Automatic Geotextile Permeability Tester – QualiGTX™ GPT A
The QualiGTX™ GPT A Automatic Geotextile Permeability Tester is designed to perform vertical water permeability testing on geotextiles and related materials with minimal operator involvement. Configured by Qualitest North America for high-volume laboratory environments, this automated geotextile permeameter reduces the time spent on water-level adjustment, timing, and calculations. Its computer-controlled system positions the water level, manages the testing sequence, measures water flow, and calculates the vertical permeability coefficient. Test reports can be uploaded or printed directly from the control screen.
Geosynthetics manufacturers, hydraulic engineering laboratories, and infrastructure quality control departments use the QualiGTX™ GPT A to evaluate filter and drainage fabrics before project application. Its 304 stainless steel specimen clamp accommodates samples measuring up to 50 mm in diameter and 20 mm in thickness, while the operator can configure a head differential of up to 250 mm. Flow measurement uses 0.1-second timing resolution, providing precise readings for high-permittivity fabrics with shorter water collection intervals. A dissolved oxygen analyzer also checks the test water before measurement begins.
The automated 70 mm head differential test follows the 0.8 to 0.2 range, minimizing operator-dependent variations and improving consistency between technicians. A 36 L stainless steel water tank features compressor cooling and PID temperature control, maintaining water temperatures between 10 °C and 60 °C. All water-contact components, including the tank, specimen clamp, and water line fittings, are constructed from 304 stainless steel. The instrument requires a floor area of 1,150 × 670 mm and has a total weight of 180 kg.
Automatic Geotextile Permeability Tester – QualiGTX™ GPT A Applications
The QualiGTX™ GPT A is suitable for laboratories involved in hydraulic, railway, and marine infrastructure projects, where filter and drainage fabric performance requires consistent batch-by-batch verification.
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Dam, Reservoir, and Canal Engineering: Evaluates the flow capacity of filter and drainage fabrics installed against earth structures exposed to continuous seepage.
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Railway Subgrade and Trackbed Materials: Qualifies geotextiles used to separate ballast from subgrade materials and facilitate water drainage away from the formation.
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Marine and Port Construction: Verifies geotextile performance in breakwater cores, quay wall backfill, and reclamation containment bunds.
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Flood Defense and Levee Works: Measures cross-plane water flow through filter layers installed behind revetments and within toe drainage systems.
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Geotextile Production Line Testing: Performs batch release inspections against published permittivity values before finished rolls are dispatched.
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Highway and Airfield Drainage: Assesses edge drain wrapping and separation fabrics installed beneath pavement structures.
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Mining and Tailings Management: Tests drainage geotextiles used in heap leach pads and tailings dam underdrain systems.
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Accredited and Third-Party Laboratories: Supports high-throughput verification testing, where consistency between operators is as important as measurement accuracy.
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Product Development and Failure Investigation: Compares pore structure and manufacturing variables with measured cross-plane water flow to support product evaluation and failure analysis.
Automatic Geotextile Permeability Tester – QualiGTX™ GPT A Key Features
The QualiGTX™ GPT A automates three time-consuming stages of vertical geotextile permeability testing: water-level adjustment, measurement timing, and coefficient calculation.
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Automated 70 mm Head Differential Test: Automatically completes the test sequence across the 0.8 to 0.2 range, allowing technicians to prepare subsequent specimens while testing continues.
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Self-Locating Zero Water Level: Automatically identifies the zero water-level reference without manual shimming or visual level estimation, maintaining consistent setup between specimens.
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Programmable Head Height: Allows users to configure any water level within the 250 mm differential range according to the applicable testing procedure or specimen characteristics.
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0.1 s Timing Resolution: Provides accurate timing for short water collection intervals, particularly when testing free-draining fabrics where manual stopwatch measurements can introduce significant errors.
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Controlled Water Supply Metering: Regulates replacement water delivery at a measured rate to maintain the required hydraulic head throughout the collection period.
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Dissolved Oxygen Analyzer: Measures dissolved oxygen in mg/L, percentage saturation, and partial pressure, documenting water conditions before testing begins.
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10 °C to 60 °C Thermostatic Tank: Provides controlled heating and compressor cooling while maintaining water temperature within ±0.5 °C for comparable results across seasonal testing conditions.
