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Tank Liners
APT is an experienced installer of one-piece tank liners. Tank liners are increasing being used for potable, recycle and waste water applications by water districts, agricultural producers, greenhouses, food processors and industrial owners. Tank liners are also used for a variety of industrial liquids including treated effluents, hydrocarbons and industrial chemicals.
In standard drop-in tank liner applications, the geomembrane is used as a primary liner to ensure the system is water / fluid tight. Depending on the type of fluid being contained and size of tank project, various potable and industrial grade materials are available.
The most common lining materials fabricated by APT for tank liners are Polypropylene, Elvaloy and PVC.
Flexible membrane liners provide an impervious barrier between the steel structure and the water environment eliminating corrosion and giving your investment a longer service life. There are a wide variety of materials available to suit almost any application. APT can supply expert advice for the most suitable material to use in your application.
Different liner materials require different fabrication and installation procedures, in most cases APT try to supply a one-piece liner to reduce installation times and minimise potential leaks. Some materials due to there nature cannot be fabricated in one piece and some larger tanks make it impractical to fabricate a one-piece liner, in these instances qualified site welders are required to conduct on site fabrication of the liner to ensure a water tight seal.
As well using liners in new tanks flexible membrane liners can be used can to refurbish old tanks to eliminate any unwanted leakage, deterioration or corrosion, and are suitable to store potable, stock, fire, and wastewater, as well as chemicals and oils. Tank liners are flexible, reliable and economical; can be fitted to open or closed tanks and are suitable for all types of tanks including concrete, galvanized, corrugated iron, fibreglassand brick. A wide variety of fluids can be contained such as Water, Effluent, Chemical, Fuel, Oil, in fact most fluids.
APT offers a range of specialised materials for the manufacture of prefabricated tank liners, including:
PVC
High quality liner, relatively low cost material manufactured from virgin materials and specially designed to meet potability requirements. Available in gauges of 0.50mm to 0.75mm, PVC tank liner is designed for use with potable water only and is certified to AS4020.
PVC was one of the first materials used for geomembrane applications and remains an economical and versatile choice.
Flexible Polyvinyl Chloride films (usually called PVC) have been used for geomembrane applications for over 40 years. PVC films are blends of rigid PVC (such as in PVC pipe) with softening agents called plasticizers. These plasticizers make the PVC soft and supple so that it can be rolled, fabricated, and placed as a liner material in complex installations. PVC is an elastic material that can conform readily to irregular shapes and differential settlement. PVC is one of the most versatile plastics available with formulations that can provide oil resistance, UV stability, low temperature resistance, and other specific properties. Standard formulations of PVC geomembrane materials are blended for longevity and low cost.
Elvaloy’s
A high performance, long life liner manufactured using Elvaloy technology from DuPont. Available in 0.75mm gauge and .90 reinforced. PTL and PTR are suitable for use with potable water and have excellent heat and chemical resistance, making it suitable for containment of a wide range of processing liquids. Elvaloy also excellent resistance to oil, fuel and sewage.
XR-5® is a versatile alloy, formulated to provide good chemical resistance and outstanding long-term resistance to UV radiation.
XR-5® has been utilized for secondary containment for more than 30 years. XR-5® combines good resistance to combustible liquids (hydrocarbons) with a high performance polyester base fabric. XR-5® is widely used as an exposed lining material, with outstanding long-term resistance to UV radiation. Exposed applications in equatorial climates often utilize XR-5® to combat extreme UV exposures. XR-5® is flexible at temperatures above freezing, and is easy to install and repair, even in remote location. Installation and repair instructions can be described to local contractors for efficient response to the client's containment needs. XR-5® is not normally used for installation in cold temperature. When cold weather installation is required two other materials are recommended. 8218 LTA and 8228 OR LTA are excellent low temperature materials, remaining flexible and durable for cold temperature installation and service. The 8218 LTA material is used for water and drilling mud containment while the 8228 OR LTA is used when hydrocarbon resistance is required. XR-3® is a polymer alloy that is more economical than XR-5® but shares many of its physical properties. XR-3® is used in less chemically demanding applications when the chemical resistance of XR-5® is not required. XR-3® carries the NSF 61 certification for potable water applications.
Polyproplene
Supported Polypropylene styles have excellent cold temperature flexibility, long term UV resistance, and substantial tensile strength. Supported styles of Polypropylene (PP (S)) combine the unique attributes of the PP polymer formulation with the mechanical strength of a 250 lb polyester scrim. PP (S) is composed of the same industry proven blend of polymers and additives that is found in unsupported styles of PP. PP (S) brings together two soft, supple PP films laminated around a reinforcing scrim layer. The resulting geomembrane is strong enough to hang vertically in the form of a baffle curtain or tank liner, and durable enough to leave exposed to the elements for many years. PP(S) is UV stabilized with 2 to 3% carbon black included in the formulation. PP(S) is chemically resistant to water purification chemicals, and carries the NSF 61 certification for contact with potable water. This resilient polymer is also inert to surfactants, which can cause environmental stress cracking in HDPE. PP(S) offers a combination of strength, flexibility, and UV resistance that makes it a clear choice for floating cover applications. PP (S) maintains it's flexibility at low temperatures, making severe winter installations or service conditions an easy application to resolve. In any water or wastewater containment project PP (S) is a clear choice when a strong and chemically resistant geomembrane is required.
