The Stress-Relieving Process
in CQI-9, 3rd Edition (Key Points)
Date:
Audience:
Location:
September 30, 2013
SMI Technical Conference
Green Valley Ranch Resort
Presenter: Daniel F Pierre III
President
JN Machinery Corp
Changes to note
2) Easier to read Process Tables
3) No AMS2750D references
4) Flexibility to determine frequency
of SAT and Instrument Calibration
7) Unifies tolerances in °C and °F.
The rest of the changes do not really
pertain to the stress relieving process.
This Presentation’s Focus:
3.1 Thermocouples
3.2 Instrumentation
3.3 SAT System Accuracy Test
3.4 TUS Temperature
Uniformity Survey
Process Table E
Internal Testing Pitfalls
3.1 Thermocouples
All sections in 3.1 will initially covered by the OEM of your oven--if you tell them the oven must comply to CQI-9
at the time of sale.
Thermocouple Certs
SAT - As per ISO17025
…and my test equipment’s certs
TUS - As per ISO17025
However, be aware of a few sections when you perform maintenance or replacement of thermocouples:
3.1.1.2 Do not splice extension wire or modify the electrical path between the thermocouple and temperature
controller.
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Thermo Coupling
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Temperature
Controller
Thermocouple
Wire
Thermocouple
3.1 Thermocouples
(continued)
3.1.2.4 ISO/IEC17025 for external calibration. In earlier versions of CQI-9, OEMs had the ability to
perform calibrations on their own equipment. Now, OEMs will have to have ISO/IEC17025
3.1.2.5 When replacing thermocouples, need a “calibrated” one, your thermocouple supplier can
provide the calibration cert. Note: they cost more than standard thermocouples.
3.1.3 Need to keep records of first use of thermocouple. If no record at time of calibration—
especially if performing calibration every 6 months—the calibrator may be required to replace the
thermocouple or perhaps NOT be able to perform calibration.
3.1.1~3.1.5 tables:
So many references to how often to change thermocouples:
3.1.1 “every 2 years”. Refers to degradation/oxidation of metal wires.
After 2 years, too much damage to the wires.
3.1.2 Reference for Calibrators. i.e for the TEST thermocouples.
3.1.5 180 uses—assuming you use 23 days/month—7~8 months.
This is
accuracy of a
thermocouple,
NOT an Oven.
This is the TEST
Thermocouple,
not the oven’s
thermocouple.
Expendable Thermocouples
Non-Expendable Thermocouples
3.2 Instrumentation
Most sections are obvious and easy to understand. External calibrators will cover these.
Notable sections if you will internally calibrate your work: (must follow ISO 17025)
3.2.1.3 Calibration frequencies: covered in detail after several more slides.
3.2.1.4 For digital recording, no more than 2 minutes between readings.
Data Recorded Every 2 Seconds
Data Recorded Every 2 Minutes
3.2 Instrumentation
Can existing ovens be converted to do digital data collection?
Yes, but at a cost….
Data logging technology is evolving so fast, that what is presented today
could be obsolete or considered “old school” in 3~6 months………
1) Upgrade to Temperature Controllers with Communications Capability.
($$$  $$)
2) Software to set parameters and collect data.
($0 to $$$, but 1 time only)
3) 2-wire cable between oven and dedicated computer (which has to be ON). ( $0 to $$)
Or: Wireless System, but…………………………………………………………………………..($$$$)
4) Data converter at computer…………………………………………………………………….
($)
5) If not hard wiring, 2-wire socket/plug on control panel. ……………………………. ($$)
6) Physical modification to oven shell and heat chamber…………………………..…… ( $0 to
$$$$! )
3.2 Instrumentation
3.2.4.2 Changing a temperature controller, leadwire, holder, or thermocouple requires a new calibration.
(i.e. change at time of calibration if you can…..)
3.2.6 Write-once, read only electronic records. Keep Original Log files locked up. Copy the data to create
a chart. Altering a log file IS detectable. i.e. does NOT have to be a “pen-on-paper” strip/chart recorder.
Sample Paperwork you will receive and file
Company Name &
Logo
JN Machinery
1081 Rock Road Lane
East Dundee, IL 60118
JNMachinery
1081 Rock Road Ln.
East Dundee, IL 60118
Tel: 24-699-9161
Oven ID _______________
Initials _____________
Cal Due ______________
Cal Date ______________
3.2 Instrumentation (“calibration”) and 3.3 SAT System Accuracy Test
Unfortunately, it is
not just a matter of
choosing whichever
method has the
least amount of
paperwork.
The path to the
least amount of
paperwork could
mean higher initial
costs.
Quarterly SAT using
Probe Method A or B
or
Monthly SAT using
Comparative Method
+
+
Annual
TUS
+
Annual
TUS
Quarterly Control Instrument Calibration
( Single Point or Multi Point )
Quarterly SAT using
Probe Method A only
+
Semi-annual Control Instrument
Calibration ( Multi Point Only )
System Accuracy Test
Typically referred to as “oven calibration”, but SAT is the more accurate term.
“Oven Calibration” has the connotation that the calibrating organization will “do
something internally” to the temperature controller to bring the system back
into proper calibrated state.
The SAT is used to confirm whether an oven remains in an accurate range.
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Thermo Couple Holder
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Temperature
Controller
Thermocouple
Wire
Thermocouple
Probe
Method “A”
Instruments
Instruments to be
managed and stored
according to ISO17025
Temperature Controllers can have what is called “Voltage Leaks”. There is a small amount of
electricity that travels along these wires. Cheap temp Controllers generally have more
leakage (40~85V)! Quality controllers will have 0.3~8V. Critical applications can require
<0.1V leakage, and these cost several hundreds of dollars.
