Katalog 1 EN - Hansa-Flex...DIN 20018-1 Textile-reinforced hoses, nominal pressure 10/16 04.03 DIN...

T

Edition: 02/2008 Catalogue 1 9

Technical Information


T

Edition: 02/2008Catalogue 110

Technical Information Note

All the information in this catalogue is based on the standards applicable at the time of publication and the regu-

lations of the employers' liability insurance associations. Product safety can only be guaranteed if our assembly

instructions are followed correctly. Failure to follow any of these instructions may affect the operational safety

of the product and invalidate our warranty. Our warranty in any event only covers HANSA-FLEX products. Our

products are constantly being updated, technical modifications are possible.

While we take every care in editing and checking the catalogue we cannot rule out possible errors or omissions

and accept no liability for the information it contains.

® 2008 HANSA-FLEX Hydraulik GmbH – www.hansa-flex.com

T


Technical Information Hose AssembliesIntroduction

Hose assemblies are the heart of the HANSA-FLEX range of products and have proven their performance a mil-

lion times over since we commenced business. This part of our range includes fittings and hose sold by the metre,

complying with all international industrial standards and in a wide variety of different types.

There is virtually no limit to the number of possible applications, whether they call for the use of standard swage

fittings, interlock fittings or re-usable fittings. The same applies to our hose products. Choosing the right type of

hose can have a decisive impact on the safe and efficient operation of a hydraulic system.

Criteria for the selection / design of hose assemblies include:

– Resistance to the carried medium – cleaning processes should also be allowed for!

– Resistance to temperature – you should also check the temperature/pressure characteristics!

– Resistance to pressure including required safety devices (also vacuum behaviour)

– Bending radii

– Any unusual stresses due to external forces or pressure pulses

– Abrasion resistance and possible protection

– Availability of hose by the metre and of fittings

– Installation conditions such as movement sequences, kinking, whipping, identification, offset angle of cur-

ved fittings, leg lengths

– Safe sealing forms (design of sealing head)

T


Technical Information Hose AssembliesSelecting the right hose for the job

The HANSA-FLEX range of products offers a huge number of hose types manufactured from a wide variety of

different materials. This means that there will be a product to match almost every conceivable application. Since

these many different hose types have to cater for an even larger number of possible applications, a number of

basic questions must be answered before the right hose can be selected:

MAXIMUM PRESSURE

The maximum working pressure (dynamic working pressure) determines the construction and selection of

the hose. Hoses with fabric braid, wire braid and even spiral wire reinforcement are available depending on

the application. The HANSA-FLEX hose programme ranges from hoses with a working pressure of 8 bar up to

extreme-pressure hoses with a working pressure of 1800 bar. Vacuum hoses can be exposed to vacuums of up

to 0.85 bar (absolute).

NOMINAL BORE

The inside diameter (bore) of the hose or tube is of particular importance in any hydraulic system.

When a fluid flows through a line, it loses pressure, and this pressure drop will depend on a mix of factors such as

the type of flow, the roughness of the line’s inside wall, the length of the line and its bore as well as the specific

gravity of the fluid and the flow velocity. This relates to a so-called fully developed pipe flow. However we also

observe a so-called ‘approach section’ which has a significant influence on velocity distribution. Further pressure

is lost when the medium flows through fittings, valves, elbows and other obstructions.

T



There are two basic types of flow:

Laminar flow exists when the fluid forms a parabolic velocity distribution. The pressure drop is proportional to

the velocity.

Turbulent flow exists when secondary mixing motions are superimposed on the main flow motion. The pressure

drop increases with the square of the velocity.

Turbulent flows predominate in practice. However the correct choice of nominal tube bore can significantly

affect the efficiency of a hydraulic system. Just a 1 % change in the bore of the tube will increase the flow resi-

stance by 5 %, assuming a constant flow rate.

General rules: If you wish to minimise pressure losses, you should choose a sufficiently large bore or clear cross-

section of the tube/hose – if in doubt, opt for the next larger bore. In this way you will reduce the rate of flow and

hence the pressure drops in the line. Generally speaking, the cross-section can be rated quite adequately using

the nomogram to determine the nominal bore of the hose (refer to the section ‘Determining the nominal bore

with the nomogram’). The hose bore should not be increased too much however as this will reduce the maximum

operating pressure/nominal pressure.

Laminar Flow

Turbulent Flow

T



TEMPERATURE AND ENVIRONMENT

The likely operating and ambient temperatures cannot be ignored when selecting the right hose assembly: Using

hoses outside their permitted temperature ranges can be expected to significantly curtail their service life.

The rubbers that are used in HANSA-FLEX standard hydraulic hoses are blended to ensure that the hoses can

usually be operated continuously within a temperature range of -40 to max. 100 °C in (temporarily 125 °C) depen-

ding on type. Different temperatures apply for compressed air. At very low temperatures, rubber blends reach

their so-called glass transition point. The glass transition point is the temperature at which the resilient behaviour

of the material approaches zero, i.e. the material becomes brittle and will break like glass under mechanical

loads. Fine radial cracks on the surface of the internal and external layers of the hose are typical signs of a hose

damaged by glass break.

