What must be done to a horizontal discharge pipe from a PSV?

• A. Slash it at 45 degrees
• B. Bend it at 90 degrees
• C. Keep it horizontal
• D. Cap it

Answer: (A)

Discharging safety valves must vent the relieved fluid away from equipment and people, in a way that prevents damage from the high-velocity jet. Cutting the outlet end at a 45-degree angle creates an angled jet that deflects the flow away from the pipe and surroundings, helping to prevent impingement on nearby structures, reduce erosion at the outlet, and direct the discharge to a safe area.

Bending the pipe 90 degrees would create unnecessary backpressure and a sharp turn that can cause flow issues and potential damage during relief. Keeping the outlet horizontal would send the jet straight out, increasing the risk of hazard to nearby equipment or personnel. Capping it would block relief altogether, which is dangerous during overpressure.

So, slashing the discharge end at a 45-degree angle best ensures safe, directed release.