Mineral Insulated

Description

Mineral Insulated Thermocouples & Resistance Temperature Detectors comprise of a metal sheath in which the thermo-electric elements/RTD element with conductors are embedded in highly compressed magnesium Oxide (MgO) insulation, thus providing the elements complete protection against oxidation and corrosion.

Thermocouples are available in type K, J, T, E, R, S, W, W3 and W5, simplex or duplex, in sheath diameters from 1mm to 19.05mm and length from a few cm to 200 meters or more. The hot junction is TIG welded and could be grounded (element hot junction welded to sheath tip giving faster response) or ungrounded (element insulated from sheath), one of which can be used as per control system requirement.

  • High Integrity construction suited to arduous operating conditions
  • High Accuracy & Stability maintained throughout operating life
  • Fast Response & High Insulation Resistance
  • Sheath can be bent & retains its form after bending to suit particular installation
  • Excellent Shock & Vibration Resistance
  • RTD are available with Platinum element, R=100 ohms, temp.coeff.0.385 ohm/°C, simplex or duplex, in sheath diameter from 3mm to 8mm and in lengths from 10 cm to several meters as per order

 General Specification

Designs

Design no.1...5 & IT40 Sr.

Response time

6 Sec.(63.2%) for 6mm OD sheath

Head                 

Provided in design no.4 & IT40 Sr.

Smallest bending radius

Twice the sheath diameter

Head material

Cast aluminum

Mounting

Adjustable compression fitting

Head type        Standard

With threaded cover & cable entry (3/4”ET/ 1/2”BSP)

(In design no.4 & IT40 Sr.)

1/8”BSP(M) upto 6mm OD sheath other sizes on request in design no.4 Flange/ Threaded in IT40 Sr.

Weatherproof

Flameproof

Standard with gasket & challan (IP65)
CMRS approved for group 1,IIA,IIB & II C, weatherproof to IP65

Extension  Cable 
(in design no.2)

Compensating Cable with fibre glass/figre
glass/SS wire braided insulation for Thermocouple. Copper cable with
Teflon/Teflon/SS wire braided Insul. For RTD other types on request

Terminal block (in design no.3,4 & IT40)

Ceramic with brass terminals & with provision for two mounting screws on 33mm PCD; terminal block is spring loaded in design no.3 & IT40

Connector
(in design no.5)

Of glass filled thermoplastic with thermocouple grade contacts & ANSI colour coaded for thermocouple (Design No.5A); Of MS, circular threaded locking type with copper contacts, 3/6 pin for RTD,(Design no.5B)

Sheath

AISI316/304/321/347/310/ 446/inconel600/ Hastalloy X in 1,5,3,4,5,6,8,12,7,15,8 & 19.05mm dia for thermocouples; AISI 316 in 3.2, 4.8, 7 & 8mm dia for RTDs.

Element

Simplex/duplex: J/K/T/E/N/S/R for thermocouples: Pt100, 2/3 wire for RTD with copper leads (Const./Ni. optional).

Thermowell
 (in IT40 Sr.)

Refer drg. No. TC260(3) for selection of Design. General construction of sensor in this case will be as per drg.no.TC259(3) using insert as per design no.3 alongwith
head & extension using nipple/union.

Insulation resistance

10 M Ohms at 500V DC, 100M Ohms on request.

 

 

PROTECTION SHEATH

Sheath Material

Composition
(Appx)

Application guidelines

Stainless
Steel 304

18-20% Cr, 8-11% Ni,
<2% Mn balance iron

Upto 900°C in oxidizing conditions. Has goods resistance to oxidation and corrosion.

Stainless
Steel 316

16-18% Cr, 10-14% Ni,
2-3% Mo, balance iron

For use upto 900°C in oxidizing conditions.  Has goods resistance to corrosion mild acid & pitting.

Heat resistance
steel SS 446

23-27% Cr, balance Iron

Upto 100°C in oxidizing conditions. Excellent resistance to corrosion in sulphurous atmosphere. For use in salt bath & molten metal.

Stainless
Steel 310

24-26% Cr, 19-22% Ni
<2% Mn. Balance iron

Upto 1100°. High resistance to nitrogenous atmosphere, deficient in oxygen. Suitable for carburizing, annealing, hardening furnaces & cyanide salt bath.

Inconel 600

72%(Min) Ni,
14-17% Cr, balance iron

Upto 1150°C under oxidizing conditions must not be placed in sulphurous atmosphere above 550°C. Suitable for carburizing, annealing & hardening furnace, cyanide salt bath etc.

Pt.6% Rh

6% Rhodium and balance platinum

For R/S type thermocouples, maximum temperature 1650°C, for use in inert oxidizing environment.

Tantalum

Tantalum

For R/S/W/W3/W5 thermocouples, maximum temperature 2200°C, for use in insert vacuum environment.

 

LIMITS OF ERROR FOR THERMOCOUPLES

LIMITS OF ERROR FOR RTD Pt 100

 

Element

Type

Temp.
Range °C

Standard

Special

Temp. °C

Class 'B'
±°C  ± Ω

Class 'A'
±°C  ± Ω

 

Fe/Const.

J

0...700

±2.2°C/0.75%

±1.1°C/0.4%

0

0.3

0.12

0.15

0.06

NiCr/Ni(Cr/Al0

K

0...1200

±2.2°C/0.75%

±1.1°C/0.4%

100

0.8

0.30

0.35

0.13

Cu/Const.

T

0.....350

±1.0°C/0.75%

±0.5°C/0.4%

200

1.3

0.48

0.55

0.20

Cr/Const.

E

0....900

±1.7°C/0.50%

±1.1°C/0.4%

300

1.8

0.64

0.75

0.27

Nicrosil/Nisil

N

0....1280

±2.5°C/0.75%

±1.5°C/0.4%

400

2.3

0.79

0.95

0.33

Pt10%Rh/Pt

S

0.....1600

±1.2°C/0.25%

-

500

2.8

0.93

1.15

0.38

Pt13%Rh/Pt

R

0....1600

±1.2°C/0.25%

-

 

 

 

 

 

 

They are used in industries, power plants, and metal melting furnaces, salt baths, industrial process control, laboratories and numerous other applications as

  • Salt Bath : Neutral/ Cyanide/ Borax/ HSS/ Chloride/ Other
  • Molten Metal : Zinc/ Magnesium/ Aluminium/ Copper/ Brass/ Ferrous Alloys/ Other
  • Process Furnaces : Glass melting/ Cracking/ Roasting/ Blast/ Calcining/ Hydrogenising/ High Pressure Stoves (specify process material)
  • Ovens & Furnace with : Reducing/ Oxidising/ Sulphurous/ Carbonising gaseous atmosphere (Specify gas details)
  • Plating : Galvanising/ Tinning

 

Fields marked with * are mandatory fields.

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