Customer
Machine
Hose
Fittings
Working pressure Static
Fix
Weather
Abrasion
Environmental
Ozone
Industrial cleaning Dynamic
Flexing
Certification requested Industry
Near the fittings?
Transportation Agriculture Earth moving
Working pressure max/min Pmax bar Pmin bar
bar bar
m/sec
per hour
mm mm
theoretical effective
l/min.
bar Pump press.
MINERAL BIO
mi -1 P
P
T
hrs/day
∞C
T ∞C
h Pressure peaks
Impulse frequency
Fluid velocity
Oil
Medium oil temperature
Working time
Installation
Anverage nr. of flexing
Min. bend radius
External temperature
Environmental conditions
Date Name
Relief valve setup
Total working
time h
Vibrations (frequency Hz, amplitude +/- mm)
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Material to be conveyed
Some applications require special oils or chemicals to be conveyed through the system. Hose selection must assure compatibility of the hose tube, cover, couplings and O-Rings with the fluid used.
Additional caution must be used in hose selection for gaseous applications such as refrigerants, compressed air or LPG, etc. When selecting a hose for gaseous applications where permeation of fluid through the hose wall may occur, consider the possibility of hazardous effects, such as explo-sions, fires and toxicity. Refer also to applicable standards for specific applications such as refrigerants. If fluids permeate through the hose tube, consider the use of perforated covers to prevent fluid cover blistering under the cover (pin-pricking).
Also ensure the compatibility of the system fluid not only with the hose tube, but also with the braid, cover, fittings and other components since permeation may expose the entire hose assembly to the system fluid.
Regarding the hydraulic fluids, mineral & biological oils, Manuli wire braided and wire spiral hoses have a wide inner tube compatibility: spiral hoses are also identified by the BIO logo on the hose lay-line. Anyway each single oil brand name has to be carefully checked, seen the wide differentiation of the additive packages used by many hydraulic oils producers in their fluids. That’s why an intense activity of oil compatibility is currently performed on the Manuli rubbers, as support to customers and OEMs.
The hose selection activity must ensure compatibility mapping of the hose tube, cover and fittings with the type of fluid to be conveyed. If the end fitting type requires an O-Ring for sealing, ensure that the O-Ring compound is also compatible with the system fluid.
For tube compound evaluations, please refer to the Manuli Rubber Industries Approved fluid compatibility chart following the evaluation criteria supplied here below reported. For spe-cific information, contact Manuli Rubber Industries.
For the mineral and biological oil classification you can refer to the following table, summarising the main characteristics of each family, advantages and disadvantages, and cost estima-tion compared to the tradiestima-tional mineral based.
For particular or unusual fluids check compatibility together 33 with MRI’s specialists.
Pressure
Knowing the system pressure, including pressure spikes, surges, etc. is of the greatest importance for the hose selection process. The hose catalogue working pressures must be equal to or greater than the system pressure, including peaks. Pressure spikes greater than the published working pressure will shorten hose life and must be taken into consideration (e.g. ref. SAE J1273).
Pressure peaks must be measured with electronic devices capable to record very short transients not measurable with traditional analogical instruments.
The rated pressure of primary and eventual secondary valve of the system gives an additional information of what can be the maximum pressure peak inside the system. The Max working Hydraulic oils classification
Mineral oils
• The traditional solution, widely industrially available, suitable for the majority of relevant applications
• Low cost if compared to alternative solutions Advantages
• Not ecologically acceptable 1 Cost
High: +80 ∞C • Suitable for the majority of relevant applications
• Limited by their poor oxidative thermal and hydrolitic stability
• May bio-degrade in the system:
the oil stability is very susceptible to water contamination
• Possible strong odours in use and formation of gums
• FIRE RESISTANCE hydraulic fluids
• Similar applicability than polyglycols
• For their high water content they can be considered ENVIRONMENTAL FRIENDLY & ACCEPTABLE
• Moderate hydraulic fluid properties
High: +130 ∞C • Limited to areas where water solubility is advantageous, for example, inland waterways, spillage of non soluble products results in a perceivable surface film
• Areas where cleaning by simple water washing is employed may also benefit
• Due to the high water solubility their use is somewhat limited or prohibited (Switzerland) due to the risk to pollute the water-bearing stratum
• Absorbed water can effect the performances
5 to 7
Synthetic esters HEES
Low: -30 ∞C
High: +90 ∞C • Better stability than vegetable oils, wider range of successful applications
• Diesters: used mainly in aviation, automotive, compressor applications
• Hindered esters: application similar to diesters and also steel rolling or industrial hydraulic
• Stability can be affected by water contamination
• The high cost tends to limit their use
6 to 10
The hydraulic hoses of the Manuli product range are not designed for immersion in the service fluid. This type of special applications should be avoided or care-fully studied with additional external protections for the hoses, selection of special hose types, e.g. with thermoplastic cover and validation on the specific appli-cation. The turbulence of the fluid, the high temperature and nature of the fluid as well as other elements may impact the properties or integrity of the hose cover material (the cover compound of the hose is designed may impact the properties or integrity of the hose cover material (the cover compound of the hose is designed to resist to oil drops and extrernal agents, not immersion in the service fluid). For more detailed information conact Manuli Rubber Industries.
pressure inside the system in fact cannot be simply equal to the pump rated working pressure, but must consider also the functional activities of the equipment (negative loads, vibra-tions, etc.) and the consequent pressure peaks.
