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Temperature Control Options for
Keen Industrial Ovens

Keen industrial ovens feature a wide range of temperature control options that are specifically tailored to our customers’ heat-processing applications.  From standard analog dial capillary thermostats, to fully programmable PID controls with ramp and soak capability, our goal is to provide flexibility to satisfy each customer’s unique heat treating requirement.  Please see detailed information below regarding the temperature control options available for Keen custom industrial ovens.  

* Please note the maximum temperature we offer is 950°F / 510°C *

Analog Dial Thermostats on Keen Industrial Ovens

This type of temperature control is the most basic we offer on Keen preheat ovens, and is suitable for simple heat-processing applications that do not require tight temperature variances or digital temperature control and display.  Analog thermostats typically have a manufacturer-stated temperature variance of around +/- 12 degrees Fahrenheit, and are used on Keen industrial ovens with lower temperature ranges with a maximum not to exceed 550°F.  There are three temperature ranges we offer on our with this type of thermostat:  150°F-300°F, Ambient-250°F, and 150°F-550°F.  We can also provide other ranges if requested.

Microprocessor-based ON/OFF Digital Temperature Controllers on Keen Industrial Ovens, Batch Ovens and Preheat Ovens

The standard digital controller on Keen industrial ovens is an ON/OFF microprocessor-based controller with digital LED temperature display. Also known as a bang-bang control, this is a basic controller that provides an economic solution for industrial oven applications in which simple on/off control is required and precise control is not crucial. The 4-digit LED temperature readout can display Fahrenheit or Celsius.  Easy-to-use tactile increment and decrement keys allow easy set point adjustment for Keen industrial ovens.

On/off microprocessor-based controllers are the simplest form of digital temperature controls available for our industrial ovens.  The output from the controller is either on or off, with no control between these two points.  For industrial oven heating control, the output is ON when the temperature is below the set point, and OFF when the temperature of the oven is above set point.  This on/off process is known as cycling.  Our controller uses an on/off differential, called hysteresis, to prevent damage to contactors and valves in rapid cycling situations.  This differential requires that the industrial oven temperature exceeds a specified amount before the controller is turned off or on again.  In the case of our controller, the hysteresis amount is approximately 3°F.  We also have manual reset limit controllers that act as a fail safe for our industrial ovens.  They are standard on all Keen industrial ovens over 3000 watts.  This device is designed to shut down the heating process when a certain temperature is reached.

Proportional Integral Digital Temperature Controllers on Keen Industrial Ovens and Batch Ovens

The next tier of temperature control offered on Keen industrial ovens is one that utilizes proportional integral control.   This is a step above and a more advanced control solution than standard ON//OFF microprocessor-based temperature controllers because it eliminates the cycling which can be problematic for applications that require tighter control over temperature variance. 

Proportional integral controls eliminate cycling or oscillating by decreasing the average power supplied to the heating elements as the temperature approaches set point.  This causes the heater to slow down so that the temperature will not exceed set point, then shut off abruptly as is the case with bang-bang controls.  Instead it approaches the set point slowly so that it can maintain a more stable temperature inside the oven cabinet.  This action – called proportioning - is achieved by turning the output on and off for short time intervals (an analogy to use would be ABS brakes and how they apply rapid intervals of pressure as a vehicle approaches stopping position).   This time proportioning – which occurs within a “proportional band” around the oven setpoint – varies the ratio of “on” time to “off” time to control the industrial oven temperature. In other words, proportional controls determine the percent of heat needed to control the process.

For example, the digital proportional controls on Keen industrial ovens and batch ovens have the proportional band factory preset at 25°F and the automatic reset (Integral) is set at 0.1 repeats/minute.  These settings will control many heat treating processes without any changes to the controller.  But if users find the oven heat treating process is unstable or too sluggish, the proportional band and automatic integral reset can be changed in the controller menu configuration. 

The objective of a proportional band adjustment is to find the proportional band setting at which the preheat oven’s process temperature stabilizes and does not oscillate.  If the batch oven controller temperature display is oscillating, the user increases the proportional band (doubling the value) until the temperature display has stopped oscillating.  To establish a quick response to control upsets, a user just adjusts for the smallest band that provides the most stable control (does not oscillate).

The objective of the automatic reset (which is the integral reset function) is to automatically remove the offset between oven process temperature and set point.  If the process is too sluggish in approaching set point, double the automatic reset.  But too much automatic reset will make the oven heating process unstable.

Proportional Integral Digital Temperature Controllers on Keen Industrial Ovens and Batch Ovens

The next tier of temperature controllers we install on Keen industrial ovens and heat treat ovens is digital PID control.  It utilizes proportional control, and a combination of integral and derivative control.  These additional adjustments enable the unit to automatically compensate for changes in the system.  Integral and derivative adjustments are expressed in time-based units, and must be individually adjusted to a particular system using trial and error.  The close industrial oven temperature control offered by PID controllers is ideally suited to heat processing that involves storage of parts with small mass because they are subject to quick temperature changes compared to parts with large mass.  PID batch oven control is also recommended in applications where the load is changed often, and when the controller is required to compensate for frequent changes in setpoint, the amount of heat available, or the mass controlled.

Dual PID and Fuzzy Logic Temperature Controllers on Keen Heat Treating Ovens, Batch Ovens and Industrial Ovens

The most advanced and sophisticated temperature control offered on Keen industrial ovens and heat treating ovens features a dual PID and fuzzy logic microprocessor-based control system.  This is a high performance single loop controller that can be used for a variety of applications beyond temperature control such as flow, pressure and level control.  Our PID Fuzzy Logic oven controller offers 5 possible outputs for single output or heat control, plus up to three alarm or event outputs.  The self-tuning function is fuzzy logic based which optimizes the PID control and minimizes overshoot.  It also features a 16 interval ramp/soak program with guaranteed soak, 3 event outputs and looping.  This oven controller also has security code protection to prevent unauthorized access.

For more information call us toll-free at 1-888-512-2870 or local 985-345-2171.


 

 


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