Page 57 - Alfagomma-Industrial-Rubber-Catalog-Revised-1-28-10

KRHCA0109 57
Care, Maintenance & Storage
Technical Data
Flexibility & Bend Radius
Flexibility and minimum bend radius are important factors in hose design
and selection if it is known that the hose will be subjected to sharp curva-
tures in normal use. When bent at too sharp an angle, hose may kink or fat-
ten in the cross-section. The reinforcement may also be unduly stressed or
distorted and the hose life thereby shortened.
Adequate fexibility means the hose should be able to conform to the
smallest anticipated bend radius without over stress. The minimum bend
radius is generally specifed for each hose in this catalog. This is the radius
to which the hose can be bent in service without damage or appreciably
shortening its life. The radius is measured to the inside of the curvature.
Formula to determine minimum hose length given bend radius and
degree of bend required:
Where:
L = Minimum length of hose to make bend (Bend must be made equally
along this portion of hose length).
A = Angle of bend
B = Given bend radius of hose
= 3.14
Example: To make a 60° bend at the hoses’s rated minimum bend radius of
15 cm:
Thus, the bend must be made over approximately 16 cm of hose length. The
bend radius used must be equal to or greater than the rated minimum bend
radius. Bending the hose to a smaller bend radius than minimum may kink
the hose and the result in damage and early failure.
Oil Resistance
The defnition of Oil Resistance is currently related to Tensile Retention %
and Volume Swell % of the tested material after immersion in ASTM No. 3 Oil
and in ASTM Fuel B for 70 hours at 100°C (212°F). The hose industry is cur-
rently classifying the materials as follows:
Safety Features
Air hose — 4:1 Safety factor. Burst vs Working pressure
Water hose — 3:1 Safety factor. Burst vs Working pressure
Steam hose — 10:1 Safety factor. Burst vs Working pressure
(Reprinted from RMA Hose Handbook 1 P-2 - Fourth Edition)
Hose has a limited life and the user must be alert to signs of impending
failure, particularly when the conditions of service include high working
pressures and/or the conveyance or containment of hazardous materials,
GENERAL CARE
AND MAINTENANCE OF HOSE
Hose should not be subjected to any form of abuse in service. It should be
handled with reasonable care. Hoses should not be dragged over sharp or
abrasive surfaces unless specifcally designed for such service. Care should
be taken to protect hose from severe end loads for which the hose or hose
assembly were not designed. Hose should be used at or below its rated
working pressure; any changes in pressure should be made gradually so
as to not subject the hose to excessive surge pressures. Hose should not
be kinked or be run over by equipment. In handling large size hose, dollies
should be used whenever possible; slings or handling rigs, properly placed,
should be used to support heavy hose used in oil suction and discharge
service.
STORAGE
Rubber hose products in storage can be affected adversely by temperature,
humidity, ozone, sunlight, oils, solvents, corrosive liquids and fumes, insects,
rodents and radioactive materials.
The appropriate method for storing hose depends to a great extent on its
size (diameter and length), the quantity to be stored, and the way in which it
is packaged. Hose should not be piled or stacked to such an extent that the
weight of the stack creates distortions on the lengths stored at the bottom.
Since hose products vary considerably in size, weight, and length, it is not
practical to establish defnite recommendations on this point. Hose having
a very light wall will not support as much load as could a hose having a
heavier wall or hose having a wire reinforcement. Hose which is shipped in
coils or bales should be stored so that the coils are in a horizontal plane.
Whenever feasible, rubber hose products should be stored in their original
shipping containers, especially when such containers are wooden crates or
cardboard cartons which provide some protection against the deteriorating
effects of oils, solvents, and corrosive liquids; shipping containers also afford
some protection against ozone and sunlight.
Certain rodents and insects will damage rubber hose products, and ad-
equate protection from them should be provided.
The ideal temperature for the storage of rubber products ranges from 50° to
70°F (10-20°C) with a maximum limit of 100°F (38°C). If stored below 32°F
(0°C), some rubber products become stiff and would require warming before
being placed in service. Rubber products should not be stored near sources
of heat, such as radiators, base heaters, etc., nor should they be stored un-
der conditions of high or low humidity.
To avoid the adverse effects of high ozone concentration, rubber hose
products should not be stored near electrical equipment that may generate
ozone or be stored for any lengthy period in geographical areas of known
high ozone concentration. Exposure to direct or refected sunlight — even
through windows — should also be avoided. Uncovered hose should not
be stored under fuorescent or mercury lamps which generate light waves
harmful to rubber.
Storage areas should be relatively cool and dark, and free of dampness and
mildew. Items should be stored on a frst-in, frst-out basis, since even under
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