25
AIRMOUNT
®
VIBRATION ISOLATION
DAMPING
Damping is defined as the ratio:
WHERE:
C = System Damping
C
c
= Critical Damping
The damping ratio inherent in an Airmount is in the order of
.03. This damping number is so small that the formulas pre-
sented in this section assume it to be zero.
PLUMBING SYSTEMS
There are three basic ways of controlling an air suspended
isolation system:
1. With a TANK VALVE in each Airmount. Each air spring is
then inflated individually. The pressure in each must be
checked periodically, because air will permeate through
the bellows.
For an idea of the permeation rate, a #116 will lose approxi-
mately 30 psig over a period of one year (from 100 psig to
70 psig). Please see page 7 for a picture of a
1
/
4
" NPT tank
valve.
2. Three Point Regulated System The Airmounts can be
connected directly to the factory compressed air system
using pressure regulating valves. This eliminates the
need for periodic inspections. The air springs should always
be connected in clusters so the mass is supported with only
THREE REGULATORS. This is illustrated below (in the
previous column) for both a four and eight Airmount system:
3. Three Point Leveled System Height control can be pro-
vided by adding height control valves to the system.
Again, there should be only THREE POINTS OF CON-
TROL, or in this case, three leveling valves. Attempting
to use more than three control points often results in the
valves hunting or fighting one another. There are sensing
systems available to control heights within ±.001 inch.
Truck type leveling valves can provide accuracy to ±
1
/
16
inch. A three point, eight air spring, leveled system is
illustrated below:
Firestone supplies height control valves and the accompa-
nying linkages from the valve to the supported system.
An Airmount Design Parameter Worksheet
can be found on page 105.
C
C
c
AIR
SPRING
AIR
SPRING
AIR
SPRING
AIR
SPRING
AIR
SPRING
AIR
SPRING
AIR
SPRING
AIR
SPRING
AIR
SPRING
AIR
SPRING
TO AIR
SUPPLY
TO AIR
SUPPLY
CHECK
VALVE
LEVELING
VALVE
LEVELING
VALVE
LEVELING
VALVE
TO AIR
SUPPLY
REGULATORS
REGULA-
TORS
REGULATORS
AIR
SPRING
AIR
SPRING
AIR
SPRINGS
AIR
SPRINGS
AIR
SPRINGS
AIR
SPRINGS
CHECK
VALVES
CHECK
VALVES
Description
Order No.
Immediate Response Valve
WC1-358-3597
Immediate Response Valve Linkage
WC1-358-3594
Time Delay Valve
WC1-358-3599
Time Delay Valve Linkage
WC1-358-3598
