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GENERAL
A number of hose specifications have been developed for specific
applications in industrial, agricultural or public service. These
specifications are based on successful performance of the hose
in the field as reported by consumers, manufacturers and
governmental agencies.
These may be used as procurement specifications or performance
standards when the application agrees with the scope of the
hose specification. The RMA has published a number of hose
specifications which are recommended for use.
Often, additional or new requirements may be imposed on hose
because of the severity of service conditions, a change in service
conditions, a change in the materials handled or in the method of
handling, or the development of new uses or procedures. Hose
specifications must then be prepared with the supplier and be
based on all conditions affecting the expected service and
performance of the hose. Generally, a hose manufacturer may
have types of hose or can devise new ones which may meet
other requirements than those covered by published standards.
For best performance, a hose should be selected to meet the
service conditions under which it is to be used. Before deciding
on size, type, and quality of hose, complete information on the
actual service requirements should be examined.
HOSE AND COUPLING SELECTION GUIDE
SERVICE CONSIDERATIONS FOR HOSE IN
CRITICAL APPLICATIONS
Hose is often used in locations and/or to convey materials where
property damage or human injury could occur if the hose and/or
associate fittings failed while in service.
The user must insure that the service conditions are known to
himself and to the hose supplier. The improper use of hose or the
use of a hose for service applications for which it was not designed
may result in serious consequences.
Some examples of improper uses of hoses include the following:
water hose should not be used for chemicals or solvents; low
pressure hose should not be used for high pressure service; only
steam hose should be used for steam service; hose for conveying
mild chemicals should not be used for strong or concentrated acids
which require special types of hose. Temperatures in or around
the hose should be known so as not to exceed supplier’s
recommendations, etc.
INFORMATION NEEDED
Hose Dimensions
(a) I.D.
(b) O.D.
(c) Length (state whether overall length or length
excluding couplings)
(d) Tolerance limitations (if normal RMA tolerances
cannot be used)
Types of Service
(a) Material to be conveyed through hose
1. Chemical name
2. Concentration
3. Temperature extremes (low and high)
4. Solids, description and size
(b) Working pressure (including surge)
(c) Suction or vacuum requirements
(d) Velocity
(e) Flow Rate
Operating Conditions
(a) Intermittent or continuous service
(b) Indoor and outdoor use
(c) Movement and geometry of use
(d) Flexibility – Minimum bend radius
(e) External conditions
1. Abrasion
2. Oil (Specify type)
3. Solvents (Specify type)
4. Acid (Specify type and concentration)
5. Temperature Range
Normal
Highest
Lowest
6. Ozone
800/543-8070 Fax 800/423-4354 www.hbdthermoid.com
GENERAL INFORMATION
32
Product information is subject to change. For full details, visit our website or contact Customer Service.
R L N OR
O
DESIGN CONSIDERATIONS
In designing hose, it is customary to develop a design ratio, which
is a ratio between the minimum burst and the maximum working
pressure.
Burst test data is compiled and the minimum value is established
by accepted statistical techniques. This is done as a check on
theoretical calculations, based on the strength of reinforcing
materials and on the characteristics of the method of fabrication.
Minimum burst values are used as one factor in the establishment
of a reasonable and safe maximum working pressure.
MAXIMUM WORKING PRESSURE IS ONE OF THE ESSENTIAL
OPERATING CHARACTERISTICS THAT A HOSE USER MUST
KNOW AND RESPECT TO ASSURE SATISFACTORY SERVICE
AND OPTIMUM LIFE.
It should be noted that design ratios are dependent on more than
the minimum burst. The hose technologist must anticipate natural
decay in strength of reinforcing materials, and the accelerated
decay induced by the anticipated environments in which the hose
will be used and the dynamic situations that a hose might likely
encounter in service.
Including all considerations, the following recommended design
ratios are given for newly manufactured hose:
1. Water Hose up to 150 psi WP: 3:1
2. Hose for all other liquids, solid materials
suspended in liquids or air, and water hose over
150 psi WP: 4:1
3. Hose for compressed air and other gases: 4:1
4. Hose for liquid media that immediately changes
into gas under standard atmospheric conditions: 5:1
5. Steam Hose: 10:1
* Reprinted with permission from the Rubber Manufacturers Association (RMA)
Hose Handbook, RMA/IP-2/2003.