Liquid Controls Mechanical Eliminators - Manual (Page 6)

6
InTrodUCTIon
Differential Valve Air Check Valve
Valve Open Valve Closed
lIMITed bleed valve PlaTes
After the air is eliminated and the reed strips pull away
from the vent ports, the air pressure on the back side of
the spring is relieved and the valve opens. To avoid the
system shock sustained by an abruptly opened valve,
the pressure must be released slowly. In order to do this,
a ″ bleed hole has been drilled into one of the valve
plates so that it sits over a bypass port. The small bleed
hole gradually releases the pressure on the valve spring
allowing it to open it slowly.
lIMITed bleed Tee asseMblIes
Some Liquid Controls mechanical air eliminator models
are designed withot bypass ports in their housings (for
example, bulk plant air eliminators). For those models
to retain the functions of a limited bleed valve plate, a
limited bleed tee assembly can be installed in the piping.
Limited Bleed Tee Assembly
Bypass Ports
Vent Ports
Bleed Hole
Valve Plates
Housing
Principles of design
aIr CheCk and dIfferenTIal valves
Air check and differential valves are spring loaded valves
on the outlet side of the meter. Most Liquid Controls
meter systems with an air eliminator also have an air
check or a differential valve. Air eliminators and air
check (or differential) valves work in conjunction to stop
the flow of product through the meter until the air is
eliminated from the system. In order to do this, the air
eliminator and the valve are piped together at installation
Air check (or differential) valves are normally closed,
but when the pump starts and pushes product into
the system, the valve spring will give way to the flow
pressure. In order to keep the valve closed when air is
being expelled from the air eliminator, the air from the air
eliminator is routed through the piping to the back side of
the valve spring. The combined force of the expelled air
and the strength of the spring keep the valve closed until
the air is eliminated.
Bypass ports provide a pathway through the mechanical air
eliminator housing to allow air (or vapor) to pass from one side
of the air eliminator to the other while the valve plate vent ports
are sealed.
Bypass Ports