14
BASIC PARAMETERS APPLICABLE TO
BOTH AIRSTROKE
®
ACTUATORS AND
AIRMOUNT
®
ISOLATORS
MEDIA
Air springs are designed for use with compressed air. Nitrogen
is also acceptable. Air springs may be filled with water or water-
glycol (automotive antifreeze) solutions. If water is to be used,
rust inhibitors should be added to protect the end closures. Two
reasons for liquid filling an air spring are:
1. To reduce the internal volume of air (and therefore,
increase
the natural frequency of the air spring) and,
2. To use a media which is incompressible. Accurate positioning
would be one reason to do this.
Petroleum base fluids (most hydraulic oils fall into this category)
are NOT RECOMMENDED. Moderately lubricated air will not
harm the bellows.
PRESSURE
Our “rule of thumb” is:
1. 100 psig maximum for 2 ply.
2. 175 psig maximum for high strength.
We recommend that there be a minimum three times safety fac-
tor between maximum internal air pressure and burst pressure.
So, as an example, if 100 psig is required, the burst should be at
300 psig or greater. For convoluted air springs, the burst pres-
sure decreases as height increases. Therefore, the determining
factors are twofold: What is the maximum height into extension
and what is the internal pressure at that point? Please see the
Airstroke Inflation Pressure Chart (for single, double, and triple
convoluted air springs) on page 17 for specific pressure vs.
height information.
For AIRMOUNT applications (where the part is used at a
height very close to the shaded area), it is best to stay within
100 psig maximum for a two ply, and 150 psig maximum for a
four ply or high strength cord air spring.
TEMPERATURE
1. STANDARD BELLOWS. Our standard industrial air springs
should be limited to use in the range:
– 35° F to + 135° F.
2. ALL NATURAL RUBBER (LOW TEMPERATURE COM-
POUND). A few of our industrial air springs are available in
all natural rubber construction. This increases the accept-
able cold or low end of the scale to – 65° F. The range then
becomes – 65° F to +135° F.
3. EPICHLOROHYDRIN (HIGH TEMPERATURE COM-
POUND). Most convoluted parts are available in this
material. The operating temperature range for it is: 0° F to
225° F. Additionally, Epichlorohydrin has very good oil resis-
tance. ALL EPICHLOROHYDRIN APPLICATIONS MUST
BE APPROVED BY FIRESTONE. For more information on
Epichlorohydrin (also known as Herclor), ask for
Technigram number 111.
CONTAMINATES
Shielding should be used to protect the bellows from exposure
to hot metal, sand, petroleum base fluids, acids, etc. Please
consult Firestone if you wish to know how the bellows will with-
stand a specific contaminant (For liquids such as acids, it is
important to know both concentration and temperature).
STORAGE
The best storage environment is a dark, dry area at normal
room temperature.
WARNING
DO NOT INFLATE ASSEMBLY WHEN IT IS UNRESTRICTED. ASSEMBLY
MUST BE RESTRICTED BY SUSPENSION OR OTHER ADEQUATE STRUC-
TURE. DO NOT INFLATE BEYOND PRESSURES RECOMMENDED IN
DESIGN LITERATURE (CONTACT FIRESTONE FOR INFORMATION).
IMPROPER USE OR OVERINFLATION MAY CAUSE ASSEMBLY TO
BURST CAUSING PROPERTY DAMAGE OR SEVERE PERSONAL INJURY.
