- thermowells

Thermowells are used to:- protect the thermometer bulb from corrosive effects,

pressure and high flow of process fluids;- allow interchangeability of the thermometer for

calibration or replacement without disturbing theprocess.

Thermal conduction between bulb and thermowell isassured by mineral oil, aluminium, copper or graphitepowder.

CONSTRUCTIVECHARACTERISTICSMaterialsAl.9 316 built-up are used or:

bar-stock in: flanges in:Carbon steel

Camon steelAISI 304AISI 316

AISI 304AISI 316

Insertion lengthBuilt-up, bar-stock or flanged thermowells are built withlengths from min. 70 to max. 600 mm.

IdenWicaHonAll built-up or bar-stock thermowells are stamped withthe type of material and tag on flanged thermowells arastamped the size, rating and material.

PRESSURE/TEMPERATURE DIAGRAMValid for bar-stock thermowells type M52-M53 only.

thermowellsRECOMMENDATIONSOperating PressureThe operating pressure that thermowells can be used at TEMPERATURE LIMITS FOR MATERIAL

decreases (see diagram) with respect to chemical APPLICATIONS

characteristics of the process fluid. Bar-stock thermowells

For further information refer to tables “Nominal - Brass -10+200%

pressure/operating pressure” in the “Information and - Carbon steel -30+350%.

Rules” section. - AISI 304 -200+800%- AISI 316 -200+8OO’C.

Built-up thermowellsFor built-up thermowells the application limits depend onthe type of welding:- +65% for tin alloy welding.- +12O*C for silver alloy welding- +400°C for argon welding.

Insertion length commonly called the “U” dimension Thermometer connection ?”U-dimension measure from process connection to the Male or female thread which can be connected, directlyend of thermowell. Available from a minimum of 70 mm or by capillary, to the thermometer. Thread sizes: 1/2”to maximum 800 mm length. NPT male or female. Other connection can be supplied.

Shank configuration Bulb length “S’The stem shape depends on the characteristics of theprocess fluid. The tapered shape for instance is forapplications with high temperature and pressure.

Process Cormecdon “F”

Bulb length, commonly called “S” dimensiot- is actuallya thermometer specification and not a thermowellspecification. It is the length from the top of the mountingthreads of a thermometer to the end of its stem.

Process connection on thermowells with flanges or withmale thread is used for attaching thermowell to process.Standard process threads are I /2”, 3/4” and 1” NPT.Flange raised face or ring joint types, dimensioned toASA 616.5 or U.N.I.

Lagging extension “F’Dimension between the process connection and theconnection.

Lagging extension “T”+ Ii 3 lnsetiion length commonly

called the “U” dimensions-T~-~~~~- U Shank

I f configuration

Lb

-1 F

Thermometer Process Connection “F” I L

connection “f” LS-

Stem length ‘3

TBT THERMOWELL SELECTION

rr

Ex_l)M63 Al!Sl316 M

I I

r

ias

Ex.2)?661 AlSl316 l/Z”Gas Steel 1”6&lRF lJl66

TYPE OF THERMOWELL:indicate code as per tab. A-B-C.

THERMOWELL MATERIAL:indicate the type of material depending on the nature,temperature, pressure and speed of the process fluid.

THERMOMETER CONNECTION:indicate the thread as per tab. A-B-C.

FLANGE MATERIAL:indicate type of material depending on nature,temperature, and pressure of the process fluidFor non-flanged thermowell indicate code X.

PROCESS CONNECTION “F”:indicate thread as per tab. A-B or indicate flangedetails as per UNI, ASA specifications from tab. D-E.

DIMENSION “U”:indicate immersion length in mm.

DIMENSION ‘IT”:indicate length of eventual lagging extension in mm.

EXAMPLE 1)M53 = Bar-stock thermowell tapered shank

PN4OO female/maleAISI 316 = Thermowell in AISI 316 stainless steel1/2” Gas = Female thread for connection to

EXAMPLE 2)M91AISI 3 1 6 =1/2” Gas =

thermometer Steel =X = Absence of flange l”6OORF =1” NPT = Male thread for process connectionUi60 = Insertion length Ul60 =T40 = Length of extension for insulation

Flanged thermowell PNlOOThermowell in AISI 316 stainless steelFemale thread for connection tothermometerFlange in carbon steelFlange as per ASA B16.5 1973specificationInsertion length

thermowellsTHERMOWELLS WITH NPT THREAD CONNECTIONTYPES AND DIMENSIONSPN25 BUILT-UP THERMOWELLS/STRAiGHT SHANK

PNIOO BAR-STOCK THERMOWELLS/STEPPED SHANK

-. w LY,i) --

P J

PN400 BAR-STOCK THERblOWELLS/TAPERED SHANK

f -II I- ”

TAB. A. TYPES AND DIMENSIONS

(1) always lower than “IJ”

THERMOWELLS WITH GAS READ CONNECTITYPES AND DIMENSIONS

LAGGING EXTENSION

Ratio between procass fluid speed and length of theimmersed part “U” for bar-stock thermwell typeM52-M53.

This table is only a guide, other conditions may changedata.

PES AND DIMENSION:

thermowellsTHERMOWELLS WITH FLANGETYPES AND DIMENSIONS

IE” NPT mz PNZ5 built-up thc?rrnoweII

l,Y Gas Bql~ PNlOO bar-stock them,o,ve,,

1,2’ NPT Es2 PNIOO bar-stwk th,,,owe,, 4TAB. 13

Flange dimensions as per U.N.I. specificationsSize PN F e

TAB. EFlange dimensions as per ASA B16.5 thread specifications

OptionalsUpon request and at extra charge the themowells canbe provided with:- plug and chain,- PTFE protection,- polished external finishing,