Model 25

Pneumatic Transmitters
Model 25 Liquid-Level Controller
Introduction
Features & Benefits
Flexible shaft design has no process-wetted pivots or links
to foul
Actuation motion of 1/32" provides precise measurement
Wide variety of flange sizes and materials simplify
mounting
Standard process wetted parts are 316SS, improving
corrosion resistance
Description
The Model 25 Liquid-Level Controller consists of a float
mounted on a short float arm connected to the free-end of a
packless flexible shaft. The fixed-end of this flexible shaft is
attached to a standard flange.
The tubular shaft has a formed center section (similar to a
bourdon tube in cross section), which permits only vertical
float motion. The rigid float arm extension within the shaft
transmits the float motion to the air pilot for operation of a
diaphragm-type motor control valve.
The Model 25 Liquid-Level Controller operates on the change
in buoyant force of the float-not the motion of the float riding
on a changing liquid level. A buoyancy change of less
than six ounces will provide full actuation of the pilot valve or
contact switch. The Model 25 also has limit stops to
maintain the shafts within the elastic limit.
A wide range of specific gravities and level-change
requirements can be accommodated via elliptical, cylindrical,
and other special floats.
These units can be mounted on the direct side of a vessel
flange or externally mounted in a float chamber. Standard
piping connections on the float chamber are 1" NPT.
Specifications
Pressure
Full vacuum to flange rating
Temperature
Minimum: 32°F (0°C)
Maximum: 300°F (150°C)
Specific Gravity
Consult Float Size Table for minimum specific gravity
Float Size Table
Material
Ball Float Size
316 SST
Hastelloy C
X
X
X
X
3-1/2" Dia.
4" Dia.
5" Dia.
Suitable for
minimum
specific
gravity of:
0.5
0.35
0.25
Options
8
Elastomer Coatings
Coating of all wetted parts to increase corrosion resistance
Available coatings: Neoprene, TFE/PTFE, Kynar
8.16
Pneumatic Transmitters
Model 25 Liquid-Level Controller
Ordering data
Float Chamber1,2 Part Numbers
Liquid-Level Controller - Pneumatic
Liquid-Level Controller - Electric
Flange Size
Float
Chambers
Steel
Casting
4"
Type 316
SS Casting
6"
Welded
Steel
Pressure
Rating
Part No.
Part No.
Part No.
150#
300#
8537-1
8537-51
8537-201
8537-224
8537-46
8537-47
Flange or Connection Material
• Steel
• Stainless Steel
Flange Size and Rating
• 4" - 150#
• 4" - 300#
• 6" - 150#
• 6" - 300#
• 1-1/2" Threaded Connection
Options
• Float Chamber
• Reverse Acting (Pneumatic Only)
• Tee Assembly (for Top Mounting)
Mounting Dimensions — For Tees
and Chambers
Standard
A
FlangeFlange Bolt
Class Size
Dia.
Circle
Steel
150
Steel
300
Steel
400
Steel
600
7-1/2
9-1/2
7-7/8
10-5/8
7-7/8
10-5/8
8-1/2
11-1/2
4
6
4
6
4
6
4
6
9
11
10
12-1/2
10
12-1/2
10-3/4
14
B
Order No.
Model Number
▲ ▲ ▲
C
S
415
430
615
630
15
C
R
T
Bolt
C
D
E3
H
J
K
Flange Tee:
Face Chamber: Chamber: Chamber: Chamber:
No. Size Thick- Center
to
Center
Length
Body
ness to Face
Ball
to Face
to Face Diameter
8
8
8
12
8
12
8
12
5/8
3/4
3/4
3/4
7/8
7/8
7/8
1
1-5/16
1
1-1/4
1-7/16
1-3/8
1-5/8
1-1/2
1-7/8
6-1/2
8
7
8-1/2
8
9-3/4
8-1/2
11
4-3/4
4-11/16
4-7/16
4-1/4
4-3/4
4-3/4
4-3/4
4-3/4
6-1/2
6-1/2
6-1/2
6-1/2
11-3/8
12-5/8
11-3/8
12-5/8
2527■■■
5-3/4
6-5/8
5-3/4
6-5/8
L
Height
at Conn.
8-1/2
9-1/2
8-1/2
9-1/2
Standard 4"-150# and 4"-300# cast-steel
chambers have 1-1/2" I.P.S. connections. Other
chambers can be furnished with 1-1/2" or 2" I.P.S.
connections. Data will be furnished on request.
1) Chambers are constructed with 1-1/2" female NPT connections, top and bottom.
2) Chambers not listed above are considered special and will be priced on application.
3) F = E + diameter of ball.
8.17
8
Pneumatic Transmitters
Model 25 Liquid-Level Controller
Technical data
Installation Drawings
Vertical Float
Displacer Chamber
In order to provide for vertical motion of the float, the mounting
nozzle should be installed with its flange face vertical and the
bolt holes straddling the center line (as shown below).
As shown below, a displacer chamber is recommended if the
liquid level can be disturbed by surges. Shut-off valves are
also advisable to allow the controller to be removed without
shut-down. Provisions can be made to periodically flush-out
the displacer chamber by connecting a purge line.
Controllers can be furnished for installation in a tee on top of
the tank. If the vertical extension is greater than 24", or if the
liquid level can be disturbed by surges, a suitable baffle or
cage that does not touch the float should be installed.
8
8.18