JULABO SL-33B Precision Boiling Water Bath Circulator

Overview

The JULABO SL-33B Precision Boiling Water Bath Circulator is a high-stability, externally certified laboratory bath engineered for applications requiring precise temperature control up to 100 °C — including sterilization validation, enzymatic reaction studies, thermal stability testing of biological reagents, and calibration of temperature-sensitive sensors. Unlike standard water baths, the SL-33B integrates dual-loop temperature regulation via JULABO’s proprietary PID1 algorithm combined with Adaptive Control Compensation (ACC), ensuring minimal overshoot and rapid thermal equilibration across the full operating range. Its stainless steel heating coil is electrochemically passivated to resist scaling and corrosion in prolonged boiling conditions, eliminating maintenance downtime associated with mineral deposition. The unit operates exclusively in heating mode with no cooling capability, optimized specifically for sustained, energy-efficient boiling performance and long-term thermal uniformity.

Key Features

• Stainless steel immersion heater with electropolished surface finish — resistant to limescale formation and compatible with deionized, distilled, or tap water under continuous operation.
• Dual-sensor temperature monitoring system: one for process control, one for independent safety cutoff — compliant with IEC 61010-1 Class II protection requirements.
• ATC1 (Automatic Temperature Calibration) function enables user-performed single-point calibration at any temperature between 20 °C and 100 °C, traceable to NIST-certified reference standards.
• Integrated low-level float switch triggers simultaneous audible alarm, visual LED indicator, and automatic power disconnection — preventing heater element damage during evaporation or accidental drain-down.
• Configurable operational modes: manual start/stop, timed auto-start, and standby mode with reduced power consumption (<5 W) while maintaining controller readiness.
• Front-panel lockout function prevents unauthorized parameter changes; password-protected settings align with FDA 21 CFR Part 11 data integrity expectations when paired with JULABO’s optional software logging module.
• Optimized airflow architecture with rear-mounted ventilation grilles and thermally isolated control electronics — validated for uninterrupted 24/7 operation at ambient temperatures up to 35 °C.

Sample Compatibility & Compliance

The SL-33B accommodates standard laboratory glassware including Erlenmeyer flasks (up to 5 L), jacketed reactors (with external circulation ports), and multi-well plates mounted on custom support racks. Its open-bath design permits direct immersion of probes, sensors, and tubing without obstruction. All wetted components comply with USP Class VI biocompatibility standards and EU Directive 2002/72/EC for food-contact materials. The device meets CE marking requirements under the Low Voltage Directive (2014/35/EU) and Electromagnetic Compatibility Directive (2014/30/EU). For regulated environments, it supports IQ/OQ documentation packages and is routinely deployed in pharmaceutical QC labs performing USP thermal validation protocols.

Software & Data Management

While the SL-33B operates as a standalone instrument with intuitive rotary encoder interface, optional integration with JULABO’s WinTemp Pro software (v4.2+) enables real-time temperature logging, export to CSV/PDF, and electronic signature-enabled report generation. When connected via RS232 or USB-to-serial adapter, the system records timestamped temperature values at user-defined intervals (1 s to 60 min), stores up to 1 million data points locally, and maintains an immutable audit trail including operator ID, parameter modifications, alarm events, and calibration history — satisfying ALCOA+ principles for data integrity in GxP workflows.

Applications

• Boiling point determination and vapor pressure studies per ASTM E1897 and ISO 2719.
• Thermal denaturation profiling of proteins and nucleic acids using UV-Vis spectrophotometers coupled via external flow cells.
• Accelerated stability testing of excipients and finished dosage forms under ICH Q1A(R3) guidelines.
• Calibration of platinum resistance thermometers (PRTs), thermistors, and digital thermohygrometers against fixed-point references.
• Pre-heating of mobile phases in HPLC systems prior to column inlet — reducing baseline drift and improving retention time reproducibility.
• Controlled boiling of culture media for microbiological assays requiring strict thermal consistency (e.g., membrane filtration methods per ISO 9308-1).

FAQ

What is the maximum allowable fill level for optimal temperature uniformity?
For ±0.03 °C stability across the entire bath volume, the working fluid must cover the heating coil by at least 3 cm and not exceed 5 cm below the bath rim.
Can the SL-33B be used with oils or other heat-transfer fluids?
No — this model is strictly rated for aqueous media only. Use of silicone oil or glycol-based fluids voids warranty and compromises safety interlocks.
Is remote monitoring supported out-of-the-box?
Ethernet or Wi-Fi connectivity is not built-in; however, analog 0–10 V output and Modbus RTU over RS485 are available via optional interface module (Order No. 9352433B-IO).
How often should ATC1 calibration be performed?
JULABO recommends quarterly verification using a calibrated reference thermometer traceable to national standards; more frequent calibration may be required in high-use or regulated environments.
Does the unit include documentation for regulatory audits?
Yes — factory-supplied documentation includes Declaration of Conformity, electrical safety test reports, and traceable calibration certificate for the internal sensor (NIST-traceable at 37 °C and 100 °C).