Prolonged use at high temperatures will also shorten the life of a hose assembly as this prematurely ages the

rubber materials. However the HANSA-FLEX range also includes hose types for temperature ranges that go

beyond the normal limits.

It should also be remembered that the outer cover of a rubber hose is sensitive to environmental influences such

as ozone or strong ultraviolet radiation. Under adverse conditions, ozone and UV rays can break up the chain

molecules of the elastomer material. As a result the material loses its resilience, becomes hard and brittle and

will break in highly stressed areas such as the outer radii on hose lines. Radial cracks that penetrate as far as the

braid reinforcement are a sure sign of this. A line that has suffered this kind of damage will be at the mercy of the

weather and will fail within a short space of time.

T



MEDIA COMPATIBILITY

In all cases it is essential to verify the compatibility of the materials from which the hoses and fittings are made

with the media which they are carrying. HANSA-FLEX hose assemblies are used with many different types of

fluids and gases in practice, and their resistance to these media cannot be predicted in every case. Details given

about resistance to media are for guidance only and can only form the basis for an initial selection of the required

hose; it is vital therefore that practical tests are conducted in important or tricky cases.

CHOICE OF FITTINGS

HANSA-FLEX hose fittings are made as standard from free-maching steel (e.g. material no. 1.0718) with an electro

galvanised surface. Stainless steel fittings (e.g. material no. 1.4571) are also available for special applications.

This material is also known by the designation V4A and is used in the chemical industry as a standard material.

When selecting fittings, ensure that the maximum working or nominal pressure of the fitting matches that of

the hose.

The section of DIN 20066 that deals with requirements and tests states that “If the hose and the hose fitting have diffe-

rent nominal pressures, only the lower nominal pressure may be used for the hose assembly.”

T



Standard Content Issue

HOSES

EN 853 Rubber hoses and hose assemblies – Wire braid reinforced hydraulic type

– Specifi cation German version EN 853:1996

02.97

EN 854 Rubber hoses and hose assemblies – Testile reinforced hydraulic type

– Specifi cation German version EN 854:1996

02.97

EN 855 Plastics hoses and hose assemblies – Thermoplastics textile reinforced hydraulic

type – Specifi cation German version EM 855:1996

02.97

EN 856 Rubber hoses and hose assemblies – Rubber-covered spiral wire reinforced

hydraulic type – Specifi cation German version EN 856:1996

02.97

EN 857 Rubber hoses and hose assemblies – Wire braid reinforced compact type for

hydraulic applications – Specifi cation German version EN 857:1996

02.97

DIN 74310-1 Air brake systems; hoses, dimensions/material/identifi cation 12.93

DIN 74310-2 Air brake systems; hoses, requirements/tests 12.93

HOSE ASSEMBLIES

DIN EN 982 Safety of machinery – Safety requirements for

fl uid power systems and their components: Hydraulics

09.96

DIN EN 12115 Rubber and thermoplastics hoses and hose assemblies for liquid

or gaseous chemicals – Specifi cation

08.99

DIN EN ISO 6134 Rubber hoses and hose assemblies for saturated steam 02.06

DIN 7716 Rubber products; requirements for storage, cleaning and maintenance 05.82

DIN 20018-1 Textile-reinforced hoses, nominal pressure 10/16 04.03

DIN 20018-2 Textile-reinforced hoses, nominal pressure 40 04.03

DIN 20018-3 Textile-reinforced hoses, nominal pressure 100 04.03

DIN 20066 Fluid power systems - Hose assemblies - Dimensions, requirements 10.02

HOSE FITTINGS

DIN ISO 12151-2 Part 2: Hose fi ttings with 24° cone connector ends with O-rings 01.04

DIN ISO 12151-3 Part 3: Hose fi ttings with ISO 6162 fl ange ends 01.04

RELEVANT STANDARDS

Hoses and hose assemblies are standardised elements of hydraulic connection systems. The many different

terms and abbreviations can often cause confusion and so we provide a brief overview at this point. In fluid

power systems, a distinction can be made between pure product standards on the one hand and standards and

guidelines governing the use of these products on the other. An extract from the relevant product standards will

be found elsewhere.

The standards that are most important at the present time are listed below:

T


SI 104 x 630 AFL90 V 180 N

Silver wire hose, series SI 100

Nominal bore: DN 4

effective installed length measured

between the sealing heads of the fittings

Fitting type:

Both ends are fitted with the same fitting

here: hose nipple with seal head and union nut, 90° version

Offset angle of the fittings

here: the fittings are mounted 180° offset

(see section “Offset of curved fittings”)

References for other accessories are appended to the order reference of the assembly:

PHD 216 x 620 AJ AJ90 SSK. This hose assembly has an additional SSK plastic chafe guard.

