Technical information about hoses

When transporting solid, liquid or gaseous media, friction on the inner wall of hose lines, for example, causes an "interfacial potential" to build up. Depending on the degree of charging, this leads to sparking, electrical breakdown or, under certain circumstances, to the ignition of flammable substances. In addition to the intensity of the contact (friction) between the medium and the hose wall, the "dielectric constant" of the hose and flow medium is decisive for the level of chargeability. This is a measure of the polarisability. Even conductive substances become charged if they are not earthed.

There are a number of guidelines and regulations for the assessment and avoidance of ignition hazards and the protective measures to be taken. At this point, we refer primarily to the Technical Rule for Industrial Safety, TRGS 727 "Avoidance of ignition hazards due to electrostatic charges", which is determined by the Committee for Industrial Safety (ABS) and published by the Federal Ministry of Labour and Social Affairs in the Joint Ministerial Gazette. TRGS 727 replaces the previous TRBS 2153 and updates it.

Masterflex products also comply with the relevant Union harmonisation legislation: Directive 94/9/EC (until 19 April 2016) and Directive 2014/34/EU (from 20 April 2016)

The surface resistance of hose wall materials can be reduced to values between 103 and 104 ohms by incorporating conductive additives. These conductive additives (e.g. conductive carbon black) form a network of contacting, conductive particles in the plastic (volume conductivity). However, due to the additives, these plastics are
ultimately available in black colour.

Another option is the incorporation of antistatic additives, which achieves a surface resistance of <109 ohms and maintains the transparency of the base materials. There are antistatic additives that achieve a corresponding surface resistance by binding the moisture in the air to the surface of the hose. However, this embodiment has the disadvantage that when conveying dry powders, for example, the lack of humidity results in poor or insufficient antistatic properties. In addition, the
abrasion that occurs during use can hinder the build-up of a suitable surface resistance. For this reason, antistatic hoses that are preferably equipped with permanently effective antistatic additives that are not dependent on an additional external component should be used in the authorised zones/applications.

For subordinate applications, e.g. in Zone 1 for "gases and liquids with low conductivity" and in Zone 21 for "non-flammable dusts/bulk materials", spiral/clip hoses with dissipation of electrostatic charges on Masterflex hoses with a wall material where a surface resistance > 109 Ohm is present can also be used. Here, however, a spiral/clip pitch < 30 mm and an overlap of the spiral < 2 mm must be ensured in order to achieve a dissipative effect.

For all applications described above, both spiral/clip ends of the conduit must always be connected to the connector in a dissipative manner. Information on the possible applications of Masterflex hoses can be found in the relevant catalogue data sheets under properties.

Limits and definitions

The following are generally electrostatically chargeable

• Hose lines with wire helix
• solids with a surface resistance >109 Ohm
• All unearthed objects made of conductive materials

The following are generally not electrostatically chargeable

• all solids and liquids with resistances below the above-mentioned limits
• all conductive materials that are earthed

In practice, this means with regard to
the use of hose lines with
wire helix/clip:

1. when handling "gases and liquids with low conductivity" in zone 1, as well as "non-flammable dusts/bulk materials" in zone 21, spiral/clip hoses can be used whose wall surface resistance is >109 Ohm, the spiral/clip pitch is <30 mm and the overlap of the spiral/clip is <2 mm. When installing the conduits, it must also be ensured that both
spiral/clip ends are earthed to the conductive connection parts.

2. increased protection is achieved when using non-chargeable hoses, e.g. antistatic hoses with a surface resistance <109 Ohm, where the exposed spiral/clip ends are also earthed to the conductive
connection parts.

3. electrically conductive conduits with a surface resistance <106 ohms offer optimum safety. For safety reasons, these hoses should also have an earthed connection between the exposed wire ends and the conductive connection pieces. Tested Masterflex hoses with the suffix "EL" fulfil these requirements in full.

