YiHeng HWS-12 Precision Water Bath Circulator

Overview

The YiHeng HWS-12 Precision Water Bath Circulator is an entry-level yet rigorously engineered benchtop thermal management system designed for routine temperature stabilization of samples in academic, industrial quality control, and R&D laboratories. It operates on the principle of convective heat transfer within a liquid medium—typically deionized water or silicone oil—to maintain uniform thermal conditions across immersed vessels. The unit employs a resistive heating element coupled with a PID-controlled feedback loop to achieve stable setpoint maintenance within ±0.3°C at 37°C (typical), with minimal spatial temperature gradient (<0.2°C across bath volume under static load). Its fixed-volume 5 L stainless steel (AISI 304) tank ensures chemical compatibility with common aqueous reagents and mild organic solvents, while the integrated internal circulation pump promotes thermal homogeneity without requiring external plumbing. Unlike open-bath systems relying solely on natural convection, the HWS-12’s forced recirculation architecture minimizes stratification and accelerates equilibration—critical for time-sensitive incubation, enzymatic assays, or solvent evaporation control.

Key Features

• Stainless steel (304) inner chamber resistant to corrosion from water, buffers, and diluted acids/bases—validated per ASTM A240 standards for laboratory-grade wet environments.
• Microprocessor-based digital controller with five-button interface enabling precise setpoint entry (0.1°C resolution), real-time temperature display, and programmable ramp-hold profiles (single-stage only).
• Dual-stage thermal safety architecture: primary over-temperature protection triggers audible/visual alarm at user-defined threshold; secondary manual-reset dry-run safeguard interrupts power when liquid level falls below heater immersion point—preventing thermal runaway during unattended operation.
• One-piece molded ABS housing rated UL 94 HB for flame resistance, with chemical resistance validated against ISO 178 for surface integrity after exposure to 10% NaOH and 10% HCl solutions.
• Adjustable aperture plate accommodating standard labware (e.g., 13–50 mm diameter test tubes, 100–250 mL beakers); no tools required for reconfiguration.
• Energy-efficient 500 W heating system optimized for rapid warm-up (≤30 min from RT to 99°C at full volume) and low standby power draw (<3 W).

Sample Compatibility & Compliance

The HWS-12 supports glass, polypropylene, and borosilicate containers up to 250 mL capacity. Its open-bath geometry permits direct immersion of reaction vessels, probe sensors, or calibration standards—ideal for USP environmental monitoring verification, ASTM D1500 color scale calibration baths, or ISO 17025-compliant reference temperature validation. While not certified to IEC 61010-1 Annex BB for Class II medical devices, it conforms to general-purpose electrical safety requirements for laboratory equipment under GB 4793.1–2007 (equivalent to EN 61010-1:2010). No CE marking is affixed; users deploying this unit in EU-regulated environments must conduct local risk assessment per Machinery Directive 2006/42/EC.

Software & Data Management

The HWS-12 operates as a standalone instrument with no native USB/RS232 connectivity or PC interface. All operational parameters—including setpoint, actual temperature, alarm status, and power-on duration—are displayed locally via a 3-digit LED screen. For GLP/GMP traceability, users may log readings manually into laboratory notebooks or integrate external data loggers (e.g., Omega OM-DAQPRO-5300) via optional PT100 probe input (not included). The device does not support FDA 21 CFR Part 11 electronic signature functionality or audit trail generation; such requirements necessitate supplementary documentation protocols.

Applications

• Enzyme kinetics studies requiring stable 37°C incubation of microplate wells or cuvettes.
• Calibration of liquid-in-glass thermometers and digital probes against NIST-traceable references.
• Accelerated stability testing of pharmaceutical formulations per ICH Q1A(R2) guidelines (40°C/75% RH simulated via water bath + desiccator setup).
• Preheating solvents prior to HPLC mobile phase preparation to reduce bubble formation.
• Maintaining constant temperature during viscometry sample conditioning (e.g., Brookfield DV2T pre-equilibration).
• Supporting ASTM D92 flash point testing when used as auxiliary heating bath for Cleveland Open Cup apparatus.

FAQ

Does the HWS-12 support refrigeration or cooling capability?
No. It is a heating-only system with a minimum operating temperature of ambient +5°C. For sub-ambient control, consider dedicated circulators with Peltier or compressor-based cooling modules.
Can the unit be used with oil as the bath medium?
Yes—silicone oils up to 250 cSt viscosity are compatible within the 99°C upper limit. Ensure oil level remains ≥2 cm above heater elements to prevent damage.
Is the dry-run protection automatic or manual reset?
It requires manual reset via front-panel key sequence after fault clearance—intentionally designed to prevent unintended restarts following low-fluid events.
What is the maximum recommended fill volume for optimal circulation?
5.0 L is the calibrated capacity; exceeding this may impair pump performance and thermal uniformity due to overflow or vortex formation.
Are replacement aperture plates available for custom vessel configurations?
Yes—YiHeng offers optional accessory kits (Part No. HWS-APK-01) containing laser-cut 304 SS inserts for 8 mm, 12 mm, and 20 mm diameters, sold separately.