P HD 206 x 1000 HS

Swage mount for P for high-pressure hose

2-layer high-pressure hose

Nominal bore: DN 6

effective installed length measured

between the sealing heads of the fittings

Fitting type:

Both ends are fitted with the same fitting

here: Swage nipple with metric male thread PN 06 HS heavy series

Technical Information Hose AssembliesHANSA-FLEX Reference System

HANSA-FLEX hose assemblies are identified using the following reference system:

The first letters and numbers describe the type of hose mount and hose. This is followed by the effective installed

length in mm (see Rating System) and the connections at hose ends 1 and 2.

If both hose ends are to be equipped with the same type of fitting, this is only indicated once, additional acces-

sories such as anti-kink protection or particulars about the offset angle of fittings are simply added at the end.

Our reference system is best illustrated by a few examples:

or:

T


P HD 525 x 2000 AOS A VA AOS 90 L 120A VA

Swage mount (P)

for extreme pressure hose (HD)

of series 500 (5), nominal bore DN 25

Length of hose assembly in mm

Metric fitting with union nut (A) and

O-ring seal (O), heavy series (S)

with pull-out protection (A),

Stainless steel

Second fitting is same as first but in 90 degree bend version (90)

with a fitted height (L) of 120 mm, pull-out protection (A), stainless steel

The swage fittings for extreme pressure hoses in the series HD 400, 500, 600 and 700 are always indicated by

the abbreviation PA. This type of reference refers to the fitting and the mount together as a pair.

P HD 210 x 2000 AOL AFL08 90

Swage mount (P)

for two-layer (2) high-pressure hose (H)

nominal bore DN 10

Hose assembly length measured in mm between

the sealing heads of the fittings

Metric fitting with union nut (A) and

O-ring seal (O), light series (L)

Metric fitting with union nut (A) with

metal sealing cone (F), light series (L)

Sealing head configuration for nominal bore DN08

Fitting, 90 degree bend type

Fittings (swage nipple) for 1 and 2 wire layers and for textile reinforced hoses are always indicated by the

abbreviation PN.

Technical Information Hose AssembliesHANSA-FLEX Reference System

or

T


Technical Information Hose AssembliesDetermining the nominal bore with the nomogram

Type of line Working pressure Flow rate v

Suction 1.0 m/s

Return 2.0 m/s

Delivery 0-25 bar 3.0 m/s

25-50 bar 4.0 m/s

50-100 bar 4.5 m/s

100-150 bar 5.0 m/s

150-210 bar 5.5 m/s

210-315 bar 6.0 m/s

How can we now determine the bore of a hydraulic line? In most cases the user will know the pump’s delivery rate

and the working pressure. The table below gives guideline values for flow rates relative to working pressure; the

value assigned to the working pressure is determined first.

T


Technical Information Hose AssembliesDetermining the nominal bore with the nomogram

100

150

200

300

400

500

600

700800900

1.000

90 80

70

60

50

40

30

20

15

10 9 8 7

6

5

4

3

2

1,5

1

Q (l/min)

Durchm. (mm) Fläche (cm2)

40

60

80

100

50

10

20

40

80100

86,3

5 43,152,5

21,61,25

10,80,630,50,40,3150,250,2

0,1

0,05

32

25

20

16

13

10

8

6

5

4

3

v (m/s)

0,80,7

0,6

0,5

0,4

0,3

0,25

0,2

0,15

0,1

0,91

1,2

1,5

2

2,5

3

4

5

6

789

20

15

10

30

The value for the flow rate is entered in the right-hand column of the nomogram, the value for the delivery rate

in the left-hand column.

The point of intersection of the line connecting these two values gives the value for the required line bore, note

the dimensions:

Example:

A system has an operating pressure of 130 bar and a flow rate Q = 60 l/min. We want to find the appropriate bore

for the hose.

Solution:

Mark the value for Q in the nomogram, select the value 5.0 m/s from the table “Guide values for flow rates” and

enter this in the nomogram in the v-column. Now draw a straight line connecting the values in the right and left

hand columns. The point where the line intersects the middle column gives the value for the bore of the hose, in

this case: d = approx. 16 mm

Bore (mm) Area (cm²)

T


Technical Information Hose AssembliesRating System

EXAMPLES OF HOSE ASSEMBLY LENGTHS

The length of a hose assembly is basically always measured between the sealing heads or, in the case of curved

fittings, between the centres of the fittings:

T


Technical Information Hose AssembliesRating System

Overall length up to DN 25 DN 32 to DN 50 DN 50 to DN 100

up to 630 +7 / -3 +12 / -4

over 630 up to 1250 +12 / -4 +20 / -6 +25 / -6

over 1250 up to 2500 +20 / -6 +25 / -6

over 2500 up to 8000 +1.5 % / -0.5 %

over 8000 +3 % / -1 %

Versatz um 270 Grad

Versatz um 90 Grad

1. Anschluss 2. Anschluss

Blickrichtung

PHD 216 x 700 AOL 90 V 270 N

V = off set angle angle = 270° N = standard

PHD 216 x 700 AOL 90 V 090 N

V = off set angle angle = 90° N = standard

OFFSET OF CURVED FITTINGS

Hose assemblies with offset fittings are designated as follows: The first connection always points up. With an off-

set of 90 degrees, the second fitting is turned counter-clockwise by 90 degrees, as shown in the lower graphic.