The determination of the surface resistance depends on the respective measuring method and is carried out for non-conductive solids in accordance with DIN IEC 60093 / VDE 0303, Part 30 (Test methods for electrical insulating materials, volume resistivity and surface resistivity of solid, electrically insulating materials).

For rubber and plastic hoses and hose assemblies, DIN EN ISO 8031 - Rubber and plastic hoses and hose assemblies, describes the determination of electrical resistance.

This standard describes

• Procedures for hoses with conductive inner layers (e.g. the measurement procedures for the hose types: Master-Clip, ...)
• Procedures for hoses with a conductive outer layer
• Procedures for hoses made of continuously conductive material mixtures (e.g. the measurement procedures for the Masterflex hose types with the suffix "EL")

The addition of conductivity additives or antistatic agents leads to a reduction in the mechanical material values (e.g. abrasion and tear resistance) and therefore to a reduction in service life. The information is based on internal and external field tests
and the currently valid regulations. It serves as a guide for the use of Masterflex hose types in potentially hazardous areas and does not claim to be exhaustive.

The information in the catalogue regarding surface resistance is based in part on official test results, information from our raw material suppliers
and internal measurements. In case of doubt, we recommend that users test hoses under operating conditions or similar conditions before final installation.

The CE marking (Conformité Européenne) means "conformity with EU directives" and is a marking under EU law for certain products in connection with product safety.

By affixing the CE marking, a manufacturer confirms that its product complies with one or more of the applicable European directives in whose scope the product falls. This is now mandatory for certain product groups.

CE-marked products are subject to the unrestricted movement of goods in every EU country, while products that are subject to mandatory labelling may no longer be traded after a certain specified date (example: the date for machines is 01/01/1995).

In general, Masterflex SE hoses do not fall under product groups requiring labelling, as according to the definition of the EU Machinery Directive 89/392/EEC, hoses are not classified as machinery, safety components or products according to the Low Voltage and EMC Directive, Medical Devices Directive, etc., but are considered components that are not CE-markable.

The hoses must therefore not be labelled and corresponding declarations of conformity (manufacturer's declarations) must also not be issued by Masterflex SE. Safety data sheets in accordance with DIN EN 292 and works certificates in accordance with EN 10204, which certify the properties of Masterflex products, can be provided if required.

All information provided by us is general information which, due to individual application possibilities, different operational conditions on site and design variations, is not binding or guaranteed.

In order for hoses to be used in the food sector, they must fulfil the relevant "food regulations and approvals". The polyurethane hose types produced by Masterflex fulfil these requirements.

The raw materials used to manufacture Master-PUR Food hoses fulfil the following food law requirements:

• EU: Under certain conditions, the Master-PUR Food series hoses comply with the requirements of Regulation (EU) No. 1935/2004 and Regulation (EU) No. 10/2011 and 1282/2011 or the German Food and Feed Code (LFGB, as of 15 March 2012) and the German Commodities Ordinance (as of 13 December 2011).

More information

The raw materials used to manufacture Master-PUR Food A tubes comply with the following food law requirements:

• EU: The Master-PUR Food A series has been tested and approved by an independent institute. The monomers used in the manufacture are listed in the Consumer Goods Ordinance in the version published on 23 December 1997 (BGBl. 1998 l p.5), last amended on 23 September 2009 (BGBI. I p.3130). The monomers used are listed in the Annexes to Directive 2002/72/EC, as amended by the most recent amending Directives 2007/19/EC of 30 March 2007 and 2008/39/EC of 7 March 2008, and EC Regulation 975/2009 of 20 October 2009. The additives used are listed in Annex III of Directive 2002/72/EC as amended by the latest amending Directives 2007/19/EC, 2008/39/EC and EC Regulation 975/2009 of 20 October 2009. Please refer to the test certificate H-192339K-10-Bg for the conditions for the requirements from the regulations. The certificate will be presented to the user on request.

