Page 307 - GoodyearEPIndustrialHose

APPENDIX c
Air &
Multipurpose
General Purpose
Heavy Duty
Push-on
Chemical
Transfer
Cleaning
Equipment
Food
Transfer
Washdown
Marine
Material
Handling
Abrasives
Bulk Transfer
Cement & Concrete
Mining
Petroleum
Aircraft Fueling
Dispensing
Dock
Transfer
Spray
Steam
Vacuum
Veyance
Water
Discharge
Suction &
Discharge
Washdown
Welding
Coupling
Systems
APPENDIX
305
HOSE TESTING METHODS
GENERAL INFORMATION
Hydrostatic pressure tests (continued):
Percent length change (elongation or contraction) is the difference between the length at 10 psi (0.069 MPa) (except wire
braided or wire spiralled) and that at the proof pressure times 100 divided by the length at 10 psi (0.069 MPa). Elongation
occurs if the length of the hose under the proof pressure is greater than at a pressure of 10 psi (0.069 MPa). Contraction
occurs if the length at the proof pressure is less than at 10 psi (0.069 MPa). In testing wire braided or spiralled hose, the
proof pressure is applied and the length recorded. The pressure is then released and, at the end of 30 seconds, the length is
measured; the measurement obtained is termed the “original length.”
c. Percent change in outside diameter or circumference is the difference between the outside diameter or circumference at
10 psi (0.069 MPa) and that obtained under the proof pressure times 100 divided by the outside diameter or circumference
at 10 psi (0.069 MPa). Expansion occurs if the measurement at the proof pressure is greater than at 10 psi (0.069 MPa).
Contraction occurs if the measurement at the proof pressure is less than at 10 psi (0.069 MPa).
d. Warp is the deviation from a straight line drawn from fitting to fitting; the maximum deviation from this line is warp. First, a
measurement is taken at 10 psi (0.069 MPa) and then again at the proof pressure. The difference between the two, in inches,
is the warp. Normally this is a feature measured on woven jacket fire hose only.
e. Rise is a measure of the height a hose rises from the surface of the test table while under pressure. The difference between
the rise at 10 psi (0.069 MPa) and at the proof pressure is reported to the nearest 0.25 inch (6.4 mm). Normally, this is a
feature measured on woven jacket fire hose only.
f. Twist is a rotation of the free end of the hose while under pressure. A first reading is taken at 10 psi (0.069 MPa) and a
second reading at proof pressure. The difference, in degrees, between the 10 psi (0.069 MPa) base and that at the proof
pressure is the twist. Twist is reported as right twist (to tighten couplings) or left twist. Standing at the pressure inlet and
looking toward the free end of a hose, a clockwise turning is right twist and counterclockwise is left twist.
g. Kink test is a measure of the ability of woven jacket hose to withstand a momentary pressure while the hose is bent back
sharply on itself at a point approximately 18 inches (457 mm) from one end. Test is made at pressures ranging from 62%
of the proof pressure on sizes 3 inches (76 mm) and 3.5 inches (89 mm) to 87% on sizes under 3 inches (76 mm). This is a
test applied to woven jacket fire hose only.
h. Volumetric expansion test is applicable only to specific types of hose, such as hydraulic or power steering hose, and is a
measure of its volumetric expansion under ranges of internal pressure.
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