Why Routing is important for Hydraulic Hoses?
-Hydraulic fittings Dubai
Improper Routing remains one of the top reasons for shortened life of a hydraulic hose. There is more to installing and routing a hydraulic hose than just tightening the end connections. Hoses have a finite life, but you can maximise the service life of a hose by following a few routing guidelines prior to the first time installation of a hose.
Correct hose length
Though metal tubing lasts much longer than a hydraulic hose, it is not flexible. Hydraulic hoses come into play whenever you need flexibility as they are designed to transport pressurised fluids even when the hose itself is moving.
For a straight line hydraulic hose installation, the length must be slightly longer than the port to port distance to accommodate the decrease in length with the hose is pressurised, as the diameter of the hose increases to contain the force applied. The length of the hose may decrease as much as 4%. If there is no allowance for this, the end fittings will be tugged at causing a leak or in a worst case scenario, catastrophic failure of the hose. While allowing enough slack is important, increasing the length too much could cause hose abrasion due to rubbing against the machinery components near it.
Contact Inflex Hydraulics to answer your questions on proper hose selection, routing and installation.
The correct bend radius.
Even though hydraulic hoses are flexible, due to its wire reinforcement it’s flexibility is also limited. The minimum bend radius rated and published by the manufacturer determines this limit. Bending the hose in an arc smaller than the minimum bend radius will result in kink in the reinforcement resulting in reduction of life of the hose.
Also, the bend cannot be too close to the end fitting. A basic rule is that the distance of the beginning of the bend of the hose from the end fitting, should be at least twice the outside diameter of the hose. So for a 2” hose, the beginning of the bend should start only after a 4” straight from the end fitting. If you require a bend closer to the end fittings, then a 90° or 45° elbow fitting should be used instead of a straight fitting. This way a smooth flow of the fluid is maintained and prevents the high pressure fluid from crashing into the inner tube and allowing the pressure to regularise before the fluid hits the bend.
Avoiding Hose Twist
Avoiding hose twist will also lengthen the service life of a hose. The lay line (the continuous writing on the side of the hose) must remain parallel along the length of the hose. If the lay line appears like a helix then the hose may have been twisted during installation. This needs to be corrected by loosening the ends, correcting the twist and tightening again using a double wrenching method, making sure the hose is not twisted.
Hoses that move continuously on mobile equipment on more than one planes i.e. if they move front and back, and up and down simultaneously, may cause the hose to twist. If a hose moves up and down only, or only forward and backward, or left to right only, it is considered to be moving in a single dimension. Single dimension movements may not contribute to twist in a hose. However, a combination of movements of left/right, up/down or front/back, known as a compound bend, will result in twisting of the hose and needs to be avoided. Special purpose hoses with higher flexibility may be needed.
Routing and clamping
As discussed in another article, primary cause of hose failure is abrasion, which affects the outside cover, exposing the wire reinforcement to the elements, causing it to rust and deteriorate reducing the life of the hose. Clamping helps keep the hose in place reducing the chances of abrasion. Again for high pressure hoses, the clamps should not be too tight to allow for the shortening movement of the hose due to high pressure. Hoses rubbing against each other can also cause abrasion so each hose needs to be clamped separately if need be.
Future proof installation.
When designing a hydraulic system, ensure that the hoses are installed in a manner that allows for easy and hassle free replacement of hoses is possible.
So finally, here is a “hose routing checklist” as a ready reference.
- Allow adequate slack as hose length shortens by as much as 4% when under pressure.
- Bend radius of the hose should not be lesser than the recommended bend radius of the hose.
- The hose must be kept straight for a distance equal to at least twice the outer diameter, from an end fitting.
- Avoid hose twist by double wrenching during installation. Use the lay line as a guide to determine this.
- Try to limit hose bends to a single plane.
- Use hose clamps to prevent abrasion of hoses
- Ensure a simple, clean and neat future proof installation of hoses.
For more information on proper routing click here…
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