The following method of installation HDPE liner is developed by Nuolian Engineering for HDPE lining of Artificial Lakes, Lagoons, Evaporation Ponds, Canals, Water Features, Fish Farms and water retaining unreinforced structures. The following instructions are intended as guidelines for the installation of HDPE Liner. However, it is vital that an individual engineer’s detailed specifications and procedures are followed.

METHOD OF INSTALLATION HDPE LINER:

1.1      Surface Preparation Geotextile & HDPE Geomembrane

The main contractor shall be responsible for surface preparation and maintaining the surface in a proper condition for the installation of the Geotextile and geomembrane Liner.

The foundation area for flexible membrane liners shall be smooth and free of projections that might damage the liner. All stumps and roots shall be removed. Rocks, hard clods, coarse gravel, and other such material shall be removed or shall be rolled so as to provide a smooth surface or shall be covered with a cushion of fine soil. The subgrade must be compacted to comply with design specifications and include a stable base to support equipment and necessary vehicle weight and shall be free of standing water.

Surface to be lined shall be smooth and free of debris, nails, roots, angular or sharp of any kind or any object which may damage the geomembrane.

The surface is to provide a firm unyielding compacted subgrade for the geotextile &geomembrane.

All fills shall consist of well-graded material, free of organics, trash, clay, balls, steel, nails, or other deleterious material that may cause damage to the Geomembrane. The surface shall have no sudden sharp or abrupt changes.

1.2     Underground Water Control:  

The underground water has to be controlled and reduce to a minimum of 1meter below the Geotextile &Geo membrane to avoid any water uplifting of the Geomembrane in the future.

1.3     Weather Conditions:

Unacceptable conditions for panel installation include precipitation or the presence of any standing water, high winds, or extreme temperatures. Ideal installation air temperatures should range between 40ºF and 90ºF. During extremely warm or cold temperatures it is recommended that frequent trial seams are made and evaluated to ensure that the welders are properly set up for the conditions. 

1.4    Preparation of Geotextile.

After preparation and acceptance of the subgrade, geotextile shall be laid in the required area where you want to install the HDPE liner. Geotextile shall be lap with Hot Air Gun. The overlap of geotextile should be not less than 100mm to 150mm.

1.5    Preparation for HDPE Geomembrane. 

The method and equipment used to deploy the panels shall not damage the geomembrane.

People walking on the geomembrane shall not wear shoes that could damage the geomembrane to engage in activities that could result in damages to the geomembrane.

Temporary ballasting such as sandbags shall be placed on the geomembrane to prevent wind damage during and after installation.

Welding shall be not commenced or continued during rain, fog, high wind.

The surface of the geomembrane to be welded shall be clean, dry.

If the out-site temperature is very high or more than 50 oC also we have to stop the work. 

1.6    Welding Procedure 

1.6.1      Wedge Welding Equipment:     

To start the welding process visual inspection shall be done by the welder.

Wedge welding consists of placing a heated wedge, mounted on a self-propelled vehicular unit between two (2) overlapped sheets that the surface of both sheets is heated above the polyethylene’s melting point. After being heated by the wedge the overlapped panels pass through a set of preset pressure wheels that compress the two panels together to the weld. The fusion welder is equipped with a device, which continuously monitors the temperature of the wedge.

1.6.2    Extrusion Welding Equipment:

Extrusion welding consists of introducing a ribbon of molten welding rod along the edge of the overlap of the two geomembrane sheets to be welded.

A hot air preheats and the addition of a molten welding rod cause some of the material of each sheet to be liquefied resulting in a homogeneous bond between the molten weld bead and the surfaces of the overlapped sheets.

1.7    Seam Preparation 

Fusion welding method of installation HDPE liner: 

Overlap the panels of geomembrane approximately 100mm- 150mm prior to welding.

Clean the seam area with a dry cloth to remove dust, dirt prior to seaming to assure that the area is clean and free of moisture, dust dirt or debris of any kind.

Adjust the panels so that the seam is aligned with the fewest possible number of wrinkles and fish mouths. 

Extrusion welding: 

When never possible, the sheet shall level prior to heat tracking into place.

The panel of geomembrane shall be overlapped by 80mm to 100mm.

A hot air device shall be used temporarily to tack the panels of geomembrane that has to be welded and care should be taken not to damage the geomembrane.

seam area automatically be cleaned during the grinding process. If necessary, a dry cloth shall be used to clean the seam prior to seaming to assure the area is clean and free of moisture, dust, dirt, and debris of any kind.

The area to be seamed and overlapped shall be ground prior to welding

Keep welding rod clean & dry. 

2.0  Inspection and Testing Procedure 

Equipment for Air Test:

An Air pump capable of generating and sustaining pressure.

A rubber hose with fitting and connections.

A sharp hollow needle with a pressure gauge capable of reading and sustaining pressure.

Procedure for Air Testing:

Seal both ends of the seam to be tested.

Insert the needle into the sealed channel created by the fusion weld.

Inflate the test channel to a pressure of approximately 25 PSI, the pressure should be maintaining.

Remove the pressure feed needle and seal the resulting hole by the Extrusion Welding. 

Spark Testing: 

Welding with copper inserted in can be tested for leaks by using spark testing equipment.

Surface moisture should be removed to avoid any interference with the spark testing.

The voltage that is used for the spark testing of the HDPE Liner is very high to enhance the test reliability. However, the current flow is minimal and it is very safe. 

Defects and Repairs: 

Any portion or any seam (Extrusion weld or Fusion Weld) is damage you can repair by the Extrusion welding machine.

Used for repairing large holes, tears, and destructive sample locations.

Grinding and welding – used for repairing sections of extruded seams.

Spot welding or Seaming- used an Extrusion welding machine. 

Responsibilities of the main contractor 

A work permit to be issued by the main contractor.

Safety for the geomembrane should be provided.

The working area should be barricaded.

The Rest area, toilets, drinking water, and electricity should be provided. 

3.0HDPE Geo membrane Risk Assessment Method of installation HDPE liner

Personnel Protective Equipment Required:

Hazards Associated with HDPE Welding

Always have the proper training and knowledge to run the specific welder you are using. Each welder is different and can present different unique hazards.

Never stick your hands or body in the line of fire in the machine. Even if the machine is “off” crawling into it to retrieve the shavings from the cut pipe can be a fatal mistake. Use an object or tool to clear the shavings or follow the manufacturer’s recommendations to safely be able to clear the shaving

Make sure all people and equipment are out of the line of fire when lifting and moving pipe. Always be mindful of where a pipe will go if it is dropped or stored energy releases; if you are in these areas then move.

Never try to lift heavy or awkward objects alone. Use heavy equipment to eliminate this hazard completely or involve a coworker to help move a manageable object

Keep your hands and body clear of the pipe when the equipment is moving it. Pinch points are abundant between the pipe and the machine anytime it is being moved into place.

Block of the work area to control unnecessary traffic in the area.

Never used damage cable.

Use the checklist before entering a confined space, for exempla Oxygen levels, Harmful Gases present, Biological Hazards, Mechanical Hazards, Electrical Hazards, Noise, Environmental, others, etc.