Be aware that hydraulic fluid under pressure can be potential-ly dangerous!
• An explosive bursts or stream of escaping fluid can cause damage to equipment or serious injury to persons nearby
• Highly pressurised fluid escaping from a small pinhole can be almost invisible and yet exert extreme force capable of penetrating the skin and other tissue, causing possible severe injury
• Pressurised fluids, if released uncontrolled, can exert an explosive force
• Hot fluids or chemicals can cause severe burns
• Some fluids are highly flammable, etc.
The maximum rated working pressure of any assembly will be defined by the lowest working pressure of the hose, the end fitting or any adaptor (consequently it is recommended to select the proper cou-plings and adaptors with working pressure higher or equal to the hose one, never lower). Always take into consideration any pressure spikes or potential pressure surges in the system, but also the fatigue mission profile of the application, number of pressure impulses per hour/day/year, in order to proper pro-vide eventual oversizing of the hose reinforcement compared to the minimum theoretical requirement. In particular also the position of the hose inside the system must be considered, seen the different functions: see the following scheme and mission profiles of the applications.
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Hose WP selection
hose WP
system pressure history system WP
time spikes P
"The hose working pressure should include the pressure surges (spikes) that, even if not indicated on many common pressure gages,
must be identified on electronic measuring instruments with a high frequency response"
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Pressure (Power) lines
High pressure, may be also over 400-500 bar Fluid velocity: Max. 8-12 m/s
Heavy duty working conditions (high fatigue stress) can be present, Manuli wire spiral and two wire braids hoses are generally requested
Suction lines
Low pressure (max 5-10 bar)
Fluid velocity: Max. 1,5 m/s (to avoid pump cavitation) Resistance to vacuum is requested up to -0,83/-0,90bar Large I.D. requested to reduce pressure drop
Spirtex/K and two wire braided hoses are designed for this applications and in particular for vacuum resistance
Drain lines
Low pressure (Max 20-30 bar) Fluid velocity: Max 3-4 m/s Small bend radius requested
Large I.D. requested to reduce pressure drop Return lines
Low pressure (Max 30-50 bar) Fluid velocity: Max. 3-4 m/s Small bend radius requested Vacuum resistance
Large I.D. requested to reduce fluid velocity and pressure drop Multitex and Astro hoses line generally suitable
For a proper hose selection in terms of pressure resistance, it is also useful to consider the following working pressure classification, with progressive fatigue stress and consequent necessary design criteria:
• low pressure up to 70 bar
• medium pressure up to 210 bar
• high pressure up to 210-350 bar
• very high pressure up to 350-420 bar or higher
Note
Pilot lines
Medium pressure (Max 100 bar) Fluid velocity: Max. 5 m/s
Compact dimensions & flexibility are a “must”
Small bend radius requested Lightness is appreciated
The Manuli solution for pilot lines is Pilot hose
Ends of coupling
Select the proper end fitting from the Manuli cata-logue, being careful to the maximum working pressure of the termination end (by the reference international specifications), in consideration of the hose to which it is applied.
Additional considerations of mechanical robustness and seal-ing capabilities of the termination ends can be advisable for heavy duty applications and/or specific installations: refer to the coupling selection criteria supplied in the relevant section of the manual; contact Manuli Rubber Industries for specific detailed information.
When replacing an assembly, identify end connections and sealing surfaces. Once thread ends have been identified, con-sult the appropriate section of the Manuli Rubber Industries catalogue for specific part number selection.
Do not mix and match hose and fittings from different suppliers: in fact relevant testing qualification programs are necessary to validate the hose and fittings compatibility.
Hydraulic hose from one supplier is seldom compatible with fittings from another; in any case the assembler is responsible for the guarantee of proper compatibility existing between the hose and fitting if the manufacturer prescriptions are not correctly followed.
Ensure that the correct inserts and ferrules are chosen for the hose type.
Delivery (Flow rate and fluid velocity)
When replacing an assembly, we can assume the system is properly sized to efficiently transport fluid, that’s why the same I.D. of the original hose can be used.
Eventually it can be useful to determine if the system is properly sized to efficiently convey the max. flow rate:
in this case follow the recommendations below.
If the system is new or altered, determine the hose I.D. needed to convey the max. flow rate considering the maximum recommended fluid velocities for each application type (pres-sure lines, return lines, suction lines) and a max. pres(pres-sure loss inside the line, in order to avoid excessive friction, vibrations 36
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