More information

In order for hoses to be used in the food sector, they must fulfil the relevant "food regulations and approvals". The polyurethane hose types produced by Masterflex fulfil these requirements.

The raw materials used to manufacture Master-PUR Food hoses fulfil the following food law requirements:

• USA: The raw materials and additives used (except stabilisers) are listed in 21 CFR (Code of Federal Regulations) § 177.2600 "Rubber articles intended for repeated use" of the FDA dated 01.04.2009. The antioxidants/stabilisers used are listed in FDA 21 CFR § 178.2010 "Antioxidants and/or stabilizers for polymers".

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The raw materials used in the manufacture of Master-PUR Food A tubing comply with the following food law requirements:

• USA The raw and auxiliary materials used (except stabilisers) are listed in 21 CFR (Code of Federal Regulations) § 177.2600 and 21 CFR § 178.2010 "Rubber articles intended for repeated use" of the FDA dated 01.04.2009 as well as in the Effective Food Contact Substance Notifications (FCS) list.

More information

DIN EN ISO 8031

Rubber and plastic hoses and hose assemblies

• Determination of electrical resistance and electrical conductivity DIN IEC 60093
• Test methods for electrical insulating materials spec: volume resistivity and spec: surface resistivity of solid, electrically insulating materials DIN VDE 0303-8
• VDE requirements for electrical testing of insulating materials; assessment of electrostatic behaviour

DIN 54345-1

Testing of textiles

• Electrostatic behaviour, determination of electrical resistance values

DIN 4102-1

• Fire behaviour of building materials and components

DIN EN ISO 6941

• Textiles, burning behaviour Measurement of flame spread properties of vertically arranged samples

DIN 66083

• Characteristic values for the burning behaviour of textile products - textile fabrics for workwear

DIN ISO 4649

• Elastomers or thermoplastic elastomers - Determination of abrasion resistance by means of a rotating cylindrical drum apparatus

DIN 53752

Requirements for TPU spiral hoses

DIN 53752

Testing of plastics

• Determination of the coefficient of linear thermal expansion

DIN 53505

Testing of rubber and elastomers

• Hardness testing according to Shore A and D

DIN 53359

Testing of artificial leather and similar fabrics

• Fatigue buckling test

DIN 53863-2

Testing of textiles

• Abrasion tests of textile fabrics, circular abrasion test (Schopper test)

DIN ISO 34-1

Elastomers or thermoplastic elastomers

• Determination of tear propagation resistance - Part 1: Strip, angular and curved specimens

DIN 53504

Testing of rubber and elastomers

• Determination of tear resistance, tensile strength, elongation at break and stress values in the tensile test

DIN EN ISO 1183-1

Plastics

• Methods for determining the density of non-foamed plastics - Part 1: Immersion method, liquid pycnometer method and tritation method

DIN EN ISO 4892

Plastics

• Artificial irradiation or weathering in appliances - Part 1: General guidance

All specifications are the result of internal tests and trials based on international standardisation recommendations and refer to a medium and ambient temperature of +20 °C. Deviating temperatures can change the pressure and vacuum specifications. Due to the design, the length of individual hose types may change as a result of the influencing variables pressure, vacuum, medium and ambient temperature.

The operating pressure, test pressure and burst pressure are determined in accordance with DIN EN ISO 7751.

When testing the vacuum resistance, the hoses are laid in a 90 degree bend while maintaining the minimum bending radius and subjected to negative pressure until they show signs of indentation or collapse. The permissible negative pressure in continuous operation is determined taking into account a standard safety factor.

The vacuum specifications for Masterflex hoses are determined in accordance with DIN 20024, point 15.

The pressure loss is the air resistance in a hose or pipework system.

When designing a ventilation system, the unavoidable air resistance must be taken into account. To simplify the determination of pressure loss, the specific pressure losses of Masterflex hoses can be taken from diagrams.

The figures are average values for hoses in a stretched state at +20 °C.

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