Dwyer TFLS User Manual

Bulletin L-33

3/4 CONDUIT
CONNECTION

1

-1/2 NPT

7/8

[22.23]

W/ EXTENSION

NO EXTENSION

“

A”

4

-7/32

[107.14]

7-5/16

[

185.74]

8-5/16

[211.14]

“

A”

Ø4-7/16

[112.73]

4

-7/8

[

123.83]

3

-5/8

[

92.08]

C

OVER

R

EMOVAL

4

-7/32

[

107.14]

8

-5/16

[

211.48]

7

-5/16

[

185.64]

SERIES
TFLS

TUNING FORK LEVEL SWITCH

MOD TFLS­SERIAL:

Series TFLS Tuning Fork Level Switch

Specifications – Perfect for Sensing Low Bulk Density or Low Dielectric Materials

Series TFLS tuning fork level switch is ideal for level control of

powders and fine grained solids, especially those with a low bulk
density. Featured in the TFLS is user-selectable fail-safe
operation of the contacts. Unit is not affected by vibration from
conveying systems, motors, or the movement of material. It can
be mounted in any position and is available with factory built
extensions for mounting on the top of the storage vessel.

Series TFLS is easy to use with no calibration required and with
no mechanical moving parts there is no routine maintenance
required. The TFLS is unaffected by the dielectric constant of the
sensed material making it superior to a capacitance level switch
for applications where the dielectric constant is too low, where
there is more than one material being used in one vessel, and
when material moisture content can change. The level switch is
also good for applications when the bulk density is too low for a
rotating paddle level switch. It can also detect granular material
submerged in liquids of low viscosity, for example sand, gravel, or
polyester chips in water.

FEATURES

• No Calibration Required

• Vibrating Fork Design: Great for low bulk density and low

dielectric constant products. Will detect products down to 1.8
lb/cu ft (30 g/l).

• Universal Power Supply: One model works from 90 to 265 VAC
and 24 VDC.

• Adjustable Sensitivity: Can be set to ignore lighter bulk density
products and only detect heavier products, such as sand in
water.

• Status Indication: External LED status indicator, and internal
indicators for normal and alarm status.

• Failsafe Setting: Output switch can be set for Normally Open or
Normally Closed condition on loss of power.

• Time Delay: Prevent false alarms from material surges.

EXTENSION 

LENGTH

NONE

6 IN

12 IN

8 IN

1
24 IN
36 IN
48 IN

DIM
“A”

9-1/4 (234.95)
15-1/4 (387.35)
21-1/4 (539.75)

7-1/4 (692.15)

2
33-1/4 (844.55)

45-1/4 (1149.35)
57-1/4 (1454.15)

SPECIFICATIONS
Service: Dry powder or bulk materials compatible with wetted

materials. Can detect bulk materials submerged in liquid.
Sensitivity: Minimum bulk density of 1.8 lb/ft

3

(30 g/l), maximum

particle size 0.4 in (10 mm).

Wetted Materials: 316 SS.
Temperature Limits: Ambient: -4 to 140˚F (-20 to 60˚C);

Process: -4 to 176˚F (-20 to 80˚C).

Pressure Limit: 145 psig (10 bar).
Power Requirement: 90 to 265 VAC, 50/60 Hz; 24 VDC.
Power Consumption: 4 VA.
Enclosure: Aluminum, powder coated.
Enclosure Rating: Weatherproof, NEMA 4X.
Switch Type: SPDT.
Electrical Rating: 5A @ 230 VAC.
Electric Connections: Screw terminals.
Conduit Connection: 3/4˝ female NPT.
Process Connection: 1-1/2˝ male NPT.
Weight: 5.5 lb (2.5 kg).
Indication Lights: External: red LED; Internal: green and red

LED’s.
Sensing Delay: (Maximum) covered probe: 2 seconds;
uncovered probe: 3 to 7 seconds.
Time Delay: Separate settings for covering and uncovering the
probe. Adjustable from 2 to 20 seconds.

PROXIMITY CONTROLS

A DIVISION OF DWYER INSTRUMENTS, INC.

P.O. BOX 373 • MICHIGAN CITY, INDIANA 46360, U.S.A.

Phone: [phone] www.dwyer-inst.com

Fax: [phone] e-mail: [e-mail]

Bulletin L-33

Do Not Bend

Do Not Shorten

or Extend

A

1

2

3

4

5

6

7

page 2

ODEL CHART

M

xample

E

Series

Enclosure

Switch

Power Supply

Probe Type

Process Connection

robe Length

P

Options

TFLS
TFLS

WW1

1

11EC

SR
EC
ES

048

1

MT

TFLS-W11EC1-048-MT

uning Fork Level Switch

T
Weatherproof
SPDT rated 5A @ 120/240 VAC
24 VDC, 90-265 VAC
Standard Rod
Extension Carbon Steel
Extension 316 SS

1

XXX

1-1/2˝ NPT male
Insertion length in inches (Only for probe type E)

MT

M25 conduit connection

SS

316 SS Enclosure

OPERATING PRINCIPLE

The TFLS incorporates a piezoelectric crystal that vibrates the fork

does not extend further than necessary into the vessel (Figure 1,

No. 5).
at its natural frequency, 85 Hz. When the fork comes in contact
with material the vibration is dampened and the switch changes

Figure 1: Installation Guide

state. As the fork becomes free of material the switch changes
back to its normal state.

INSTALLATION
Unpacking

Remove the TFLS from the shipping carton and inspect for
damage. If damage is found, notify the carrier immediately.

Mounting Location

The TFLS is rated for industrial environments with few restrictions,
however certain considerations must be made to ensure for
optimal sensing and extended operational life.

• The process temperature and ambient temperature must be
with- in the specified limits for the instrument.

• It is recommended to use a suitable material to protect and seal
the process threads such as TFE tape.

• Position the tines using a wrench on the hexagonal flats above
the process connection. Do not position by turning the housing.

• The probe must be located away from tank inlets or chutes
where material may fall on the probe during filling or emptying
(Figure 1, No. 2). If this is not possible a baffle may be installed
above the probe to protect it from falling material (Figure 1, No. 3).
The baffle must be installed a minimum of 8” (200 cm), see

Figure 2: Fork Protection

dimension A in Figure 1, above the probe so that material will not
become packed between the probe and the baffle.

• For mounting horizontally install with conduit entry facing down
so condensate does not enter the enclosure.

• For mounting horizontally position the tines vertically, narrow
edges up, so that material flows freely through them. The TFLS is
designed so that if the conduit opening is pointed down the tines
will be in the proper orientation. No. 6 in Figure 1 shows incorrect
mounting, No. 7 correct mounting.

• For mounting horizontally with materials that may stick to the
tines it is recommended to mount the probe angled down so that
material slides off easily (Figure 1, No. 7).

• The tines should not be bent, shortened, lengthened, or altered
in any way (See Figure 2).

• For top mounting the tines can be mounted in any position
(Figure 1, No. 1).

• When using mounting nozzles, make sure the length is proper so
that the tines extend far enough into the vessel to vibrate free of
material buildup on the vessel wall. Also make sure the nozzle