RTD T53, T54, T55

Summary

Product identification

The Endress+Hauser T53, T54, and T55 are explosion-proof thermocouple assemblies designed for process industries. They are available with spring-loaded inserts and enclosures.

Application

These MgO (Magnesium Oxide) insulated thermocouples are suitable for various process and laboratory applications, including:

• Chemicals
• Petrochemicals
• Refineries
• Offshore Platforms

Measuring principle

The devices utilize thermocouples, which are robust temperature sensors based on the Seebeck effect. They measure temperature differences by generating a thermoelectric voltage (emf) when two dissimilar electrical conductors are subjected to a thermal gradient. The emf magnitude is dependent on the conductor materials and the temperature difference between the measuring junction and the cold junction. Absolute temperature is determined if the cold junction temperature is known or measured and compensated for. Thermocouple types and their voltage/temperature characteristics are standardized by IEC 60584 and ASTM E230/ANSI MC96.1.

Measuring system

The system can incorporate Endress+Hauser iTEMP temperature transmitters. These transmitters offer enhanced accuracy and reliability compared to directly wired sensors.

Transmitter Outputs and Protocols

• Analog output: 4 to 20 mA
• Digital communication: HART®, PROFIBUS® PA, FOUNDATION Fieldbus™
• Optional: Bluetooth® connectivity

Application Example Components

• Mounted thermometer with head transmitter: The core sensor assembly.
• RIA15 process display: Records and displays the analog measuring signal from the head transmitter. It can show the measured value digitally and as a bar graph indicating limit violations. Powered by the 4 to 20 mA or HART® loop.
• RN42 active barrier: A 17.5 VDC, 20 mA device with a galvanic isolated output for supplying loop-powered transmitters. It operates with an input voltage of 24 to 230 V AC/DC, 0/50/60 Hz.

Input

• Measured variable: Temperature (temperature-linear transmission behavior).
• Measurement range:
  • Type T: –270 to +400 °C (–454 to +752 °F)
  • Type J: –210 to +1200 °C (–346 to +2192 °F)
  • Type E: –270 to +1000 °C (–454 to +1832 °F)
  • Type K: –270 to +1372 °C (–454 to +2500 °F)
  • Type N: –270 to +1300 °C (–454 to +2372 °F)
• Upper temperature limits for various sheath diameters (¹⁄₄ in):
  • Type T: 370 °C (700 °F)
  • Type J: 370 °C (700 °F)
  • Type E: 820 °C (1510 °F)
  • Type K: 1150 °C (2100 °F)
• Note: Temperature limits are for guidance and may affect stability or life. Thermocouples with 316 SS sheath and assemblies with 316 SS thermowells are rated for a maximum of 927 °C (1700 °F).

Output

• Signal Transmission:
  • Directly-wired sensors (without transmitter).
  • Via Endress+Hauser iTEMP temperature transmitters using common protocols (4 to 20 mA, HART®, PROFIBUS® PA, FOUNDATION Fieldbus™).
• iTEMP Transmitter Advantages:
  • Dual or single sensor input (option).
  • Pluggable display (option).
  • High reliability, accuracy, and long-term stability.
  • Mathematical functions.
  • Thermometer drift monitoring, sensor backup, and diagnostic functions.
  • Sensor-transmitter matching for dual input transmitters.

Field Transmitter Features

• HART®, FOUNDATION Fieldbus™ or PROFIBUS® PA communication.
• Backlit display for readability in various lighting conditions.
• Displays measured value, bargraph, and fault indication.
• Dual sensor input (on some models).
• High reliability in harsh environments.
• Corrosion detection (on some models).

Galvanic Isolation

Endress+Hauser iTEMP transmitters offer galvanic isolation (e.g., 2 kV AC) to prevent ground loops, particularly when using grounded thermocouples for fast response times.

Power Supply

• Head mounted transmitter TMT18x (single input): 11.5 to 35 V (non-Ex), 11.5 to 30 V (Ex).
• Other transmitters: Specific voltage ranges apply (e.g., 11.5...35 V, 11.5...30 V Ex).

Electrical

Integrated Overvoltage Protection (Optional)

This module protects electronics from overvoltage in signal and power supply cables.

• Maximum continuous voltage (rated voltage): UC = 42 VDC
• Nominal current: I = 0.5 A at Tamb. = 80 °C (176 °F)
• Surge current resistance:
  • Lightning surge current D1 (10/350 µs): Iimp = 1 kA (per wire)
  • Nominal discharge current C1/C2 (8/20 µs): In = 5 kA (per wire), In = 10 kA (total)
• Temperature range: –40 to +80 °C (–40 to +176 °F)
• Series resistance per wire: 1.8 Ω, tolerance ±5 %

Grounding

The device must be connected to the potential equalization system. The connection between the housing and ground must have a minimum cross-section of 4 mm² (13 AWG).

