Specification #199202 For Polyethylene Upright Storage Tanks Revision: F - 11/21/03 1. Scope 1.1 This specification covers upright, cylindrical, flat and/or cone bottom tanks molded in one- piece seamless construction by rotational molding. The tanks are designed for above- ground, vertical installation and are capable of containing chemicals at atmospheric pressure. Included are requirements for materials, properties, design, construction,dimensions, tolerances, workmanship, and appearance. 1.2 This specification does not cover the design of vessels intended for use at pressures above or below atmospheric conditions. It is also not for vessels intended for use with liquids heated above their flash points, temperatures above 140 degrees Fahrenheit for Type I materials, or temperatures above 130 degrees Fahrenheit for Type II materials (see section 4.1 for material classifications). 2. Applicable Documents 2.1 ASTM (American Society for Testing and Materials) Standards: D618 Conditioning Plastics and Electrical Insulating Materials for Testing D638 Tensile Properties of Plastics D790 Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulation Materials D883 Definitions of Terms Relating to Plastics D1505 Density of Plastics by the Density-Gradient Technique D1525 Test Method for Vicat Softening Temperature of Plastics D1693 Test Method for Environmental Stress-Cracking of Ethylene Plastics D1998 Standard Specification for Polyethylene Upright Storage Tanks D2765 Degree of Crosslinking in Crosslinked Ethylene Plastics as Determined by Solvent Extraction D2837 Method for obtaining Hydrostatic Design Basis for Thermoplastic Pipe Materials D3892 Practice for Packaging/Packing of Plastics F412 Definitions of Terms Relating to Plastic Piping Systems 2.2 ARM (Association of Rotational Molders) Standards: Low Temperature Impact Resistance (Falling Dart Test Procedure) 2.3 ANSI Standards: B-16.5 Pipe Flanges and Flanged Fittings 2.4 OSHA Standards: 29 CFR 1910.106 Occupational Safety and Health Administration, Flammable and Combustible Liquids 2.5 UBC CODE: Uniform Building Code 1997 Edition 3. Chemical Compatibility 3.1 Chemical compatibility shall be according to the following chemical resistance guides: Pruett, Kenneth M., "Chemical Resistance Guide for Elastomers", Compass Publications. Pruett, Kenneth M., "Compass Corrosion Guide II", Compass Publications 3.2 These references shall be considered as general guidelines only. In many cases, combinations of these chemicals are used in such a way that only the customer (by testing molded product samples) can make a determination in regards to acceptability. 4. Classification 4.1 Tanks are classified according to type as follows and it is the responsibility of the purchaser to specify Type I or Type II. 4.1.1 Type I - Tanks molded from cross-linkable polyethylene resin. 4.1.2 Type II - Tanks molded from linear polyethylene resin (not cross-linkable resin). 5. Materials 5.1 The material used shall be virgin polyethylene resin as compounded and certified by the manufacturer. Type I tanks shall be made from crosslinkable polyethylene resin as manufactured by Exxonmobile Chemical, or resin of equal physical and chemical properties. Type II tanks shall be made from linear polyethylene resin as manufactured by Exxonmobile Chemical, or resin of equal physical and chemical properties. 5.2 All polyethylene resin material shall contain a minimum of a U.V. 8 stabilizer as compounded by the resin manufacturer. Pigments may be added at the purchaser's request, but shall not exceed 0.25% (dry blended) of the total weight. 5.3 Mechanical Properties of Type I tank material: PROPERTY ASTM VALUE Density (Resin) D1505 0.938-0.946 g/cc Tensile (yield Stress 2"/min) D638 3000 PSI Elongation at Break (2"/min) D638 >300% ESCR (100% lgepal, Cond. A, F50) D1693 >1000 hours ESCR (10% lgepal, Cond. A, F50) D1693 >1000 hours Vicat Softening Degrees F. Temperature D1525 250 Flexural Modulus D790 100,000 PSI 5.4 Mechanical Properties of Type II tank material: PROPERTY ASTM VALUE Density (Resin) D1505 0.940-0.948 g/cc Tensile (yield Stress 2"/min) D638 2950 PSI Elongation at Break (2"/min) D638 >1000% ESCR (100% lgepal, Cond. A, F50) D1693 550 hours ESCR (10% lgepal, Cond. A, F50) D1693 48 hours Vicat Softening Degrees F. Temperature D1525 235 Flexural Modulus D790 129,000 PSI 6. Design Requirements 6.1 The minimum required wall thickness of the cylindrical shell at any fluid level shall be determined by the following equation, but shall