This rule is used to determine the fitting offset with HANSA-FLEX orders; other manufacturers or customers may

specify this offset differently. The offset must always be checked accordingly therefore.

DESIGNATION OF A HOSE ASSEMBLY WITH A CURVED FITTING

With the re-issue of DIN 20066 in October 2002, the direction of the offset angle was standardised for the first time.

HANSA-FLEX has now adopted this standard and has changed its original reference from “clockwise” to “counter-

clockwise”. The new direction of rotation is indicated in the reference system by a “V” in front of the angle and an “N”

after it.

PERMISSIBLE DIFFERENCES IN LENGTH FOR HOSE ASSEMBLIES IN MM TO DIN 20066:

Direction of

viewing

1st connection 2nd connection

270 degree off set

90 degree off set

T


Technical Information Hose AssembliesSafety Information

The potential hazard posed by high-pressure lines to personnel and the environment is often underestimated

in practice. Oil needles, burst fittings and burst lines can even result in fatalities in extreme cases. This section

therefore describes our own experience and explains the requirements contained in the various relevant regu-

lations and standards.

STORAGE AND SERVICE LIFE OF HOSES AND HOSE ASSEMBLIES

Because the elastomers used to manufacture hydraulic connectors undergo an ageing process, there is a limit

to their storage lives and service lives. Incorrectly stored hydraulic hoses can become prematurely brittle, for

example. We have already mentioned the harmful effects that ozone and strong UV rays can have.

Important: Arc welding gives off high levels of ozone, so thorough ventilation should always be provided when wel-

ding work is carried out. Hose sold by the metre should be stored as far away as possible from locations where welding

is carried out. Significant amounts of ozone are also produced at the carbon brushes of electric motors and the starters

of sodium vapour lamps.

Because of their ageing process, the storage and service lives of hose assemblies is laid down in the regulations of the

employers liability insurance associations and in the current version of DIN 20 066 and DIN 7716:

GENERAL

The physical properties of most rubber products will change under unfavourable storage conditions or if

handled incorrectly. The result can be a reduced service life, with the products being rendered unserviceable by

excessive hardening, softening and permanent deformation as well as flaking, cracking or other surface defects.

These alterations can be brought about by the action of oxygen, ozone, heat, light, humidity, solvents or by

storage under stress.

If properly stored and handled, rubber products will remain virtually unchanged in their properties over long

periods (several years). This does not apply to non-vulcanised rubber blends however.

STOREROOM

The storeroom should be cool, dry, free of dust and adequately ventilated. Storage outdoors – even if protected

from the weather – is not permissible.

T



TEMPERATURE

The temperature at which rubber products are stored depends on the products to be stored and the elastomers

that are used. Rubber products should not be stored at temperatures below –10 °C or over +15 °C; the upper limit

may be exceeded up to +25 °C. Higher temperatures than these are only temporarily permissible.

However products made from certain types of rubber such as chloroprene rubber may require a storage tem-

perature that is never less than +12 °C. The most favourable storage temperature for non-vulcanised rubber

products and rubber blends as well as adhesives and solvents is between +15 °C and +25 °C. Temperatures higher

than this must be avoided, lower temperatures should be avoided. Adhesives and solvents should not be stored

below 0 °C.

Products that are exposed to low temperatures during storage and transport may become stiff or lose their

adhesive power. These products should be conditioned at temperatures of +20 °C or more for a time before

commissioning or further processing. This is best done while they are still in their packaging as this will avoid

moisture accumulating on the product itself.

HEATING

In heated storerooms, rubber products must be shielded from the heat source. The distance between the heat

source and the goods in storage must be at least 1 m. A greater distance is required in wind heated rooms.

HUMIDITY

Avoid storage in humid rooms. Care must be taken to prevent condensation. Humidity should be kept below

65 %.

LIGHTING

The products should be protected from light, especially from direct sunlight and strong artificial lighting with a

high ultraviolet component.

The storeroom windows should therefore be coated with red or orange protective paint (never blue).

Preference should be given to illumination with standard type bulbs.

T



OXYGEN AND OZONE

The products should be protected from air changes, especially draughts, by being wrapped, stored in airtight

containers or other means. This applies especially to articles with a large ratio of surface area to volume, e.g. rub-

berised materials or cellular articles. As ozone is particularly harmful, the storerooms may not house any ozone

emitting equipment such as electric motors or other appliances that might generate sparks or other electrical

discharge. Combustion gases and vapours that could produce ozone through photochemical processes should

be eliminated.

