Hose (tubing)

Hose means a flexible line to promote solid, liquid and gaseous materials. A hose provided with couplings, which is referred to as a hose line; it can also be a compression fitting can be used.

Use

In almost all areas of daily life and technology Hoses are to be found in many variations. They are stronger than hose lines to transport liquid and gaseous substances, where pipelines for physical or economic reasons can not be used, for example on mobile source and target locations where access is difficult or when pipes were too difficult or too expensive. Even as a protective sheathing or insulation tubes find application. Especially in ancient times used to hoses also for storing liquids.

A tube having specified dimensions, shapes and bends, which is provided as a component for a particular device is called tube form.

Similar as in pipes are used for hoses dimensions to specify the inside diameter. For historical reasons are to do frequently encountered Dimensions in inches, for example, " ½ -inch hose ." The standardization of diameters was carried out in the first half of the 18th century during the Industrial Revolution particularly in England, which related the inch scale. It was not until 1875, major European countries agreed to the Metre Convention. As with screen sizes and vehicle tires, the customs is colloquially still widespread even in hose size. Correctly specifying the nominal width according to EN ISO 6708 by the name of DN ( nominal diameter engl. ) is followed by a, about the inner diameter in millimeters corresponding dimensionless number. For household use ( garden hose, etc.), it is sufficiently accurate to assume that DN number as an approximate measure in millimeters.

In addition, the inner diameter may be provided for each tube and the outer diameter (OD = Outside Diameter ), the wall thickness and length. The designation DN 6-15 can mean, for example, that the tube has a nominal diameter ( inside diameter ) of 6 ( about 6 mm ) and a length of 15 meters.

Materials

Hoses can be manufactured from it depending on the use of different materials and combinations:

• Natural rubber ( rubber)
• Synthetic rubbers (such as EPDM, NBR, SBR)
• Plastics (eg PVC, PUR - polyurethane, PA - polyamide, PE - polyethylene, silicones)
• Glass fibers
• Metals (note: pure metal tubes are sometimes called flexible tubes called )
• Plant fibers
• Animal raw materials
• Technical fabrics

Production

Hoses can be produced in many different ways.

• Extrusion

There are basically different methods to extrude tubing.

At the one hand, the tubes are made directly by a tool. From the extruder comes the finished hose. These hoses are smooth inside and outside usually. One speaks of smooth tubes. Pneumatic hoses are produced, for example, in this manner, however, many plastic films, which are first produced as Blasfolienschläuche and then longitudinally sliced ​​to the sheet. Many hoses thus produced are reinforced with a fabric leg position.

In another technique, the complete tube is not extruded, but a continuous profile, which is then wound helically and is welded along the edge. These hoses are inside and outside often more or less wavy, depending on the profile shape. They are often reinforced by fabric inserts, wire or plastic spiral.

Another way of manufacturing hose, the extrusion onto a mandrel. This can be a flexible plastic mandrel or a rigid metal mandrel. In the production on a metal mandrel one is limited in the length of the tube to be produced, since such a spike also has to be removed. In the manufacture by means of flexible spikes greater lengths are possible. The removal of the mandrels is then the final step to manufacture. In some areas of these mandrels are also inserted after the extrusion. In addition, the pins limit the inner diameter of the tube.

• Weld together

In plastic tubes, the welding is usually a step in the production. Extruded tubes in the extruded profile is welded into a tube, see above. In film tubes prefabricated plastic films already be wound up (width in the centimeter range ) helical and lap-welded. Most of these hoses are reinforced with a steel or plastic helix.

• Vulcanization

One or more layers of material are vulcanized to form a tube here. The tubes are made of a core ( inner layer ) with the required properties, a carrier material above and another layer on the outside as mechanical protection. Depending on the requirements and structure of the composition may vary widely. By suitable materials so you can make hoses for almost all claims. The tubes are usually only wrapped on a mandrel and then cured. Subsequently, the mandrel is removed again. Vulcanizing may be necessary for single ply products but also if the selected material has to be crosslinked in order to obtain defined properties or resistance.

• Stitch up

The materials are helically or sewn longitudinally to form a tube.

• Jam

Most thin endless fabric strips are clamped in a U-shaped metal helically to form a tube. The U-profile is also referred to as a clamping profile. Hence the term clamping profile hose or CP- hose (clamp profiles).

• Wrap

It can be wound on a mandrel a plurality of layers of material. By overlapping and combination of layers of material and jamming this at the ends is obtained after removal of the mandrel a hose.

Application Examples

Even in ancient stocks were stored in flexible containers, of leather or animal casings, which were called hoses. Some common modern applications:

Also in the car and other vehicles are tubes in many places indispensable. Examples:

• Tubular
• Washer
• Air Intake Hose
• Cooling water hose
• Power Steering
• Brake Hose, See also: Braided Hose
• Harness
• Air preheating
• Heating
• Motor control ( under-and over -pressure hoses )

Physics

Hoses are exposed to multiple mechanical, and thermal, chemical and electrical stresses often. In hydraulic systems ( including the brake system in a car part ) transferred to high pressures, in Feuerwehrsaugschläuchen is strong negative pressure. Coolant hoses are loaded by pulsating pressure fluctuations, temperatures above 100 ° C and chemical additives, oil and hydraulic hoses through aggressive constituents of the oils. Air intake hoses to cool down heavily at high flow velocities. When used in pneumatic conveying hoses must withstand heavy wear.

In all these burdens hoses must remain flexible, may not contract or expand, not brittle or soften and must be resistant to chemical influences.

The diameter of the tube affects only the flow rate; not printing. The latter decreases with running medium with increasing length of the tube.

Mathematics

Topologically hoses are hollow cylinders, no matter how they are arranged or pre-formed or which cross-sectional shape they have. Air hoses in vehicle tires are from this perspective Tori.

One of the main physical quantities of a tube is the so-called pressure loss. During each feed through a tube caused friction losses that need to be considered in the design.

This friction losses depend on the material to be conveyed, the tube diameter, the conveying speed, the surface condition of the tube wall, and very much on the transfer form. A newly -laid hose produces a significantly lower pressure drop than one which is laid in many bows.

With open on one side hoses to the hose only affects the pressure loss. Then it is almost independent of pressure, the said conveyor device (e.g., a pump) can produce.