not be less than 0.187 in. thick. T = P x O.D./2 SD = 0.433 x S.G. x H x O.D./2 SD T = wall thickness SD = hydrostatic design stress, PSI P = pressure (.433 x S.G. x H), PSI H = fluid head, ft. S.G. = specific gravity, g/cm^3 O.D. = outside diameter, in. 6.1.1 The hydrostatic design stress shall be determined by multiplying the hydrostatic design basis, determined by ASTM D2837 using rotationally molded samples, with a service factor selected for the application. The hydrostatic design stress is 600 PSI at 73 degrees Fahrenheit for Type I and Type II materials. In accordance with the formula in 6.1, the tank shall have a stratiform (tapered wall thickness) wall. 6.1.2 The hydrostatic design stress shall be derated for service above 100 degrees Fahrenheit and for mechanical loading of the tank. 6.1.3 The standard design specific gravity shall be 1.5 or 1.9. 6.2 The minimum required wall thickness for the cylinder straight shell must be sufficient to support its own weight in an upright position without any external support. Flat areas shall be provided to allow locating large fittings on the cylinder straight shell. 6.3 The top head must be integrally molded with the cylinder shell. The minimum thickness of the top head shall be equal to the top of the straight wall. The top head of tanks with 2000 or more gallons of capacity shall be designed to provide a minimum of 1300 square inches of flat area for fitting locations. 6.4 Tanks with 2000 or more gallons of capacity shall have a minimum of 3 lifting lugs integrally molded into the top head. The lifting lugs shall be designed to allow erection of an empty tank. 6.5 The tank shall be designed to provide a minimum of 4 tie-down lugs integrally molded into the top head. The tie-down lugs shall be designed to allow tank retention in wind and seismic loading situations without tank damage. Refer to section 12.2 for tank tie-down accessories. 7. Dimensions and Tolerances 7.1 All dimensions will be taken with the tank in the vertical position, unfilled. Tank dimensions will represent the exterior measurements. 7.1.1 The tolerance for the outside diameter, including out of roundness, shall be per ASTM D1998. 7.1.2 The tolerance for fitting placements shall be +/- 0.5 in. in elevation and 2 degrees radial at ambient temperature. 8. Test Methods 8.1 Test specimens shall be taken from fitting location areas or piggy-back test methods. 8.2 Low Temperature Impact Test 8.2.1 Test specimens shall be conditioned at -40ø Fahrenheit for a minimum of 2 hours. 8.2.2 The test specimens shall be impacted in accordance with the standard testing methods as found in ASTM D1998. Test specimens < 1/2" thickness shall be tested at 100 ft.-lb. Test specimens > 1/2" thickness shall be tested at 200 ft.-lb. 8.3 Degree of Crosslinking Test (% Gel - Type I Only) 8.3.1 The test method used is to be the o-xlene insoluble fraction (gel test) per ASTM D2765 Method C. This test method is for determination of the ortho-xlene insoluble fraction (gel) of crosslinked polyethylene. 8.3.2 The percent gel level for Type I tanks on the inside 1/8 in. of the wall shall be a minimum of 65%. 8.4 Ultrasonic Tank Thickness Test 8.4.1 All tanks 2000 gallons or larger shall be measured for tank wall thickness at 6", 1 ft., 2ft., etc. on the tank sidewall height at 0ø, 90ø, 180ø, and 270ø around the tank circumference with 0ø being the tank manway and going counter-clockwise per ANSI standard drafting specifications. A copy of this test report can be ordered when placing the original tank order. All tanks shall meet design thickness requirements and tolerances. 8.4.2 Tanks smaller than 2000 gallons are only periodically measured at the start of a production run or after any design changes. Customers can place an order for tank wall thickness measurements on smaller tank sizes when placing the original order. A copy of the test report will be provided if ordered. 8.5 Hydrostatic Water Test 8.5.1 The hydrostatic water test shall consist of filling the tank to brim full capacity for a minimum of four hours and conducting a visual inspection for leaks. A hydrostatic water test will be conducted if ordered by the customer. 8.6 The tank shall be visually inspected to determine such qualities as are discussed in Section 9. 9. Workmanship 9.1 The finished tank wall shall be free, as commercially practicable, of visual defects such as foreign inclusions, air bubbles, pinholes, pimples, crazing, cracking and delaminations that will impair the serviceability of the vessel. Fine bubbles are acceptable with Type II tanks to the degree in which they do not interfere with proper fusion of the resin melt. 9.2 All cut edges where openings are cut into the tanks shall be trimmed smooth. 