ISO/TR 17784:2003 pdf download

ISO/TR 17784:2003 pdf download.Rubber and plastics hoses and hose assemblies -Guide for use by purchasers, assemblers, instailers and operating personnel.
The hose supplier should be notified of all requirements to which the hose needs to conform in order to make the right choice of materials. This includes all chemical, physical and mechanical. Hoses that are not purchased against a standard should only be used for media recommended by the manufacturer’s list. The manufacturer’s advice should be obtained if there is any doubt as to the suitability of a particular hose for a specific application.
3.1.2 Maximum working pressure, proof pressure’) and minimum burst pressure
The hose manufacturer has information regarding maximum working pressure, test pressure and burst pressure for hoses (see also ISO 7751 regarding the ratio of working pressure to burst pressure). The user has information on the rated system pressure and the working pressure.
As a general rule, the hose working pressure will be selected so that it is greater than the rated pressure in the user’s system.
NOTE Pressures are sometimes divided into three classes, such as “low pressure”, “medium pressure” and “high pressure”. However, hose manufacturers do not use these pressure categories and these terms should not be used, as the national or international standards will not refer to them.
One manufacturer may well refer to a hose with a working pressure of 10 bar2) as a “medium-pressure” hose while a different manufacturer may still refer to a hose for a 200 bar pressure as a “low-pressure” hose.
The pressure-resisting strength of a hose is determined mainly by the reinforcement. The pressure-resisting strength of tubing (a hose without reinforcement) depends on its wall thickness and material of construction.
3.2 Electrical conductivity
3.2.1 General
Hoses are divided into three types with regard to electrical conductivity, namely electrically bonded, conductive and non-conductive (or discontinuous or insulating) hoses.
3.2.2 Design of electrically bonded hoses
Designs of electrically bonded hoses differ according to the type of hose. Electrically bonded rubber and plastic hoses contain conducting wires (see Figure 1). These wires are always applied spirally, either crosswise or in parallel during manufacture. The wires are connected to the metal couplings at the hose ends in such a way that an uninterrupted pathway with low electrical resistance is obtained throughout the assembled length when hose assemblies are coupled to each other. “Composite” or multilayer hoses (see 6.3) have no conducting wires but are equipped with two conducting metal helixes. In this case, the two helixes should be firmly connected to the hose coupling. Problems may arise in practice where one of the two ends of a coated internal helix is not connected through as a result of an assembly fault. The other wire will then still ensure a conductive connection so that the manufacturing error is not discovered when taking electrical measurements. The non-connected internal helix may cause sparking. Coated internal helixes should therefore be so designed that the electrical connection on both the internal and external helixes can be checked. This may be achieved, for example, by connecting the external helix to the coupling in such a way that it can be disconnected in order to check the electrical connection of the internal helix (to the coupling).
3.2.3 Design of conductive hoses
The construction of conductive hoses differs entirely from the designs described in 3.2.2 through the absence of wire contacts with the couplings. The rubber composition contains a quantity of specially conductive carbon black such that the cover of the hose is conductive. The hose couplings discharge the static electricity through the connecting points of the installation in which the hose is fitted, or to earth. An anti-kinking spiral is often incorporated into the hose during manufacture but it is not electrically connected to the couplings. Hoses of this kind should be made with wire-free cuffs (see ISO 1823, ISO 2928, ISO 2929 and ISO 5772).
3.2.4 Design of non-conductive (or discontinuous or insulating) hoses.