ISOTECH Water Triple Point Cell Storage Unit Model 18233

Overview

The ISOTECH Model 18233 Water Triple Point Cell Storage Unit is an engineered benchtop enclosure designed exclusively for the long-term, thermally stable storage of sealed water triple point cells (WTPCs) — primary fixed-point standards defined by the International Temperature Scale of 1990 (ITS-90). Unlike general-purpose refrigeration or ambient storage cabinets, the 18233 maintains a precisely controlled, uniform thermal environment near 0.01 °C (273.16 K), minimizing thermal gradients, mechanical disturbance, and condensation risks that could compromise cell integrity or reproducibility. Its architecture supports metrological continuity by preserving the physical state of the high-purity ice–water–vapor equilibrium within each cell, ensuring minimal drift in realized triple point temperature over extended periods. The unit is not a calibration instrument per se, but a critical infrastructure component in national metrology institutes (NMIs), accredited calibration laboratories, and ISO/IEC 17025-certified temperature labs where traceability to SI base units must be demonstrably maintained.

Key Features

• Simultaneous storage of up to four standard 150 mm or 200 mm sealed water triple point cells in individual, vibration-damped cradles;
• Passive thermal stabilization via high-efficiency insulation and low-thermal-conductivity support structure — no active cooling or heating elements, eliminating electronic noise and power dependency;
• Stainless steel internal chamber with inert, non-outgassing surface finish to prevent contamination of cell envelopes;
• Hermetically sealed access door with dual-stage silicone gasketing to maintain internal humidity stability and exclude ambient moisture ingress;
• Integrated temperature monitoring port compatible with calibrated Pt100 or SPRT probes for periodic verification of thermal uniformity (±0.5 mK typical axial gradient);
• Benchtop footprint (W × D × H ≈ 320 × 320 × 410 mm) optimized for cleanroom or metrology lab integration with minimal floor space requirement.

Sample Compatibility & Compliance

The Model 18233 accommodates cylindrical, fused-quartz or borosilicate glass WTPCs conforming to ASTM E2704–22 and ISO/IEC 17025 Annex A3 requirements for fixed-point cell geometry and seal integrity. It is compatible with cells from major manufacturers including Fluke Hart, Isotech, and Sartorius. While the unit itself carries no direct accreditation, its design enables laboratories to meet clause 6.4.7 (Reference Materials and Equipment) of ISO/IEC 17025:2017 and supports adherence to EURAMET cg-18 (Guidelines on the Realization and Use of the Water Triple Point). No electrical safety certification (e.g., CE, UKCA) is required due to its passive thermal architecture; however, it is supplied with UK-manufactured documentation compliant with UKAS traceability expectations.

Software & Data Management

The 18233 operates without embedded firmware or proprietary software — consistent with good metrological practice for primary standard storage systems. Temperature verification is performed externally using accredited reference thermometers and data loggers (e.g., Keysight 34972A, Omega OM-DAQPRO-5300), with recorded values archived manually or via laboratory information management systems (LIMS) supporting 21 CFR Part 11 audit trails. ISOTECH provides a comprehensive user manual detailing recommended storage protocols, handling procedures, and verification intervals aligned with BIPM CCT-WG3 best practices. Optional calibration certificates for associated verification probes are available upon request.

Applications

• Long-term archival storage of WTPCs between calibrations or inter-laboratory comparisons;
• Stabilization of cells prior to use in SPRT calibration cycles under controlled thermal soak conditions;
• Supporting uncertainty budgeting in temperature calibration labs by minimizing cell-to-cell variability induced by inconsistent storage;
• Enabling compliance with ISO 17025 Clause 7.7 (Uncertainty of Measurement) through documented thermal history of reference standards;
• Facilitating participation in CIPM Key Comparisons (e.g., CCT-K3, CCT-K8) where cell stability over multi-year periods is rigorously assessed.

FAQ

Does the Model 18233 actively cool or heat the chamber?
No — it relies entirely on passive thermal mass and insulation to maintain thermal stability near 0.01 °C. Ambient lab temperature should be held between 18 °C and 25 °C for optimal performance.
Can I store other fixed-point cells (e.g., gallium or indium) in this unit?
No — the 18233 is dimensionally and thermally optimized specifically for water triple point cells. Other fixed points require dedicated storage environments with different thermal setpoints and mechanical support configurations.
Is the unit supplied with calibration documentation?
The unit itself is not calibrated, but ISOTECH provides a Factory Test Report confirming dimensional compliance, material certification, and thermal uniformity verification data at time of shipment.
What maintenance is required?
Annual visual inspection of gasket integrity and internal chamber cleanliness is recommended. No scheduled servicing or consumables are required.
Does ISOTECH offer installation or commissioning support?
Yes — optional on-site verification services are available, including thermal mapping and integration guidance for ISO/IEC 17025 documentation workflows.