10. Tank Fittings (Nozzles) 10.1 Fittings - Threaded Bulkhead 10.1.1 Threaded bulkhead fittings are available for below liquid installation depending on the tank diameter and the placement of the fitting in the tank. Fittings must be placed away from tank knuckle radius' and flange lines. Consult Sierra Sales for placement questions. The maximum allowable size for bulkhead fittings placed on a curved sidewall section of tanks 48 in. to 142 in. in diameter is 2 inch size. Tank wall thickness must be considered for bulkhead fitting placement. The maximum wall thickness for each fitting size is shown below. Fitting Size Maximum Wall Thickness 1/2 in. 0.750 in. 3/4 in. 0.875 in. 1 in. 0.875 in. 1-1/4 in. 0.875 in. 1-1/2 in. 0.875 in. 2 in. 1 in. 3 in. 1.125 in. (Flat Surface Only) 10.1.2 The bulkhead fittings shall be constructed of PVC, PP, or other specified material. Gaskets shall be a minimum of 1/4" thickness and constructed of 40-50 durometer EPDM, 60-70 durometer Viton®, or other specified material. 10.2 Fittings - Bolted Double 150 lb. Flange Fittings 10.2.1 Bolted double flange fittings are required for below liquid level installation for sizes above 2 in. depending on the tank diameter and the placement of the fitting in the tank. Fittings must be placed away from tank knuckle radius' and flange lines. Consult Sierra Sales for placement questions. Bolted double flange fittings provide the best strength and sealing characteristics of any tank fitting available. Allowable fittings sizes based on tank diameter for curved surfaces are shown below. Tank Diameter Maximum Bolted Fitting Size Allowable 48 in. - 86 in. 3 in. 90 in. - 102 in. 6 in. 120 in. - 142 in. 8 in. The bolted double flange fittings shall allow tank wall thickness up to 2 1/2 in. 10.2.2 The bolted double flange fitting shall be constructed with 2 ea. 150 lb. flanges, 2 ea. 150 lb. flange gaskets, and the correct number and size of all-thread bolts for the flange specified by the flange manufacturer. The flanges shall be constructed of PVC Type I, Grade I or other specified material. Gaskets shall be a minimum of 1/4" thickness and constructed of 40-50 durometer EPDM, 60-70 durometer Viton® or other specified material. There shall be a minimum of 4 ea. full thread bolts. The bolts may have gasketed flanged metal heads or bolt heads encapsulated in Type II polyethylene material. The encapsulated bolt shall be designed to prevent metal exposure to the liquid in the tank and prevent bolt rotation during installation. The polyethylene encapsulation shall fully cover the bolt head and a minimum of 1/4" of the threads closest to the bolt head. The polyethylene shall be color coded to distinguish bolt material (white - 316 S.S., yellow - Hastelloy C276, red - Monel, green - Titanium). Each encapsulated bolts shall have a gasket to provide a sealing surface against the inner flange. 10.2.3 Standard orientation of bolted double flange fittings shall have bolt holes straddling the principal centerline of the tank in accordance with ANSI/ASME B- 16.5 unless otherwise specified. 10.3 Fittings - Bolted Stainless Steel Fittings 10.3.1 Bolted stainless steel fittings are available for below liquid level installation depending on the tank diameter and the placement of the fitting in the tank. Fittings must be placed away from tank knuckle radius' and flange lines. Consult Sierra Sales for placement questions. Allowable fittings sizes based on tank diameter for curved surfaces are shown below. Tank Diameter Maximum Bolted Fitting Size Allowable 48 in. 3 in. 64 in. - 142 in. 4 in. The bolted stainless steel fittings shall allow tank wall thickness up to 2 1/2 in. 10.3.2 The bolted stainless steel fittings shall be constructed with a minimum of 4 fully threaded 3/8 in. studs. Each fitting shall have two gaskets and two flanges. One gasket shall be compressed between the inside of the tank wall surface and the inside flange of the fitting. The other gasket shall be compressed between the outside tank wall surface and the outside flange of the fitting. The stainless steel fittings come standard with female pipe threads on both the inner and outer flanges. Other threading arrangements may be specified. The fittings shall be constructed of Type 316 stainless steel. Gaskets shall be a minimum of 1/4" thickness and constructed of 40-50 durometer EPDM, 60-70 durometer Viton® or other specified material. 