0.3 ~ 85 Volts!
Photo shows a Thermocouple Holder
with a Test Probe Hole in the middle
(currently, 2 thermocouples are
connected here, this is a Dual
Thermocouple Holder for a 1-Zone
Oven and its Over-Temperature
thermocouple.
A Probe with a diameter as large
as ¼” can fit inside this hole.
The Test Probe is less
than 50 mm from the
thermocouple tips
Be aware that there is a small
risk a probe can end up in the
shadow of thermocouple tips
Probe Method “B”
Note: Probe Method B can be useful on larger ovens when the control panel is not easily
viewable from the probing position.
Comparative Method
Not all ovens are set up to use the Comparative Method:
1)Older ovens without an Over-Temperature Controller.
2)Multizone Ovens will have a TC without a test instrument <50mm away and still need Probe “A”
or “B” method.
3)Ovens with Over-Temps, but are not next to (<50mm) the control thermocouple.
4)Investment cost to permanently install a test instrument.
5)When purchasing a new oven and you plan to use Comparative Method, inform your Oven
maker that you want an established Delta. (Usually no cost for the Delta data, but there can be
added cost for an initial calibration certificate.)
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Comparative Method
3.3.4.3.4 If both devices have their respective thermocouples in the same
protection tube they shall be of a different type.
J & J
J & K
✗ ✓
Some Ovens will dictate which method you can use without an initial investment cost.
You may not be able to do the same method on all ovens, which is acceptable as the probe
method used will be noted on the oven cert, however, Mixed Methods can not be in conflict
of the CQI-9 regulations.
3.2 Instrumentation (“calibration”) and 3.3 SAT System Accuracy Test
( Review of
all test
methods )
Quarterly SAT using
Probe Method A or B
or
Monthly SAT using
Comparative Method
+
+
Annual
TUS
+
Annual
TUS
Quarterly Control Instrument Calibration
( Single Point or Multi Point )
Quarterly SAT using
Probe Method A only
+
Semi-annual Control Instrument
Calibration ( Multi Point Only )
3.4 Temperature Uniformity Surveys
Performed Annually, or after a major rebuild/modification.
Key to success in performing the TUS is to Define Your Workzone
Typically, the final 1/3 of the chamber is where
“stress relief” occurs. A potential “workzone”
can be defined as the final 40% of a chamber,
less the final 8% (where ambient air will affect
chamber temperature).
Workzone
Time through oven
Temperature Uniformity Surveys
Typical data logging apparatus
Notes:
• These 3 Controllers and the 3 thermocouples all
have to have current calibration certificates.
• The thermocouples need records of the number
of uses to remain valid for use.
• The apparatus (and thermocouples) have to be
stored and monitored (temp/humidity) as per
ISO/IEC17025.
Temperature Uniformity Surveys
Placing thermocouples right at the walls, at 1” from walls and 2” (max 50mm) from walls did
not show much difference. However, missing and degraded curtains DID show worse results
at the oven walls.
Recommendation: Set your instrument to approximately 1” from walls, but do not beat
yourself up to measure distance to wall so precisely.
If you fail a test, consider first that perhaps your curtains need attention.
However, it is possible that a failed test is an indication that your process is not optimal and
you are over-loading the oven.
This is the exact area out of all CQI-9 regulations that will probably cost springmakers the
most money to achieve compliance. Pushing the envelope a little too far to maximize the
amount of product through an oven—either too much product or too fast a belt speed—will
reveal itself during TUS, and ultimately require investment into a larger oven.
3.4.3.1 TUS Data Collection
Use the normal belt speed as your regular product. Slower belts do provide better results,
too fast belts will show parts in oven do not even get to the set temperature.
A good curve shows that the workzone is in control.
No more than a 30 second interval data collection. Not recommended. The maximum
length of study is 3 x thermocouples x 60 minutes. One data file can easily handle readings
every second.
Temperature Uniformity Surveys
Batch Ovens
Experience shows that older ovens fail at front
corners (or middle if french doors) when the
door seal degrades.
You CAN pass a test if you declare your workzone
accordingly. Make sure you place a message on
the oven showing which position(s) are NOT
permissible locations for placing product in oven.
Temperature Uniformity Surveys
A problem with CQI-9 regulations as represented in section 3.4.3.1 is that it more closely affects
annealing and normalizing and possibly could be “not applicable” for stress relieving.
On its own, the sections doesn’t sound too bad:
“TUS test thermocouples shall be traversed through the
furnace at a traverse speed typically used in production
(and representing all test locations as required in table………)”
I would suggest that if SMI wants to develop a “best practices” regarding CQI-9,
beforehand, organize a roundtable discussion or a committee to discuss “oven capacity”
and “belt speed” as it relates to the question “when does the actual stress relief occur?”
Process Table E relates to Stress Relief
Do not miss the Glossary. It is tremendously helpful!
Alarm systems (if set per acceptable
limits) satisfy the sign-off requirement
Internal Testing Pitfalls
Manual vs Automatic data collection
Belt speed.
Curtains/no curtains
NOT changing damaged or well-used thermocouples (TUS)
Mixing thermocouple types (J, K)
Data-collecting is a bit of an art. Training and experience is necessary.
A System with “Double Negatives”
A few samples of thermocouple terminations showing thermocouple type.
Outer
covering
Shield
material
Wire
insulation
Bare wire
T
K
J