Do not shut off asphalt valves that can trap asphalt in strainers and asphalt piping heated by hot oil jackets.

Otherwise, heat may cause trapped asphalt to expand and suddenly rupture components in its piping, especially strainers.

The rupture can occur suddenly, without warning. As a result, asphalt at 300° F can spray into nearby areas and cause severe injuries.

NOTE: Hot oil jackets heat two piping systems in which asphalt could be trapped:

1. the asphalt fill system (see top half of drawing).

2. the asphalt supply/return system (see bottom half of drawing).

So, always keep at least one valve open in each of these two systems. When the valves are open, asphalt can expand freely into a storage tank.