Isotech 970-1, 970-2 Instruction Manual

MODEL 970-1 & 970-2

CALIBRATION FURNACE

INSTRUCTION MANUAL

_____________________________________________________________________

Isotech North America
158 Brentwood Drive, Unit 4
Colchester, VT 05446

Phone: [phone]
Fax: [phone]

[e-mail]

www.isotechna.com

M970-07/04

PAGE 1

MODEL 970-1 & 970-2

CALIBRATION FURNACE

______________________________

1200 Deg.C. Three Zone

Horizontal Tube

Temperature Calibration Furnace

Instruction Manual

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CONTENTS

Section Description Page No.

1 Warranty 3
2 Operational Safety 4
3 Health & Safety Instructions 5
4 Product description 6 /7
5 Product Features 8
6 Product Specifications 9 / 10
7 Theory of Operation 11 / 12
8 Unpacking, Inspection and Assembly 13
9 Furnace Installation 14
10 Electrical Supplies 15
11 Furnace Operation & Calibration 16 / 17
12 Calibration Performance Optimization 18
13 Safety Features 19
14 Automatic Calibration & Furnace Control 20

Appendix

1 Furnace Diagram 21
2 Furnace Electrical Diagram 22
3 Metal Block 2.9in.dia.side A 23
4 Metal Block 2.9in.dia.side B 24
5 Metal block furnace assembly & probe mounting 25
6 Metal block probe mounting 26
7 Automatic Thermocouple Calibration System 27
8 Uncertainty report TU2—Immersion Errors 28 to 31

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1.Warranty

This instrument has been manufactured and tested in accordance with the manufacturer’s

specification and quality control procedures. It was inspected & tested to safety standards
for electrical insulation, earth impedance and is fully compliant with electrical safety class
1, under IEC 1010-1.

This instrument is guaranteed for 12 months against electrical and mechanical breakdown

caused through defective materials or workmanship providing correct operation and safety
procedures have been used. In addition correct electrical and mechanical installation has
been performed to avoid personal injury or fire from high temperature operation (100 to
1200deg.C.) using recommended health and safety features (refer to Section 5).

Any mechanical or electrical failure caused from miss-use or by not using recommended

safety features will not be covered.

In the event of failure covered by this guarantee, the instrument must be returned to the

supplier for examination and will be repaired or replaced at our discretion and returned at
our cost.

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2. Operational Safety

Personnel using this equipment must be trained in its use and good measurement

practice. It is essential personnel understand the hazards of this equipment when
operating at high temperatures (100 to 1200 deg.C.) and precautions needed in its use.
Refer to safety features section 13 and the Health and Safety instructions section 3.

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3. Health and Safety Instructions

(1) This manual must be read completely.

(2) This product must be electrically and mechanically installed correctly as detailed in this

manual with correct safety features being used (section 3 &13)

(3) Safety notices warning of high temperature must be clearly visible and any necessary

barriers installed to prevent accidental touching / burns by laboratory/operational staff
when operating at high temperatures above 300 deg.C.

(4) Operators must wear appropriate protective clothing as detailed under Safety Section

13.

(5) Operators must be suitably trained in the use and handling of high temperature items.

(6) Do not dismantle or open/work inside this equipment without first isolating it from the

electrical supply and allowing it to cool to ambient temperature.

(7) Do not operate this product outside its recommended temperature ranges in the

specification.

(8) Ensure any other materials are kept away from the hot parts of this furnace, especially

when operating to maximum temperature to prevent the risk of fire.
e.g. liquids or oils reaching their flash/automatic flammability point.

(9) Other local plant/laboratory health and safety instructions / regulations must be

operated.

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4. Product Description

The 970 furnace series provides a 3zone electrically heated, horizontal tube furnace as

illustrated in Appendix 1. The heated length is divided into 3 zones each with its own
temperature controller, power regulator to the heater winding and a thermocouple
temperature sensor. The power supplied to the end zones is automatically adjusted to
compensate for the heat loss occurring at either ends of the central tube, using a “Master­Slave” configuration with the centre zone control in order to maintain all 3 zones at a
uniform temperature. This system provides a much longer uniform horizontal temperature
zone than other systems, e.g. single zone vertical or horizontal furnaces. Also adjustment
of the end zone controllers at some points over the wide furnace operating range (100 to
1200 deg.C.) enables the variable losses at the furnace ends to be corrected (extra power
to correct for insulation losses and different operating loads such as number and size of
sensors being calibrated). This provides a similar “flat” uniform zone at any set point
control temperature over 100 to 1200 deg.C. to within better than 0.2 deg.C over a 200mm
central furnace length using a suitable metal equalizing block in the central work tube.

