Station · Pipelines
Mainline Block Valve
A large valve on the mainline, often with an actuator, that can close to isolate a segment of the pipeline.
What it does
Limits how much product can escape after a rupture and lets crews isolate a segment for repairs. Rules set the maximum spacing between valves by how populated the area is.
Basics
| Type | Full bore valve, often actuated |
| US gas example (49 CFR 192.179) | Any point within 10 miles of a valve in Class 1, 2.5 miles in Class 4 |
| Operation | Manual, local actuator or remote from the control center |
Common failures
- Valve that does not close fully when needed, so the segment cannot be isolated
Troubleshooting
- Symptom
- Pressure keeps falling downstream of a closed block valve
- Likely cause
- Seat leak
- What to check
- Stroke and test the valve, plan seat repair or replacement