CYLINDRICAL STEEL TANK STANDARD SPECIFICATION

1 BALMORAL TANKSCYLINDRICAL STEELTANK Designed and manufacturedContents1 Tank overview 12 Tank design and key components 13 STANDARD tank accessories 44 Galvanizing 45 Epoxy and polyester coatings56 Rubber tank liners 57 Liner repair 68 Liner material SPECIFICATION : wras approved butyl79 Liner material SPECIFICATION : edpm710 Effect of chlorinated water on butyl and epdm liners811 Hot dip galvanized sheet quality 812 Renovating damaged coatings 1013 Galvanized products: zinc patina 1114 Wet storage stain: prevention and cure1215 Liner approval13 CYLINDRICAL WATER tanks | TECHNICAL SPECIFICATIONB almoral TanksBalmoral tanks specialises in the design andmanufacture of GRP, STEEL sectional andgalvanized CYLINDRICAL STEEL bolted liquid storagetanks. These tanks are primarily used for thestorage of water in the potable water, firesprinkler and irrigation markets.

2 The galvanized CYLINDRICAL tanks are siteassembled using overlapping and boltedgalvanized STEEL panels that are manufacturedwithin the company s facility in the upon the application or design code,a choice of either a synthetic rubber membraneliner or mastic is used to seal the tank togetherwith a plastic coated trough deck roof galvanized tanks provide an economical,reliable and low maintenance solution for gained through the supply of over5000 tanks worldwide and our ISO 9001:2008accreditation ensures consistent quality ofproduct and service for the design, manufactureand installation of liquid storage document has been written to providerelevant information for CYLINDRICAL galvanizedwater storage tanks designed and manufacturedby Balmoral tanks . These modular site bolted storage tanks aremanufactured from galvanized STEEL panels andsealed using either internal synthetic rubbermembrane liner or flexible mastic.

3 The tanks are typically used for:wPotable water storage wFire water storage wIrrigation water storageCYLINDRICAL WATER tanks | TECHNICAL SPECIFICATION11 Tank overviewThe tank shell is constructed from galvanized STEEL panelsthat are bolted together using bolts, nuts and are bolted together in a defined configuration withthe thicker panels at the bottom of the tank where theliquid pressure fixed rolled angles are provided as a means ofsecuring the shell to the foundation, a means of fixing theroof to the shell and to provide additional shell stiffeningas tank shell is sealed using either an internal syntheticrubber membrane liner or mastic seal between theoverlapping corrugated deck roof cover, ladder, platform, pipe-workand other accessories are supplied to meet panels and components can also be epoxy coated tomeet particular aesthetic site requirements.

4 2 Tank design and key components General design philosophyTanks are designed using the following criteria unlessotherwise agreed: wTank shell is designed to accommodate full hydraulic load minus the free-boardwWind speed of 45 m/s (tank empty) wNon seismicwLive/roof load of Tank panels STANDARD tank panels are manufactured from a pre-galvanized STEEL sheet, maximum thickness 5mm, withapproximate overall dimensions of 2530mm, 2580mm or2630mm long, dependent upon vertical bolt patterns, andapproximately 1250mm high dependent on the sheet andtank shell design. 6mm, 8mm and 10mm tank panels mustbe manufactured in mild STEEL to STANDARD upon the galvanizing thickness required (seeBalmoral tanks Galvanized Information in separatedocument) the panel material will conform to thefollowing standards :wBS EN10327 pre-galvanized coating 300g/m.

5 STANDARD thicknesses are 2mm, , 3mm, 4mm, 5mm. Sheets requirements above 5mm must use hot dipped galvanized materialwBS EN10025 c/w hot dipped galvanized coating 600g/m to BS EN 1461. STANDARD thicknesses , 3mm, 4mm, 5mm, 6mm, 8mm and Top and bottom rolled angleThe top and bottom of every tank shell is fitted witha STEEL angle ring that is rolled to the specificdiameter of the tank. The top angle ring stiffens andmaintains the concentricity of the shell as well ascreating fixing points for the roof sheeting. Thebottom angle ring provides a section that can befixed to the foundation, thus securing the tank shellto the concrete base. The cross-section of the angles is 60x60x6mm and issupplied in lengths of 2420mm. Every angle is rolled, toe-out , to suit the tank shell diameter. The verticalor rolled face of each angle has fixing holes to matchthe bolt pitch of the STANDARD shell panel.

