te 71L/71H
High pass or low pass
pneumatic selecting relay
Automatically selects the higher or
lower of two input signals
Mite 73
Snap-acting air signal monitor
Accepts up to four inputs and can
be reset automatically
Mite 74
Snap-acting control relay with
integral 3-way or 2-way valve
Combines a Mite 70 with a
precision 3-way or 2-way valve
Mite 85
Snap-acting 3-way valve
with two trip points
Our most versatile circuitry for
sophisticated applications
Mite Series
70/71/73
74/85 Built to make decisions with
crisp precision cycle after cycle.
Mite Series
70/71/73/74/85
S P E C I F I C A T I O N S M I T E 7 0 , 7 1 , 7 3 , 7 4 , 8 5
Mite 70
Mite 71L/71H
Mite 73
Mite 74
Mite 85
Pressure Rating
100 psig max.
120 psig max.
Temp. Limits
-40F to +180F
Port Sizes
Tapped for 1/4 NPT with 1/8 internal ports
Dimensions
2.5 Dia. x 3.5
3.375 Dia. x 2.5 2.5 Dia. x 4.25 2.5 Dia. x 5
See Drawing
Materials
Aluminum, Plated Steel, Neoprene, Brass and Stainless Steel
Mite 70
Description
Set to trip on either an increasing or decreasing control signal,
the Mite 70 will vent one port to atmosphere while it locks up the
pressure in a second line. The tripped position is then held indefi-
nitely until the control signal is restored and a manual reset
button is pushed. The trip point is adjustable from 1 to 100 psi
with a simple screw stem. The Mite 70 can also be tripped on
demand from a separate remote signal. Use the Mite 70 to open
safety valves in emergency situations, trigger an alarm while
locking up a valve or actuate diaphragm motor valves, air
cylinders or other pneumatic actuators.
M I T E 7 0 O P E R A T I O N
Super Mite 71L/71H
Description
The Super Mite 71 will automatically select the higher or lower of
two pneumatic inputs and pass it downstream while blocking the
other. Capable of almost instantaneous selection, the Super Mite
71 can separate pressure differentials as low as a tenth of a psi.
Although ordered as either high or low pass, the Super Mite 71
can easily be converted in the field from one to the other. The
Super Mite 71 can be relied on to open or close valves when a
signal pressure drops or rises past a determined value. They can
also be used to prevent a valve from opening or closing beyond
a critical point.
M I T E 7 1 H O P E R A T I O N - Selecting High Signal
3.375"
2.5"
.25" NPT
HIGH
LOW
LOW
.25" NPT
HIGH
A
B
C
D
The Dahl Mite series of pneumatic relays are
engineered to switch, lock or vent various ports
based on either an increasing or decreasing
pneumatic signal. Their passive design, as well as
precise, unerring and immediate decision making
abilities make them the ideal solution to critical
safety and emergency process controls found in the
petroleum, chemical, gas-field or pharmaceutical
industries. Their rugged, simple construction
provides uncompromising reliability and long term
performance with either air or gas service.
A
Variable Instrument Air Signal
B
Signal Output (Locks up when tripped)
C
Signal Output (Vents when tripped)
D
Remote Pneumatic Trip A
B
F
C
E
D
A
B
C
G
H
I
D
C
Mite 73
Description
The Mite 73 is similar in design and function to the Mite 70. A
sensitive line monitoring diaphragm and up to four inputs allow
even more versatility. When tripped by either an increasing or
decreasing signal, one input is vented to atmosphere while the
other is locked up. The Mite 73 can be tripped by remote and
is also capable of being reset pneumatically for fully automated
control.
M I T E 7 3 O P E R A T I O N
Mite 74
Description
The Mite 74 combines the Mite 70 control relay with a precision
2-way or 3-way valve in a single compact package. Either an
increasing, decreasing or remote signal can be used to channel
air as needed. The Mite 74 can also be used in combination with
either of the Super Mite 71s so that it will trip when either of two
signals drops or rises beyond a set pressure. Once tripped, the
Mite 74 will hold its settings until the proper control signal is
reestablished and the reset button is pushed.
M I T E 7 4 O P E R A T I O N
Controller Signal
20 psig
Supply
Vent
Valve
Mite 70
D
A
315 psig
Control
Signal
Mite 71H
Mite 71L
Constant
5 psig
Supply
Constant
10 psig Supply
515 psig 510 psig
A
C
B
A
C
B
Mite 71 Low Selector
20 psig
Supply
Mite 74
G
A
H
I
315 psig
Control Signal
315 psig
Control Signal
20 psig
Supply
Mite 73
A
C
E
Gas Line
AirtoOpen V
alve
0 or 20
pisg
T Y P I C A L A P P L I C A T I O N S
Actuate an on-off valve when
controller signal increases to
set point. Supply pressure at A is
transmitted to valve from C when
Mite is operating. When trip occurs,
valve is vented to atmosphere.
