Vent and relief lines discharge gas from regulators, relief valves, and other devices to a safe location. In an industrial installation, the routing of these lines is just as important as the supply piping.
Vent and relief are not the same
A vent connection may serve the breather or control chamber of a device, while a relief valve opens to limit an unwanted pressure rise. The function of each line must be known before any intervention is made.
Safe discharge point
The outlet must not be located near building openings, air intakes, ignition sources, or points where gas could accumulate. The exact location is determined by the design and current requirements.
Flow resistance
A line that is too small, too long, or obstructed can create backpressure and affect the operation of the device. For this reason, arbitrary changes to the cross-section or routing are not permitted.
Water and insects
Terminals must be protected to prevent the ingress of rainwater, foreign objects, or insects. An obstructed vent line can cause erratic behavior in a regulator or other instrument.
Maintenance
During periodic inspection, the mechanical condition, support, free passage, and discharge position are checked. Any change in the area around the terminal must be evaluated, because a point that was initially safe may no longer be so after plant modifications.
