Damping; Plumbing Systems - Firestone EMDG198 User Manual

AIRMOUNT

DAMPING

Damping is defined as the ratio:
WHERE: C = System Damping
C = Critical Damping
c
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
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
AIR AIR
SPRING SPRING
AIR AIR
SPRING SPRING
AIR AIR
SPRINGS SPRINGS
AIR AIR
SPRINGS SPRINGS
VIBRATION ISOLATION
®
C
C
c
1
/ " NPT tank
4
REGULATORS
TO AIR
SUPPLY
CHECK
VALVES
REGULATORS
TO AIR
SUPPLY
CHECK
VALVES
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 ±
inch. A three point, eight air spring, leveled system is
illustrated below:
LEVELING
VALVE
AIR
SPRING SPRING
AIR
SPRING SPRING
AIR
SPRING SPRING
AIR
SPRING SPRING
LEVELING
VALVE
Firestone supplies height control valves and the accompa-
nying linkages from the valve to the supported system.
Description
Immediate Response Valve
Immediate Response Valve Linkage
Time Delay Valve
Time Delay Valve Linkage
An Airmount Design Parameter Worksheet
can be found on page 105.
AIR
REGULA-
TO AIR
AIR
TORS
SUPPLY
CHECK
AIR
VALVE
AIR
LEVELING
VALVE
Order No.
WC1-358-3597
WC1-358-3594
WC1-358-3599
WC1-358-3598
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