Thermowells are protective tubes used to house temperature sensors in harsh industrial environments. They can be made from various corrosion-resistant materials in different styles. Key considerations in thermowell selection include insertion length for accurate temperature measurement, bore diameter to fit the sensor, and vibration resistance. Thermowell accessories include connection heads, terminal blocks, and fittings to integrate the sensor into process piping or vessels. Tempsens provides custom thermowells and accessories for applications up to 17,000°C along with quality certification and packaging for protection during shipping.

1. THERMOWELLS & ACCESSORIES

2. Thermowells
• In case the environment is corrosive or harsh, it is recommended that thermocouple / RTD should
be placed in a Thermowell or protection tube.
• These wells can be made from different materials like SS304, SS316, HRS446, Inconel, Monel,
Ceramic, etc.
• The construction can be fabricated or solid drilled bar stock.

3. Construction of Thermowells
Stepped Shank Also called “reduced tip”. The shank O.D. is reduced over the last 2½” of the
“U” dimension from the standard root diameter to ½” O.D. The stepped
shank is available with a 0.260” bore diameter only.
Straight Shank Shank O.D. is the same from the root diameter (“Q” dimension) to the tip
diameter (“D” dimension). The straight shank is generally used with a
0.385” or larger bore diameter, but is also available with a 0.260” bore.
Tapered Shank Shank O.D. is gradually reduced from the root diameter (“Q” dimension) to the
tip diameter (“D” dimension). The tapered shank is recommended for
heavy duty applications characterized by high vibration, pressure,
temperature, and/or velocity.

4. Construction of Thermowells
Process Connection External means to connect thermowell to process system. Wells can be
threaded, bolted (to matching flange), clamped, or welded in place.
Instrument Connection Internal threads to connect temperature instrument to thermowell.
“U” / "IL" Dimension Length of thermowell immersed into process system. Measured from
the base of the process connection to the end tip of the well.
“T” / "EL" Dimension Also called “lag length” or “lagging extension”. Extends length between
the instrument and process connections to accommodate vessel or
piping insulation.
“S” Dimension Instrument insertion length into thermowell. Equal to bore length.
“D” Dimension Also called “tip diameter”. Diameter of thermowell shank at the end tip
of the thermowell. This dimension may vary with process connection
and/or shank design as per ASME PTC 19.3
Bore Diameter Dimension of internal bore to match the diameter of the instrument
inserted into the thermowell.

5. Selection Consideration of Thermowells
Insertion Length For best temperature measurement accuracy, the “U” dimension should be
long enough to permit the entire temperature-sensitive part of the
measuring instrument to project into the medium being measured.
Liquid temperature measurement: one inch or greater.
Gas temperature measurement: three inches or greater.
Bore Diameter Will depend on inset size, Inset is normally 6/ 8 mm
Thermowell Style Tapered shank wells provide greater stiffness for the same sensitivity. The
higher strength to weight ratio gives these wells higher natural frequency
than for equivalent straight shank wells, thus permitting operation at higher
fluid velocities.
Vibration effect The calculations necessary to provide adequate strength under given
conditions are familiar enough to permit proper choice of wall thickness and
material.
Less familiar are the vibrational effects to which thermowells are subjected.
Fluid flowing past the well forms a turbulent wake (the Von Karman Trail),
which has a definite frequency based on the diameter of the well and the
velocity of the fluid. The thermowell must have sufficient stiffness so that
the wake frequency will never equal the natural frequency of the thermowell
itself. If the natural frequency of the well were to coincide with the wake
frequency, the well would vibrate to destruction and break off.

6. Thermowells/Protection Tubes
Material Selection
Material Recommended
maximum
temperature
Remarks
Carbon steel 538⁰ C For non corrosive liquid and gases
Cast Iron 700⁰ C For Molten Aluminum
SS 304 870⁰ C Resistant to oxidation and corrosion. Generally used in
wet process application such as stem line, oil refineries
and chemical solution.
SS316 870⁰ C Good resistance to corrosion application
Superior to SS304 in corrosion resistance, resist putting
in phosphoric and acetic acids
SS 310 1100⁰ C Superior to SS316, used for high corrosive resistance at
elevated temperatures
Inconel 1150⁰ C Excellent mechanical properties and oxidation resistance
at high temperatures, used for furnace parts, heat
treatments. And heating element sheathings in nuclear
engineering. Do not use in Sulphur applications.
Monel 450⁰ C Good resistance to corrosion by sea water sulfuric,
Hydrochloric and phosphoric acids.
Mostly used in chemical industries

7. Thermowells/Protection Tubes
Material Selection
Material Recommended
maximum
temperature
Remarks
HRS 446 1090⁰ C Excellent resistance to oxidation and corrosion at high
temperature, do not use in carbonizing atmospheres.
For sulphuric applications, salt bath and molten metals.
Nickle 1090⁰ C Excellent resistance to attack by many chemicals at high
temperature. Do not use in sulfur above 538⁰ C
Ceramic tube 60%
alumina
1500⁰ C High temperature application, beyond 1200⁰ C to 1400⁰
C. Contaminates the noble metal element on long term.
Ceramic tube
99.7% Allumina
1700⁰ C Gas tight protection, excellent resistance to thermal and
mechanical shocks.
Recrystallized
Silicon carbide
1600⁰ C Good thermal shock properties, direct flame
impregment and abrasion applications.

