Installation of geomembrane

The surface to be cleaned must be smooth and free of debris, nails, roots, or sharp objects of any kind or any object that may damage the geomembrane.

The surface should provide a compact and uniform substrate for the geomembrane.

The surface must consist of graded material and be free of organic matter, debris, clay, balls, steel, nails, or other harmful materials that may damage the geomembrane.

1. 

   Preparation of geomembrane surface:

The base area for flexible membrane liners should be smooth and free of bumps that may damage the liner.
All stumps and roots must be removed. Rocks, hard clods, coarse sand and other such materials shall be removed or shall be smoothed to provide a smooth surface.
The subgrade must be compacted to conform to design specifications, have a firm foundation to support the necessary equipment and vehicle weight, and be free of standing water.

2. Groundwater control:

Groundwater should be controlled and should be at least 1 meter below the geomembrane to prevent future geomembrane leakage.

3. Weather conditions:

Unacceptable conditions for installing the panels include rain or the presence of any stagnant water, strong winds or extreme temperatures. The ideal installation air temperature should be between 40°F and 90°F. In extremely hot or cold temperatures, it is recommended that test seams be made and evaluated frequently to ensure that the welders are properly adjusted for the conditions.

Preparation for installing geomembranes (HDP)

The method and equipment used to deploy the panels should not damage the geomembranes.

People who walk on geomembranes should not wear shoes that can damage the geomembrane to participate in activities that could lead to damage to the geomembrane.

Sandbags or similar should be placed over the geomembrane to prevent wind damage during and after installation.

Welding should not be started or continued during rain, fog, strong wind.

The geomembrane surface to be welded must be clean and dry for geomembrane installation.

If the outside temperature is too high or more than 50 degrees Celsius, we have to stop working.

4. Welding method:

Wedge welding equipment:

A visual inspection must be done by the welder to start the welding process.

Wedge welding involves placing a heated wedge on a self-propelled vehicle between two (2) overlapping sheets, the surface of both sheets being heated above the melting point of polyethylene. After being heated by the wedge, the overlapping panels are passed through a set of pre-set pressure wheels that press the two panels together to form a weld. The fusion welder is equipped with a device that continuously monitors the temperature of the wedge.

Extrusion welding equipment:

Extrusion welding involves inserting a ribbon of molten welding rod along the overlapping edge of two geomembrane sheets for welding.
The hot air is preheated and the addition of a molten weld bead causes some of the material in each sheet to liquefy, resulting in a homogeneous bond between the molten weld bead and the surfaces of the overlapping sheets.

5. Seam preparation:

Fusion welding method for HDPA liner installation:

Stack the geomembrane panels 100-150mm apart before welding.

Before welding, clean the seam area with a dry cloth to remove dust, dirt, to ensure that the area is clean and free of moisture, dust or any kind of debris.

Adjust the panels so that the seam is aligned with the least amount of wrinkling possible.

Extrusion welding:

If possible, the sheet should be leveled in place before heating.

The geomembrane panel should overlap between 80 and 100 mm.

For gluing the geomembrane panels that need to be welded, a hot air device should be used temporarily and care should be taken not to damage the geomembrane.

The seam area is automatically cleaned during the welding process. If necessary, a dry cloth should be used to clean the seam before the seam to ensure that the area is clean and free of moisture, dust, dirt and any kind of debris.

The area to be seamed and overlapped must be smoothed before welding

Keep the welding rod clean and dry.

6. Geomembrane installation inspection and test method:

Equipment for air testing:

An air pump capable of generating and maintaining pressure.
A rubber hose with fittings.
A sharp hollow needle with pressure gauge capable of reading and maintaining pressure.
Air test steps:
Close the two ends of the seam to be tested.
Insert the needle into the seal channel created by the fusion weld.
Inflate the test tube to a pressure of approximately 25 Pa, the pressure should be maintained.
Remove the pressure feed needle and close the resulting hole with extrusion welding.

Spark test:

Welds with inserted copper can be tested for leakage using spark test equipment.

Surface moisture must be removed to avoid any interference with the spark test.

The voltage used for the spark test in the HDPE liner is very high to increase the reliability of the test. However, the current is minimal and very safe.

Faults and repairs:

Any part or any seam (extrusion welding or fusion welding) is a damage that can be repaired by an extrusion welding machine.
It is used to repair large holes, tears, and damaged sample locations.
Grinding and welding – used to repair parts of extruded seams.
Spot welding is done using an extrusion welding machine.

7. Risk assessment in geomembrane installation:

Required protective equipment:

Hazards associated with HDPA welding

Always have the proper training and knowledge to operate the particular welder you are using. Every welder is different and can pose different unique hazards.

Never put your hand or body in the line of fire in the machine. Even if the machine is turned off, reaching into it to retrieve shavings from a cut pipe can be a fatal mistake. Use an object or tool to remove the chips or follow the manufacturer’s recommendations to safely remove the chip.

Ensure that all persons and equipment are clear of danger when lifting and moving pipe. Always be aware of where the tube will go if it falls or releases stored energy. If you are in these areas, run away.

Never try to lift heavy or awkward objects by yourself. Use heavy equipment or call a colleague to help move an object to completely eliminate this hazard
Keep your hands and body away from the pipe when the equipment is moving the pipe. Whenever the tube and device are moved in place, there are many twist points between the tube and the device.

Workplace block for unnecessary traffic

Never use a damaged cable.

Use a checklist before entering a confined space, for example oxygen levels, noxious gases present, biological hazards, mechanical hazards, electrical hazards, noise, environmental, etc.