TH53, TH54, TH55

Summary

Product identification

The TH53, TH54, and TH55 are magnesium oxide insulated thermocouple assemblies designed for installation in barstock thermowells. They are intended for use in all types of process industries, including heavy industries, due to their rugged design.

Application Areas

These sensor assemblies are suitable for process industries such as:

• Chemicals
• Petrochemicals
• Power plants
• Refineries
• Offshore platforms

Measuring Principle

The sensors utilize the Seebeck effect, where a voltage is generated when two electrical conductors of different materials are subjected to a thermal gradient. This thermoelectric voltage depends on the materials and the temperature difference between the measuring junction and the cold junction. Absolute temperature is determined by knowing or measuring the cold junction temperature.

Measuring System Components

Endress+Hauser offers a complete system for temperature measurement points, including:

• Power supply unit/barrier
• Display units
• Overvoltage protection

Input

Measured Variable

• Temperature (temperature-linear transmission behavior)

Measurement Range

Upper temperature limits for various thermocouple types with a ⌀¼" Sheath OD:

• Thermocouples with 316 SS sheath and assemblies with 316 SS thermowells are rated for a maximum temperature of 927 °C (1 700 °F).
• The stated temperature limits are for guidance and do not guarantee satisfactory life or performance.

Output

Output Signal

• Directly-wired sensors: Sensor measured values forwarded without a transmitter.
• Via iTEMP temperature transmitters: Support various common protocols.

Family of temperature transmitters

Endress+Hauser iTEMP transmitters offer improved accuracy and reliability compared to directly wired sensors, reducing wiring and maintenance costs.

• 4 to 20 mA head transmitters: Offer flexibility and can be quickly configured via PC using provided software.
• HART® head transmitters: 2-wire devices with one or two measuring inputs and one analog output, supporting resistance and voltage signals. Optional Bluetooth® interface available.
• PROFIBUS® PA head transmitters: Universally programmable with PROFIBUS® PA communication, providing high measurement accuracy.
• FOUNDATION Fieldbus™ head transmitters: Universally programmable with FOUNDATION Fieldbus™ communication, approved for major process control systems.
• Head transmitter with PROFINET® and Ethernet-APL™: 2-wire device with two measuring inputs, supporting PROFINET® protocol.
• Head transmitter with IO-Link®: IO-Link® device with a measurement input and IO-Link® interface for digital communication.

Advantages of iTEMP transmitters

• Double or single sensor input (optionally).
• Attachable display (optionally).
• High reliability, accuracy, and long-term stability.
• Mathematical functions.
• Thermometer drift monitoring and sensor backup/diagnostic functions.
• Sensor-transmitter matching.

Field transmitter

Field transmitters with HART®, FOUNDATION Fieldbus™, or PROFIBUS® PA communication feature backlighting for easy reading in various conditions. They offer dual sensor input, high reliability in harsh environments, mathematical functions, and monitoring features.

Galvanic Isolation

Endress+Hauser iTEMP transmitters offer galvanic isolation (U = 2 kV AC) to prevent issues like ground loops, particularly with grounded thermocouples requiring fast response times.

Power Supply

See diagram for terminal assignments for head-mounted transmitters (TMT8x dual input, TMT7x single input) and field-mounted transmitters (TMT162 dual input, TMT142B single input).

Integrated Overvoltage Protection

An optional overvoltage protection module can divert surges from signal cables and power supply to ground without affecting transmitter functionality.