6 The horizontal or flat face of each bottom angle hasslots to suit the appropriate size and number of hold-down angles are bolted to the tank shell through thehorizontal seams and are positioned to miss thevertical bolt seams of the shell hoop. Splice anglesstrengthen the joint between the angles and create acomplete ring. The top angle ring is secured with thehorizontal face above the fixings of the tophorizontal bolt bottom angle ring is secured with the horizontalface below the fixing of the bottom horizontal boltseam. Wind stiffening angles Any wind stiffening requirements are fulfilled by agalvanized leaf truss size of leaf truss for any given stiffening ring isdictated by the stiffness requirement. The standardleaf truss depth is 80mm, however in some areas ofhigh wind loading, leaf truss sizes can increase inboth thickness and leaf truss components link together as they wraparound the shell to create a solid stiffening ring,secured directly to the horizontal tank seam with asingle bolt.

7 Each sheet in a course requires five leaftruss sections and are designed to be fitted aroundother WATER tanks | TECHNICAL Shell fixing The tank is secured to the foundation with fixings thatare located externally around the circumference of thetank shell. The bottom angle is secured with either expandingmechanical anchors or chemically fixed on the size of the tank and the wind loadingoverturning moment, the anchors will be either M12 andpass through the bottom angle, or M16 or larger andpass through clamping brackets. A minimum of twoanchors per angle are anchor fixings have a Design Load = x MinimumSpecified Yield Strength. The magnitude of lifting forcedue to wind loading, and therefore the anchor fixingselection, can be determined from the FreeboardA space between the top of the tank and top of theoverflow assembly is created to account for slightvariations in liquid level and sloshing that can occurfrom the filling process.

8 This space is called the Freeboard and is set to a minimum of 150mm withgreater allowances being made for larger tanks that mayhave an increased sloshing affect. The freeboard may need to be further increased tocomply with certain national standards , ie, LossPrevention Certification Board s LPS 1276 approvalstandard requires a minimum 50mm space between themaximum liquid level and the lowest section of the roofstructure . Dead water Water can only be pumped out of the tank whilst theoutlet is submerged. Dead water is the volume of waterbetween the floor of the tank and the bottom of thesuction Tank capacity Tank shells are designed to withstand hydraulic pressurescreated by the contained volume of water. The Effective Capacity is the usable volume of liquidwithin the tank. Freeboard and dead water volumes must be subtractedfrom the wall height volume to gain the effectivecapacity.

9 The Effective Capacity in cubic metres is calculated Tank loads and stresses The tank panels are overlapped and bolted alongvertical and horizontal seams. Bolt pitches are spaced tooptimise material and bolt yield whilst maintaining therequired seal. The vertical seams are designed towithstand all hoop stresses caused by the static head ofthe contents. The horizontal seams are designed towithstand all vertical loads that are imposed on the shell. The hoop stress that is caused by the static load of thecontents is greater at the bottom of the tank, ie, thegreater the depth of liquid, the greater the head ofpressure. Where the hoop stresses increase beyondallowable levels, tank plate thicknesses increase asrequired. As plates thicken, the quantity of bolts within aseam pattern increases to disperse bearing stress on theshell material and shear stress on the bolts.

10 Vertical loads imposed on the shell are those transferredfrom the tank roof and the specified roof load. As withhoop stresses vertical loads are greatest at the bottom ofthe tank. A combination of the roof loads and tank shellweight must be dispersed through the horizontal boltseam at the base of the tank. When vertical loads increasebeyond allowable levels, a close horizontal bolt pitch willbe used to reduce bearing and shear bolts are used to fasten panels in the constructionof the tank shell. The bolt Design Shear Stresses = xUltimate Tensile Strengths, which range from 510 to1035 MPa and are used as the shear values require. As required, additional strength is added in the form ofwind stiffening angles to prevent the shell buckling. Theangles are fixed around the outside of the tank on ahorizontal bolt seam to create a complete stiffening wind speed of 45m/s is used unless otherwise analysis of wind stiffening requirements is on a tankby tank basis.