10.4 Fittings - Siphon Tube Fittings 10.4.1 Siphon tubes may be added to the fittings specified in sections 10.1, 10.2 and 10.3. Siphon tubes will allow these fittings, when used as drainage fittings to provide better tank drainage. 10.5 Fittings - Unitized Molded Outlet (SUMO) - Patent #5,374,026 10.5.1 The SUMO fittings shall be an integral part of the tank and provide complete drainage of liquid through the sidewall of a flat bottom container without the use of a special support structure or concrete pad. The standard outlet provided is a PVC socket which allows solvent weld PVC pipe attachments at the tank pad level. This option is offered in 4 places(0, 90, 180, 270 degree tank locations) at the tank pad level. It provides a metal reinforcement completely isolated from any chemical attack. 10.5.2 The tank attachment shall be constructed from a PVC schedule 80 male adapter and is standard in 2,3,4 or 6 in. sizes on select tank sizes. This provides a schedule 80 pipe socket attachment (Except for the 6 in. size). Other outlet attachments are available in a variety of materials. The fitting orifice shall not be less than schedule 80 interior pipe size per ANSI B36.10-1979. O-rings shall be constructed of 70 +/- 5 durometer Viton® or other specified material. 10.6 Fittings - Self-Aligning Threaded Bulkhead 10.6.1 Self-Aligning fittings are available for installation in vapor phase applications on curved surfaces depending on the spherical dome radius and the placement of the fitting on the tank dome. Fittings must be placed away from tank radius'. Consult Sierra Sales for placement questions. The maximum allowable size for self- aligning fittings placed on a spherical section of the tank is shown below. Tank Diameter Maximum Fitting Size Allowable 45 in. - 48 in. 2 in. 64 in. - 142 in. 3 in. Tank thickness and fitting angle may need to be considered for self-aligning fitting placement. The maximum thickness and installation angle for fitting sizes are shown below. Fitting Size Maximum Angle Maximum Thickness 1 in. 27 degrees 1.000 in. 2 in. 25 degrees 0.750 in. 3 in. 20 degrees 1.000 in. 10.6.2 The self-aligning fittings shall be constructed of PVC or other specified material. Gaskets shall be a minimum of 1/4" thickness and constructed of 40-50 durometer EPDM, 60-70 durometer Viton®, or other specified material. 10.7 All tank fitting attachments shall be equipped with flexible couplers or other movement provisions provided by the tank customer. The tank will deflect based upon tank loading, chemical temperature, and storage time duration. Tank piping flexible couplers shall be designed to allow 4% design movement. Movement shall be considered to occur both outward in tank radius and downward fitting elevation from the neutral tank fitting placement. 11. Tank Attachments 11.1 Tank Attachments - Sight Level Gage 11.1.1 The sight level gage shall be constructed of flexible PE tubing to allow for tank contraction and expansion due to loading and temperature changes. The level gage shall be connected to the tank with 2 Ea. appropriate 3/4" fittings as described in section 10. Each fitting can have valves installed for isolation or drainage purposes. 11.2 Tank Attachments - Float Level Gage 11.2.1 The float level gage shall be constructed of a guided float on the inside of the tank connected to a weight indicator on the exterior of the tank with a 1/4" rope. The weighted indicator shall move along inside a clear guide pipe and may be equipped with an optional gallonage indicator board. The gallonage indicator board is made of PVC material and may be attached to the clear guide pipe. The board shall be stenciled with one hundred gallon marks and labeled every five hundred gallons. The level gage shall be connected to the tank at an appropriate tank flat on the tank dome with a 3" threaded bulkhead fitting and held along the tank sidewall with appropriate 1" fittings and stand-off connections. 11.2.2 The float level gage rigid components shall be constructed of PVC or other specified material. The rope shall be constructed of polypropylene or other specified material. Gaskets shall be constructed of EPDM, Viton® or other specified material. 