PTRA-PTRM

Supported Applications

The Omega PTRA and PTRM series consists of ceramic thermocouple protection tubes designed for high-temperature applications. These cast ceramic components provide mechanical strength and thermal stability in demanding environments.

• PTRA models utilize OMEGATITE® 450 (99.8% Al₂O₃) composition.
• PTRM models utilize OMEGATITE® 300 (85% mullite, 15% glass) composition.

Operating Conditions & Performance

The series supports maximum service temperatures of up to 1700°C (3092°F) for OMEGATITE® 450 and 1400°C (2552°F) for OMEGATITE® 300. Both materials are gas tight with a water absorption of 0.00.

Mechanical Properties

The documented physical properties distinguish the two material grades:

• OMEGATITE® 450 (PTRA): Compressive strength >300,000 psi; Tensile strength 30,000 psi; Transverse strength 55,000 psi. Hardness is rated at 9 on the Mohs Scale.
• OMEGATITE® 300 (PTRM): Compressive strength >190,000 psi; Tensile strength 18,000 psi; Transverse strength 27,000 psi. Hardness is rated at 7.5 on the Mohs Scale.

Thermal and Electrical Properties

The coefficient of linear thermal expansion varies by temperature range for OMEGATITE® 450: 6.2 x 10⁻⁶ (24 to 250°C), 7.4 x 10⁻⁶ (24 to 500°C), 8.5 x 10⁻⁶ (24 to 1000°C), and 9.8 x 10⁻⁶ (24 to 1500°C). OMEGATITE® 300 coefficients are listed as 3.3 x 10⁻⁶, 4.0 x 10⁻⁶, and 5.0 x 10⁻⁶ for the lower temperature ranges.

• Dielectric Strength: >230 volts/mil (OMEGATITE® 450) or 250 volts/mil (OMEGATITE® 300).
• Volume Resistivity: 10¹³ ohm cm for both materials.

Configuration Options

The series is available in various inside and outside diameters with standard lengths of 12, 18, and 24 inches, as well as metric sizes. Tubes can be ordered open-end or configured with optional fittings.

Fitting Options

Tubes may include one of three fitting configurations appended to the model number:

• 1: ½ x ½" NPT (fits tubes 6.0 to 12.5 mm OD).
• 2: ½ x ¼" NPT (fits tubes 8.0 to 19.0 mm OD).
• 3: ⅜" x 27NS Brass Ferrule, 50 mm (2") long (fits tubes 17.5 mm OD to ¼" OD).

Model Numbering

The model number format is PTRA-<Inside Diameter>-<Length> for OMEGATITE® 450 and PTRM-<Inside Diameter>-<Length> for OMEGATITE® 300. For tubes with fittings, append the fitting number (1, 2, or 3) after the model number.

Key Product Differences

The primary distinction between series variants is the ceramic material composition and its associated performance envelope:

• PTRA Series: Constructed from OMEGATITE® 450 (99.8% Al₂O₃). Offers higher compressive strength (>300,000 psi) and a maximum service temperature of 1700°C (3092°F).
• PTRM Series: Constructed from OMEGATITE® 300 (85% mullite, 15% glass). Offers lower compressive strength (>190,000 psi) and a maximum service temperature of 1400°C (2552°F).

Special lengths are available upon consultation with Sales. For metric sizes and molten metal applications, the source directs users to OMEGATITE® 650.