Loftus Labs

Kiln Automation and Control System

2020

Contents

Hop Kiln Control System Overview

Components. 

Operation. 

Status, Warnings and Alarms. 

Exception Operations. 

    Hole has Blown in the Hop Bed.

    Switching from manual, to auto control of the kiln. 

Hop Drying Process Description and Process Examples. 

Hop Kiln Control System Overview

The automated hop drying system designed and implemented by Loftus Labs & BT Loftus Ranches is a PLC/computer based control and remote monitoring system for the efficient processing of the hops. The system also allows web/remote viewing of the hop drying process via Loftus Labs MTx Web Software, and iPhone/Android mobile access.

The system: 

• Gives User control over kiln operations, with Kiln Temperatures, Hop Baking Temperatures, and Fan Aggressiveness
• Controls VFD/Fan Speed to reduce blowouts, but maximize throughput
• Controls kiln temperature according to desired hop temperature
• Controls Aggressiveness of VFD/Fan according to desired throughput, a higher aggressiveness pushes the fan to maximize Fan speed according to pressures; a lower aggressiveness lessens the fan speed to avoid blowouts.
• Displays real-time, per second, operational data and recent history of kiln performance
• Displays and sends Alarms for burner outage and high temperature
• Records 5-minute data for recordkeeping and tracking
• Reports are made available via the MTx web software
• Mobile iPhone and Android viewing
  
   

How does this system work?

Hops are placed in a 2-3 ft. deep kiln. An airflow is passed over a burner, heating the air, and flowing through the hop kiln, heating, and drying the hops. Infrared thermocouples within the hops measure and report the temperature of the hops. The measurement of hop weight, kiln plenum pressure, temperature, and hop temperature along with control of the VFD speed/kiln temperature allows efficient adjustments of VFD speed and temperature to maximize kiln throughput, increase quality, consistency and repeatability.

This system is monitored and controlled via a local operator interface; there is a monitoring screen and a control screen. Remotely, kiln operations can be monitored through the MTx website or mobile phone, on or off site.

Components

Kiln Plenum Temperature

The plenum temperature is installed just beneath the hops within the plenum.  This measurement is utilized to control and maintain the kiln plenum temperature.

Infrared Thermocouple for Measuring the Hop Temperature

Installed within the hop bed, the infrared thermocouple sensor is inserted into the hops. Knowing the temperature of the hops allows the user to make adjustments to the system to achieve a desired hop temperature, for optimal drying.  The placement of the sensor should be away from the edges of the kiln.  The depth should be at a consistent level from the kiln floor every run, 6-15”.  

Temperature Control

The control of the temperature set point can also be in automatic or manual mode. In automatic mode, an initial kiln temperature is set, which may be higher than desired hop temperature. Then the kiln temperature is automatically lowered such that the hops are dried at the input Hop Temperature Set Point.

Pressure Sensor

A pressure sensor measures the static pressure within the kiln plenum.

Load Scales

Load scales are installed on the kiln floor, weighing them throughout the process of the Hops drying. This weight is used to measure the amount of moisture in the hops, and to optimize the air flowrate, such that the air flow rate never overcomes the weight of the hops, blowing a hole in the hops, and consequently sacrificing the integrity of the hop bed.

VFD/Fan Control

The control of the kiln VFD can be automatic, or manual. In automatic mode, the VFD is controlled by the system to optimize the drying process. In manual mode, the VFD is set according to the dial on the control screen.

Control Room

Consists of a computer with two operational screens, one monitors the kiln and displays live data, and the other provides user controls for adjusting kiln operation set points.

Control Panel

The control panel consists of a PLC and instrumentation to measure, control and log the data input/output variables.

Operation

System Startup

Make sure there is power to the panel.

There is one main on/off switches that need to be on inside the panel.

In older panels there may be additional on/off switches on a PS150.

Kiln Startup

1. Make sure any VFD/Burner Manual Controls are on Auto or Remote. 
2. Insert the Hop Temp probe within the kiln bed.  The hop temperature sensor is placed 6-15 inches off the kiln floor, near the middle of the bed.
3. Make sure ‘Variety’ and ‘Field’ is correct for each kiln.
4. Make sure the following setpoints are set for to the variety:
   1. Set the ‘Kiln Initial Temperature Setpoint (F)’ temperature, in the box at the top of the control Page. This sets the temperature of the kiln during the “Initial Heat” stage of the drying process.

                 2. Set the ‘Hop Temperature Setpoint (F)’, the desired drying temperature of the Hops, usually 125-140F (directly     below the “Auto Temp Control” Switch, this is the desired Hop baking temperature.

                 Upon starting, the Kiln Temperature will initially raise to the Kiln Initial Temperature, and then the Kiln                                       Temperature will automatically lower through the drying process to keep the Hop Temperature at the desired                          cooking temperature.

                 3. Set the Aggressiveness Factor (1-6), determines when in the process the VFD begins ramping down from 60Hz                       such that blowholes don’t occur.  

                 4. Minimum VFD Speed (Hz), usually 30-35 Hz; the minimum speed is the lowest speed for control, the speed of                       the fan at the end of the dry cycle,

Set the ‘Aggressiveness Factor’ and ‘Minimum Auto Speed’ according to the Variety of Hop, and the desired speed of drying.  A heavy and denser hop will handle a higher Aggressiveness Factor and Minimum Auto Speed.  

A good practice is start with a new Variety using an ‘Aggressiveness Factor’ of 3, and a ‘Minimum Auto Speed’ of 30 or 35Hz.  Adjust up or down depending on the results of the dry process.  If it took too long to dry the hops with no blows, then one or both of these factors can be increased. Conversely, if the kiln was blown early in the process, the ‘Aggressiveness Factor’ needs lowered; and if the blown late in the process, then the ‘Minimum Auto Speed’ may need lowered.

        5. Turn on VFD Speed Automation on the Control Screen.

        6. Turn on Kiln Temp Automation on the Control Screen.

        7. Manually turn on the Burner, this starts the automation process.

        8. To ‘Save Settings’ for this Variety/Field, right click on the ‘Save Settings’ button at the top of the page.  The next time you select this Variety/Kiln these settings will automatically load for the kiln.

Status, Warnings and Alarms

The current conditions within a kiln are displayed on the Monitoring Screen:

The Kiln Start Time and Run Time, as well as a Cooldown Timer are shown at the top of the Kiln Monitoring View.   The Cooldown Time is the length of time the Burner has been off, but the Fan remains ON.

Measurement values are displayed, including Kiln and Hop Temperatures, pressure and Hop Net Weight, which is the Hop Weight as influenced by air pressure.

A Kilns’ burner status is displayed by the color of the circle labeled “Burner Status”.

Watch the warning lights that the burner is out on the screen and the flashing blue light by the hop beds.

A physical alarm, and warning light, if utilized, will light under conditions of a ‘Burner Outage’, or an Over Temperature.

Exception Operations

Hole has Blown in the Hop Bed

Turn the fan down to a manageable level via the rotary dial, this will also take the VFD off of automation.   After correcting the blown hole, manually increase the VFD speed by small increments to the desired speed, you’ll likely need to manually control the VFD speed via the rotary dial in the case of a blown bed when the hops are relatively dry.

Switching from manual, to auto control of the kiln

To change a kiln from manual to automatic control, 

• For VFD/Fan:   switch the button under the fan speed dial to auto,

• For temperature: switch the button labeled “Auto Temp Control” 

These changes are separate and applicable to each individual kiln.

Hop Drying Process Description and Process Examples

The following graphs compare hop temperature, kiln temperature, VFD (air speed), and net weight of the hops in the kiln to drying time of the hops.

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