The “radial” uniformity is obtained by the concentric even furnace winding around the

outer diameter of the main furnace tube. This enables uniform radial temperatures for a
series of holes on a common P.C.D. (pitch circle diameter) using a centrally placed
equalizing block in the centre tube.

This 970 furnace is provided in 2 main versions:-

(1) Model 970-2 with a centre main work tube of 3.15ins. (80mm.) internal diameter

When using the main 80mm. i.d. furnace tube a large (up to 3in. diameter) metal
equalizing block can be used allowing for a large number and variety of probe sizes to
be accommodated. This also allows probes with larger “head” diameters / shapes to
be fitted in addition to short probe length designs.

When very short probes are calibrated, the metal equalizing block can be moved
closer to one end of the furnace. With the use of the 80mm. main centre work tube
only, the insulated separately spaced outer furnace end plates can be removed, to
allow larger and shorter access to the inside work tube and larger equalizing block to
3ins. Diameter.

(2) Model 970-1. This uses an additional centre work tube within the main tube. This

tube is supported by the insulated separate outer end furnace plates shown. This
provides improved horizontal heat uniformity along the furnace length. Also complete
electrical isolation is provided at higher temperatures (600 deg.C. and above) for the
metal equalizing block and probes tested from the heater windings / outer main
furnace tubes. This prevents small spurious voltage input when using very sensitive
digital voltmeters for more precise primary standard thermocouple calibrations by
comparison calibration techniques.

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This separate centre work tube is normally 2.55ins. internal diameter (65mm) and can
be used with metal equalizing blocks up to 2.3 ins. Diameter (58mm) for mounting
probes to calibrate. This smaller diameter / area work tube maintains a lower
horizontal uniformity over the temperature range using a metal equalizing block of 200

to 250mm.length.

This separate work tube is easily replaced compared to the main outer work tube

which is wound with the heater windings. This also enables a range of smaller work
tube diameters to be easily fitted by simply changing the 2 insulated outer end plates
and metal covers. These insulated and separately spaced outer end plates from the
main furnace provide an additional “heat barrier” at the hot furnace ends when
temperatures above 600 deg.C. are used.

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8. Product Features

(1) Wide temperature range (100 to 1200 deg.C).

(2) High stability and low thermal gradient temperature source for calibration by

comparison.

(3) For use with wide range of sensors including large metal sheathed sizes to over 0.75

ins. diameter and facility to calibrate short sensors.

(4) Large immersion depths and low immersion depth errors.

(5) Probe immersions up to 22 ins. from one side.

(6) Probe immersion / calibration from both ends of furnace, doubles calibration volume

and throughput.

(7) Wide range of replaceable internal furnace tube diameters from fixed 3.15 in.

diameter (80 mm) to 2.55 / 0.5 in. (65 to 12.5 mm.) replaceable tube range.

(8) No moving parts / high reliability.

(9) Automatic 3 zone temperature control with individual adjustment of end zone power

over temperature range to compensate for losses and provide very low horizontal
temperature uniformity errors.

(10) Over-temperature “alarm cut-out’.

(11) Maximum power limit facility on all zones.

(12) Controlled ramp rate setting to provide temperature rise limit (deg.C. / min.).

(13) Three phase or single phase operation on supply lines.

(14) Input power circuit breaker with overload cut-out.

(15) Three pole isolation contactor to furnace heater zones.

(16) AUTOMATIC CALIBRATION- When furnace used with TTI7 or DVM / scanner and
TTI7 E software a fully automatic, large capacity, thermocouple calibration system
can be operated overnight using 10 to 24 TC channels with 3 or more sets of TC
channel data at 3 to 15 or more pre-set temperature points with automatic report
writing.

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6.Product Specifications

Model 970-2 Model 970-1

(1) Temperature Range : deg.C. 100 to 1200 100 to 1200
: deg.F. 200 to 2190 200 to 2190

(2) Temperature Stability :100 to 800 deg.C. within :- 0.1 deg.C. 0.05 deg.C.
200 to 1500 deg.F. within :- 0.18deg.F. 0.09 deg.F.

