Guide to selecting the right hydraulic hose and fittings for your replacement hose.
Hydraulic Hose suppliers in Dubai
Hoses are vital components of any hydraulic system. Over the years, hydraulics have become more and more complicated. While hose dimensions are being reduced to fit into smaller spaces, pressures keep getting higher. Thousands of different fittings are available for hundreds of types of hoses, so how do you know which hose and fitting to select when it is time to replace a hose assembly? This detailed guide will help you in this unenviable but important task.
Dash size or hose I.D. needed for the application
Dash size (or sixteenth of an inch, for example Dash 8 is ½” bore) indicates the inner diameter of a hose, which is how the fluid power industry primarily measures hydraulic hoses. This is usually printed on the layline of the hose or can be measured manually. Proper flow velocity for a hydraulic system is determined by the inner diameter. A flow that is too slow will cause fluid energy loss and result in sluggish performance, whereas too high a flow may damage the system, cause hose leakage and pressure drops. So first step is to identify and validate the correct inner diameter of the hose.
Fluid temperature and ambient temperature
Temperature is a critical factor when determining the right kind of hose and the twin aspects of media temperature and ambient temperatures need to be considered. Media temperature is the temperature of the media being transported by the hose and ambient temperature is the temperature outside of the hose. The temperature rating for the replacement hose should exceed the greater of the two temperatures. Also, some fluid media may increase the effects of temperature, hence the media type is also an important consideration for selection of a hose.
Every application needs a unique solution
How will the hose be used in the system? The answer to this question should form an important role in the selection. The following factors will help answer the question;
- Type of equipment involved
- Environment factors
- Mechanical loads applied to the assembly
- Routing requirements that are integral part of the assembly
- Various industry standards such as SAE, EN and DIN have set specific requirements with respect to size, type, burst pressure, tolerances and impulse cycles of hoses.
Talk to hose specialists at Inflex Hydraulics for your specific requirement.
Bend radius of hose for your application.
Bending a hose allows easy routing. The minimum radius that the hose may be bent through while operating at the maximum allowable working pressure determines the bend radius of a hose. If a hose is bent below the minimum bending radius it will lead to loss of strength of the hose and result in hose failure. A bending may be done only after a minimum straight line length of 1.5 times of the hose outside diameter (O.D) is allowed between the point at which the bend starts and the hose fitting.
The Abrasion factor
The external conditions for an application is an important consideration for selection of a hose. Hoses that are exposed to rubbing, get worn on the outer wall into the braiding and the braiding weakens gradually to a point when it cannot contain the pressure resulting in a burst and failure of the hose. Most hoses have a neoprene exterior, however if your hydraulic hoses rub against machinery or materials, against the boom or jib, or an application where the hose can rub back and forth a high abrasion resistant outer is the way to go. Studies have found that external abrasion is one of the leading causes of hose failure.
Media compatibility
Needless to say, hoses, covers, fittings and o-rings (the entire hose assembly) must be compatible with the media being transported. Incompatible media will cause several problems to not only the hose assembly but to the entire system. Refer to the chemical resistance chart of all components of the hose assembly to determine the right hose system, fittings , covers and o-rings.
Pressure ratings
System working pressure as well as surge pressures must be considered and these pressures must be below the rated maximum working pressure of the hose. Again, the maximum working pressure of a system is the lowest rated part or piece of the assembly. For instances, if the hose is rated at a lesser pressure than the fittings, the maximum working pressure of the whole assembly is the working pressure of the hose. Pressure ratings for fittings and hoses can be found in the published engineering specifications.
End fittings selection
For a leak free sealing, the mechanical interfaces between the hose and fittings must match the selected hose with proper mating thread end. These come in two types the field attachable type and the permanent types.
- Field attachable fittings are the clamp type or the screw together type. The screw together fittings consist of a outer shell placed over the outer diameter of the hose and a insert fitting that goes into the inner bore of the hose and is screwed into the outer shell.
- Permanent fittings are used primarily by large scale builders, equipment manufacturers and maintenance shops. These are crimped fittings that are cold-formed onto the hose with machines. Most rubber and thermoplastic hoses are made this way and are very dependable at a relatively low cost. Portable machines produce this on-site and on demand hence are very widely used.
Thread type is also a very important factor when selecting a hose. There are several different types
- German DIN hose fittings
- British Standard Pipe (BSP)
- American NPTF (standard), SAE 37⁰, SAE 45⁰ Flare, SAE O-rings (Boss Type, O-ring Face Seal (ORFS) Flange Fittings and four bolt split flange type
- French Gas Fittings
- Japanese Fittings
Finally after all things considered and selecting the right hoses and fittings, a hose assembly is only as good as the assembler who installs them. Each fitting style and hose has an individual assembly procedure to be strictly followed by the assembler. This can make the vital difference between a safe leak free hydraulic system and an accident waiting to happen.
Call Inflex Hydraulics , your hydraulic hose suppliers in Dubai, to consult on your hydraulic hose requirements and get the right fit for your individual needs.