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Automatic Volume and Time Capture: Records collected water volume alongside elapsed time, eliminating manual readings and reducing data transcription errors.
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Automatic Coefficient Calculation and Reporting: Processes measured flow data to determine the vertical permeability coefficient and generates reports for direct uploading or printing.
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Selectable Test Configurations: Offers multiple vertical permeability testing protocols through the software, allowing one instrument to accommodate different reporting requirements.
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Computer Control with a Short Learning Curve: Guides technicians through the testing process and retains configuration parameters between runs, simplifying operation and staff handovers.
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Temperature Deviation Correction to 0.1 °C: Adjusts measured temperature values to support viscosity corrections based on verified readings rather than nominal temperature settings.
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User-Tunable PID with Auto-Tuning: Allows the thermal control system to be adjusted to laboratory ambient conditions through user-configurable PID parameters and automatic tuning.
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304 Stainless Steel Tank and Specimen Clamp: Provides corrosion resistance under continuous water exposure and repeated specimen clamping.
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304 Stainless Steel Water Line Fittings: Maintains a corrosion-resistant water flow path, reducing the risk of corrosion products contaminating specimens or affecting measurements.
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Electrostatic Powder-Coated Working Vessel: Adds surface protection to the stainless steel vessel for reliable operation in humid laboratory environments.
Theory and Method
Water flow perpendicular to a geotextile follows Darcy's law under laminar flow conditions, where the discharge rate remains proportional to the hydraulic gradient across the specimen. The QualiGTX™ GPT A establishes a defined hydraulic head difference across a clamped sample and measures the water volume passing through a fixed 50 mm aperture during a recorded time interval. Permittivity is calculated by dividing the discharge rate by the specimen area and hydraulic head, with the resulting value expressed in inverse seconds. Multiplying permittivity by the nominal specimen thickness converts the result into a permeability coefficient expressed in velocity units.
The main challenge in achieving repeatable permeability measurements is controlling operator-dependent variations rather than simply obtaining an accurate reading. Differences in head height adjustment, measurement start and stop times, and visual judgments about when the water level becomes stable can all influence test results. The QualiGTX™ GPT A addresses these variables by automatically locating the zero water level, positioning the water at the programmed head, and controlling the collection interval using its internal timing system. Eliminating these three manual judgment points helps reduce measurement variation between technicians testing identical materials.
Maintaining a constant hydraulic head is essential for applying Darcy's law throughout the measurement process. As water passes through the specimen, the supply level naturally decreases. This reduction changes the hydraulic gradient and can cause the flow rate to decline during testing. The QualiGTX™ GPT A regulates replacement water delivery at a controlled rate to maintain the selected water level and preserve consistent test conditions. Dissolved gases can also affect flow measurements because microbubbles within the geotextile pore structure may obstruct water pathways. The integrated dissolved oxygen analyzer therefore checks the water condition before measurement to help identify this potential source of interference.
Automatic Geotextile Permeability Tester - QualiGTX™ GPT A Technical Specifications
| Parameter |
Specification |
| Maximum Head Differential |
250 mm |
| Specimen Clamp Inner Diameter |
Ø50 ± 0.5 mm (304 stainless steel) |
| Maximum Specimen Thickness |
20 mm |
| Timing Range |
0 to 9,999 s |
| Timing Accuracy |
0.1 s |
| Temperature Measurement Range |
0 °C to 110 °C |
| Temperature Control Range |
10 °C to 60 °C |
| Temperature Control Accuracy |
±0.5 °C |
| Thermometer Accuracy |
0.1 °C |
| Temperature Correction Accuracy |
±0.1 °C |
| Dissolved Oxygen Range |
0 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 Resolution |
0.01 mg/L; 0.1 %; 1 hPa |
| Water Supply Tank Capacity |
36 L |
| Temperature Control Modes |
Cooling and heating |
| Cooling Method |
Compressor unit |
| Temperature Control |
PID with auto-tuning |
| Compressor Power |
550 W |
| Internal Circulation Pump Power |
100 W |
| Circulation Pump Flow Rate |
15 L/min |
| Total Power |
1 kW |
| Dimensions (W × D × H) |
1,150 × 670 × 1,580 mm |
| Weight |
180 kg |