Butyl Rubber & EPDM
Butyl rubber sheeting is a flexible synthetic rubber membrane based on butyl rubber. This is an elastomer with molecular crosslinks produced by the copolymerization of isobutylene and small amounts of isoprene. Its various properties make it an ideal material for lining water tanks. Rubber is elastic, not just flexible. Regardless of temperature, it always reverts to its original form. Rubber has unsurpassed dimensional stability, elasticity and long-term durability. Its characteristics are unaffected by cold, heat and stretching Rubber has a unique ability to withstand physical stresses, forces and movements. Rubber actually stretches better than other materials, because it stretches evenly. Butyl rubber sheeting has outstanding ageing and weather-resistant properties. Its crosslinked molecular structure gives excellent protection against ageing over a long period of time even when exposed to the atmosphere, sunlight, ultraviolet radiation and ozone. Butyl rubber sheeting contains no plasticisers or additives which can evaporate or be leached out over the years. Its strength and elasticity remain virtually unchanged over many years, without shrinking, hardening or cracking. Butyl sheeting remains flexible and is generally unaffected by temperature over the range -30 degrees centigrade to +120 degrees centigrade. For prolonged periods of exposure to 70 degrees centigrade maximum contact our office for further advice). Butyl rubber sheeting is highly elastic, stretching at least 300% and retaining its water-proof properties when fully extended. Due to butyl rubber's high degree of flexibility, damage by rough handling is minimised, and it readily adapts itself to soil subsidence and surface irregularities. It has excellent resistance to abrasive wear, tearing, flex-cracking and puncturing. However, it may be damaged by sharp tools, spades, picks, knives, etc. It is recommend that clean rubber soled footwear is used when installing or inspecting butyl rubber liners. A geotextile protective underlay (polymatting) is available for extra protection against puncturing. Butyl rubber sheeting has been used for the storage of a wide range of materials. As stated before, the product contains no plasticisers or additives which can evaporate or be washed out over the years and is non toxic to animals, fish or plant life. APT is available to discuss particular needs and can provide specialist advice on the storage of a range of materials and liquids, as well as offering alternative linings should the need arise. With particular regard to the use of chlorine for water tank treatment, note the following: Sterilisation to BS6700 of water tanks requires that 50 ppm of chlorine (completely and thoroughly dispersed throughout the tank) is held in the tank for a period of 24 hours, followed by a drain down and flushing through of the system, prior to filling with clean drinking water. Although butyl rubber sheeting is extremely tough and resistant to puncture, in the unlikely event that this should occur, a repair can be carried out simply, quickly and economically on site. In most cases, technicians effect the repair using a heat/pressure process, thereby ensuring that the installation is back in operation in the minimum of time. (The same process is utilised when manufacturing liners to your requirements or carrying out modification work). Alternatively, for overseas installations, specially prepared adhesive repair patches can be supplied. Butyl rubber sheeting is available in standard thicknesses of 0.75mm (0.030"), 1.0mm (0.040") and 1.5mm (0.060") in both standard and WRc approved grades. Other thicknesses are available for specific projects.
HDPE
HDPE is a smooth, high density polyethylene (HDPE) geomembrane produced from virgin polyethylene resin. This polyethylene resin is designed specifically for flexible geomembrane applications. It contains approximately 97.5% polyethylene, 2.5% carbon black and trace amounts of antioxidants and heat stabilizers; no other additives, fillers or extenders are used. HDPE has outstanding chemical resistance, mechanical properties, environmental stress crack resistance, dimensional stability and thermal aging characteristics.
High Density Polyethylene (HDPE) is the most common field fabricated geomembrane material. The popularity of High Density Polyethylene (HDPE) is primarily due to its low initial material cost and excellent chemical resistance. This allows thicker sections to be used compared to other geomembrane materials. A thick, durable, HDPE liner can be placed in exposed applications where the cost of other materials would be prohibitive. HDPE has excellent chemical resistance, which is often the driving force behind the selection of HDPE. HDPE is a field assembled lining material that cannot be practically fabricated in the shop. All HDPE projects, regardless of size, must be installed by trained installers. HDPE is a versatile material, which is used widely across all applications. One of the main uses of HDPE is for landfill base liners where its chemical resistance is used to good effect. HDPE can also be used in a multitude of secondary containments, pond linings, and water containment projects. HDPE is best used as an exposed lining material, and has the UV resistance required for many years of outstanding service.
Since HDPE is a field fabricated material welding and testing need to be completed with great care.
The extrusion welder was the first welding technique developed for HDPE. It is a thickness dependant technique that requires a minimum material thickness to create an effective weld without distortion. Extrusion welds in sheet less than 1.0 mm (40 mil) thick are not recommended. Extrusion welds in 1.0 mm (40 mil) HDPE show some distortion and can sometimes be very difficult to prepare around intricate pipe penetrations and mechanical attachments. 1.5 mm (60 mil) HDPE can be reliably extrusion welded in most situations and is recommended in most applications. Welds in 2.0 and 2.5 mm (80 mil and 100 mil) are excellent and are recommended in applications that require exceptional durability. Extrusion welds are very slow and are typically used only for repairs and details. Extrusion welds are very difficult to prepare on vertical or overhead walls, and require a minimum clearance of 1 m (3 ft). This is especially important in sump details where a minimum clearance must be maintained underneath the lowest pipe penetration.
Hot wedge welders have become the technique of choice for HDPE installers over the past 10 years. Wedge welders are fast, produce excellent welds in sheet from 1.0 mm to 2.5 mm (40 to 100 mil), and can be easily tested. Hot wedge welders today produce two weld tracks separated by a small unbonded channel. By sealing off both ends of this channel, and then pumping it full of air, entire seams can be checked quickly and effectively. Weather is a major factor in all HDPE lining installations. Precipitation in any form, whether rain, snow, dew, or fog can bring HDPE installation to a halt.
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