Quality And The Process

Manufacturing requirements

When utilising polyethylene to design and manufacture containers, the following factors need to be taken into account:

  • container shape and design
  • pressure or mechanical stress development during storage
  • changes in the plastic resin with time
  • leaching of additives from the polymer
  • exposure of the container to UV radiation in addition to the chemical environment
  • compounding chemical effects on polyethylene from contents
  • physical changes in the polymer during processing, eg, degradation
  • storage and environmental temperatures
  • type of manufacturing process utilised
  • effects of any additional additives incorporated prior to processing, g. pigments, which may be subdivided into:
    • plasticisation or swelling
    • oxidation (chemisorption of oxygen into the polymer chain)
    • transmission through the plastic wall
    • stress-cracking (defined by ASTM D883 as an internal or external crack in a plastic caused by tensile stresses less than its short-time mechanical

The requirements below highlight details of the RotoTank™ water and liquid storage tanks that require special attention during the manufacturing process:

  • the quality of all incoming raw materials are controlled, recorded and maintained to demonstrate achievement of the required quality and effective operation of RotoTank™’s quality management system
  • adequate records are be kept of routine inspections and tests carried out to ascertain that the quality of all manufactured components are as

Manufacturing process

Raw materials are received mostly in pellet form from the primary LLDPE resin supplier. This is technically supported by the relevant plastic resin producer.

The raw material is pre-weighed before being dosed into the mould. Each product’s mass is determined by standards prescribed by ARMSA (Association of Roto Moulders of South Africa and Agre’ment South Africa). Each separate product is produced according to a designated and computer-controlled recipe which determines oven-time, cooling time and rotation speed ratio.

Wall thicknesses and surface finish are closely monitored.

Installation requirements

It is essential that the tanks are installed as per the installation instructions in warranty:

  • the storage tanks should be supported on a solid, level base that can bear the weight of the tank when it is full
  • the base should be free from sharp objects such as stone, nails, bolts and unlevelled concrete stone, etc. there must be no overhang of the tank on the base.
  • where an elevated platform is utilised this platform must be installed in accordance with an Engineer’s certificate of compliance.
  • installation near hot exhaust gases must be avoided.
  • according to legislation a bund wall must be installed with storage of hazardous chemicals or fuels.
  • pipe fittings should be connected but stress Appropriate thread sealer could be used
  • the filling rate should not exceed the overflow

Handling

The RotoTank™ Water and Liquid Storage Tanks are manufactured to withstand normal handling during transportation and installation. To avoid unnecessary damage, care should be exercised in handling the tanks which should not be:

  • dragged over an abrasive surface
  • man handled in a manner whereby a point load is exerted on the tank or it rests upon a sharp object
  • over-tightened and distorted during transportation

Storage

Tanks should be stored in a manner that does not compromise the structural integrity of the tanks and preferably standing its base in a vertical position.

Non-UV protected tanks must be protected from direct sunlight.

Maintenance

RotoTank™ products offer an 8 year warranty if used appropriately and if used for their intended purpose.