The hot oil piping system consists of piping that circulates hot oil (thermal fluid) heated by the two hot oil heaters. It has a main supply line connected to the outputs of the two heaters. It has a main return line connected to the inputs of the heaters. The heaters are connected in parallel with each other.
The hot oil is circulated by three centrifugal pumps that are connected in parallel with each other. The system circulates about 12,000 gallons of hot oil.
The hot oil circulating in the main supply line is maintained at a temperature of 425–450 degrees F.
The asphalt storage tanks, steam generator, and heat exchanger have independent parallel piping circuits connected to the main supply and return lines. The coils of each tank are separated into independent circuits, each with its own control valve.
Each storage tank has a thermocouple to sense temperature of its contents and a controller that provides 4 to 20 mA output signals for temperature control. Temperature control is provided by a motorized three-way valve that modulates the flow of hot oil in the circuit in response to the 4 to 20 mA signals.
A warm-oil pump skid is also connected to the main supply and return lines. The skid has four pumps that circulate hot oil in four independent circuits. Hot oil circulating in these circuits is maintained at a temperature of 350 degrees F. These four circuits heat the following items:
- Asphalt piping and pumps for asphalt storage tanks.
- Asphalt piping and pumps for tank cars and hot box.
- Polymer blending system.
- Waste oil storage tanks.
The asphalt piping is heated by trace heating lines that are heated by the hot oil. The trace heating lines consist of 1-inch piping running beneath all asphalt piping. However, the trace lines are not one continuous run of piping. Instead they are arranged into numerous independent parallel circuits, each heating only a relatively short length of asphalt piping.
The flow of hot oil in each circuit can be adjusted independently to balance the flow among the circuits. Thus, each trace heating circuit heats a portion of asphalt piping consisting of two six-inch lines and one eight-inch line. The trace heating also heats the asphalt pumps.