11.3 Tank Attachments - Ultrasonic Level Indicator 11.3.1 The ultrasonic level indicator shall consist of a 2 or 3 in., 4 - 20 mA output PVC sensor and a 3-1/2 digit display unit. The sensor may be equipped with male pipe threads and be connected to the tank with a PE bulkhead fitting, or the sensor may be Teflon® faced and flanged bolted to the tank with encapsulated 316 S.S. bolts. The sensor is connected to a display unit that is mounted to the containment tank. The display unit box shall be Nema 4 rated and factory pre-wired for 110 VAC power. All connections shall be labeled to prevent errors in field installation. The display unit is preprogrammed for the tank ordered. The display will show hundreds of gallons (display x 100 = gallons). 11.4 Tank Attachments - Manway and Fill Cap (Non-sealed) 11.4.1 Fill caps are available in a 10 in. vented-threaded style on various tank sizes with a minimum opening diameter of 7.125 in. Cap attachment shall be provided with all standard 10 in. cap placements with a polyurethane cap tie. Check Sierra Sales specification drawing for availability and position. 11.4.2 Manways are available in a 18 in. vented-threaded style (minimum opening diamter of 16 in.), a 24 in. vented threaded style (minimum opening diameter of 22 in.) And a 24 in. slip fit style (minimum opening diameter of 19.25 in.) On various tank sizes. Check Sierra Sales specifications drawing for availability and position. 11.4.3 All caps and manways shall be constructed of polyethylene material. 11.5 Tank Attachments - Bolted Sealed Top Manway 11.5.1 Sealed manways are available in 18, 20 and 24 in. sizes on certain tanks in selected positions. Consult Sierra Sales for placement positions. 11.5.2 The sealed manway shall be constructed of polyethylene material. The bolts shallbe polypropylene or other specified material. The gaskets shall be closed cell crosslinked polyethylene foam and Viton® materials. 11.6 Tank Attachments - Down Pipes and Fill Pipes 11.6.1 Down pipes and fill pipes shall be prepared per the customer approved drawings and specifications. All down pipes and fill pipes shall be supported at 5 ft. maximum intervals with support structures. Standard support structure design shall utilize bulkhead fitting tank attachments. Other optional designs are available. All designs shall be done according to the specific need of the customer. 11.6.2 All down pipes and fill pipes shall be constructed of PVC or other specified materials. 11.7 Tank Attachments - U-Vents 11.7.1 Each tank must be properly vented for the type of material and flow rates expected. Vents must comply with OSHA 1910.106 (F) (iii) (2) (IV) (9)normal venting for atmospheric tanks or other accepted standard, or shall be as large as the filling or withdrawal connections, whichever is larger but in no case less than 1 in. nominal inside diameter. U-Vents are offered in sizes from 1 in. to 6 in. with or without screening. Consult Sierra Sales for necessary venting and placement information. 11.7.2 All U-vents shall be constructed of PVC or other specified materials. 11.8 Tank Attachments - Flange Adapters 11.8.1 Flange adapters may be purchased as optional equipment to adapt threaded or socket fitting outlets to 150 lb. flange connections for connection to piping system components. Flange adapters are available in PVC, CPVC or other specified materials. Flange adapter construction shall utilize schedule 80 components in sizes ranging from 3/4" to 8" depending on material required. 12. Tank Accessories 12.1 Tank Accessories - Ladders 12.1.1 Ladders shall be constructed of painted mild steel, stainless steel, FRP or other specified material. 12.1.2 Safety cages shall be provided with ladders as optional equipment unless required by OSHA standards. 12.1.3 All ladders shall be designed to meet applicable OSHA standards. Reference: OSHA 2206; 1910.27; fixed ladders. 12.1.4 Ladders must be mounted to the tank to allow for tank expansion and contraction due to temperature and loading changes. All top ladder mounts shall be connected to integrally molded in attachment lugs that allow for tank movement. 12.1.5 Mild steel parts shall be deburred and painted with a chemical resistant enamel paint. 12.2 Tank Accessories - Tie Down Systems 12.2.1 The tie down system shall be designed to withstand 110 MPH wind loads. Tie down systems must meet seismic zone 4 requirements per UBC 1997 code. Any anchor bolts shall be provided by the customer per the instructions and the base plates for the system. 12.2.2 The tie down system shall be offered in either painted mild steel, 304 stainless steel or other materials as specified by customer requirements. 