Close an on-off valve when
either of 2 signals drops to a
set point. Lower of 2 control
signals is constantly fed to A.
Supply pressure at I is transmitted
to valve H when
Mite is operating. When trip occurs,
valve is vented to atmosphere from
G.
Close an on-off valve in a gas
line when line pressure drops
below a set point. Supply
pressure at A is transmitted to
valve from C when Mite is
operating. When gas line pressure
monitored at Edrops below set
point, trip occurs, and valve
operator is vented to atmosphere.
Set 2 pneumatic pressure limits
(high and low) within the range
of a control signal, i.e., a double
pneumatic stop. Output from
Mite 71H must stay within 5 to 15
psig when connected as shown.
Output from Mite 71L to valve must
stay within 5 to 10 psig.
A
Variable Instrument Air Signal
B
Signal Output (Locks up when tripped)
C
Signal Output (Vents when tripped)
D
Remote Pneumatic Trip
E
Remote Pneumatic Reset
F
Pneumatically Nullifies E
A
Variable Instrument Air Signal
B
Signal Output (Locks up when tripped)
C
Signal Output (Vents when tripped)
D
Remote Pneumatic Trip
G
Trip to Open
H
Common
I
Trip to Close 8 Columbia Drive / Amherst, NH 03031 USA
Website: www.controlair.com
Email: sales@controlair.com
603-886-9400 FAX 603-889-1844
P/N 441-625-049 04/20/07
Mite Series
Ordering
70/71/73/74/85
Information
Mite 85
Description
The Mite 85 allows you to establish two adjustable trip points that control
flow through a 3-way valve. An increasing signal that exceeds the high trip
point will open I port to H. A decreasing signal pressure that drops below
the low trip point will vent port H. This switching action is reversible and
repeatable without having to manually reset. Use the Mite 85 to passively
switch to a secondary controller in case the primary system fails.
Warranty
ControlAir, Inc. products are warranted to be free from defects in materials and
workmanship for a period of eighteen months from the date of sale, provided said
products are used according to ControlAir, Inc. recommended usages. ControlAir,
Inc.s liability is limited to the repair, purchase price refund, or replacement in kind,
at ControlAir, Inc.s sole option, of any products proved defective. ControlAir, Inc.
reserves the right to discontinue manufacture of any products or change products
materials, designs or specifications without notice.
1/4 NPT
typ.
15/32 x 9/32
(11.9 x 7.1)
Mounting holes
typ. 2 places
Shown 90
out of true position
5-9/16
(141.29)
4-11/16
(119.06)
5/32 typ.
(4.00)
11/32
(8.73)
1-23/32
(43.65)
1-1/32
(26.21)
1-3/8
(34.92)
A
B
C
G
H
P
I
2-13/64
(56.00)
1-5/8
(41.30)
7/16
(11.11)
2-9/16
(65.08)
B
A,G
C,H,P
T Y P I C A L A P P L I C A T I O N S
Switching
On failure of primary controller
signal A port, valve will switch
to secondary controller signal
until primary signal is regained.
3-way valve flow paths
There are two flow paths in the 3-way valve; I to H (G blocked)
and G to H (I blocked). Flow can be in either direction (e.g. I to H
or H to I).
As the operator signal increases from the low to the high end of the
span, the flow path is G to H (I blocked). When the high trip
setting is reached, the flow path switches to I to H (G blocked).
As the operator signal decreases from the high to the low end of the
span, the flow path is I to H (G blocked). When the low trip setting
is reached, the flow path switches to G to H (I blocked).
In the dead band (between high and low trip settings), the flow path
can be either, depending on the direction of the operator signal.
A
Operating Signal
B
Supply Adjustment
C
Vent Adjustment
G
Vent
H
Common Outlet
I
Supply
Use this coding system to order
Mite 70 & 73
70-Mite 70
73-Mite 73
Reset Button
Std Normal
Lng Long
Signal
Hi Signal > 50 psi
Lo Signal < 50 psi
Mite 74
Valve
2 way 2-way valve
(
H port locks on trip)
3 way 3-way valve
(
H port vents out G port on trip)
Reset Button
Std Normal
Lng Long
Signal
Hi Signal > 50 psi
Lo Signal < 50 psi
Mite 71 Pressure
Hi
Higher of 2 pressures
Lo
Lower of 2 pressures
Mite 85
Supply
Hi Supply > 50 psi
Lo Supply < 50 psi