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Guarded Heat Flow Meter: Thermal Insulation Testing Equipment Specs
Quick Answer: A guarded heat flow meter (HFM) measures thermal conductivity of insulation materials under steady-state conditions following ASTM C518 and ISO 8301. Silver Automation Instruments supplies the HFM-500 system with plate temperatures from -20 °C to 80 °C and heat flux range 0 to 500 W/m². The complete package includes the heat flux transducer, control unit, calibration certificate, and Windows software.
How the Guarded Heat Flow Meter Works
The guarded heat flow meter places a solid sample between two flat plates. One plate is heated, the other is cooled. A guard surrounds the metering area to eliminate lateral heat loss. The heat flux transducer measures the heat flow traveling through the sample in one direction. By recording the plate temperatures, the sample thickness, and the heat flux, the system calculates thermal conductivity in W/(m·K). A single test takes about 30 to 60 minutes once the specimen reaches thermal equilibrium. Most engineers skip the guard adjustment step because modern units auto-stabilize the guard temperature.
Key Specifications to Check
Plate temperature range is the first spec buyers ask about. Our HFM-500 system operates from -20 °C to 80 °C, covering foam, mineral wool, and aerogel testing. For high-temperature EPS labs, we can extend the hot plate to 100 °C on request. Plate dimensions are typically 300 mm x 300 mm or 200 mm x 200 mm. The metering area must comply with ASTM C518 requirements. Thermal conductivity accuracy runs from ±1% to ±2% depending on the sample homogeneity. The heat flux sensor resolution is 0.1 W/m². Silver Instruments uses hermetically sealed transducers with low long-term drift. The cooling side can be air-cooled or connected to a recirculating chiller. A building material lab in Thailand chose the HFM-500 with a small recirculating chiller to hold the cold plate at 10 °C while testing roof insulation.
Understanding the Measuring Standards
Most guarded heat flow meter setups follow ASTM C518, ISO 8301, JIS A1412, and EN 12667. In practice, testing houses in the Middle East often request GOST compliance documentation. Silver Instruments can calibrate the unit to NIST or PTB traceable references. The heat flow meter transducer is factory-calibrated against NIST SRM 1450d fiberglass board. We supply a full calibration certificate with every HFM-500, no extra charge for the first year.
Real Applications in Thermal Insulation Testing
Third-party labs use these devices for expanded polystyrene (EPS), extruded polystyrene (XPS), polyurethane foam, mineral wool, and vacuum insulation panels. A construction QC lab in Vietnam runs daily checks on rockwool insulati
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Why Choose Silver Automation Instruments for Your HFM System
We are not a huge multinational. We are an SME that ships to over 40 countries in Southeast Asia, Oceania, Latin America, Africa, and the Middle East. The standard HFM-500 delivery time is 4 weeks ex-works Nanjing. You get remote setup support over a WhatsApp video call. We did exactly that last month for a new lab in Peru. The included software runs on Windows 10 and 11, exports data to CSV, and does not lock you into any proprietary file format. The list price for a basic air-cooled HFM-500 starts at USD 12,500. That covers the heat flow meter, control electronics, calibration certificate, and a one-year warranty. Spare transducers are available from stock.
Send us your sample material, required temperature range, and plate size. We will propose the exact configuration within one working day. Email: [email protected]. Tel: +86-25-68650347. WhatsApp: +86-25-52155837. WeChat: +86 15365082610. We answer most technical inquiries in under 12 hours.
Frequently Asked Questions
What is the difference between a guarded heat flow meter and a guarded hot plate? A guarded hot plate measures absolute thermal conductivity with higher accuracy but costs more and runs slower. A guarded heat flow meter uses a calibrated heat flux transducer for faster comparative tests and is the common choice for industrial QC per ASTM C518.
What sample sizes can I test? The standard HFM-500 accepts flat specimens up to 300 mm x 300 mm and thickness from 5 mm to 100 mm. Smaller plates (200 mm x 200 mm) are available for limited material samples.
How do you calibrate the heat flux transducer? We calibrate against a NIST reference material at multiple temperature points. Each transducer ships with a calibration table and certificate. Annual recalibration service is available from our Nanjing lab.
Can the HFM-500 measure the conductivity of wet insulation? Yes, but you must avoid free water dripping onto the plates. Use a vapor barrier film around the sample. The measurement uncertainty increases slightly due to moisture migration during the test.
What is the typical lead time and warranty? The standard HFM-500 ships within 4 weeks. Warranty is 12 months on the electronics and transducer. Extended warranty is optional.