ASPHALT EMULSIONS: STORAGE AND HANDLING
PRODUCT INFORMATION
Emulsified Particle
Asphalt Emulsion
Charlotte® Millpac Bakersfield plant
This graph shows the fineness of VSS Emultech® emulsions.
-----10um------
A very fine VSS Emultech® emulsion
>>>>>Flocculation
Coalescence
Settlement
Any action that forces particles together will coarsen the emulsion.
Pumping
Over heating
Freezing
Over mixing
Contamination with other emulsions, cutbacks or other materials.
Take care of these and the emulsion will perform, ignore them and you may get problems.
Use the right tanks, the right equipment and handle properly. The following are general points to consider. Talk to VSS for more detail.
Storage tanks:
Go to www.saunco.com for tank information and purchase.
Tank Foundations:
Emulsions weigh about 1 kg per liter, that's about 8.3 lbs per gallon(US). The tank foundations must be designed for the maximum volume plus the tank shell and attached equipment. Vertical tanks are best set on a concrete pad. This pad is a structural member and should be designed by a competent civil engineer. Foundations also must be properly designed.
Horizontal tanks are acceptable but not recommended. They require a saddle at each end and, for long tanks, one in the middle. Individual foundations for each saddle are acceptable.
Tanks may be raised on a platform to allow gravity feeding or for space considerations.
Materials:
Tanks may be made from mild or stainless steel, high density polyethylene, polypropylene copolymer and most engineering plastics. Use of polymer or plastics will depend on the heating system to be used.
Vertical:
These are recommended as they have less surface area and thus less exposure of emulsion to air. They occupy less space and are easier to heat, insulate and monitor levels.
Horizontal:
These tanks are often less expensive and easy to procure. They may be set on a slight slope to facilitate draining and circulation. Old gasoline oil and rail tank cars are acceptable for this application. For raised tanks the load is spread over a wider area making construction easier.
Tank Features:
General:
All Vertical tanks require a manhole for cleanout located about 0.6m(2ft) from the bottom and on the side wall. A safety ladder and roof catwalk is recommended. An internal ladder can be very useful. Manholes at the top of the tank are recommended.
All government and company engineering standards must be employed.
All tanks must be earthed.
Liquid level control by counterweight or electronic means is recommended.
Used tanks must be thoroughly steam cleaned before use.
When cutting used tanks for transportation be very careful to ensure that no flammable product is present.
Insulation of tanks is required where the product must be stored hot or freezing may occur. This can be done with 50-75mm of rockwool or similar clad with aluminum cladding.
Bunding may be required, spill protection is recommended. This is a ditch around the tank, usually with some absorbent material like sand or scoria that can take 1.1-1.25 times the tank volume.
A suitable drain should be provided to prevent tracking of spills by trucks.
Tanks should not be located near high tension power lines.
Tank plumbing:
Proper plumbing is very important. Provide a 1-3/4inch(1.9-2.5cm) sampling line for each tank at about 2 ft(0.6m) above bottom of tank.
A full sized suction line (same size or larger than the transfer pump inlet). Keep the suction line short with as few bends as possible. Inside the tank install an elbow at the bottom of the suction inlet. Keep the end of the elbow about 5cm (2 inches) above the tank bottom.
Always provide a return or recirculation line. This should be the same size or no less than one size smaller than the suction line. Inside vertical tanks turn the return line to the wall of the tank and away from the suction line. Allow the return pipe to extend several feet inside the tank.
In horizontal tanks allow the return line to extend halfway into the tank.
The return line should be near the bottom of the tank so that it is below the level of the liquid at all used fill levels. This prevents foaming.
Plan out the tank farm so that the transfer pump can draw from more than one tank. The transfer pump must be able to unload the supply tanker, recirculate the storage tank and load user equipment.
Mixers may be used in the tank. They may be simple propeller mixers operated at low RPM or larger anchor sweep mixers.
Do not over mix the emulsion. It should require mixing once a week or for a short time before load out.
Heating Systems:
- Hot Oil: A separate hot oil heater or extra circuit on an existing heater can be used. Oil temperature must be 85C(185F) or below. Coil design is important and spiral in shape.
- Hot Water Heating: Hot water coils with water at 40-50C are suitable for many emulsion applications.
- Steam Coils
- Solar
- Electrical. Contact vss@slurry.com for details.
Coils are finned tubes, the surface area and number of loops is determined by the size of the tank.
Consult vss@slurry.com for more information.
Emulsion lines and transfer pumps should be jacketed and traced. This ensures trouble free startup and fewer blockages.
Recommended Storage Temperatures:
Pumps:
Most pumps can be used with emulsions. However as emulsions can shear and the particles be pushed together it is advisable to take precautions:
- Positive displacement pumps.
The rotating gears will shear the emulsion. Allow extra clearance of 3-4 thou in the pump or use an old and worn pump. The pump should be jacketed and heated. A relief valve is essential. The pump should be an alloy type. Generally packing seals are recommended. - Centrifugal Pumps.
The material is fed into the center of the pump by gravity and a high speed impeller flings it out and through the outlet. No special requirements are needed. - Vane or other pumps. Contact vss@slurry.com
- Sizing the pump and motor.
Choose the flow rate required and increase it by 25-50%. This will ensure longer pump life, create less harshness between close pump tolerance parts And permit better handling of high viscosity emulsions. Always go one power setting higher than the pump manufacturer recommends erg if 5Hp is recommended use 7.5Hp. - Location.
Always locate the pump close to the source of the liquid. Pumps push better than they suck. The pump should be able to be maintained without removing it so ensure there is room! Maintain a positive head, that's is ensure that the liquid level of the tank is above the suction port of the pump. - Strainers: protect the pump with in line basket strainers.
Plan for:
- Maximum flexibility and utility
- Expansion
- Suction piping is short and at least the same size as the suction port of the pump. Make it larger for longer pipe runs or if the materials are more viscous.
- At the tank outlet use a reducer one size larger than the suction line at the tank outlet.
- Use of an elbow inside the tank will ensure no scum will foul the lines.
- Never use the same pump for anionic and cationic emulsions unless a flushing system is installed.
- Try pumps by hand turning to ensure they are free of metal burrs after installation.
- Minimize tees and elbows.
- Never us direct flames on lines
- Use reversible pumps
- Use unions and flanges to allow pipes to be taken out in sections for blockages.
Switch Loading:
If more than one type of product is to be used in tanks follow the following table:
Dos and Don'ts:
DO clean tanks, lines and equipment
Do mix emulsions every 1-2 weeks and before unloading
Do transport full containers
Do trace emulsion lines with hot water or electric tape
Do Agitate or circulate when heating emulsions
Don't pump excessively
Don't mix anionic and cationic
Don't Freeze
Don't use blow torches unless you have no choice then exercise care
Don't heat emulsions vigorously and never more than 85C
This information is given in good faith by VSS Emultech® but VSS Emultech® or any related company holds no responsibility or gives or implies any warranty for or about its use.