800 to 1200 deg.C. within:- 0.2 deg.C. 0.10 deg.C.
1500 to 2190 deg.F. within:- 0.35deg.F. 0.18 deg.F.

(3) Temperature Uniformity : (using metal block)
Horizontally : 100 to 800 deg.C. within:- 0.1 over 6 ins. 0.05 over 8ins
200 to 1500 deg.F. within:- 0.18over 6ins. 0.09 over 8ins

800 to 1200 deg.C. within:- 0.2 over 6 ins. 0.10 over 8ins
1500 to 2190 deg.F. within:- 0.35over 6 ins. 0.18 over8ins.

Radially : 100 to 800 deg.C. within:- 0.1 deg.C. 0.05 deg.C.
200 to 1500 deg.F. within:- 0.18deg.F. 0.09 deg.F.

800 to 1200 deg.C. within:- 0.2 deg.C. 0.10 deg.C.
1500 to 2190 deg.F. within:- 0.35deg.F. 0.18 deg.F.

(4) Internal work tube diameter :- 3.15ins.Fixed 3.15ins.Fixed
& 2.55ins. or
( 80 mm.) 2.55 to 0.5ins.
as specified.
(80mm / 65mm
to 12.5mm )

(5) Electrical Heaters (110 V. AC.) 1 x Centre Zone :- 1.5 kW.8.1ohm 1.5kW.8.1ohm
2 x End Zone,each 1.75kW7.9ohm 1.75kW7.9ohm

(6) Electrical Supply 3 phase (star) 3 phase (star)
110 V. / phase 110 V. / phase
2x16A.+1x13A 2x16A.+1x13A
Total 5.0 kW. Total 5.0 kW.
OR OR
1 phase 110 V. 1 phase 110 V.

5.0 kW. 45 A. 5.0 kW.45 A.

(7) Overall dimensions (Length x Height x Depth) ins. 32 x 21.5 x 12 32 x 21.5 x 12
mm. 813x533x305 813x533x305

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Model 970 – 2 and 970 – 1

(8) Temperature control :- Centre zone master controller with
input range 0 to 1200 degC.

2 x end zone “slave” controllers
with input differential range of
+/- 7 mV. (+/-200 deg.C.)

(9) Over temperature trip controller :- 0 to 1200 deg.C. range to 1 deg.
C.resolution with relay closure
output on overtemp.

(10) Control / measurement thermometers :- Centre zone : 4 x N type TC
1- centre zone control
2- end zone control differential
1- independent overtemp. alarm
& front socket indication.)

End Zone: 2 x N type TC -1 in each
end zone centre for end zone
differential control.

2 x separate end zone indication
TC’s on front panel positioned 2.1
ins.(53mm.) from inside each end
of outer end zone winding at 3.0 ins
(75 mm.) inside outer end of main
furnace body.

(11) Electrical isolation & safety :- Supply input , 2 pole isolation circuit
breaker and over current protection
trip for single phase or 3 pole for 3
phase.
3 pole latching isolation relay to
heater power regulators / heaters
with main latching furnace power
ON and OFF indicator push button
switches linked to independent over
temp TC alarm to isolate heater
power via 3 pole heater power relay

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7. Theory of Operation

Furnace Control

As illustrated in Appendix 1 the 970-1 and 970-2 horizontal tube furnaces are divided into

3 heated zones, each with its own temperature controller and thermocouple for measuring
and control. The centre zone operates independently as the “master” control to maintain
the furnace centre at its desired set point control value. The two end zones are operated
in a “master – slave” configuration with the temperature input to the end zone controllers
being the difference between the centre zone TC and the end zone TC. As the centre
zone temperature rises the differential input voltage / temperature raises the temperature
of the end zone. The end zones automatically track the centre zone temperature in order
to maintain a constant temperature and horizontal profile.

The power to the outer end zones is automatically adjusted to compensate for heat loss

changes at the ends of the furnace. In order to compensate for variable heat losses
occurring at the furnace ends over its wide operating temperature range and with the
variable “load” conditions (small / large thermometer diameters and the quantity and type
of probes inserted for calibration) the differential “Set-Point” input controls on the end zone
controllers are used to increase or decrease an “offset” control voltage. This will raise or
lower the end zone temperature to obtain a “flat” uniform temperature over the furnace
length.