• Connection data:
  • Maximum continuous voltage (rated voltage): UC = 42 VDC
  • Nominal current: I = 0.5 A at Tamb. = 80 °C (176 °F)
  • Surge current resistance: Iimp = 1 kA (per wire), In = 5 kA (per wire) / 10 kA (total)
  • Temperature range: –40 to +80 °C (–40 to +176 °F)
  • Series resistance per wire: 1.8 Ω, tolerance ±5 %

Fieldbus Connector

• Type: PROFIBUS®-PA or FOUNDATION Fieldbus™
• Dimensions: 190 mm (7.48 in) height, 26.5 mm (1.040 in) diameter, NPT 1/2”
• Connector: M12 for PROFIBUS®-PA, 7/8-16 UNC for FOUNDATION Fieldbus™
• Ambient temperature: –40 to 150 °C (–40 to 300 °F)
• Degree of protection: IP 67

Wire Specifications

• Thermocouple grade, TFE insulated 20AWG, 7 strands with stripped ends.
• Electrical connection: Flying leads, standard 139.7 mm (5.5 in).

Thermocouple Color Codes (ASTM E-230)

Performance Characteristics

Response Time

• Thermocouple assembly TH55 (without thermowell):
  • Grounded junction (⌀¹⁄₄"): 1.3 s
  • Ungrounded junction (⌀¹⁄₄"): 2.9 s
• Thermocouple assemblies with thermowell (TH53, TH54):
  • Stepped thermowell: 15 s
  • Tapered thermowell: 20 s
  • ¾" straight thermowell: 25 s

Response times are influenced by thermowell wall thickness, spacing between insert and thermowell, sensor packing, and process parameters.

Maximum Measured Error (Thermocouples according to ASTM E230)

Transmitter Long-term Stability

• ≤ 0.1 °C (0.18 °F) / year or ≤ 0.05 % / year.

Insulation Resistance

• 1000 MΩ at 25 °C (77 °F) for MgO insulated thermocouples with ungrounded hot junction (test voltage 500 VDC).

Calibration Specifications

• Manufacturer provides comparison temperature calibrations from –20 to +300 °C (–4 to +573 °F) on the ITS-90.
• Calibrations are traceable to NIST standards and conform to ASTM E220.
• Three-point calibrations are available if specified temperatures are within the recommended range.

Installation Conditions

Orientation

• No restrictions.

Installation Instructions

• Thermowell immersion length should be at least half the pipe diameter to minimize measurement errors from heat conduction.
• Minimum immersion lengths for assemblies with thermowell:
  • Stepped thermowell: 63.5 mm (2.5 in)
  • Tapered thermowell: 114.3 mm (4.5 in)
  • ¾" straight thermowell: 101.6 mm (4 in)
  • Weld-in thermowell: 114.3 mm (4.5 in)
• TH55 assemblies are designed for use in existing thermowells.

Environment

Ambient Temperature Range

• Terminal head without mounted transmitter: Depends on head, cable gland, or fieldbus connector.
• Terminal head with mounted head transmitter: –40 to 85 °C (–40 to 185 °F).
  • SIL mode (HART 7 transmitter): –40 to 70 °C (–40 to 158 °F).
• Terminal head with mounted head transmitter and display: –20 to 70 °C (–4 to 158 °F).
• Field transmitter:
  • Without display: –40 to 85 °C (–40 to 185 °F).
  • With display and/or overvoltage protection: –40 to +80 °C (–40 to +176 °F).
  • SIL mode: –40 to +75 °C (–40 to +167 °F).

Shock and Vibration Resistance

• 4 g / 2 to 150 Hz as per IEC 60068-2-6.

Process

Thermowells are used in moving fluids. Limiting values depend on temperature, pressure, medium speed, immersion length, and materials. Calculations for stress and vibration can be performed according to ASME PTC 19.3-2016.

Mechanical Construction

Design, Dimensions

Dimensions are provided in inches.

Hot or Measuring Junction

• Grounded junction: Thermocouple junction welded into the sheath end, providing faster response than ungrounded junctions. Not recommended for Type T thermocouples. Requires transmitters with galvanic isolation.
• Ungrounded junction: Thermocouple junction isolated from the sheath. Provides electrical isolation against interference and is recommended for extreme temperatures, rapid thermal cycling, and corrosion resistance.

Weight

• 1 to 30 lbs.

