Pipeline 101
Valves

The 800 mile-long Trans Alaska Pipeline System (TAPS) has 176 valves that control oil flow through its 48-inch mainline pipe. Most of these valves are environmental safeguards that ensure safe operation and limit the potential size of spills, especially at stream crossings and other environmentally sensitive areas. There are 81 check valves that allow one-way oil flow and prevent the reverse of flow. And pipeline operators can open and close 95 gate valves to block the flow of oil in either direction.