Technical Information Hydraulic Hoses
General guideline for the use of our hydraulic hoses
The selection of the correct hose type is very important for proper and safe use in operation. Therefore, when selecting our products, please always check the suitability for the application areas used by you and/or your customers and instruct your customers about the functional range of the products and their limitations accurately. Under this section you will find all the important technical information and specifications relating to our hydraulic hose products.
The appropriateness of the chosen product for the customer's specific application can only be determined in individual cases and is dependent on the definite installation situation (especially the hose curvature), the combination of the coupling and the compatability of the medium with the inner coating of the hose (inner core). Further information in the sub-items of this menu (see left side) provide a brief overview on these topics, but do not replace specialist advice in individual cases. Please obtain specialist advice in the event of any uncertainty!
The number of possible operating hours falls if the hose is used under unfavourable operating conditions. These include maximum operational pressure, maximum temperature and minimum bending radius. When several of these factors coincide, the product deteriorates more rapidly and therefore must be replaced sooner. Therefore please verify the operating conditions regularly and adapt the replacement cycle to them.
Our hydraulic hoses and pressure washer hoses are not designated for sale to the general public and do not fulfill the conditions for “GS-certification” (voluntary certification related to tested safety). If you or your customers should intend to sell our pressure washer hoses to the general public / or in case you require pressure washer hoses suited for GS-certification please contact a Semperit specialist.
Wrong product selection or improper installation of the hoses can result in damage or failure of the hose, (often also serious) material damage and personal injury. Particularly in applications with high operational pressure, non-compliance with the specifications can result in serious risk of injury! Therefore, in case of doubt, please seek specialist advice!
Hose and working medium
The hose inner surface (inner core) must be appropriate for the medium used in the application (oil, water, air, gas) as otherwise the hose can be damaged or destroyed by working medium or its contents and can thus fail, which can result in (partial or even serious) material damage or personal injury.
Our hydraulic hoses are generally suitable for mineral- and synthetic oil-based hydraulic fluids (HL, HLP, HLPD, HVLP), for oil-water emulsions (HFAE, HFAS, HFB) and water-glycol solutions (HFC), as well as for vegetable- and mineral oil based lubricants. In individual cases there may be restrictions due to manufacturer-specific oil additives. For safety reasons, we would invite inquiries for individual cases. Suitable for compressed air up to a maximum of 50 bar and 80°C with restricted service life. Not suitable for hydraulic fluids based on chlorinated hydrocarbons or phosphate esters (HFD-R/S/T)
In principle, there is suitability for biologically degradable hydraulic fluids (bio-oils, HETG, HEPG, HEES), but this can be restricted by manufacture-specific oil additives.
For safety reasons, we would invite inquiries for individual cases.
If no specific hose lenghts have been ordered, the percentages of different lengths in any given delivery shall be as follows:
According to EN 853 - 857
min. 80 % in lengths over 20 m
max. 20 % in lengths over 10 m to 20 m
max. 3 % in lenghts over 1 m to 10 m
no length of hose may be less than 1 m
The acceptable tolerance on the specified coil length is +/- 2 %
min. 90 % in lengths over 25 m
max. 10 % in lenghts over 5 m to 25 m
no length of hose is less than 5 m
The acceptable tolerance on the specified coil length is +/- 2 %
1. correct choice of hose assemblies
Hydraulic hose assemblies are used to transmit forces by means of oil pressure, and consist of flexible hydraulic hoses to which fittings are attached at either end to ensure safe, interlocking connections.
The correct choice of a hose assembly is influenced by many factors, particulary dynamic working pressure, resistance to media handled, operating temperature - both of the medium and of the surroundings.
Follow the instructions...
However, legal and other regulations must also receive careful consideration where hydraulic hose assemblies are used, and the manufacturer should be informed about them when you make your inquiry.
In many cases, observing the instructions for installation will determine the service life of a hydraulic hose assembly.
2. determination of hose dimensions
The necessary inside diameter of a hose assembly is determined by the projected working pressure and the proposed rate of flow.
Never underdimension hoses...
Underdimensioning hose assemblies results in a high rate of flow of the medium. This ensuing turbulence causes in considerable loss of pressure, noise and increased temperatures. This can be detrimental to the entire system.
If underdimensioned valves necessitate smaller hose inside diameters, we recommend the use of suitable adapters which then cause only local constrictions in the system.
3. dynamic working pressure decisive
In practice hydraulic hose assemblies are subjected to dynamic loading. A hose assembly must therefore be designed for operation at the maximum permissible working pressure specified for the respective hose type and size.
Safety factor 4 : 1
The working pressure of a hydraulic hose assembly is normally a quarter of the theoretical or specified bursting pressure. This safety factor of 4:1 conforms to SAE, DIN and EN-regulations.
Dynamic operating pressures...
is the most frequently operating condition in hydraulic systems. Pure static load is the absolute exception and therefore the "Static Working Pressure" has been eliminated from the standards.
Consider peak pressures...
a hose with a higher pressure rating than the actual working pressure of the installation should be selected for systems in which sudden peak pressures occur.
4. Bursting pressure must never be reached
The values specified for bursting pressure are minimum values. They apply only to unused hose assemblies.
