Instruction Manual

Page 2
GENERAL DESCRIPTION
The Series KTD Thermal Differential Switch is the state-of-the-art in gaseous and liquid flow switching or liquid level /
interface control. Flow or level detection is accomplished by using a high resolution thermal differential technique. The
standard sensor wetted parts are of durable 316L series stainless steel, all welded construction with no moving parts. The
switch is easy to install and adjust, giving reliable, low maintenance performance in the most demanding applications.
PRINCIPLE OF OPERATION
MODEL DESCRIPTION
- - - - - -
Model
Process Connection
Sensor Material
Insertion Length (Inches)
Input Power
Configuration
Options
Options
Options (cont.)
Options (cont.)
Options (cont.)
Description Code Description Code Description Code Description Code
No Options 00 Extended Neck EN Additional Cable CA SS Tag TG
RTD Output RT *High Temp (850ºF) HT Variable Insertion VI
Live Tap LT *Medium Temp (572ºF) MT Factory Calibration CB
CE Approved CE Explosion-proof Window XW Thermocouple Output TO
Sensor
Installed in
Tee
TE
* Remote Mounting Required
Model
Sensor Materi
al
Description Code Description Code
Level Switch KTDL 316L SS S6
Flow Switch KTDF 304 SS S4
304L SS SL
Process Connection
Hastelloy-B HB
Description Code Hastelloy-C HC
½” NPT 050 Inconel 600 IO
¾” NPT 075 Monel MN
1” NPT 100 Alloy-20 A2
1½” Sanitary 3A1 Special Material SM
1” 150# ANSI Flange RA1
2” 150# ANSI Flange RA2
Input Power
1” 300# ANSI Flange RB1 Description Code
2” 300# ANSI Flange RB2 110 Vac 110
Low Flow Sensor LFS 220 Vac 220
Special Connection SPL 24 Vdc 24D
24 Vac 24A
Configuration
Description Code
Insertion Length
Integral Mounting LE 002.00 (standard)
Remote Mounting RE 000.50 – 120.00 (optional)
The Series KTD Thermal Differential Switch uses a thermal differential technique to measure liquid level or interface
by sensing changes in the thermal heat transfer characteristics of the media where it is located. The sensor consists
of a pair of matched Resistance Temperature Detectors (RTD’s) encased in twin 316 series, stainless steel tubes.
One RTD is self-heated using a constant DC current. The other sensor is unheated and provides an accurate ambient
process temperature reference. The thermal differential created between the heated and reference RTD pair is
a function only of the media with which the sensor is in contact. The differential is greatest when no liquid is present
(dry condition) and decreases as liquid quenches the switch sensors (wet condition).
Hydrocarbons generally have lower heat-transfer characteristics than aqueous-based materials so liquid-liquid
interface detection is possible. In general, any two media will exhibit some difference in heat-transfer characteristics.
Thus, the switch can be calibrated to detect the interface between two immiscible liquids.
This switch can also be used as a no-flow or a low flow switch. In this case the actual flow of the liquid or gas
provides the cooling effect. In other words, the lower the flow rate the greater the temperature differential between the
(2) RTD’s.
Solid-state electronics transform the temperature differential into a voltage that is compared to a control voltage to
actuate a relay and indicate a change in state (wet vs. dry). The instrument head at the top of the unit contains the
Switch electronics board which is easily removable from the instrument head so that field wiring can be connected to
the field terminal block.