Fluke Process Instruments

Application

Measure the bottom facing edge of aluminium slabs (10,000kg) in a so-called "pusher-kiln".

Problem to solve

Avoid excessive whole life costs  - thermocouple replacement £4k each. 

For each measurement, the thermocouple/thermowell assembly is raised by a sliding mechanism to allow contact with the lower surface of the slab. The measurement can only be performed when the slab is not moving. 

The thermowell tip suffers damage over time due to wear and unintentional slab movement before safe retraction of probe.

Converting to a non-contact measurement principle potentially allows continuous temperature data and vastly reduced cost of ownership.

How IR can add value

Continuous measurement at each stage of the process will allow (in time) "finer" tuning of the heating control to reduce energy costs and improve hot rolling process - reduced wear on machinery and better finished product.

Whole life costs for an IR sensor:

Annual calibration costs of approximately £300 per sensor

Compressed air - unknown (volume sufficient only to maintain  positive pressure

Replacement of the Endurance sensor front window £35 (only as necessary)

How Fluke/Endurance can add value

• Video sighting allows operator to check that view is not blocked (upwards facing sensor)
• Analog and industrial field-net output (Profinet or Ethernet/IP) allows easy integration to legacy control systems
• Endurance mA output flexible scaling (even outside of temperature range) prevents the need to re-scale a control system no longer supported by an integrator or end-user having no internal resources to make change
• Field-calibration function in DTMD allows end-users to check and adjust if they calibrate in-house
• mA calibration signal can be used to validate analog input of control system 

Primary Challenge - Measurement/Emissivity Uncertainty

Aluminium is known to potentially problematic in terms of surface emissivity.

The temperature at the test point of the process is known to be between 545 and 595°C .

Setting a "close fit" emissivity value and evaluating emissivity stability was necessary.

Using the Endurance "match" function, 570°C was chosen and entered using DTMD software - resulting in a calculated and emissivity parameter of 0.598.

There are no "hot reflections" affecting the measurement (t-ambient correction not needed).

Due to demo unit availability the sensor used E3MH. An E2M would also be a logical choice.

Commercial/Selling Guidance

• Once validated, the Endurance will likely take the purchase route of  replacing each thermocouple location upon next failure.
• Emphasize having 1 or 2  "floating" spare sensors for emergency back-up for critical measurement points and calibration rotation.
• Standardize on same sensor version for all locations (where possible).
• Look for other measurement opportunities - for example, heat treating of coiled aluminium sheet - it is likely that once a repeatable measurement is proven, the customer will look for other opportunities to use IR temperature measurement.

Customer Feedback

Measurements are very much in line with thermal modelling.

Black = raw data

Red =  sensor with output value (Tobj) with  10s averaging applied as post processing

Cross Selling

Process mA calibrator or DMM with mA measurement function with 0.01mA resolution