Lubricants in Machines

Introduction:
Lubricants play a crucial role in reducing friction and wear between moving surfaces in machines. They help in reducing heat generation, preventing corrosion, and improving the overall efficiency and lifespan of the machinery. While there are various types of lubricants available, this question specifically focuses on the option 'D', which states that the flow of compressed and purified air can act as a lubricant in machines.

Explanation:
Compressed and purified air can indeed act as a lubricant in certain applications and under specific conditions. Here's how:

1. Compressed Air:
Compressed air can be used as a lubricant in machines that operate under pneumatic systems. In pneumatic systems, compressed air is used to transmit power and control the movement of various components. The air is compressed and stored in a tank or reservoir and then released to perform work. During the release of compressed air, a thin layer of air molecules forms between the moving parts, acting as a lubricant. This air cushion helps reduce friction and wear between the components, allowing for smooth operation.

2. Purified Air:
Purified air refers to air that has been filtered and treated to remove impurities such as moisture, oil, and particulate matter. In some applications, purified air can be used as a lubricant in machines. For example, in cleanroom environments or in industries where oil-based lubricants are not desirable, purified air can be used to minimize friction and provide lubrication. This is particularly important in sensitive equipment where contamination from traditional lubricants can be detrimental.

Advantages of Air as a Lubricant:
- Non-Contaminating: Compressed and purified air does not leave any residue or contaminants on the machine surfaces, making it suitable for applications where cleanliness is essential.
- Cost-Efficient: Compared to traditional lubricants, the use of compressed air can be more cost-efficient, as there is no need for regular lubricant replenishment or maintenance.
- Adjustable Lubrication: The lubricating effect of compressed air can be adjusted by controlling the pressure and flow rate, allowing for fine-tuning of the lubrication requirements.

Conclusion:
While traditional lubricants such as oils and greases are commonly used in machines, the flow of compressed and purified air can also act as a lubricant in specific applications. It provides advantages such as non-contaminating lubrication, cost-efficiency, and adjustable lubrication. However, it is important to note that the suitability of air as a lubricant depends on the specific requirements and operating conditions of the machinery.