Wire Specifications

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

Thermocouple Color Codes (ASTM E-230)

Performance Characteristics

Reference Conditions

Data relevant for determining accuracy of temperature transmitters.

Response Time

• Thermocouple assembly T55 (ungrounded, ¹⁄₄" insert): 2.9 s (63% response time per ASTM E839).
• With Thermowell:
  • Stepped thermowell: 15 s
  • Tapered thermowell: 20 s
  • ³⁄₄" straight thermowell: 25 s

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

Maximum Measured Error (Thermocouples per ASTM E230)

Note: For °F errors, calculate in °C and multiply by 1.8.

Transmitter Long-Term Stability

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

Insulation Resistance

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

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 and conform to ASTM E220.
• Three-point calibrations are available.

Installation Conditions

• Orientation: No restrictions.
• Immersion Length: Critical for accuracy; should be at least half the pipe diameter.
  • Minimum immersion lengths for thermowells (T53/T54):
    • 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)
• T55 Assemblies: Only for use in existing thermowells.

Shock and Vibration Resistance

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

Environment

Ambient Temperature Range

• Terminal Head:
  • Without mounted head transmitter: Depends on terminal head and cable gland.
  • With mounted head transmitter: –40 to 85 °C (–40 to 185 °F)
    • SIL mode (HART 7): –40 to 70 °C (–40 to 158 °F)
  • With mounted head transmitter and display: –20 to 70 °C (–4 to 158 °F)
  • With mounted 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)

Mechanical Construction

Dimensions

Dimensions are provided in inches and millimeters. Key dimensions include:

• Spring travel of insert: ½"
• Tolerance of XA length: +/- ¼"

T53 Dimensions

• Immersion length RTD sensor = Thermowell drilled length XA = A = U + 38.1 mm (1.5 in) + T
• Insert overall length X = A + E
• Pipe sizes: Nom. ¾” (Dia. 1.050"), Nom. 1” (Dia. 1.315")

T54 Dimensions

• Immersion length RTD sensor = Thermowell drilled length XA = A = U + 50.8 mm (2 in) + T
• Insert overall length X = A + E

T55 Dimensions (without thermowell)

• Extension E: Specified length (4 to 100 in).
• Immersion length Thermocouple sensor XA: Varies based on insert type (e.g., TU221).
• Lamination Nipple Union Nipple (LUN): 101.6 mm (4 in) or 177.8 mm (7 in).
• Spring travel of the insert: ½"

Housing - Terminal Heads

• All terminal heads conform to DIN EN 50446.
• TA30H:
  • Flameproof (XP) version.
  • Protection class: IP 66/68, NEMA Type 4x (Ex-version: IP 66/67).
  • Temperature range: –50 to +150 °C (–58 to +302 °F) for rubber seal (without cable gland).
  • Material options: Aluminum (polyester powder coating) or Stainless steel 316L.
  • Threads: ½" NPT, ¾" NPT, M20x1.5, G½".
  • Weight: Aluminum approx. 640 g (22.6 oz), Stainless steel approx. 2400 g (84.7 oz).
• TA30H with display window:
  • Similar specifications to TA30H.
  • Weight: Aluminum approx. 860 g (30.33 oz), Stainless steel approx. 2900 g (102.3 oz).
  • Optionally available with TID10 display.

Field Transmitter Housing

• TMT162 (dual input) / TMT142B (single input):
  • Protection class: IP67, NEMA type 4x (TMT162); IP66/67, NEMA type 4x (TMT142B).
  • Material: Die-cast aluminum (AlSi10Mg) or Stainless steel 316L.
  • Display: Brilliant backlit, rotatable in 90° increments.
  • Cable entry: 2x ½" NPT.
  • Optional: Integrated Bluetooth® interface (TMT142B).
  • SIL certification (TMT162 with HART 7).

Materials

Process Connection and Thermowell Materials

• 1. AISI 316/1.4401 can be used to 800 °C (1472 °F) to a limited extent under low compressive loads and in non-corrosive media.

Process Connection

• T53: Threaded (NPT ½", ¾", 1"), Socket weld (NPS ¾", 1"), Weld-in (NPS ¾", 1").
• T54: Flange (ASME B16.5 compliant).
• T55: Extension neck types (Type N, Type NUN) with ½" NPT external thread.

Supplementary Documentation

• Technical Information (TI): Planning aid, technical data, accessories.
• Brief Operating Instructions (KA): Quick start guide.
• Operating Instructions (BA): Comprehensive reference document.
• Description of Device Parameters (GP): Detailed explanation of parameters.
• Safety Instructions (XA): Relevant for specific approvals.

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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)

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