they shall be performed at an ambient temperature of (23 ± 2) °C using oil-free air or in nitrogen.

The allowable total error of the measured values are as follows:

flow: ±5 %;

pressure: ±1 %

The pressure resistance test shall be performed under hydraulic pressure.

Eight samples of the quick-action couplings with shut-off valves shall be tested. The two elements of each of these samples shall be carefully marked to ensure that all tests are performed using the same pair of elements.

Figures 2 to .4 show the principle of the tensile load test and examples of the test rigs for gas tightness and resistance to radial loads.