OTHER FACTORS

Solvents, fuels, lubricants, chemicals, acids, disinfectants and similar products should not be kept in the store-

room. Rubber solutions must be stored in a special room according to the official regulations governing the

storage and handling of flammable fluids.

STORAGE AND HANDLING

Care must be taken to ensure that the products are stored free from stress, i.e. not under tension, compression

or other deformations, as stresses can result in permanent distortion and crack formation (O-rings for example

should not be stored hanging on hooks). Certain metals, especially copper and manganese, have an adverse

effect on rubber products. The products must not be stored in contact with these metals but be protected by

packaging or by a layer of suitable material. Articles such as antistatic films or bags made from paper, polyethy-

lene or polyamides (nylon) are suitable for this purpose.

The materials of the containers for packing and cover material must not contain any substances harmful to the

products, e.g. copper or cuprous alloys, petrol, oil or similar substances. Films that contain plasticizers must not

be used for packing. If the products are powdered, the powder must not contain any substances harmful to

them. Suitable substances for powdering are talcum, whiting, fine mica powder and rice starch. Contact between

products of different compositions should be avoided. This applies in particular to rubber products of different

colours. The products should remain in store for as short a time as possible. Where products are stored for longer

periods of time, care should be taken to ensure that new products are stored separately from existing articles.

N.B.: It is standard business practice to store hydraulic hoses are stored according to the FIFO principle.

FIFO (First In First Out) describes a method of storage in which the date of entry into store determines the date

of withdrawal. This means that the hose that has been stored longest is used first. Stainless steel reinforcements

must be protected from rust film.

T



max. 4 JahreAlter der Schlauchware

max. 6 Jahre Verwendungsdauer der Schlauchleitung

HerstellungsdatumSchlauchware

HerstellungsdatumSchlauchleitung

max. 2 Jahre LagerdauerSchlauchleitung

Lagerungs- und Verwendungsdauer gem. DIN 20066

CLEANING AND MAINTENANCE

“Rubber products can be cleaned with soap or warm water. The cleaned articles must be dried at room tempera-

ture. After longer periods of storage (6 to 8 months) the products can be cleaned with a 1.5 % solution of sodium

bicarbonate. Traces of cleaning fluid should be rinsed off with water. Effective and particularly gentle cleaning

products are recommended by the manufacturer.

Solvents such as trichlorethylene, carbon tetrachloride and hydrocarbons must not be used for cleaning. The

use of sharp objects, wire brushes, emery cloth etc. must also be avoided. Rubber-to-metal composites should

be cleaned with a mixture of glycerine and ethyl alcohol (1:10). If disinfection is necessary, it should be carried

out after the rubber products have been thoroughly cleaned. The disinfectant must not be used as a cleaning

product at the same time.

Choose a disinfectant that is compatible with rubber. Oxygen or halogen releasing products such as potassium

permanganate or chlorinated lime in particular can be harmful, especially to products with thin walls.

Rubber products for medical uses may only be disinfected using the products recommended by the manufac-

turer. The service life of certain rubber goods can be extended by a special coating (wax emulsion, shellac and

similar products). Such coatings are not recommended for rubber products for medical use.” It should be noted

that special cleaning and storage processes will be essential if there is a requirement for freedom from silicone.

The latest version of DIN 20066 lays down the following requirements:

“Even when properly stored and protected from excessive stress, hoses and hose assemblies undergo a process of

natural ageing. Their service life is limited as a result. Incorrect storage, mechanical damage and excessive stress are

the most frequent causes of failure. In individual cases the service life can be defined as follows based on practical

experience, and contrary to the following guide values: When constructing the hose assembly, the hose (as sold by the

metre) should not be more than four years old.

The service life of a hose assembly including any storage time of the hose assembly should not exceed six years. The

storage period itself should not exceed two years.”

The chart below presents this situation:

How long can hose assemblies be used for?

– Follow the general requirements of EN 982, Point 5.3.4.3 Hose Assemblies.

– Storage and service lives according to DIN 20 066 as a recommendation.

– Section § 52 (3) of Accident Prevention Regulation (UVV) 14 Hoist Platforms requires a maximum service life

for hose assemblies of 6 years.

Storage and service life according to DIN 20066

max. 4 years age of hose material

max. 6 years service life of hose assembly

max. 2 years storage life of hose assy.

Date of manufacture of hose matl.

Date of manufacture of hose assy.

T



INSPECTION CRITERIA

The safety rules for hydraulic hose assemblies of the German Federation of the statutory accident insurance insti-

tutions for the industrial sector, and the latest version of DIN 20066, state that the functional capability of hose

assemblies must be assessed at specified intervals.

The relevant rules lay down clear criteria for the replacement of hose assemblies; hose assemblies must be

replaced when an inspection reveals the following damage:

– Damage to the outer cover of the hose down to the reinforcement, e.g. from chafing, cuts or cracks.

– Embrittlement of the outer cover through cracking of the hose material.

– Deformation which does not conform to the natural shape of the hose or hose assembly, whether under

pressure or not, or during bending, e.g. separation of layers, blistering.

