Lesson 9 - Gases SAQ
This lesson allows you to test yourself on the material covered in the Gases lesson and determine the level to which you have met the learning outcomes.
Suggested Response - Q2
** a) What are the relative advantages and disadvantages of screw compressors versus reciprocating compressors?
b) Would you expect to find more reciprocating compressors in a bigger or smaller brewery? Explain your answer.
Response:
a) Screw compressors offer several advantages:
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They are relatively quiet and have low vibrations.
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They have higher efficiency than reciprocating compressors, as most of the energy is used to rotate the shafts.
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They are well suited to continuous operation.
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They can easily be fitted with variable speed drives.
The disadvantages of screw compressors are:
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They are relatively expensive compared to reciprocating compressors.
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They are not suitable for start-stop operations.
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Whilst they don’t require as much maintenance as reciprocating compressors, the maintenance is very specialised.
Reciprocating compressors offer some advantages:
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They are relatively cheaper than screw compressors.
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Their maintenance is simple and can often be done in-house.
The disadvantages of reciprocating compressors are:
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Due to the heat generated during use, reciprocating compressors have a duty cycle. That means they are only allowed to operate for a certain time before they need to cool off. Consequently, they either require a large air receiver or more than one air compressor to ensure a steady supply of air.
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They have more wearing parts that need replacement, and over time even the pistons may need replacement due to wear.
b) Reciprocating compressors are mostly found in smaller breweries. This is because they are cheaper and easier to maintain. They also are better adapted to start-stop operations. Smaller breweries typically do not run continuously, and thus the demand for air can fluctuate a lot more.