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De-Aired Geotextile Permeability Tester

De-Aired Geotextile Permeability Tester
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Geotextile Permeability Testers
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De-Aired Geotextile Permeability Tester - QualiGTX™ GPT D

QualiGTX™ GPT D geotextile permeability tester measures the vertical water flow characteristics of geotextiles and related products under no-load conditions. Qualitest North America built the system around a de-aired, temperature-controlled water supply so laboratories obtain flow readings free of the entrained air that distorts conventional permeameter results. An industrial touchscreen computer manages specimen clamping, head positioning, timing, and calculation. Test engineers receive a finished vertical permeability coefficient without stopwatch work or hand computation.

Civil engineering laboratories, geosynthetics manufacturers, and infrastructure quality-control departments use the QualiGTX™ GPT D to qualify filter fabrics before they go into subgrades, embankments, and drainage layers. The instrument holds a 50 mm specimen, applies a user-set head difference up to 250 mm, and collects the water passing through the fabric over a timed interval. A dissolved oxygen analyzer confirms the test water meets the deaeration requirement before flow begins. Results generate a report that uploads or prints directly from the control station.

Switchable water-supply configurations let one machine cover several vertical permeability protocols without hardware changes. Operators select the required configuration from the control screen, and the system routes water through the matching supply unit. A 50 L stainless steel thermostatic tank with PID control holds water within ±0.5 °C, which matters because viscosity, and therefore measured flow, shifts with temperature. The result is repeatable data across shifts, operators, and seasons.

De-Aired Geotextile Permeability Tester - QualiGTX™ GPT D Applications

The QualiGTX™ GPT D serves laboratories that qualify geosynthetic filter and drainage materials for civil, hydraulic, and transportation infrastructure.

  • Geotextile Manufacturing Quality Control: batch verification of woven and nonwoven fabrics against published permittivity and flow-rate values before shipment
  • Highway and Roadway Construction: acceptance testing of separation and filtration fabrics placed between subgrade soils and aggregate base courses
  • Dam, Levee, and Canal Engineering: evaluation of filter layers that must pass seepage water while retaining fine soil particles behind the fabric
  • Railway Subgrade Engineering: qualification of geotextiles used to control mud pumping and maintain drainage under ballast
  • Port, Coastal, and Reclamation Works: testing of fabrics for revetments, breakwater cores, and dredged-fill containment where hydraulic loading is continuous
  • Landfill and Environmental Containment: verification of leachate collection and drainage layer materials that sit above liner systems
  • Erosion Control and Land Drainage: assessment of filter fabrics for French drains, trench drains, and slope protection systems
  • Third-Party and Certification Laboratories: independent verification of supplier data for tender submissions and project acceptance
  • Materials Research and Product Development: comparison of fiber type, pore structure, and manufacturing process against measured cross-plane flow
De-Aired Geotextile Permeability Tester

De-Aired Geotextile Permeability Tester - QualiGTX™ GPT D Key Features

The QualiGTX™ GPT D combines water conditioning, automated specimen handling, and computed results in a single floor-standing station.

