FILTER WASHWATER TROUGHS
PART 1 - GENERAL
1.1 WORK INCLUDED
A. Furnish and install filter washwater troughs for each filter including all materials, equipment and labor required for a complete installation in each filter.
1.2 RELATED WORK
A. Division 3 - Concrete.
B. Section 13223 - Filter Disinfection.
1.3 REFERENCES
A. ASTM Test Methods: D638; D570; D790; D2583.
PART 2 - PRODUCTS
2.1 DESIGN
A. Trough carryoff capacity shall be 4,000 gallons per minute each with a free board of at least 2 inches.
B. The troughs shall be designed to support, within the stress and deflection limitations, the gravity, buoyant and lateral loads described as follows:
1. The downward vertical loads shall include the weight of the trough and attachments, such as weir plates and spreader bars in addition to the weight of water in the trough and any additional loads shall be considered.
2. The buoyant load shall act vertically upward. Its magnitude shall be equal to the weight of the displaced water when the filter is filled from below with the trough empty. The line of action passes through the centroid of the submerged cross-sectional area.
3. The lateral loads acting against the trough side walls which are induced by differential water
levels on either side of the trough wall. The maximum differential load occurs when the trough is empty and the tank is full or when the trough is full and the tank empty.
C. Troughs shall accommodate temperature-induced stresses resulting from differences in coefficients of thermal expansion (contraction) between the trough and the tank/support materials. Troughs shall accommodate an expansion (contraction) of c inch per 20 feet of trough over range of -10o F to 100o F without exceeding deflection or strain limits.
D. The trough system shall be designed to resist torsional oscillations induced by the flow of water over the trough edges.
E. Maximum vertical deflection under full buoyant or gravity load shall be less than or equal to the unsupported length of trough in inches divided by 1,000. The maximum allowable deflection shall be 3/16 inches. Maximum trough side wall horizontal defection under full lateral load shall be less than or equal to the trough depth in inches divided by 100. Maximum allowable bottom deflection shall be 3/16 inches. Trough bottom deflection (oil canning) under full buoyant or gravity load shall be less than or equal to the trough width in inches divided by 100. The maximum allowable bottom deflection shall be 3/16 inches.
F. Troughs shall be designed so that the maximum wall stress under the most severe loading condition is less than or equal to 1,500 pounds per square inch (psi).
2.2 MATERIALS
A. Resin shall be a commercial grade, polyester thermosetting resin which has been found acceptable for the service conditions.
B. Fillers shall not be contained in the resin with the exception of a thixotropic agent, which can be used for viscosity control if there is no interference with laminate quality or chemical resistance. Pigments, dyes or colorants, determined by a minimum of five (5) years of acceptable service conditions, that will not fade or chalk from the original color standard. Ultraviolet protection in the form of pigmentation or ultraviolet absorbers shall be included in the resin. When metal reinforcements are used, each shall be free of rust, oil and any foreign matter and encapsulated with a minimum of c-inch thick laminate. Glass reinforcement shall consist of chemically bonded surface mat and shopped strand or chopped strand mat. The surface mat shall be Type
C, 10 to 20 mils thick with a silane finish and a styrene soluble binder. The glass content shall not exceed 20 percent by weight. Chopped strands shall be Type E glass with a silane finish and styrene-soluble binder.
2.3 QUALITY
A. Inner surface of the trough shall be smooth and resin rich. Outer surface shall be reasonably smooth with no glass fibers exposed. Laminations shall be dense without voids, dry spots, cracks or crazes. Air bubbles shall be held to a minimum.
B. Inner surface of the trough shall be reinforced with a glass surfacing mat. This shall be followed with a chopped strand glass laminate with a maximum 2 ounces per square foot in a minimum of two (2) layers. Void content of the complete laminate shall not exceed 2.5 percent of laminate volume.
C. Top edges of the trough shall be level and parallel with a tolerance of plus or minus c inch measured when the trough is not loaded. Length of a trough section shall have a tolerance of plus or minus c inch per 10 feet of length. Laminate thickness tolerance shall be plus c inch minus 0.
D. Thickness at supports such as saddles shall be a minimum of 1.5 times nominal trough thickness. E. End flanges and blind ends shall be a minimum of 1.5 times the nominal trough thickness.
F. An integrally molded water stop shall be provided on the trough when the trough is grouted into and/or passes through a wall.
G. ABS spreaders (1-inch diameter) shall be bolted between trough walls on approximate 2-foot centers.
H. Mechanical and physical properties shall conform to those listed in the table below.
FILTER WASHWATER TROUGHS
LAMINATE MECHANICAL AND PHYSICAL PROPERTIES (731F)
Item ASTM Test Method 3/16-inch 1/4-inch
Ultimate Tensile Strength (PSI x 103 min.) D638 11 12
Flexural Strength (PSI x 103 min.) D790 16 19
Flexural Modulus of Elasticity (PSI x 106 min.) D790 0.9 0.9
Barcol Hardness (Min.) D2583 35 35
Water Absorption (% Max.) D570 0.2 0.2
PART 3 - EXECUTION
3.1 INSTALLATION
A. All trough mounting brackets, hardware and stabilizers shall be Type 18-8 stainless steel and supplied by the trough manufacturer.
B. Troughs shall be protected during on-site storage and installation from contamination.
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