Equalization Blocks
To provide a constant temperature zone for probes being calibrated with improved

uniformity and short term stability, metal equalization blocks can be fitted to the furnace
tube with suitable close fitting holes (0.015 / 0.02 ins. – 0.4 / 0.5 mm. clearance ). Refer to
examples in Appendix 3 and 4 for the 970-2 furnace. This will also improve immersion
errors as detailed in Appendix 8 – thermometry uncertainty report TU 2.

Calibration Capacity
The advantage of this type of furnace is that probes can be loaded from each end of the

furnace into holes drilled into each end of any equalization block. This doubles the probe
calibration capacity for each calibration program of multiple temperature points. Refer to
the furnace operation and calibration instructions and calibration performance optimization
Sections 13 and 14 for detailed use and operating positions of the equalization block.

Electrical

As illustrated in the electrical diagram under Appendix 2, the supply input is connected to

an independent circuit breaker (combined switch and overload current trip) This provides
both over-current and short circuit protection with complete electrical isolation of the
furnace and electrical controls / instrumentation.

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The operating supply input can be 3 phase 110 V. per phase at 16 amps for the end zone

and 13.5 amps for the centre zone. This is fed through a 3 pole latching 20 A. per line
isolation relay to each of the 3 furnace heater zones via the series “regulator” (solid state
control relay). This allows the 5 kW. total load during maximum heating power to be
divided onto the 3 phase supply (1 heater zone per phase).

As shown, an alternative single phase supply at 110 V. 5kW.(42 amps) can be used by

connecting the input 3 phase terminals in parallel . This single phase supply is fed via the
same 3 pole latching relay to the 3 furnace heater zones.

A separate fused (3A) supply from the main terminals after the input supply circuit breaker

feeds a distribution bus-bar for the local control equipment (controllers, relays, indicators).

A furnace power ON button with green ON lamp operates the 3 pole latching 20 amp. per

line isolation relay RL2 to the 3 separate furnace zone heaters and solid state control
relays.

A separate furnace power OFF button with red indicator lamp switches off the 3 pole

isolation relay supply to the 3 zone heaters and solid state relays to isolate main power to
the furnace, while leaving the temperature controllers operating.

Over temperature alarm and “cutout”
An entirely independent TC on the centre zone and an over temperature controller on the

front panel can be set to provide an “alarm” in the event of the furnace temperature
exceeding a pre-set high limit. The alarm controller closes a set of output contacts which
operates a separate control relay RL1 to trip the main furnace 3 pole relay RL2 to isolate
power to the furnace, switching on the red front panel over-temperature indicator. This
protects the furnace if any fault causes permanent full power to be applied which would
cause over-heating of the furnace and “burn-out” of the windings

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8.Unpacking, Inspection and Assembly

Unpacking / Inspection

Visually check for any physical damage to the shipping container and carefully inspect the

equipment area adjacent to any damaged packing.

Check there are no missing items from the delivery note. Inform supplier immediately of

any missing items or damage. Retain all packing material in case of damage for
inspection by Insurance assessor.

Furnace Assembly

970-1 furnace using separate internal work tube.

Unpack and insert tube carefully into centre of the main furnace tube, cleaning to remove

any packing material or dust. Ensure main furnace work tube has no packing material
particles, removing and cleaning inside of tube.

Using assembly instructions, position the 10mm. furnace end insulation plate into the

metal end plate with 4 holes. Using the bolts/washers provided, attach furnace end plates
to end of furnace over the protruding separate work tube from furnace end. The metal
end plate/cap must be external to the furnace end. (Furnace end insulating plate is next to
the main furnace end with a 10mm. gap). Repeat for the opposite end of furnace, so that
the separate work tube sits in the centre of furnace, supported by the insulated end plates
and metal end caps.

NOTE : A large plain metal washer is placed on end of the 4 bolt threads (next to insulated

end plate) before offering and fixing the end plate assembly to the 4 tapped holes on the
furnace ends.

Assemble the furnace control and electrical system unit to the tubular furnace, connecting

the 2 flexible cable covers with the furnace thermocouple leads and heater supply cables
to the control unit rear panel entrance glands.