– Damage or deformation of the hose fitting (compromised sealing function); minor surface damage is not a

reason for replacement.

– Hose working loose from its fitting.

– Corrosion to the fitting that affects function and strength.

– Installation instructions not followed.

– Storage life and service life expired.

REPAIRING HOSE ASSEMBLIES

The current version of DIN EN 982 “Safety of machinery – Safety requirements for fluid power systems and their

components” should be mentioned in this context; this standard lays down clear guidelines for the repair of hose

assemblies for hydraulic connections. It states for example that:

“Flexible hose assemblies shall not be constructed from hoses which have been previously used as part of the hose

assembly. Flexible hose assemblies shall fulfill all performance requirements specified in the appropriate European

and/or international standard(s). Hose manufacturer’s instructions for storage must be followed. The recommenda-

tion of a service life for hose assemblies should be taken into consideration.”

We would point out that DIN EN 982 is a B2 standard and as such has quasi-statutory status, i.e. it may form the

basis of a judicial decision in legal cases. This fact should be borne in mind in the event of claims for liability.

DIN EN 982 provides other important requirements for hydraulic connections:

“Hose assemblies must be installed such that

– the length that is necessary to avoid kinking and tensile stressing of the hose during operation is provided; the

recommended bending radius should not be exceeded.

– twisting of the hose, e.g. by the blocking of a rotary connection, is kept to a minimum;

– they are arranged and protected in such a way that the abrasion of the outer cover of the hose is minimised;

– they are suitably supported if the weight of the hose assembly could result in excessive stress.”

It further states that:

“If damage to a hose assembly would create a hazard from whipping, the hose must be restrained or guarded.

If damage to a hose assembly would create a hazard from the leaking medium under pressure, the hose must be

guarded.”

T


HANSA-FLEX HD 208 EN 853 2 SN 8 WP 350 BAR 2Q06

Hose type and nominal bore

Standard

Maximum permitted working pressure

Quarter of manufacture


IDENTIFICATION OF HOSES AND HOSE ASSEMBLIES

Given the previously mentioned natural ageing process to which hoses and hose assemblies are prone, appro-

priate product identification is an important requirement laid down in the relevant standards and safety regu-

lations.

DIN 20066:

“Every hose assembly must be permanently identified with the mark of the hose assembly manufacturer, the assembly

date (year and month) and the maximum permitted dynamic working pressure of the hose assembly.”

The identification of hose sold by the metre is laid down in the respective hose standards. The current version of

EN 853 for example states that:

Hoses must be continuously identified with the following minimum particulars at intervals of 500 mm:

– the name and mark of the manufacturer, e.g. HANSA-FLEX

– the number of this European standard EN 853

– the type, e.g. 2 SN

– the nominal bore size, e.g. DN16

– the quarter and last two digits of the year of manufacture, e.g. 4Q06

Example:

T



wrong right

INSTALLATION OF HOSE ASSEMBLIES

The life and safe use of a hydraulic hose assembly are largely dependent on proper installation.

TORSION

If a hose assembly is installed in a twisted position, the mutual friction between the layers of reinforcement will

significantly curtail service life. The layers of reinforcement are subjected to pulsating pressure and tend to return

to their neutral initial position. The result will be excess stress at the point of hose retention!

The following can be used as a guide value: A twist of 7° reduces life by 80 %.

When the assembly is installed therefore it is essential to ensure that it cannot twist on itself, e.g. when the union

nuts are tightened! (Hold in position with a wrench.)

OVER-BENDING

Over-bending a hose assembly beyond its minimum bending radius will inevitably reduce its service life and

loading capacity, with gaps appearing in the wire braid on the outside bend as a result of the larger area that it

has to cover. This can result in so-called ‘oil needles’.

A maximum permitted bending radius is prescribed for every hose type depending on its nominal bore.

The opposite effect occurs on the inside bend: The layers of reinforcement are upset – they do not lie close

enough to the inner layer and lose their pressure-bearing properties as a result.

Over-bending usually occurs (and this is frequently overlooked) immediately after the connection, when it is

kinked too sharply.

T



wrong right

wrong right

rightwrong

Provided the installation conditions allow, a bend in a hose assembly should be introduced following a straight

section whose length is 1.5 times the hose outside diameter. An anti-kinking sleeve or similar device should be

fitted in such cases if necessary.

In some cases it is also possible to prevent over-bending by the judicious selection of suitable fittings:

T



rightwrong

Caution: “Oil needles” are fine jets of fluid that penetrate the hose wall through to the exterior under high pres-

sure. If such jets occur, the system must be immediately shut down; persons must not come into contact with

the jets under any circumstances! A jet of this type will immediately penetrate human tissue where it will spread.

Hydraulic fluids are contaminated with bacteria which can cause life-threatening blood poisoning when such

injuries occur! Such injuries may not even be painful because of their small size and the high pressure. A doctor

must be consulted immediately if hydraulic oil penetrates human tissue!

