The following information will aid the emulsion end user in selecting the proper storage tank.
Emulsions usually weigh 1 kg/L (8.3 to 8.4 Ib/gal). The tank foundation should be designed for the weight of the maximum volume to be stored plus the weight of the tank shell. Vertical tanks are best set on a concrete foundation while horizontal tanks require a saddle for each end and one in the middle, or as required by local building codes.
Emulsion storage tanks can be either vertical or horizontal.
These type tanks are normally preferred over horizontal tanks because less of the emulsion is exposed to the atmosphere which causes a scum to form on top of it. Other advantages of vertical tanks are they occupy less land area, are easier to heat, easier to insulate if required and their emulsion level can be measured more easily.
These tanks offer the advantage of being less susceptible to high tension power lines because of their low profile, easier to recirculate completely and easier to drain completely since they are usually set on a slight slope.
AII vertical tanks should have manholes for clean out located approximately 0.6 m (2 F) from their bottom. There should be a safety ladder on the outside and a manhole on top of the tank. Governing safety standards should be used at all times. Any tank should be properly vented and provided with a suitable electrical ground. Some type of liquid level and measurement indicator can be installed if needed. Used tanks are acceptable, provided they are thoroughly cleaned, usually with steam, and the necessary tank features installed.
Be extremely careful when cutting on used tanks especially if they have previously contained some type of petroleum product. Only certified personnel using accepted industry safety standards should modify these types of tanks.
Proper plumbing of a tank is very important. Provide a 19 to 25 mm (3/4 to 1 in.) sample line for each tank. The line should be located approximately 0.6 m (2 ft) above the tank bottom with the line extending 0.6 m (2 ft) inside the tank.
Fittings should also be supplied for the installation of a tank thermometer or RTD. Usually 3/4".
Always provide a full-size suction line, that is, the same size as the transfer pump inlet or larger. Keep the suction line as short as possible and with as few bends as practical. Inside the tank, install an elbow at the suction inlet keeping the bottom of the elbow approximately 50 mm (2 in.) off the tank bottom.
Always provide a tank return or re-circulate line. This line should be the same size or no less than one size smaller than the suction line. Inside the vertical tank, turn the return line to the wall of the tank and away from the suction line. Allow the pipe to extend several feet inside the tank. Inside horizontal tanks, allow the return line to extend halfway into the tank. This permits better recirculation in both type tanks. It is best to always place the return line near the bottom of the tank. If the return line must enter higher in the tank bring the line inside the tank and back to the tank bottom. Never allow emulsion to drop through the air, always return it to a submerged outlet or one very near the tank bottom.
Arrange tank plumbing so the transfer pump can draw from more than one tank. Be sure the plumbing is arranged to permit the transfer pump to unload the supply tanker, recirculate the storage tank and load the user equipment. The emulsion can be loaded either through the top or bottom of a tanker. However, if loading through the top the loading hose or pipe should be lowered near the bottom of the tank.
Tanks can be located as desired as long as they are approved by local authorities. Tanks should not be located near high tension electric power lines because of the electrical charge around the wires could affect the electrical charge on the emulsion particles causing instability or even cause an arc between the tank and the wires. Protection from spillage must be provided as required by local codes. Some standards call for a berm around the storage area that provides a volume from 1.10 to 1.25 times the volume of the largest tank.
Provision should be made for small spills that can occur at the loading site. A suitable drain or other method should be used to prevent tracking asphalt outside the loading area.