Pressure Relief Valves should never be installed in

• A. Parallel
• B. Series
• C. On the roof
• D. Inside the cabinet

Answer: (B)

Relief valves must have a direct, unobstructed path to vent to the outside and operate reliably at their set pressure. When a relief valve is placed in series with another valve, the discharge from the first valve has to pass through the second one. That creates back pressure on the upstream valve, which can prevent it from opening at the intended pressure or from reseating properly after relieving. It also reduces the overall relief capacity because the two valves share the same flow path instead of providing a straightforward, uncompromised vent. In short, the series arrangement can mask or delay relief and compromise safety, which is why it should never be used. The safe approach is a single relief valve with a direct path to the atmosphere, venting outside rather than inside a cabinet.