Working principle and test steps of Hydrostatic head Tester

Introduction

The hydrostatic head tester is designed to test the pressure that the material does not come into contact with the exuded water droplets side when the water pressure is continuously raised in a standard atmospheric environment, which is the hydrostatic pressure value of the material. It can quickly and accurately test out the encountered resistance when water penetrates through the material, to assess the material waterproof and moisture permeability.

Applications

Waterproof testing for outdoor sportswear, umbrellas, and waterproof fabrics; and testing the liquid and blood permeability of protective materials for jackets and medical protective clothing. Dynamic, static, and custom program methods are used to test the water repellency of textiles under a specific pressure. The specimen is fixed to a test area of ​​the specified size. An air compressor pumps 0-5 bar of air into a tank filled with distilled water. The tank is connected to a test head, applying a specific pressure to the specimen. The pressure curve is displayed in real time on the screen, and various test standards are built in for user convenience.

Basic principle of the test

Apply increasing (dynamic test) or consistent (static test) water pressure to the sample until water seeps out from three different locations of the sample. After testing at least 3 samples, measure and calculate the average maximum water pressure of the fabric (measured in mBar or cmH2O). This value is the water repellency of the sample.

The specific method is that the sample is fixed on a test area of ​​standard area, and an air compressor adds 0-5 bar air to a water tank filled with distilled water, and a certain pressure of water is applied to the sample. The test can be performed by dynamic or static methods.

(1) Dynamic method: The hydrostatic pressure resistance of the sample is determined by testing the pressure when a fixed number of water droplets seep out of the side of the sample that is not in contact with water at a certain pressure increase rate.

(2) Static method: The hydrostatic pressure resistance of the material is determined by testing the water seepage of the sample under a certain hydrostatic pressure and maintaining the pressure for a certain period of time.

Procedure

Cut the test fabric into a 100mm x 100mm specimen. Place the specimen in the clamp and tighten the clamp securely. Press the "up" button. A metal container containing 700ml of water begins to rise at a constant speed, driven by a motor. Water pressure is applied to the specimen in the clamp. Water penetration is measured by observing the color change of the indicator paper covering the filter paper specimen through the plastic window of the clamp. When the initial signal of the indicator paper changing color (from blue to pink) appears, immediately read the water level on the scale in Pa (mmH₂O). Press the "up" button again to stop the metal container from rising. Record the reading as the filter paper water permeability test data.

Open the clamp, remove the specimen and indicator paper, wipe the clamp's material window dry with a soft cloth, and check the water level in the clamp. Refill the clamp with water if necessary. Replace the clamp with another specimen and indicator paper and repeat the above test steps.

If indicator paper is installed, its preparation method should refer to the relevant provisions of GJB 1152-9l, "General Specification for Military High-Efficiency Air Filter Paper."

Notes

1. After completing a water resistance test, press the lower button to lower the metal container to the initial position of the scale. Then press the lower button again to stop the metal container and prepare for the next test.

2. Adjust the frequency on the inverter panel to change the metal container's ascending speed.