970-2 furnace with internal fixed work tube only
Attach the 2 metal furnace end caps and 10mm insulated end plates using the 4 bolts as

detailed above.

Assemble the furnace control and electrical system unit to the tubular furnace as above.

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9. Furnace Installation.

Install on a solid, stable surface / bench with adequate space for ventilation (minimum 24

ins. on both sides and 40 ins. above furnace) Allow sufficient end space for loading
maximum probe length with a minimum distance to any other instruments or wall of 30
ins. This allows heat generated from furnace at its maximum operating temperature to
escape freely. Ensure no inflammable materials are used in mounting or close vicinity of
furnace which could ignite in case of extreme catastrophic external damage to furnace at
high operating temperatures.

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10. Electrical Supplies / Connections.

Ensure local supply line, wall socket or break-out box is available for correct rating of

supply to be used. (3 phase 190 V. 5 kW. – 110 V. per phase, star with neutral and
earth / ground connection OR single phase 110 V. 5 kW. 42 amp)

Using 3-phase supply
Connect 3 phase star supply + neutral + ground (5 wire) cable rated at 20 amps per line

with neutral and ground rated at 35 amps. from laboratory / plant supply box through
furnace control unit cable entry to the 3 phase circuit breaker input, neutral bus-bar and
ground (earth) connections in the furnace control unit.

If a 3 phase supply previously requested, a cable will be supplied and wired at factory

from furnace control unit cable entry for connection to local supply box.

Using single phase supply.
Connect single phase (Line, Neutral and ground / earth) 3 wire cable rated at 50 amps
per line from local supply box through furnace control unit cable entry. Connect 2 wire

line and neutral leads to 2 inputs on circuit breaker and ground (earth) wire to earth bus­bar terminals.

If single phase supply not previously requested it is necessary to change input power

connection in furnace control unit as follows :-

(A) Connect 3 “Line” supply terminals (R, Y, B on drawing appendix 2) together using

the copper bus-bar strip provided.

(B) Disconnect L2 to Y lead and using 50 amp cable link provided, connect L2 to the

Neutral 1, 2 and 3 bus-bar terminals.

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11.Furnace Operation and Calibration.

Insert required metal equalization block into furnace work tube. Use large 3in. diameter
metal blocks in the main outer work tube and smaller blocks (up to 2.55 ins. Diameter) in
the separately mounted model 970-1 furnace tubes. The large 3 ins. Diameter blocks
are used when large capacity calibration is required or for large head and short probe
designs. For 3 in. diameter block design using ceramic tube insulators (refer to Appendix

5) ensure the block is mounted with ceramic tubes in lower half of block resting on the
work tube.

Position block in the furnace to suit the probe length being calibrated. For long
thermometers / standard probes, position block in centre of furnace (Appendix 5). For
medium length probes (11 to 12 ins.) position block as shown in Appendix 6. For short
or extra short probes (8 / 9.5 ins. or 4.5 / 5.5 ins.) position the block as illustrated close
to one end of furnace.

Prepare thermocouples for calibration (refer to Section 2.2 Calibration Procedures CP10
manual) and insert into correct holes in block for close fitting (refer to Appendix 3 and

4). Connect thermocouples either directly to measuring instrument or via TC
compensating wire. Connect reference thermocouple to instrument channel (AO or BO
for TTI7 instrument) and position in metal block. Using high temperature continuously
rated Kaowool to 1200 deg.C., insulate carefully the ends of the furnace to prevent heat
losses particularly around air gaps where probes protrude.

Switch on laboratory supply to furnace.
Switch on the furnace control instrument circuit breaker, the instrument RED supply lamp
is lit and main RED OFF lamp adjacent to furnace power off button illuminates. All 3
temperature controllers and over temperature control unit front panels are illuminated.

Set “Over-temp” controller “up – down” controls to 50 deg.C. above maximum calibration
temperature to be used. Set centre “furnace control” unit to the first lowest calibration
temperature on lower controller display using the up/down arrow keys.

Press furnace power ON green button on furnace control unit. The furnace will start to
heat up and the upper furnace centre controller display will start to rise. The two end
zone controllers will shortly indicate they are driving power to the furnace end zones
after their differential input increases with rise in centre zone temperature. Their top left
lamps will either flash almost continuously or remain permanently on.