ABRASION

If a hose is laid across an edge, its outer layer can chafe through as a result of the hose’s inherent movements.

This also applies to hoses that are laid in close proximity to one another: The hoses will chafe each other to the

point of rupture.

Outcome: The wire braid is no longer protected from corrosion and failure is just a matter of time.

Hoses are also available with an extra layer of protective PVC, however they have the disadvantage of a higher

bending radius that makes the hoses stiffer. The action of the plasticizer that is present in the material of PVC

hoses must also be taken into consideration.

T



rightwrong

rightwrong

wrong right

TENSILE STRESS

Tensile stresses on hose assemblies must be avoided at all cost as this will compromise the secure retention

of the hose. Please remember that hose assemblies can become slightly shorter when under pressure, so they

should always be installed with a certain amount of slack, and possible movement cycles must also be taken into

account:

* Note: There are certain applications where tensile stresses cannot be avoided, e. g. spring-loaded tension rollers.

In this case the maximum permitted operating loads must be agreed with the manufacturer.

HOSE CLIPS

Hose clips should be avoided where they would impede the hose’s natural movement and change in length:

The reversal of the pulsating oil flow sets up a pumping motion in the bend in the hose shown on the left, the

outer layer will eventually be destroyed by the hose chafing in the clip.

Hose clips should therefore only be installed in straight hose sections so far as possible. Changes in the diameter

of the hose must also be allowed for.

T



WHIPPING

The dangerous ‘whipping’ that occurs when a hose ruptures can be prevented by the appropriate design. The

HANSA-FLEX Stopflex safety system that achieves a secure connection between hose and machine component

is particularly suited for installation in both new and existing systems. The following items are suitable for retro-

fitting:

– Covers

– Duct guides

COLD FLOW

Even without the effect of temperature, elastomers do not display an ideally elastic behaviour. Despite its che-

mical and physical crosslinking, the rubber material can have a tendency to creep even between the nipple and

the mount. This viscoelastic behaviour leads to leaks around the hose mount or causes the hose fitting to ‘drift’.

Peeling the top rubber (outer layer) within the prescribed area can eliminate at least this potential hazard on the

hose.

RESISTANCE TO GASES AND VAPOURS

Permeation or effusion, i.e. the potential migration of gas molecules through the inner layer of the hose, must

be taken into consideration when selecting a suitable hose. This effect is also dependent on pressure. The conse-

quence is a loss of medium or accidental concentrations of gases or gaseous fuels and combustibles. These gases

are potentially flammable, explosive or toxic. The selective discharge of possible gas concentrations beneath the

outer cover is known as ‘pricking’, a technique that is used with compressed air lines over 16 bar or with hot water

hoses, for example.

T



CAVITATION

BASIC PRINCIPLES

Cavitation occurs in a fluid flow system when the local static pressure falls below the vapor pressure, and the fluid

spontaneously evaporates in the confined space. The result is vapour-filled fluid cavities. These vapour bubbles

implode when the original pressures are reached. The implosion sets up pressure waves that peak locally at

hundreds of bar and with frequencies of several thousand Hertz. Cavitation can also occur when back-pressures

are unacceptably low (0.8 to 0.7 bar absolute). Air that is dissolved in the oil is released in a vacuum. On the high-

pressure side these bubbles are immediately compressed again, including under the influence of temperature.

EFFECTS OF CAVITATION

The harmful effects of these ‘blows’ on the material surface of hose walls are enormous. Within just a few hours

the surface will sustain a ‘woodworm-type’ attack, and sections of hose wall or flow guides will break away. Vibra-

tion with reaction forces of high magnitude can also take place.

CAUSES OF CAVITATION

Possible causes include:

– sudden increases in the velocity of the fluid due to constrictions and pressure surges

– the high temperature of the hydraulic fluid

– excessive flow velocity due to changes in delivery rates, resistance and hence a drop in pressure in the

suction section of the system

– poor ventilation of the oil reservoir

– high pressure differentials

– the condition of the hydraulic fluid (age, level of air)

WAYS OF CONTROLLING CAVITATION

The following measures should be taken:

– a low suction height

– an adequately large hose rating

– adequately rated suction filters

– smooth machined surfaces

– minimum amount of oil in the air

– a possible increase in inlet pressure on the suction side

T



STATIC ELECTRICITY

BASIC PRINCIPLES

Static electricity is an electrical charge that accumulates on the surface of materials of the same or different type

following a mechanical separation.

Mechanical separation occurs:

– With solid materials: lifting off, rubbing, crushing, pouring

– With fluids: flowing, pouring, spraying (electrically charged mists)

– With gases and vapours: Although gases and vapours do not charge up in the purest form, it should

be remembered that solid or fluid impurities or even solid or fluid elements

formed by condensation can cause an electrical charge.

Prime examples include cleaning processes that use steam or water jet appliances, paint spraying, solvent trans-

port and the handling of fuels and combustibles in solid or liquid form.

