5
Tuffy Liquid Level Control with Pneumatic Switch
1.4
Airline Connections
1. Inlet air should be filtered with a 5 micron or finer filter.
This will extend the life of the valve mechanism.
2. Connect the inlet air line to the
1
⁄
4
" NPT connection for
either air inlet A or air inlet B, depending on the valve
action desired (refer to Figure 3). Inlet air pressure should
be between 0–200 psig. Refer to Figure 1 for location of air
inlets.
3. Connect outlet air line to the
1
⁄
4
" NPT connection on the
bottom of the valve. This air outlet is designated with a
“C”. Refer to Figure 1 for location.
4. If 3-way function is used, attach the exhaust air line to the
appropriate
1
⁄
4
" NPT connection based on valve action
described in Figure 3.
2.0
Reference Information
2.1
Description
Tuffy liquid level switches are designed for horizontal
mounting in a tank or vessel through threaded or flanged
pipe connections. Standard models are equipped with a
three-port/two-position valve actuated by a magnetically
actuated pivoted cam mechanism. This instruction manual
covers Tuffy level controls which have pneumatic switches.
For Tuffy controls with electric switches, please consult
Bulletin 44-607.
2.2
Theory of Operation
At a “low operating level” of liquid in a tank or vessel (refer
to Figure 4), the float moves the magnet upward and into
the field of the switch mechanism magnet. As a result, the
magnets repel causing the pivot arm and valve plunger to
move so that air is allowed to pass from air inlet A to air
outlet C. As liquid level rises, the float moves the magnet
downward until the switch mechanism magnet reverses
position, allowing the valve plunger to move so that air is
allowed to pass from air inlet B to air outlet C (refer to
Figure 5).
For direct acting low level operation, air inlet A is closed off
when liquid level increases. Conversely, for high level opera-
tion, air inlet B is closed off when liquid level recedes.
For reverse acting operation, air inlet A is used for high level
and air inlet B is used for low level. Plug the air inlet that is
not in use to prevent foreign materials from entering.
Figure 3
N.O.—Direct acting: Air supply on switch condition.
N.C.—Reverse acting: Air cut-off on switch condition.
2-Way
2-Way
3-Way
3-Way
Port
N.O.
N.C.
N.O.
N.C.
Diverter Selector
(direct) (reverse) (direct) (reverse)
A
Inlet
Plug
Inlet
Exhaust
Outlet
Outlet
B
Plug
Inlet
Exhaust
Inlet
Outlet
Inlet
C
Outlet
Outlet
Outlet
Outlet
Inlet
Outlet
Float
Tuffy body
(Non-magnetic)
Magnet
Pivot
Falling level
Air inlet (B)
(no air flow)
Air inlet (A)
Air outlet (C)
Pivot arm
Magnet
pivot
Spring
Valve
plunger
Valve body
Float
Pivot
Rising level
Tuffy body
(Non-magnetic)
Air inlet (B)
Air inlet (A)
(no air flow)
Air outlet (C)
Spring
Valve
plunger
Valve body
Magnets
Pivot arm
Magnet
pivot
Figure 4
Low Level Operation—Direct Acting
Figure 5
High Level Operation—Direct Acting
