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The work truck industry often takes common knowledge for granted. In this article, we will review types of hydraulic hose, easy ways to understand laylines, and what different hydraulic hose ratings mean.
The main purpose of hydraulic hose is to allow fluid movement&#;in this case, hydraulic oil&#;between two port locations in a hydraulic system. Oftentimes, as an added benefit, hydraulic hose absorbs vibration and noise.
Parts of a hydraulic hose
Inner tube
- Typically flexible
- Allows the transfer of fluid
Reinforcement layer
- Three types: braided, spiral, and helical (typically for suction/vacuum)
Outer layer
- Designed to withstand harsh weather conditions, abrasions, or chemicals
Understanding laylines
The information printed on the length of the hydraulic hose is known as the hose layline. This information includes the manufacturer and/or brand, hose series, construction standard(s), internal diameter, maximum working pressure, and any additional approvals.
How are hydraulic hoses classified by pressure ratings?
Hydraulic hoses can be classified by the pressure they are designed under normal operating conditions: low pressure, medium pressure, and high pressure. Hoses can also be classified by construction/reinforcement type, temperature range, and other performance characteristics.
- Low pressure: Below 250 PSI and most commonly with textile/fabric braid reinforcement
- Medium pressure: Up to 3,000 PSI and most commonly with wire braid reinforcement
- High pressure: 3,000&#;6,000 PSI with a mix of wire braid and spiral braid reinforcement
Reinforcement types for hydraulic hose
BRAIDED
The braided wire has a crisscross pattern that allows flexibility (these wires sit on top of each other). This type of overlapping braiding of the wire allows for flexibility to make tight bends and significantly improves burst resistance.
Braided hose is the most popular type of hydraulic hose and is available in a variety of sizes and pressure ratings. It is typically designed for medium to high pressures. Applications such as dump trucks, log splitters, snow plows, and farm equipment commonly use braided hoses. However, it is not ideal for high-impulse applications, like rock crushers, where there are severe vibrations that can cause the braids to stretch and separate.
Type
Description
Muncie Power's offering
1-wire
- Less common than 2-wire hose
- Used in lower-pressure hydraulic systems
2-wire
- Most common braided hose
- Used in medium-pressure hydraulic systems
3-wire
- Speciality braided hose
- Used in medium- to high-pressure hydraulic systems
- Offers the working pressure of a 4-wire spiral hose in a more flexible, lighter-weight hose
Textile (1- or 2-wire)
- Used in low-pressure hydraulic systems
SPIRAL
Spiral hose is considered a heavier-duty and stronger hose. It is typically suitable for high-pressure applications as compared to a braided hose. Applications such as mining equipment, earthmovers, oil and gas, and some cranes commonly use spiral hose. This hose also works well with high-impulse applications. The spiral wires are parallel to each other and wound around the hose (these wires appear more layered or stacked evenly on top of each other).
Type
Description
Muncie Power's offering
4-wire
- Typically used in heavy equipment requiring very high pressure (4,000&#;6,000 PSI)
- Good at handling impulse
6-wire
- Typically used in heavy equipment and high-pressure applications where a larger diameter hose is required (up to 6,000 PSI)
HELICAL
A helical hose is an embedded helically-coiled wire between multiple layers of braided wire or textile reinforcement to prevent the hose from collapsing.
Type
Description
Muncie Power's offering
Helical
- Typically used for vacuum and suction applications
- Used as an inlet hose on all types of hydraulic systems
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Inner Diameter Measurement
The inner diameter (I.D.) is measured in inches. The range is typically 1/4"&#;2" I.D. for hydraulic hoses.
How to select the best hydraulic hose for your work
A common industry acronym, STAMPED, is used to help determine the best hydraulic hose for your application.
Why UPVC Pipes Are Ideal for Underground ApplicationSize
This is the inside diameter of the hose, although the outside diameter is also needed when working within a confined space.
Questions to consider: What is the inner diameter (I.D.)? What is the outer diameter (O.D.)? What is the required length?
Temperature
It&#;s important to know that the chosen hose will withstand the highest temperatures it will be expected to withstand.
Questions to consider: What are the temperatures of the fluid? What are the surrounding temperatures?
Application
This is the application and environment in which the hose will be used.
Questions to consider: What kind of an application? Will the connection points be rotated, dragged, or experience excessive vibrations?
Material
The kind of fluid will be running through the hose.
Questions to consider: What kind of material is transferred? Is it compatible with the tube of the hose?
Pressure
It&#;s critical to know the maximum required pressure as well as the safety rating to understand the burst rating of the hose.
Questions to consider: What is the maximum system pressure? Is this a pressure or vacuum application? Are there pressure spikes?
Ends
It&#;s necessary to know the types of ends that will go on the hose, including the thread style and the material.
