Before you spec your hoses, ?STAMP? them!

Parker Hannilin uses a system of measurement called Dash Numbers to indicate hose and fitting size. The Dash Number, or Dash Size, is the measure of a hose?s Inner Diameter (ID) in sixteenths of an inch.

This measuring system of the inside diameter of the hose is universallyused by the fluid power industry today. Don?t know the hose size? Check the layline. If the original printing has worn off, the original hose must be cut and the inside diameter measured. Be sure to measure the overall assembly length and fitting orientation before cutting the hose.

The hose ID must be sized accurately to obtain the proper flow velocity. A flow that is too slow results in sluggish system performance, while a flow that is too high causes excessive pressure drops, system damage, and leaks.

When specifying the hose, there are two temperatures you need to identify. One is the ambient temperature, which is the temperature that exists outside the hose where it is being used; the other is the media temperature, which is the temperature of the media conveyed through the hose.

Very high or low ambient temperatures can have adverse affects on the hose cover and reinforcement materials, resulting in reduced service life.

Media temperatures can have a much greater impact on hose life. For example, rubber loses flexibility if operated at high temperatures for extended periods.

Parker hoses carry different temperature ratings for different fluids. For example, the 811HT hose has a temperature range of -40?C to 125?C for petroleum-based hydraulic fluids. However for water, water/glycol, and water/oil emulsion hydraulic fluids, the range drops to a rating of up to 85?C. Air is rated even lower at up to 70?C.

Some media can increase or decrease the effects of temperature on the hose. The maximum rated temperature of a hose is specific to the media.

Before selecting a hose, it is important to consider how the hose assembly will be used.

Answering the following questions may help:
? What type of equipment is involved?
? What are the environmental factors?
? Are mechanical loads applied to the assembly?
? Will the routing be confined?
? What about hose fittings – permanent or field attachable?
? Will the assembly be subjected to abrasion?

Sometimes specific applications require specific hoses. For example, the family of abrasion-resistant hoses would best handle applications where hoses will encounter rubbing or abrasive surfaces with both Tough and Super Tough covers.

When application space is tight, bend radius is another important consideration. Parker offers a full line of hoses designed for one half SAE bend radius at full SAE-rated pressures. Its compact hoses? increased flexibility and smaller outer diameter allows faster, easier routing in small spaces, reducing both hose length and inventory requirements.

Industry standards set specific requirements concerning construction type, size, tolerances, burst pressure, and impulse cycles of hoses. Parker hydraulic hoses meet or exceed standards such as:
? SAE (Society of Automotive Engineers).
? EN (European Norm).
? DIN (Deutsche Institute fur Normung).
? ISO (International Organisation for Standardisation).

Governmental agencies control additional standards for particular industries such as transportation and shipping. You must select a hose that meets the legal requirements as well as the functional requirements of your application.

What will the hose convey? Some applications require the use of specialised oils or chemicals. Consequently, the hose you order must be compatible with the medium being conveyed. Compatibility must cover not just the inner tube, but the cover, hose fittings, and O-rings as well.

When considering hose pressure, it is important to know both the system working pressure and any surge pressures and spikes.

Hose selection must be made so that the published maximum working pressure of the hose is equal to or greater than the maximum system pressure. Surge pressures or peak transient pressures in the system must be below the published maximum working pressure for the hose.

All Parker hydraulic hoses have passed the industry rated specifications for burst pressure and carry a 4:1 design factor unless otherwise noted. Burst pressure ratings for hose are for manufacturing test purposes only. They are not an indication that the product can be used above the published maximum working pressure.

Care must also be taken when looking at the ?weakest link? of the hose assembly. A hose assembly is rated at the maximum working pressure of the hose and the fitting component. Therefore the maximum working pressure of the hose assembly is the lesser of the rated working pressure of the hose and the end connections used.

Here is an example: An F471TC0101040404-60? hose assembly (which consists of 471TC-4 hose and two 10143-4-4 fittings) would have a maximum working pressure of the lesser of the three components. In this case the fittings have a 12,000 psi rating. The hose has a 5800 psi rating. Therefore the maximum pressure rating of the hose assembly would be 5800 psi.

Source: Parker Hannilin

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