GILLIG LOW FLOOR, Руководство по обслуживанию

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22
Air System
Double Check Valve
Double check valves are used to
direct a flow of air into a com -
mon line from either of two
sources, whichever is at the
higher pressure. They may be
used for directing airflow for
specific functions or to select
the higher pressure of either of
two sources of air as a supply
source. See Figure 6- 25 for ex-
amples of double check valves.
operation
As air under pressure enters
either end of the double check
valve’s inlet port, the moving
shuttle or disc responds to the
pressure and seals the opposite
port, assuming that it is at a
lower pressure than the other. The air flow continues out the delivery port of the double check valve. The
position of the shuttle or disc will reverse if the pressure levels are reversed. Double check valves are
designed so that the shuttle or disc can never impede the backflow of air in the exhaust mode.
preventive maintenance
Every 100,000 miles, 12 months, or 3,600 operating hours, disassemble, clean and inspect, and inspect
all parts.
operating and leakage test
1. Install an accurate test gauge in the outlet port or in a line from the outlet port.
2. Apply and release air to one inlet port and note that gauge registers application and release.
3. Repeat by applying and releasing air to the other inlet port.
4. Disconnect line from one inlet port.
5. Apply air to other inlet port and coat opposite inlet port with a soap solution. Permissible leakage
is a 1" bubble in 5 seconds.
6. Repeat Steps 4 and 5 with the other inlet ports.
Figure 6-25, Typical Double Check Valves
O-Ring
Cap
Body
Shuttle
Guide
Shuttle
Valve
O-Ring
Cap
Body
Valve
Guide
Valve
Disc
Supply
Supply
Delivery
Delivery
Supply
Supply
Delivery
Delivery