Chemical Storage Tanks
Polyethylene resins used for rotational moulding of storage tanks show excellent resistance to a wide range of chemicals and are generally resistant to inorganic acids, alkalis and aqueous solutions. They contain ultra-violet stabilizers to reduce the effect of photo-oxidation and show excellent impact resistance, are very good electrical insulators and show low thermal conductivity relative to metal When contemplating the use of polyethylene in building storage tanks, designers should however avoid its use at temperatures below minus 20 or above 40 deg C and restrict use in contact with surface active substances such as alcohols, soaps and wetting agents.
Polyethylene is suitable for storing acids such as Sulphuric and Citric, alkalis’ such as Sodium Hydroxide and Ammonium Hydroxide, plus a wide range of other chemicals. Tank fittings in chemical applications are typical also made from polyethylene and are welded to the tank prior to delivery. Stainless steel fittings are used in some applications and if necessary can be fitted on site.
In specifying storage vessels customers are encouraged to clearly state the nature of the liquid being stored, the physical environment in which the tank is to be installed and what, if any, additional hazards may exist.
West Coast Poly manufacturing processes are designed to achieve the optimum properties from the moulded material and can offer impact testing in accordance with AS/NZ 4766. Welded fittings are installed by qualified personnel in accordance with DVS 2207 and non-destructive spark testing of welds or hydrostatic testing of vessels can be provided.
The provision of a Material Safety Data Sheet and maximum service temperature range is essential if the vessel is to carry a manufacturer warranty.
Points to Consider
Our aim at West Coast Poly is the selection of the most cost effective long-term solution to your storage requirements and without the right information we can't do our job properly. In industrial applications additional hazards can arise that would not normally be encountered with rainwater storage, the items listed below are for guidance only:
West Coast Poly tanks are manufactured to cope with the harsh West Australian environment and are suitable for external installation. West Coast Poly uses Qenos Alkatuff material which has a UV performance level of UV 20 which is more than twice the Australian standard requirement of UV8. This material is standard for our storage tank range so that customers can be assured they are getting the highest UV protection available.
The properties of polyethylene are affected by temperature and special consideration needs to be given where the tank is to be subjected to liquid temperatures above 35 deg C or below minus 20 deg C. The external air temperature is generally not as important as the temperature of the liquid being stored, however your supplier should be made aware if the tank is to be subjected to temperatures other than ambient.
Pressure or Vacuum
Tanks are typically manufactured for hydrostatic loading only and should not be subjected to pressure or vacuum.
Specific Gravity (SG) of liquid
Our tanks are typically manufactured for liquids weighing no more than 1 kg per litre ( SG 1.0), if heavy liquids like dissolved fertilizers, brine solutions, etc are to be stored in the tank then you must advise us at the time of order so that greater wall thickness can be used.
Tanks are generally designed for external installation at ground level in a non-hazardous environment. They must be fully supported across their entire base area, (refer installation section for details). If your tank is to be inside or close to a building, elevated above ground level, partially or totally buried, located in a traffic area or in any other situation, which increases the level of hazard, you should advise us so that an additional safety factor can be applied.
Areas of high wind, cyclone susceptibility or seismic activity are the most common additional hazards, however, flooding, soil subsidence, feral animals, caustic cleaning solutions and many other factors can play a part. You are the best judge of the hazards in your environment, so please inform us, “we can’t provide for something we don’t know about”.