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Conditions Affecting Hose Performance
Assuming the correct hose has been selected for the application, hose performance can be adversely affected by many variable conditions. The major ones are:
- Exposure to severe external abuse such as kinking, bending, high end pull, crushing or abrasion.
- Exposure to higher-than-rated working pressures or to high surge pressures.
- Exposure to higher-than-rated temperatures.
- Misapplication or exposure to corrosive liquids or gases outside the range of listed application information.
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1. External abuse - Hoses should be placed where they will not be run over by equipment or subjected to high end pull. Hoses should not be bent below recommended minimum bend radius. This could result in kinking the hose or reducing its pressure resistance. Large diameter hoses also may require additional support to reduce external abuse.
2. Hose and System Pressures - In establishing and determining pressures related to hose and the systems to which they are applied, it is necessary to consider separately the characteristics of the hose and the system.
- The system can have several pressures depending on pressure sources and surges imposed by the operator or mechanical components.
- A given hose has a fixed characteristic with respect to the pressure it can withstand and still give satisfactory life.
3. High Temperatures - The allowable temperature ranges for Industrial Hoses are
established by the manufacturer and should not be exceeded. High temperatures can degrade rubber stocks very quickly rendering the hose no longer serviceable.
4. Misapplication - Failure to follow application information and procedures for selection, installation, care, maintenance and storage of hose may result in the hose's failure to perform properly and may result in damage to property and serious bodily injury.
5. Internal Abrasion - For applications of a highly abrasive nature where the hose makes one or more bends, hose should be rotated
90° periodically to lengthen service life.
The hose manufacturer establishes, through design and testing, the recommended rated working pressure for the hose. It is the responsibility of the user to accurately determine the system pressure. Steady state pressure can be measured readily by gauges. Surges are difficult to measure and may require the use of electronic pressure pickup devices. Also, surge valves depend on so many variables that a series of tests are usually required to obtain a valid set of readings. However, if there are extreme surges in the normal operation, or if there is the likelihood of abnormal operation of the system, the magnitude of these pressures must be determined.
Considering the recommended rated working pressure of the HOSE and the various pressures of the SYSTEM, the hose is matched to the system using proper application engineering principals.
Abstracted from the GoodYear Industrial Hose Catalog
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Basic Hose Construction
Hose has three parts: cover, body or carcass and the tube or lining.
The Cover is the outermost layer of the hose. It protects against wear,
abrasion, cuts, weather and general destruction encountered in normal
service.
The Body or Carcass is the reinforcement supporting structure of the
hose. It can be simple or complex and may be made of cord, yarn, fabric,
wire, or any combination of these.
The Tube or Lining is the innermost element of the hose and is in
contact with the material being carried. Therefore it must be resistant
to the properties of that material.
The Four Basic Methods Of Hose Construction
Although there are thousands of types of hose for specialized applications, there are only 4 basic construction methods used. Since each of these 4 methods embodies certain fundamental characteristics that make it particularly suitable for certain functions, an understanding of these methods may assist you in making the best
choice. Keep in mind that a reference to any one of these types of construction will imply all the characteristics and benefits outlined here plus specific features attained through the proper compounding of rubber, choice materials, and variation in plies and thickness to ensure that each hose is exactly right for the job it is designed for.
TYPE I: Vertical Braided Hose
Entire hose length cured in one operation.
A. Extruded seamless tube.
B. Seamless reinforcing braids of synthetic textile wire, or other material- applied by high speed vertical or horizontal braiders.
C. Rubber layers between braids establish positive bond between braids when vulcanized.
D. Extruded seamless cover.
Braided Hose Advantages
Extremely flexible. High resistance to kinking. Cover either smooth or wrapped.
Available in long continuous lengths. Very economical process because of continuous
production methods.
TYPE 2: Spiral Hose
Built by machine with either textile or wire cord reinforcement applied so that each ply is laid at a given angle for maximum dimensional stability.
A. Extruded or calendered tube.
B. Reinforcement of synthetic textile wire or other material
C. Rubber layers between reinforcement plies to establish positive bond
D. Cover
Spiral Hose Advantages
Extremely flexible. Resistant to kinking. Smooth bore, uniform tube. High strength with long length capability.
TYPE 3: Hand Built Spiraled Ply Hose
Built by hand on a mandrel. Cured under pressure applied from outside by cloth
wraps and steam.
A. Calendered, or "built-up" tube to fit service.
B. Tailor-made spiral wrapped fabric.
C. Wire reinforcement where needed
D. Cover stock of selected gauge and compound. Wrap cured
Hand Built Spiraled Ply Hose Advantages
Craftsman-built to special requirements. Wide variation in sizes, constructions, and materials. Built-in strength to fit most rugged job requirements. Couplings, fittings, nipples, flanges and beaded ends can be built in. Available in lengths up to 50 feet, in sizes up to 18 inches. On larger diameters, consult your Goodyear representative.
TYPE 4: Knitted Hose
A. Extruded seamless tube.
B. Seamless woven textile jacket.
C. Interwoven wire helix reinforcement where needed
D. Extruded seamless cover
Knitted Hose Advantages
Flexible and lightweight. Highly crush resistant. No length changes under pressure.
Resistant to kink, assuring continuous full flow.
Abstracted from the GoodYear Industrial Hose Catalog
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