Microdia Newletter No 46 thermocouples
5
www.microdia.ch Your expert in extrusion SWISS MADE °microdia °microdia N EWSLETTER N O 46 2015 Thermocouples in the wire & cable industry. Wire and cable industry extruder temperature control is either made by individual temperature regulators in ordinary lines or by the line’s PLC in modern machines. Temperature range goes from 50° to 400° depending of the processed compound . Two kind of thermocouples among the numerous existing types are preferred: 1.– J type Fe—Constantan 2.– K type Ni—CrNi
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Microdia extrusion tips. J & K type thermocouples are widely used on wire & cable industry extruders and cross heads. This newsletter compares both type and explains the risks of replacing J by K or K by J and their consequences.
Transcript of Microdia Newletter No 46 thermocouples
www.microdia.ch Your expert in extrusion
SWISS MADE
°microdia
°microdia
N EWSLETTER N O 46 2015
Thermocouples in the wire & cable industry.
Wire and cable industry extruder temperature control is either made by individual temperature regulators in ordinary lines or by the line’s PLC in modern machines. Temperature range goes from 50° to 400° depending of the processed compound . Two kind of thermocouples among the numerous existing types are preferred:
1.– J type Fe—Constantan 2.– K type Ni—CrNi
www.microdia.ch Your expert in extrusion
SWISS MADE
°microdia
°microdia
Newsletter No 46 Pa ge 2
Extrusion temperature ranges
compound Process temperature
°C
Process temperature
°F
HDPE 160 - 190 320 - 370
LDPE 140 - 180 280 - 350
PA 220- 290 420 - 550
PC 250 - 300 480 - 570
PVC 150 - 180 300 - 350
FEP 350 - 380 660 - 720
Rubber 50 - 120 120 - 250
J type thermocouple
General purpose with good sensitivity of 50 µV / °C
At 200°C J type Thermocouple delivers 10.779 mV.
J type junction is made of :
Iron (FE)
Constantan (copper-nickel alloy ( 55% Cu 45% Ni. )
Temperature ranges from - 40 °C to + 750 °C
K type thermocouple
Sensitivity of 41 µV / °C lower than J type but more corrosion resistant.
At 200°C K type Thermocouple delivers 8,138 mV.
K type junction is made of :
Nickel alloy ( 90% Ni 10% Cr )
Nickel alloy ( 95% Ni 2% Al 2 % Mn 1% Si )
Temperature ranges from - 200°C to + 1350 °C
Generally used on high temperature extruders running FEP, ETFE, PFA PEEK, PET etc.
www.microdia.ch Your expert in extrusion
SWISS MADE
°microdia
°microdia
Newsletter No 46 Pa ge 3
Thermocouples Identification
J type. Iron (+) Constantan (-) Most commonly used on extruders and cross head were process temperatures
are below 300°C ( 572 F).
Iron (+) wire sensitive to
corrosive fumes.
K type. Chromel (+) Alumel (-) P r e f e r r e d o n h i g h t temperature extrusion lines
processing fluoropolymers.
J and K types are identified by a color code. Unfortunately British, American,
French and German standards are quite different and confusing.
German DIN standard is widely accepted in Europe and many other countries.
www.microdia.ch Your expert in extrusion
SWISS MADE
°microdia
°microdia
Newsletter No 46 Pa ge 4
Important notice.
Example:
At 200°C J type Thermocouple delivers 10.779 mV.
At 200°C K type Thermocouple delivers 8.138 mV.
At 265°C K type thermocouple delivers 10.766 mV.
If by mistake, a J type is replaced by a K type thermocouple, the
thermoregulator set to 200°C will stabilize at 265°C while displaying
only 200°C. !!
When replacing a thermocouple, it is important to pay attention to the type J or K.
If the wrong type is used, the temperature regulator will apparently work fine, set
temperature and measured temperature display will match.
BUT the real temperature will be wrong !
Either too high replacing a J type by a K type or too low replacing a K type by a J type.
www.microdia.ch Your expert in extrusion
SWISS MADE
°microdia
°microdia
Newsletter No 46 Pa ge 5
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