Specification #CL 0291
CEMENT (SILICEOUS) LINING SPECIFICATIONS
The lining is composed of commercial grade silica aggregate of 100-mesh and 325-mesh particle size, a cementitious binder material, calcium hydroxide, water repellents, and hygroscopic salts. The materials, when combined and mixed with water make a low soluble material which has when set, a coefficient of thermal expansion approximately equal to that of steel. The materials when mixed with water form a plastic mixture showing no unwetted parts.
The materials do not contaminate hot or cold water with odors or toxic matter and contain no greases, resins, stearate, stearic acid derivative, sand, mica or pumice. Materials that will deteriorate when continually immersed in hot or cold potable water under the normal pressures maintained in public utilities are not used. The materials have a weight loss less than 4.0 percent after being immersed in a carbon dioxide solution for a continuous period of 72 hours.
Galvanized steel mesh is attached to the inside surfaces of the tank to ensure proper adhesion of the lining. The lining material is applied in two coats with a stiff brush, trowel or other hand tool. The first coat is not less than 0.125″ thick and the second coat is 0.375″ thick to provide uniform thickness of 0.50″ thick. The first coat is thinned to the consistency of heavy cream and applied with a stiff brush. The first coat is cured sufficiently to insure bond with the tank steel surfaces but not allowed to dry out to affect the quality of the bond between the two coats of lining. The lining material is cured and adheres firmly to and covers the interior of the tank.
The joint between the lining and tank at the taps is sealed to prevent corrosion behind the lining. Only enough siliceous material is mixed at one time that can be applied and finished in 30 minutes. No tempering of mixture with water is permitted. Immediately after the application of the lining material, all openings of the tank are closed and secured by pressure sealing and the tank allowed to stand without water for a minimum of 24 hours. Drying or curing of the lining by a fan or other forced methods is not permitted. The water absorption of the lining is not more than 17 percent of the dry weight.
On Hanson cement lined vessels, FNPT connections are all 304 stainless steel. Flange and heater collars are 304 stainless steel. All openings are closed or plugged during storage and shipment.
Note: Cement lined tanks must be kept closed so that the cement can remain moist and will cure without cracking. The lining must not be allowed to dehydrate prior to the vessel being put into service. Extreme care must be taken during shipping and handling so that the lining is not damaged.