For initial adjustment of end zone controller offsets to correct for end zone losses and
improve horizontal temperature uniformity in the furnace and metal block, adjust
up/down end zone controller arrow keys. For 300 deg.C initial temperature control
adjust up keys for +0.4mV. on each end zone. For control to 500 deg.C set end zones
to +0.6 mv.

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Monitor the furnace temperature using the standard reference probe on the measuring
instrument or plot as a graph using PC soft-ware. When final temperature stabilization is
re ached the end zones should be in control with their control lamps blinking to indicate
an average control power input to the furnace end zones.

Checking horizontal uniformity
The temperature uniformity from end to end of the furnace will vary depending upon the
end zone losses. These vary with the temperature value, being much higher at 600 to
1200 deg.C. The total losses and end zone “temperature droop” will also be dependant
on the end zone insulation and its packing density used, together with the size, type and
number of probes inserted.

To check and adjust/trim the furnace end zone differential “offsets”, insert a long TC
probe into the centre hole of the equalization block in furnace. It is assumed that the
block has been mounted centrally between the furnace ends. While recording this
probe in the centre position, slowly re-position it at l in. intervals and monitor the
temperature change. Leave the probe at each position for approximately 5 mins.
dependant on probe response time to achieve thermal equilibrium. The temperature
profile over +/- 4 ins. from the centre of the block can be monitored. The end zone
controller up/down keys can be adjusted to obtain the best uniformity.

The reference and probes under calibration can be scanned and monitored by an
attached DVM/scanner or using the TTI7 digital thermometer / scanner system. Refer to
Section 16 for automatic calibration and data logging under computer control.

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12.Calibration Performance Optimization

The horizontal profile of the furnace should be carefully monitored over the length of any

equalization blocks under the standard test conditions for the probes used and the end
zone insulation. Short probes calibrated using the equalization blocks closer to the
furnace end, will need more care to obtain the maximum insulation / lowest end loss with
adjustment of the particular furnace end controller used to obtain the lowest gradient.
When using the equalization block in the centre of the furnace with long probes, additional
Kaowool insulation can be used at each end of the furnace to reduce heat loss and
improve the gradient in conjunction with the end zone controller differential “offset
adjustment”.

To establish radial uniformities use two identical size and thermal properties probe which

closely fit (within 0.4 mm. approx.) 2 diagonally opposite holes A and B. Make comparison
measurements in these two hole positions measuring test probe TP in position A and the
reference probe RP in position B.

Error test probe TPE = 0.5 [ (PosA. TP – Pos B.TS )+(Pos B.TP-Pos.A.TS) ]

When mounting probes in metal block, holes used should be on the same P.C.D. for best

radial uniformity.

It is important all probes use close fitting holes and are inserted to the same depth to

reduce thermal immersion errors. In 3 zone horizontal tube furnaces with blocks mounted
closer to the furnace centre immersion depth errors are considerably lower compared to
alternative systems and designs because of the additional heat area in front of each probe
or block before the furnace end and room temperature.

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13. Safety Features

This furnace is protected with electrical safety features to trip the supply on continuous

overload or short circuit.

The thermal heating is protected by an independent over-temp cut-out to trip the supply.

For personal safety, we strongly recommend the use of protective clothing including face

masks or goggles. In addition, thermal gloves and / or thermal insulated tongs used when
inserting or removing hot objects from the furnace.

It is recommended to have a local heat resistant surface or brackets / holders to receive

hot objects / probes removed from the furnace.

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14.Automatic Calibration and Furnace Control

Refer to Appendix 7 furnace automatic calibration system diagram.

This furnace can be used with the TTI7 PRT / TC multichannel digital thermometer or
DVM’s / Scanner systems, in order to automatically ramp the furnace to several pre-set
control temperatures . When stability is reached and monitored by the reference probe

and software at each set point (set in the PC software) the TTI7 / scanner will scan
and record the reference and unknown probes . The data at each temperature with
probe serial number and customer reference is stored in a data file . A TTI7 RW
automatic report writer used in conjunction with the TTI7 E calibration software can
calculate and print out a complete calibration report. Alternatively the TTI7 E data files
can be downloaded to other information and report writing systems.

Refer to TTI7 E software manual and the CP10 Calibration Procedures manual Section

2 for further details and instructions.

This provides fully automatic calibration at a pre-set number of temperature points,

with the system unattended