The bursting pressure of a hose or a hose assembly must therefore remain a purely theoretical value for the user. In view of the safety requirements imposed on any installation, this value must never be reached - or even approached - in practice.
It is incorrect to assume that comparable hoses of different manufactures have longer service life under the same operating conditions the higher the rating for bursting pressure is. Designers should therefore take dynamic pressure values into consideration!
5. Monitoring high pressure gas systems
High pressure gas systems are dangerous and require regular inspection.
Hose assemblies used in gas systems have to be suitably protected against mechanical damage and chemical end environmental influences.
The hoses of such installations should also be connected in such a way that they cannot whip in the event of a defect occuring.
Perforated outside cover...
The outside cover of a hose assembly used for the conveyance of gaseous media must be perforated.
6. test pressure as safety check
Hose assemblies are statically tested by the manufacturer at suitable test pressures; neither leaks nor failure must occur.
7. temperature affects service life
The operating temperatures given for hoses are the maximum temperatures of the medium. Ambient temperatures must also be taken into consideration (see below).
Continuous operation at high temperatures can affect the service life of the hose and the reliable seating of the fittings.
Temperature resistance depends on medium
Hose assemblies cannot therefore be used for any medium over the specified temperature range. In case of doubt please ask us.
Hoses assemblies will have a considerably longer service life if they are not continually used at the limits of their working pressure, bend radius and temperature of medium and environment.
8. Allow for changes in Length
Every hose is subject to certain changes in length under working pressure.
The standards specify that these values can vary between -4 % and +2 % at maximum working pressure.
This change in length must be taken into consideration in each case when calculating the nominal length of a hose assembly with fittings.
9. check chemical resistance
The chemical resistance of the rubber lining is an important factor to consider when selecting a hose assembly. This should be viewed as a function of the concentration and nature of the duration of exposure to the medium.
In principle the rubber lining is resistant to hydraulic liquids on mineral- or synthetic oil basis, to glycol water mixtures and oil water emulsion but not resistant to phosphate ester based liquids (HFD).
10. observe minimum bend radius
The specified minimum bend radius apply to stationary hose assemblies at maximum working pressure.
The service life of a hose assembly is impaired if bends of less than the recommended minimum bend radius are used. Working pressure should be reduced in such cases.
Impulse test measures performance
The impulse test is the most severe test for a hose assembly, reproducing practical operating conditions very closely.
Semperit's quality assurance department therefore continually takes samples and subjects them to impulse test in quality in production runs.
This test is carried out as follows: the hose assembly under test is given the minimum bend radius specified by the standard and subjected to an alterning load varying between a flushing pressure of approx. 10 bar and a pressure equal to 125 % or 133 % of its dynamic working pressure.
Testing up to 1.000.000 load cycles...
Depending on the type of hose, the sample is expected to withstand at least 150.000, 200.000 or 400.000 load cycles under these conditions.
Special Semperit designs such as 1 SN-K, 2 SN-K and SPC-2 are additionally impulse tested up to 1 million cycles.
Further details of test methods and quality requirements, such as chemical and physical tests, media resistance, ageing characteristics etc. can be found in the SAE J 343, EN 853 to 857 and ISO 1436 standards.
The storage temperatur should be below 25°C and articles stored away from direct heat sources.
The relative humidity should not exeed 70%.
The hoses should be stored in a dark place away from sunlight and strong artificial light. Exposure to ozone and UV radiation will shorten the service life of a hose.
The oldest hoses or assemblies in stock should always be used first.
For further details see ISO 8331..
Not only can damaged hydraulic hose assemblies cause a company unexpected expense, under certain circumstances they can also lead to severe accidents. This can be avoided if sufficient attention is devoted to the early detection of damage.
Conditions for safe operations
- Choice of a suitable hose assembly for the required working pressure, conditions of operation and nominal diameter
- Operating range in accordance with relevant standards or other regulations
- Professional installation, correct and careful laying
- Immediate replacement of damaged hose assemblies
Main causes of damage
- Mechanical damage
- Too much bending
- Extreme tension
- Above-average twisting
- Severe compression
- Unsuitable medium
Possible consequences of damage
- Damage to outer cover down to steel wire reinforcement - may result in corrosion of wire reinforcement
- Deformation or embrittlement of outer cover
- Damage or deformation of hose fittings
- Possibility of bursting
Regular checks for early detection of damage
- Perfect condition of outer cover of hose - no cracks, bubbles, deformation, wear or kinking
- Proper attachment of fittings
- Proper laying - avoid extreme kinking, too much tension, violent twisting
- Check for leakage
Procedure for replacement of hoses
- Guarantee the absence of pressure
- Check suitability of replacement hose
- Install replacement hose
- Restore operating pressure
- Check for leaks
Correct Installation increases the service life of hose assemblies
- Under pressure, alterations of +2 % to -4 % can occur in the length of hose assemblies. Hoses should therefore be installed with slack or curves.
- Hose assemblies should never be installed twisted (no torsion).
- Hose assemblies should not be bent excessively - use elbow fittings instead!
- Note minimum bend radius!
- If vertical displacement occurs, allow for amount of travel.
- Protect from external damage (use protective spirals).