Firestone EMDG198 manual Damping, Plumbing Systems, Description Order No

AIRMOUNT® VIBRATION ISOLATION

DAMPING		C
Damping is defined as the ratio:
		Cc
WHERE:	C = System Damping

Cc = 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

AIR	AIR
SPRING	SPRING	REGULATORS
		TO AIR
		SUPPLY
AIR	AIR	CHECK
SPRING	SPRING	VALVES
AIR	AIR
SPRINGS	SPRINGS
		REGULATORS
		TO AIR
		SUPPLY
		CHECK
AIR	AIR	VALVES
SPRINGS	SPRINGS

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:

LEVELING
VALVE
AIR	AIR
SPRING	SPRING
AIR	AIR	REGULA-	TO AIR
		TORS
			SUPPLY
SPRING	SPRING
AIR	AIR		CHECK
			VALVE
SPRING	SPRING
AIR	AIR
SPRING	SPRING	LEVELING
		VALVE
LEVELING
VALVE

Firestone supplies height control valves and the accompa- nying linkages from the valve to the supported system.

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

An Airmount Design Parameter Worksheet can be found on page 105.

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