Application Note

Application Note: 100206
Kayden Instruments

Acid Level Detection - Petro-Chemical


Overflow Level Protection, Acid


Refinery, Gallup, New Mexico, USA


Kayden CLASSIC 800 Series Thermal Dispersion Flow, Level, Interface & Temperature Switch & Transmitter

Pump Detection Acid Level

Reliable and repeatable level control is critical in order to prevent contamination of the process upstream or downstream. The acid must not be allowed to flow into the process except when required as a chemical additive.

Prior to Kayden, the customer tried a competitor’s thermal switch and a gap switch in this application. Kayden was chosen and has succeeded where the other instruments failed:

  • The Kayden CLASSIC 800 Series allows the customer to independently and incrementally adjust the level of heat, the range, and the (relay) set points to achieve high sensitivity and fast response to changes in the media level.
  • Previous failures were caused when the acid literally ate through the sensors and entered the electronics enclosures. All Kayden sensors are welded (not brazed). All flanged sensors (this unit required a 3/4” flanged sensor built from Monel) are welded front and back to resist failures caused by corrosion and vibration.

For a level switch to perform well in this application it must resist failures caused by:

  • corrosion and / or “sludging” damage to the sensor
  • temperature extremes - depending upon location and operation the instrument will see high temperatures (including steam)
  • water contamination - feed water and cooling water often contains sediment and high mineral content
  • electromagnetic interference

The Kayden CLASSIC 800 Series Thermal Dispersion Flow, Level, Interface Temperature Switch is used to provide the critical control for acid additive level. The switch is set to activate or deactivate the feed valve, either directly or as is done in this case through a master control system, using either of the independent relay contacts or the 4-20mA analog output.

Although often overlooked in level applications in favor of more complicated and expensive technologies, Kayden thermal dispersion switches provide digital repeatability and fast response in a rugged package that is not bothered by coating on the probe and will not drift, seize, or ever require calibration.

Easy, Display Panel controls and display make set-up fast and easy. Unlike float, paddle or gap switches Kayden switches feature all-welded sensors, no-moving-parts design, true digital electronics with autodiagnostic functions, two independent relay timers, a Bypass Timer for auto pump restart, simultaneous process temperature monitor and a 4-20mA analog output corresponding to the process level (flow).

Two CLASSIC Switches
Classic 800 Display Panel
Display Panel

Display Panel Indicators:

Relay 1

On steady when Relay 1 is energized

Relay 2

On steady when Relay 2 is energized


Indicates a self-test error or fault condition

Set Point 1

On steady when viewing Set Point 1

Set Point 2

On steady when viewing Set Point 2

Run Mode

Flashing when switch is operating


Flashing when the Start-up Bypass Timer is active

Thermal Signal

Displays Thermal Signal

The Thermal Signal increases as:


The flow rate increases


The sensor is submerged


The sensor is submerged by the second liquid of greater thermal conductivity

Applicable CLASSIC 800 Models

Classic 810
Classic 810
Classic 812
Classic 812
Classic 814
Classic 814
Classic 816
Classic 816
Classic 828
Classic 828
Classic 830
Classic 830
Classic 832
Classic 832

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