If a screw compressor has low air delivery, what could be the possible reasons?

In a screw compressor, low air delivery can be a result of various factors that impede the normal operation and performance of the compressor. Each of the listed scenarios can significantly contribute to reduced air output.

A restricted inlet can reduce the volume of air entering the compressor, resulting in low delivery rates. If the air cannot flow freely into the compressor, the overall efficiency and output are negatively affected.

A stuck blowdown valve can prevent the compressor from adequately regulating its internal pressure, which could lead to inefficient compression and therefore lower air delivery. The blowdown valve's primary function is to release pressure in case of over-pressurization, but if it remains closed or partially closed, it can restrict performance.

Similarly, a plugged air/oil separator can obstruct the separation of air from oil, which can lead to insufficient air flow and lower output. If the separator is not functioning correctly, the compressor cannot maintain the necessary operational conditions to deliver the expected volume of air.

Since any of these issues can independently affect the air delivery of the compressor, all of them collectively contribute to the problem. Thus, stating that all the factors listed in the options could lead to low air delivery is valid, making the selection of all the scenarios as a correct answer reasonable.