Compressed Air for Control Instrumentation
(a) Three Requirements for Compressed Air:
For reliable and safe operation of control instrumentation, compressed air needs to meet the following three requirements:
- Cleanliness: The air must be free from contaminants like dust, oil, and moisture. These contaminants can clog control valves, damage instrument components, and interfere with accurate signal transmission.
- Dryness: Excessive moisture in the air can lead to corrosion within the piping and instrumentation. It can also form ice crystals at low temperatures, causing malfunction of control valves and instruments.
- Consistent Pressure: The air pressure needs to be consistent and within the specified operating range for the control equipment. Fluctuations in pressure can lead to inaccurate readings and unreliable operation of control systems.
(b) Identifying Components in Worksheet Q3 (Assuming the Worksheet depicts a system for control instrumentation compressed air):
**Based on the information you provided, I cannot directly access or see the contents of Worksheet Q3. However, I can give you a list of typical components found in a system for producing compressed air for control instrumentation: **
- Air Compressor: This is the main component that compresses atmospheric air to a higher pressure.
- Intake Filter: Filters air entering the compressor to remove dust and other contaminants.
- Air Intake Silencer: Reduces noise generated by the air intake process.
- Intercooler (Optional): Cools the compressed air between compression stages, improving efficiency.
- Aftercooler: Cools the compressed air after final compression to remove moisture and reduce condensation.
- Separator: Separates condensed water and oil droplets from the compressed air stream.
- Air Receiver: A storage tank that holds the compressed air and helps maintain a constant pressure for the system.
- Drain Valve: Automatically removes accumulated condensate from the air receiver.
- Pressure Regulator: Regulates the air pressure to a specific level required for the control instrumentation.
- Line Filter: Provides additional filtration for the compressed air before it reaches the control equipment.
- Lubricator (Optional): Injects a small amount of oil mist into the air stream for lubrication of certain pneumatic components (if required by the system design).
Note: The actual components used in a specific system might vary depending on factors like the required air quality, flow rate, and pressure. The worksheet might also include additional components or show them in a different configuration.
Based on the revised image you sent, where you circled number 13 in red, it appears to be a Safety Relief Valve.
Here’s why:
- Safety Relief Valve Placement: Safety relief valves are typically installed in compressed air systems to protect them from excessive pressure build-up. In the diagram, component number 13 is located on the pipe leading out of the air receiver (component number 6). This is a common location for a safety relief valve in such systems.
- Function of Safety Relief Valve: If the pressure in the system rises above a preset limit, the safety relief valve opens automatically, releasing compressed air to prevent the system from exceeding its pressure rating and potentially rupturing pipes or equipment.
While not explicitly labelled in the diagram, considering its location and function, component number 13 most likely represents a safety relief valve.