8. Facilities
 CNC Turning Centers – 13 Nos
 Turn Mill center – 1 No.
 VMC Machines –1 No.
 Deep Hole Drilling Machines up to
1500mm drilling capacity – 17 Nos
 Manual Lathe Machines – 60 Nos
 Cutting Machines – 8 sets
Machining Facilities
Testing & Calibration
Welding Facilities

9. Facilities
 Laser Welding (YAG) – 2 Numbers
 Programmable Micro Plasma
Welding Machines 3 Numbers
 TIG Welding machines with pulse
modulation and rotary positioner –
10 Nos
 Resistance Welding
 Approved and qualified Welders
 WPS and PQR for each job
 Full penetration welding
Welding Facilities
Machining Facilities
Testing & Calibration

10. Facilities
Testing & Calibration
Machining Facilities
Welding Facilities
 PMI setup for chemical analysis of
Alloys
 Pressure test setup
 Helium & Nitrogen leak detector
 Profile Projector
 Dye penetration test setup for weld
joints
 Ultrasonic thickness test
 Mechanical checks - lengths, gauges,
concentricity checks
 Radiography

11. Thermowells
Material : SS304, SS316, SS316L, SS321, SS310,
HRS446, INCONEL 600/800, 601
Hastalloy, Monel, Titanium etc.
Type : Drilled barstock, Fabricated
Construction : Tapered, Straight
Process Connection : Screwed, Flanged
Certification : IBR certification on request

12. Thermowell Models

13. Special Thermowells/Protection Tubes
• Metal Thermowells with Tungsten
carbide/Ceramic/ PTFE/PVDF/PFA coatings.
• Solid sintered tungsten carbide
• Silicon carbide(Re-crystallised & Nitride Bonded)
• Platinum thimble
• Tantalum, Titanium, Nickle cladding,
• Tantalum Tungsten (Ta10W) Alloy
• Graphite
• Silicon Nitride
• Other Materials in various sizes available on
request

14. Protection Tubes
Material : Re-crystallised Alumina 99.7%
Type : KER 710(C-799) Open Ended, Close
Ended
Length : 350, 530, 600, 650, 740, 900, 1030,
1200, 1430 mm etc.
OD x ID : 6x4, 8x5, 10x6, 12x8, 15x10, 20x15,
24x18mm etc.
Insulating Tubes : 2/4/6 Holes etc.
OD : 1.5, 2.8, 3.5, 5.5, 8.5 etc.
Material : SS304, SS304L, SS310, SS446,
Inconel-800/600,Hastalloy,
Titanium etc.
Type : Open Ended, Close Ended ,Round
Ended Length : As per requirement
Ceramics Stainless Steel Tubes

15. Quality Test Certificate

16. Accessories
Material : Die cast aluminium, Stainless steel,
Plastic etc.
Types : A, B, C, DAN, DAN-W, KNE etc.
Single entry, Double entry, miniature
Cable Entry : M24x1.5, M20x1.5, 3/4" ET, 1/2"
NPT/BSP
Bottom Entry : ½” BSP, M20x1.5, 1/2" NPT
Protection Class : IP 65, IP 67, Ex-proof II A/II B, II C
Connection Heads
Terminal Blocks
Material : Ceramic
Terminal : Two, Three , Four, Six, Eight

17. Accessories
Connectors
• Plug and jack compensated for thermocouples.
• J, K, N, R, S, B, T, E, Types
• Standard, Miniature, Panel mounted, Simplex, Duplex
• Material : Glass Filled Nylon and Ceramic
• Colour Coding : Various Standards
• Lemo Connectors
Compression Fittings
Material
AISI SS316, SS304 ,SS303, Carbon Steel, Brass
Thread
NPT, BS

18. Accessories
Precision Pipe Fittings
Material
AISI SS316, SS304 ,SS303, Carbon Steel, Brass
Thread
NPT, BS
Seal Pots & Accessories
Material
SS316, SS304, SS303, Carbon Steel, Brass etc.
Thread
NPT, BSP

19. Accessories
Flanges
Bayonet Caps
Material
AISI SS304,SS316, SS316L,Carbon Steel, Cast Iron etc.
Size
1/2" to 4" & Others
Rating
150# to 2500# etc.
Material
SS316, SS304, SS303, Carbon Steel, Brass etc.
Thread
NPT, BSP

20. Pyrometer Accessories
Airpurge Unit Adustable mounting
(8000-04) Stand
Water cooling
Jacket

21. Packaging & Dispatch
 A unique serial number along with material is marked on
each thermowell manufactured by Tempsens.
 This unique serial number for each thermowell ensures
vendor accountability for each and every thermowell.
 If required, Tag numbers are also marked on it.
 Thus, there is 100% full traceability for every thermowell
manufactured in Tempsens.
 Special attention is given to deliver the most fragile or the
bulkiest products.
 Thermowells first are packed with PVC sleeves to protection
it from Scratching and then these are packed in carton and
the finally in wooden boxes before dispatch.
 We ensure that Thermowells are delivered in perfect
condition at the destination.

22. TEMPSENS INSTRUMENTS (I) PVT. LTD. : UNIT #2
A-190, Road No. 5, MIA, Madri
Udaipur - 313 003 (Rajasthan) INDIA
Phone : +91-294-3052929/3052953
Fax : +91-294-3052950
Temperature Sensing, Heating & Cables
THANK YOU!