Floating Covers


	Floating covers consist of flexible membrane lining material applied to float on top of contained liquid to create an economical reservoir. Floating Covers are commonly used for the containment of treated potable water, odour control, dilution control and in the control of algae and evaporation. They offer an economical roof for tanks and concrete reservoirs for water storage and are one of the few techniques available to economically cover very large volumes of fluid or liquid.


	Aquatan’s very flexible and durable Reinforced Polypropylene Floating Covers (Float-A-Roof^®) are designed to operate with minimal supervision and maintenance, at any normal basin water levels with an emphasis on safety for operators and on safe storage of the liquid it contains. Aquatan’s floating covers will give many years of trouble-free operation with limited servicing.

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	MATERIALS


	Aquatan’s Floating Cover Systems are fabricated from a reinforced flexible Polypropylene geomembrane lining material. Our geomembranes are manufactured in an ISO 9001:2000 accredited facility using a proprietary process in which two layers of polypropylene compound are calendered to fully encapsulate a woven polyester reinforcing scrim. The result is one of the best performing thermoplastic floating cover geomembranes on the market today.


	COVER DESIGN


	Our covers are self-tensioned and no adjustment is required in normal operation. It will remain tensioned regardless of the liquid level in the reservoir. The following components should be carefully considered for the successful design and construction of a floating cover system:

PERIMETER FIXING

FLOATS AND WALKWAYS

The Aquatan Floating Cover System can either be attached to a concrete perimeter anchorage beam by way of a steel battening system, or anchored in a perimeter anchor trench.

Floats and walkways are constructed utilizing closed cell polyethylene foam blocks which are wrapped in polypropylene cover material. The walkways must be configured to safely support a fully kitted scuba diver of 150 kg mass gaining access to the manhole hatches to perform maintenance under a range of water levels between TWL and empty. Floats and walkways maintain the cover configuration both during operation and static modes.


	HATCHES


	At least one access hatch must be incorporated into the floating cover to allow an escape of incoming liquid/borne air, regular sampling of the water and direct access and entrance should a diver be required to inspect the interior surfaces of the reservoir while it is in operation. The access hatch is usually situated above the inlet and/or outlet.


	RAINWATER DISPOSAL


	All Aquatan Floating Covers have properly located and formed rainwater collection troughs or drains incorporated in their designs. Rainwater disposal is achieved by the formation of ballasted sumps in the troughs. These encourage free flow of rainwater to a submersible pump in the sump. The water is pumped to an existing overflow system via a flexible tube. Overflow Overflow structures are to be designed to prevent ingress of air beneath the cover.

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	LIQUID TO BE CONTAINED

MOLASSES:
In warm weather, and, if stored for long periods, molasses can release gas. If not released from the storage facility, gas can build up under the cover and form large gas bubbles. These can inhibit flow of incident rainfall to low points for removal, as well as migrate across the surface under windy conditions.

Molasses has a high viscosity and flow beneath the cover can result in drag of the cover at initial filling. This can result in the generation of stresses in the cover.

Since 1984, Aquatan has successfully constructed many Floating Covers for a multitude of liquid storage facilities and a wide variety of applications. Please feel free to call on our experience at any time.


	PHYSICAL PROPERTIES

Physical Properties - Reinforced Polypropylene Geomembranes
Property	Test Method	Certified Value 0.90mm	Certified Value 1.14mm	Certified Value 1.52mm
Reinforcing Piles		1	1	1
Thickness, minimum Overall, mm Over scrim, mm	ASTM D-751 Optical Method	0.90 0.28	1.12 0.30	1.45 0.46
Breaking Strength kN	ASTM D-751 Method A, Avg	1,22	1,34	1,45
Low Temperature Flexibility^oC	ASTM D-2136 1/8” mandrel	-54	-54	-54
Puncture Resistance minimum kN	FTMS 101C Method 2031	1.56	1.78	1.89
Tear Strength, kN	ASTM D-5884	0.45	0.45	0.45
Dimensional Stability, (% change, max)	ASTM D-1204 180^o/82^oC 1 hr.	-0.5	-0.5	-0.5
Hydrostatic Resistance min. Mpa	ASTM D-751 Method A Procedure 1	2.58	2.75	2.93
Ply Adhesion Minimum kN/m	ASTM D-413 Machine Method, Modified	5.25	5.25	5.25
Water Absorption max % wt.change	ASTM D-471 30 days @ 21^oC	<1%	<1%	<1%
ESCR (Env.Stress Crack Resistance ) min.hrs.,no failure	ASTM D-1693 3000 hrs	Does not exhibit ESC	Does not exhibit ESC	Does not exhibit ESC
UV Resistance	ASTM G155 Xenon Arc 80^oC/10 000 hrs (12 600 kJ/m²)	Pass	Pass	Pass
Typical Fabricated Seam Properties
Bonded Seam Strength, min kN	ASTM D-751 modified	0.78	0.89	0.98
Peel Adhesion min kN/m	ASTM D-413 modified	3.5 or FTB**	3.5 or FTB**	3.5 or FTB**
** Film Tear Bond


	ADVANCED TECHNOLOGY REINFORCED POLYPROPYLENE The advanced technology in reactor-processed resin that Aquatan uses for Floating Covers offers many benefits to engineers responsible for Floating Cover application design. As a chemically inert polymer, polypropylene does not contain any post reactor modifiers that can be extracted over time or have a negative impact on the surroundings.

AQUATAN REINFORCED POLYPROPYLENE BENEFITS:
·	Decades of real world environmental experience
·	No plasticizers to leach out leaving the material brittle or weak
·	Superb cold weather flexibility and performance
·	The ability to conform to surface contours
·	Excellent weatherability and UV resistance for exposed applications backed by up to a twenty year weathering warranty
·	A low coefficient of thermal expansion and contraction for superb dimensional stability and lay-flat characteristics
·	Not susceptible to environmental stress cracking (ASTM D-1693)
·	A reinforcing scrim for maximum tear and puncture resistance
·	Excellent chemical resistance to most industrial effluents
·	An environmental friendly manufacturing and seaming process without the use of adhesives.


	POTABLE WATER AND INDUSTRIAL GRADES AVAILABLE Aquatan’s Reinforced Polypropylene Geomembranes are available in both industrial and potable water grades. Potable water grades meets with the requirements for contact with drinking water as outlined in NSF/ANSI-61. The UK Secretary of State for Environment, Food and Rural Affairs has, under Regulation 31 of the Water Supply Regulations, approved Aquatan Reinforced Polypropylene Geomembranes for use in public water supplies. Aquatan Reinforced Polypropylene Geomembrances have also been tested in accordance with applicable ASTM, FTMS, NSF and GRI test methods.

	THICKNESS AND COLOUR OPTIONS Aquatan’s Reinforced Polypropylene Geomembranes are available in three thickness options to meet virtually every need: 0.9, 1.14, 1.52mm. Our material is delivered to site on rolls 1.92m wide x 275m long. The standard colours for our industrial grades are slate brown/black and black/black. The standard colours for our potable water grades are white/tan, tan/black and black/black. For other colour combinations, please feel free to contact us.

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	10 Diesel Road PO Box 633 Isando 1600 South Africa


	Telephone: +27 (0)11 974 5271 Fax: +27 (0)11 974 4111 E-mail: aqua@aquatan.com


	All Contents Copyright © 2011 Aquatan (Pty) Ltd. \| Webmaster: Celestine Ventures cc. Date of entry: February 2004 \| Latest Upload: 18 March, 2011