Page 274 - untitled

Parker Hannifin Corporation

Parflex Division

Ravenna, Ohio

268

Hydraulic &

Pneumatic

Hose & Fit.

PTFE

Hose &

Fittings

Thermoplastic

Tubing

Coiled Air Hose,

Fittings

& Accessories

Truck (Fleet)

Products

Tooling &

Equipment

Hose

Accessories

Technical &

Design

Information

Approvals &

Guides

Alphanumeric

Index

4.6 Electrical Shock –

Electrocution could occur if hose con-

ducts electricity through a person. Most hoses are conductive.

Many contain metal or have metal fittings. Even nonconductive

hoses can be conduits for electricity if they carry conduc-

tive fluids. Be aware of routing or using hose near electrical

sources. When this cannot be avoided, select appropriate

hose. Nonconductive hoses should be

considered. SAE J517–100R7 and 100R8 hoses, with orange

covers marked “Nonconductive” are available for applications

requiring nonconductive hose.

4.7 Mechanisms Controlled by Fluid Power –

Mechanisms

controlled by fluid in hoses can become hazardous when a

hose fails. For example, when a hose bursts, objects

supported by fluid pressure may fall, or vehicles or ma-

chines may lose their brakes or steering. If mechanisms are

controlled by fluid power, consider safe modes of failure that

minimize risks of injury or damage.

5. Hose Selection and Routing –

A wide variety of interacting fac-

tors influence hose service life and the ability of each

fluid-power system to operate satisfactorily, and the combined

effects of these factors on service life are often unpredictable.

Therefore, these documents should not be construed as

design standards. For applications outside the

specifications in SAE J517, SAE J514, or other relevant design

standards, performance of hose assemblies should be

determined by appropriate testing. Carefully analyze each

system. Then design routings and select hose and related com-

ponents to meet the system-performance and hose-

service-life requirements, and to minimize the risks of per-

sonal injury and/or property damage. Consider the following

factors:

5.1 System Pressures –

Excessive pressure can accelerate

hose assembly failure. Analyze the steady-state pressures,

and the frequency and the amplitude of pressure surges, such

as pulses and spikes. These are rapid and transient rises in

pressure which may not be indicated on many

common pressure gauges and can be identified best on

high-frequency-response electronic measuring instruments.

For maximum hose service life, hose selection should be

based on a system pressure, including surges, that is less

than the hose maximum working pressure. Hose may be used

above its maximum working pressure where reduced life

expectancy is acceptable. SAE J1927 provides on method to

help predict wire-reinforced hose service for a given hydraulic

application, where the surge pressure peaks vary, and/or the

highest pressure peaks occur infrequently.

5.2 Suction –

For suction applications, such as inlet flow to

pumps, select hose to withstand both the negative and

positive pressures the system imposes on the hose.

5.3 External Pressure –

In certain applications, such as in

autoclaves or under water, the external environmental

pressures may exceed the fluid pressure inside the hose. In

these applications, consider the external pressures, and, if

necessary, consult the manufacturers.

5.4 Temperature –

Exceeding hose temperature ratings may

significantly reduce hose life. Select hose so the fluid and am-

bient temperatures, both static and transient, fall within the

hose ratings. The effects of external heat sources should not

raise the temperature of the hose above its maximum operat-

ing temperature. Select hose, heat shields, sleeving, and other

methods for these requirements, and route or shield hose to

avoid hose damage from external heat sources.

5.5 Permeation –

Permeation, or effusion, is seepage of fluid

more permeable than others. Consider the effects of

permeation when selecting hose, especially with gaseous

fluids. Consult the hose and fluid manufacturers for

permeability information.

5.6 Hose-Material Compatibility –

Variables that can affect

compatibility of system fluids with hose materials include, but

are not limited to:

A.

Fluid Pressure

B.

Temperature

C.

Concentration

D.

Duration of exposure

Because of permeation (see 5.5), consider compatibility of

system fluids with the hose, tube, cover, reinforcement, and

fittings. Consult the fluid and hose manufacturers for

compatibility information.

NOTE–

Many fluid/elastomer com-

patibility tables in manufacturers’ catalogs show ratings based

on fluids at 21° C, room temperature. These ratings may

change at other temperatures. Carefully read the notes on the

compatibility tables, and if in doubt, consult the

manufacturer.

NOTE–See pages 282-289 for chemical resis-

tance information.

5.7 Environment –

Environmental conditions can cause hose

and fitting degradation. Conditions to evaluate include, but are

not limited to:

A.

Ultraviolet light

B.

Salt water

C.

Air pollutants

D.

Temperature

E.

Ozone

F.

Chemicals

G.

Electricity

H.

Abrasion

If necessary, consult the manufacturers for more information.

5.8 Static-Electric Discharge –

Fluid passing through hose

can generate static electricity resulting in static-electric

discharge. This may create sparks that can puncture hose. If

this potential exists, select hose with sufficient conductivity to

carry the static-electric charge to the ground.

5.9 Sizing –

The power transmitted by pressurized fluid varies

with pressure and rate of flow. Select hose with adequate size

to minimize pressure loss, and to avoid hose damage from

heat generation or excessive velocity. Conduct calculations, or

consult the manufacturers for sizing at flow velocities.

5.10 Unintended Uses –

Hose assemblies are designed for the

internal forces of conducted fluids. Do not pull hose or use it

for purposes that may apply external forces for which the hose

or fittings were not designed.

5.11 Specifications and Standards –

When selecting hose and

fittings for specific applications, refer to applicable govern-

ment, industry, and manufacturer’s specifications and stan-

dards.

5.12 Unusual Applications –

Applications not addressed by

the manufacturer or by industry standards may require spe-

cial testing prior to selecting hose.

5.13 Hose Cleanliness –

The cleanliness requirements of

system components, other than hose, will determine the

cleanliness requirements of the application. Consult the

component manufacturers’ cleanliness information for all

components in the system. Hose assemblies vary in

cleanliness levels; therefore, specify hose assemblies with

adequate cleanliness for the system.

Selection, Installation & Maintenance