Material

Process connection and thermowell materials:

• 1. Can be used to a limited extent up to 800 °C (1472 °F) for low compressive loads and in non-corrosive media.

Process Connection

Available process connections include:

• TH53: Threaded (NPT 1/2", 3/4", 1"), NPS for socket weld (3/4", 1"), NPS for weld-in (3/4", 1").
• TH54: Flange (ASME B16.5 rated).
• TH55: Thermowell connection with extension neck lengths (Type N: 1/2" NPT external thread; Type NUN: 1/2" NPT external thread with various extension lengths).

Housing

Terminal Heads:

• Internal shape and size comply with DIN EN 50446, flat face, with a 1/2" NPT thermometer connection.
• TA30H: Flameproof, explosion-protected, available with one or two cable entries.
  • Degree of protection: IP 66/68, NEMA Type 4x (Ex-version: IP 66/67).
  • Temperature: –50 to +150 °C (–58 to +302 °F).
  • Material: Aluminum or Stainless steel 316L.
  • Display window: Safety glass.
  • Threads: NPT 1/2", NPT 3/4", M20x1.5, G1/2".
  • Weight: Aluminum approx. 860 g, Stainless steel approx. 2 900 g.
• TA30R:
  • Degree of protection: IP69K (standard), IP66/68 (with display window).
  • Temperature: –50 to +130 °C (–58 to +266 °F).
  • Material: Stainless steel 316L.
  • Cable entry threads: NPT 1/2", M20x1.5.
  • Weight: Standard 360 g, With display window 460 g.
• TU401:
  • Protection class: IP65 (NEMA Type 4x).
  • Temperature: –40 to 130 °C (–40 to 266 °F).
  • Material: Aluminum alloy or rubber/silicone seal.
  • Cable entry: M20x1.5 or plug M12x1 PA.
  • Weight: 300 g.
• TU401 (TA30D style):
  • Protection class: IP66/68 (NEMA Type 4x).
  • Temperature: –50 to +150 °C (–58 to +302 °F).
  • Material: Aluminum.
  • Cable entry: G 1/2", 1/2" NPT, M20x1.5.
  • Weight: 390 g.
• TU401 (TA30S style):
  • Degree of protection: IP65 (NEMA Type 4x).
  • Temperature: –40 to +85 °C (–40 to +185 °F).
  • Material: Polypropylene (PP), FDA-compliant.
  • Cable entry: 3/4" NPT, M20x1.5.
  • Weight: approx. 100 g.

Field transmitters:

• iTEMP TMT162:
  • Protection class: IP67, NEMA type 4x.
  • Material: Die-cast aluminum or Stainless steel 316L.
  • Display: Rotatable, backlit.
  • Cable entry: 2x 1/2" NPT.
  • SIL certification as per IEC 61508:2010 (HART-protocol).
• iTEMP TMT142B:
  • Protection class: IP66/67, NEMA type 4x.
  • Material: Die-cast aluminum or Stainless steel 316L.
  • Display: Rotatable, backlit.
  • Integrated Bluetooth® interface (optional).

Certificates and Approvals

Current certificates and approvals can be found on the Endress+Hauser website.

Ordering Information

Detailed ordering information is available from sales organizations or the Endress+Hauser Product Configurator online.

Accessories

Various accessories are available, including mounting brackets, cable glands, configuration kits, and integrated overvoltage protection modules.

System Components

Accessories

• RIA14 Loop-powered field indicator
• RN42 active barrier, wide range power supply
• RMA42 Process transmitter with control unit

Documentation

Available documentation includes Technical Information (TI), Brief Operating Instructions (KA), Operating Instructions (BA), Description of Device Parameters (GP), and Safety Instructions (XA).

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Disclaimer This extraction may miss figures, footnotes, or revisions. Contractual data must match the OEM PDF revision used on the project.

Official datasheet (PDF)

Lenntech datasheet mirror