Questions to consider: What should you look for to ensure quick connect fitment and compatibility (i.e., male or female, angled or straight, JIC thread, metric, etc.)?
Delivery
This is the delivery requirements for the hose.
Questions to consider: Delivery time from the manufacturer? Testing, quality, packaging, etc.
Standards for hydraulic hose
In North America, the typical hydraulic hose standards we use are set by the Society of Automotive Engineers (SAE). Muncie Power Products provides a series of hydraulic hose standards in the 100R Series, defined under SAE Standard J517.
In Europe, there are two main standards: the International Standards Organization (ISO) and the European Norm/Standard (EN). These ISO and EN standards are also growing in popularity in North America.
If you have additional questions, please call our customer service team at 844-745-.
Figure 3. Shown are the relative lengths of unwound strands from a hose construction using a 10-in. fitting-to-fitting length.
Equal load sharing requires equal reinforcement length among all ligaments, and a single-layer reinforcement construction loads to the neutral angle because the internal forces drive the ligaments to that point. So, shouldn&#;t the same rule apply to multiple-layer reinforced hose assemblies? To find the answer, Figure 3 graphs the lengths of unwound ligaments applied to a hose construction with pitch angles of 53°, 56°, and neutral angle of 54° 44&#;. The 56° ligament is about 1¼-in. longer than the 53° strand. The longer strand supports about 93% as much of the load as the shorter strand based on the calculated strain. Based on spring-rate and original ligament length, the inside layer &#; at a 53° pitch angle &#; must carry more hydrostatic pressure load than the ligaments in the outside layer.
But what if the inside strands swell as the layer moves toward the neutral angle? This phenomenon is stipulated by the force balance presented by Colin Evans in Hose Technology. It happens in a single-layer design, whereby the fittings move toward one another as the reinforcement applied at 53° moves toward the neutral angle. The question is whether the same thing will occur in a multi-layer construction.
The inner layer will carry a larger load because it has a stiffer spring rate. Furthermore, it will swell as the braid angle moves to the neutral angle (the inner ligaments will elongate some &#;L from the hydraulic forces). However, the ligaments in the outer layer will not elongate to carry load. Why not? The inner braid responds to the hydrostatic forces, so the braid angle of 53° is compelled to move toward the neutral angle. Thus, the hose segment between the fittings shortens from 10 to about 9.83 in.
So, what happens at the outer braid? Ligaments in the 56° layer are 17.88-in. long, but they can only provide reinforcement if they are strained. However, the distance between the fittings has shortened by about 0.17 in., because the reinforcement on the inside layer has moved toward the neutral angle. The resulting braid angle for the outer layer rotates to about 56.6° &#; and may compress! The braid angle for the upper layer rotates and, in the absence of friction, the strands may not share any load because they&#;re not being strained.
The load-sharing arrangement becomes less effective as the pitch angle difference increases between the upper and lower layers. The staggered braid angle geometry multilayer reinforcement solution fails as a solution because the short strands carry the majority &#; and possibly all &#; of the load.
Optimal multi-layer construction
All internal and reinforcement forces are balanced when the ligaments come to rest at the neutral angle. The internal forces cause the reinforcement ligaments to elongate in proportion to the strands&#; spring rate. Equal load sharing is achieved when all ligament lengths are the same because the strain is uniform. Figure 3, again, shows the relationship between the pitch or braid angle and the ligament helix length based on a 10-in. fitting-to-fitting length. When all ligaments are applied at the neutral angle &#; whether there are one or 10 reinforcement layers &#; each will have a helix length of 17.32 in. for a 10-in. base length between fittings. The ligament length stays the same regardless of its location within a multi-layer construction, as long as it&#;s applied at the same pitch angle.
Because ligament length governs load sharing, it&#;s critical for all ligaments to be applied at the same braid angle to ensure they&#;re all the same length. The challenge is to make the same ligament length throughout the construction. The control strategy behind the manufacturing process is the key to optimizing hose construction.
Summarizing important points
In conclusion, the ligaments resist the hydrostatic forces by tension. The ligaments align themselves against those forces by seeking the neutral angle. All reinforcement ligaments are springs and have a spring rate expressed by its tension versus elongation ratio. The spring rate leads to the critical design and manufacturing factor &#; the overall ligament length as determined by the measurement from one fitting to the other. Equal load sharing requires that all of the reinforcement ligaments be applied symmetrically to ensure all are as close to the same length as manufacturing tolerances allow.
Peter Stroempl is principal engineer at Fluid Routing Solutions Inc., Lexington, Tenn. He can be reached at [ protected].
Contact us to discuss your requirements of sae 100 r15. Our experienced sales team can help you identify the options that best suit your needs.
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