  • Integrated De-Aeration and Thermostatic Water System: conditions test water in one circuit so operators skip separate vacuum deaeration equipment and the transfer steps that reintroduce air
  • Dissolved Oxygen Measurement System: reports oxygen content in mg/L, percent saturation, and partial pressure, giving documented proof that water quality met the method requirement
  • Industrial Touchscreen Computer Control: guides setup, records the run, and stores parameters, keeping operation consistent between technicians
  • Automatic Specimen Clamping: seats and seals the specimen without manual tightening, removing a common source of edge leakage and operator variation
  • Automatic Head Positioning: drives to the entered head difference and locates the position without shimming or manual leveling
  • Constant Water Level Device: maintains the driving head for the full duration of the run so the hydraulic gradient does not drift
  • Two-Unit Lateral Supply Stabilization: brings the head to target quickly and damps surface fluctuation, shortening the wait before readings can start
  • Switchable Supply Configurations: change between test protocols from the control panel, letting one instrument replace several dedicated permeameters
  • Automatic Flow Collection and Timing: measures collected volume against elapsed time to 1 s resolution, eliminating stopwatch error
  • Automatic Permeability Calculation and Reporting: converts raw flow data into the vertical permeability coefficient and generates a report for upload or printing
  • 304 Stainless Steel Wetted Parts: specimen clamp and water tank resist corrosion through long service in continuous-contact conditions
  • Electrostatic Powder-Coated Working Vessel: adds a protective finish over stainless steel for durability in humid laboratory environments
  • Corrosion-Resistant Silicone Sealing Rings: hold the specimen seal over repeated clamping cycles without hardening or leaking
  • Adjustable PID Control with Auto-Tuning: lets users tune the thermal loop to their laboratory conditions instead of accepting fixed factory settings
  • Temperature Deviation Correction: trims measured temperature to 0.1 °C so viscosity corrections stay accurate
  • Internal and External Circulation Modes: circulate internally for testing, or draw conditioned liquid out to heat or cool external vessels, extending the unit's laboratory use
  • Outdoor Condenser Unit Cooling: moves compressor heat out of the laboratory and lowers energy consumption during long temperature holds

Theory and Method

Geotextile permeability testing rests on Darcy's law, which relates flow through a porous medium to the hydraulic gradient across it. The QualiGTX™ GPT D holds a constant head difference across the clamped specimen and measures the water volume passing through a known area over a timed interval. That flow rate, divided by area and head, gives permittivity: volumetric flow per unit area per unit head. Multiplying permittivity by specimen thickness returns the vertical permeability coefficient used in drainage and filtration design.

Dissolved air is the main source of error in this measurement. Tap water carries oxygen and nitrogen in solution, and pressure changes release that gas as microbubbles inside the fine pore structure of a nonwoven fabric. The bubbles block flow paths and push the measured flow rate down, producing a permeability value below the material's true performance. The QualiGTX™ GPT D strips dissolved gas before testing and verifies water quality with a dissolved oxygen analyzer.

Water viscosity falls as temperature rises, so a fabric passes more water at 30 °C than at 15 °C. Test methods correct results to a reference temperature, and that correction holds only when the water temperature is known and stable. The QualiGTX™ GPT D circulates water through a PID-controlled thermostatic tank, holds it to ±0.5 °C, and corrects temperature readings to ±0.1 °C. A two-unit lateral supply stabilizes the head quickly and keeps the surface level steady, so the driving gradient holds constant throughout the run.

De-Aired Geotextile Permeability Tester - QualiGTX™ GPT D Technical Specifications

ParameterSpecification
Maximum Head Differential250 mm
Specimen Clamp Inner DiameterØ50 ± 0.5 mm
Maximum Specimen Thickness20 mm
Timing Range0 to 9,999 s
Temperature Measurement Range0 °C to 110 °C
Temperature Control Range5 °C to 100 °C
Temperature Accuracy±0.5 °C
Temperature Correction Accuracy±0.1 °C
Dissolved Oxygen Range0 to 20 mg/L; 0 to 200 %; 0 to 400 hPa
Dissolved Oxygen Accuracy±1.5 % FS
Dissolved Oxygen Repeatability±0.5 % FS
Dissolved Oxygen Resolution0.01 mg/L; 0.1 %; 1 hPa
Water Supply Tank Capacity50 L
Cooling Capacity13,000 W
Circulation ModesInternal and external
Temperature Control ModesCooling and heating
Cooling MethodOutdoor condenser unit
Compressor Power1.5 hp (approx. 1.1 kW)
Internal Circulation Pump Power100 W
External Circulation Pump100 W, adjustable flow
Circulation Pump Flow Rate45 L/min
Temperature ControlPID with auto-tuning
Heating TimeRoom temperature to boiling, approx. 30 min
Cooling TimeBoiling to 20 °C, approx. 90 min
Water Conditioning System Power Supply380 V, 50 Hz, 12 kW
Test Operation Power1 kW
Dimensions (W × D × H)1,380 × 780 × 1,870 mm
Weight160 kg

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Geotextile Permeability Testers