12.2.3 Mild steel parts shall be deburred and painted with chemical resistant enamel paint or galvanized. 12.3 Tank Accessories - Tank Heating Systems 12.3.1 Heating systems for use with polyethylene tanks shall be designed to meet specific requirements such as tank material type, tank size, low ambient temperature, and desired maintenance temperature. 12.3.2 All control components of the heating system shall be mounted in water tight, high impact plastic box(es) with a gasketed cover. 12.3.3 All heating system components shall be Nema 4 rated and factory pre-wired for 110 or 220 VAC. All connections shall be labeled to prevent errors in field installation. 12.3.4 Each control box shall carry a decal attached to the inside surface of the cover, on which an electrical wiring diagram will be printed. 12.3.5 Each control box shall contain two temperature controls. One control shall regulate the maintenance temperature setting and the other control shall regulate the high temperature setting. The maintenance temperature setting should be set at the desired maintenance temperature. The high temperature setting shall be adjusted to 10 degrees above the desired maintenance temperature to a maximum of 130 degrees Fahrenheit. All control systems must be designed with a power off failure mode. 12.3.6 The heating panels shall be designed to wrap around and lie flat against the surface of the tanks. The heating panels shall have a maximum heating density of 0.222 watts per square centimeter. All heating panels and sensor bulbs shall be attached to the tank with 2" wide duct tape. Under no circumstances shall cable type heaters be used with polyethylene tanks. 12.3.7 Insulation used shall be polyurethane foam with a density of 2.0 - 3.0 lb./ft. ^3 with an "R" value of 8.33/in. The foam shall be applied with a nominal thickness of 2" to all external tank surfaces except the tank bottom shell. 12.3.8 Upon completion of application and curing of the insulation, two full coverage coats of latex mastic coating shall be applied to the surface of the insulation in such manner as to seal the insulation from the outside environment. The latex mastic can be ordered in gray (standard) or white in color. 12.4 Tank Accessories - Cone Bottom Tank Stands 12.4.1 Cone Bottom Tank Stands shall be offered in 30 and 45 degree cone styles with rated gross weight capacities for all Sierra Sales cone bottom tanks. The stands shall be designed for a minimum of 2.4 safety factor accounting for wind and seismic loads. Ratings are based on stands anchored to an appropriate concrete support structure and the tank adequately secured. 12.4.2 Cone bottom tanks stands shall be offered in painted mild steel or as specified by customer requirements. Mild steel parts shall be deburred and painted with a chemical resistant enamel paint. 13. Marking, Packing and Packaging 13.1 The tanks shall be marked to identify the product, date (month and year) of manufacture, capacity, and serial number. The tank shall be shipped with a 3 of 9, HRI bar code label containing tank description, manufacturing order number, part number, serial number, manufacturer, and date. 13.2 The proper caution or warning signs as prescribed by OSHA standard 29 CFR 1910.106 shall be customer determined and supplied. 13.3 All packing, packaging, and marking provisions of ASTM Practice D3892 shall apply to this standard. 13.4 Customer specified labeling is available. 13.5 Tank shrink wrapping and bagging is available upon customer request. 13.6 All fittings that do not interfere with tank shipment shall be installed unless otherwise specified. Fittings and accesories that interfere with tank shipment or could be broken during shipment are shipped separately. 14. Shipping 14.1 Since there are variations in methods of shipping, Sierra Sales's instruction shall be followed in all cases. 14.2 Consult the Sierra Sales "Guidelines for Use and Installation" booklet included with your tank for unloading instructions on specific tanks. This booklet can be found attached to the cap or manway area on the inside of the tank. Tanks with capacities of 2000 gallons or more have molded-in lifting lugs provided to assist with tank handling. 14.3 Upon arrival at the destination, the purchaser and/or his agent shall be responsible for inspection for damage in transit. If damage has occurred, a claim should be filed with the carrier by the purchaser, and the manufacturer should be notified prior to the tank being put into service. Download Sierra Sales's specification for Single Wall Tanks.