The level of electrical charge depends on the intensity and extent of the separation processes, not on the con-

ductivity of the materials used.

If the charge is strong enough, a discharge will take place in the form of sparks, brush discharge or corona

discharge, with the possible ignition of an explosible atmosphere as a result.

Ignitable discharges can occur between an insulated or earthed conductive object and a

– charged insulated conductive object, and

– a charged non-conductive material.

Proper earthing is therefore vitally important, especially when using non-conductive items of equipment or such

items in combination with conductive equipment.

Reference regulations:

– Guidelines “Static Electricity”, BGR 132 (was ZH 1/200)

– “Hose Assemblies – Safe Use”, BGI 572 (was ZH 1/134)

STATIC ELECTRICITY IN HOSE ASSEMBLIES

Electrically chargeable materials such as rubbers and synthetics can be made adequately conductive by con-

structional measures, e.g. metal reinforcement or additives such as soot. Consideration should be given to the

possible loss of conductivity caused by damage to the hose reinforcement or the loss of continuity between the

reinforcement and the hose fitting, as well as by segregation or structural alterations.

In hose assemblies, the amount of static charge depends largely on the flow velocity. The charge current rises as

the flow rate increases, while at a constant flow rate it rises with an increasing nominal bore and/or tube diame-

ter. Electrostatic charges can also be observed if there is a strong or sudden change in the direction of flow.

T



The flow rate should not exceed 6 m/sec when using standard hoses. Steam transmission is made critical by the

high flow rates that are caused by adiabatic expansion. In conditions of free expansion, velocities of more than

16m/sec occur. Since this expansion will result in a charge of static electricity, ensuring the electrical conductivity

of hose products and hose assemblies is a matter of the utmost importance. The electrical resistance between

the fittings of a hose assembly must be less than or equal to 106 Ω in the dry condition with the assembly exten-

ded.

STATIC ELECTRICITY OUTSIDE HOSE ASSEMBLIES

Hazardous charges of static electrricity can be expected to occur in the presence of vapours, or when cleaning

and filling containers and tanks. These discharge energies are enough to ignite mixtures of gas and vapour or

dust and air. Hazardous areas can also exist around open jetting operations with steam (steam jet degreasers)

and the spraying of insulated conductors with the charged open jet owing to the very high exit velocities of the

vapour from the nozzle and its consequent expansion. Dangerous discharges can even occur in saturated steam

when escaping from a rubber hose. The presence of water vapour in a container or tank will not reduce the

charge of the fluid or minimise the field strengths in the vapour chamber.

CHANGES IN LENGTHS AND DIAMETERS OF HOSE ASSEMBLIES

It is well known that hose assemblies can alter axially and radially under pressure, undergoing a negative or

positive linear change; an increase in diameter is also often observed.

This behaviour is by no means ideal, unlike the behaviour of steels springs which can be readily identified and

calculated. Detecting alterations in hose assemblies is based on tests carried out on a specific test specimen, i.e.

by a ‘volumetric expansion test’.

The positive or negative linear change must be allowed for when determining the length of hose assemblies so

as to prevent hoses from kinking and fittings from being pulled out. Increases in diameter can pose a problem

with hose fastenings that are too tight and insufficiently elastic, or when the hose assembly is used as a control

line. Pressure and volume are known to be characteristic variables that affecting triggering response and hence

the characteristics of a control circuit. It should also be remembered that intentional increases in volume can help

mitigate pressure peaks (buffer function).

T



These alterations are a function of the braid angle, the material and the type of braiding used for the reinforce-

ment. These three criteria determine the mechanical properties of the hose which in turn bring about alterations

in behaviour. Pressure and nominal bore are also parameters which can lead to alterations in a hose assembly.

Finally, a knowledge of the ultimate elongation and tensile strength of the hose reinforcement can be used to

calculate the bursting pressure of the hose, and this will then find its way into the relevant standards after the

completion of a series of tests and experiments. Conversely, technical specifications for the design of a particular

type of reinforcement can of course result in the defined product when applied in conjunction with experience

gathered in the field of hydraulic hose development.

The relevant standards and manufacturers’ instructions may quote numerical values, but these general figures

are no substitute for practical experience with axial expansion and contraction, or changes in diameter. They can

only give an indication that changes occur and in what orders of magnitude (extreme limits) they can be expec-

ted. A qualitative assessment and analysis must assume that a change in volume will always mean a change in

linear extension and diameter.

It is a fact that even with new designs and original equipment, insufficient attention is given to these pheno-

mena, with the result that maintenance engineers are inevitably faced with the duty of not accepting enginee-

ring solutions without criticism. This applies especially to the necessary rating of the hose assembly length.

T



Katalog 1 EN - Hansa-Flex...DIN 20018-1 Textile-reinforced hoses, nominal pressure 10/16 04.03 DIN...

Documents

Transcript of Katalog 1 EN - Hansa-Flex...DIN 20018-1 Textile-reinforced hoses, nominal pressure 10/16 04.03 DIN...