Exam Question
Describe with a sketch a pneumatic relay and show how feedback can be achieved when such a relay is used in conjunction with a flapper mechanism. (16)
Class 2 (2nd Engineer)
MEKG
📅 Mar 2025
Reference Answer
### 1. Introduction to the Pneumatic Relay
A pneumatic relay is a device used in control systems to act as a power amplifier. It takes a low-volume, low-pressure input signal (typically from a flapper-nozzle mechanism) and converts it into a high-volume, high-pressure pneumatic output signal. This amplified output has sufficient power (air volume and pressure) to operate a large final control element, such as a diaphragm-actuated control valve, which the initial signal would be too weak to move.
### 2. Construction
A typical pneumatic relay consists of the following key components, which should be clearly labelled in a diagram:
A pneumatic relay is a device used in control systems to act as a power amplifier. It takes a low-volume, low-pressure input signal (typically from a flapper-nozzle mechanism) and converts it into a high-volume, high-pressure pneumatic output signal. This amplified output has sufficient power (air volume and pressure) to operate a large final control element, such as a diaphragm-actuated control valve, which the initial signal would be too weak to move.
### 2. Construction
A typical pneumatic relay consists of the following key components, which should be clearly labelled in a diagram:
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