4.2.1. Activation and Energy Generation

In the upward stroke, air is supplied into the lower cylinder, pushing the hammer into the upper cylinder. The air that was already in the upper cylinder is expelled through the exhaust.

In the first part of the operation of a double acting hammer, we focus on the upward stroke. This begins when compressed air is introduced into the lower cylinder. As the air fills this cylinder, it exerts pressure, which forces the attached hammer upward into the upper cylinder. At the same time, air that was previously in the upper cylinder needs to escape; therefore, it is pushed out through an exhaust outlet. This process effectively raises the hammer and completes the upward stroke.

Imagine a balloon filled with air representing the lower cylinder. When you push down on the balloon, the air will push up against anything above it. In this analogy, the hammer is like an object above the balloon, rising as you compress the air inside it.

During the downward stroke, air is supplied to the upper cylinder, pushing the hammer back into the lower cylinder. Air in the lower cylinder is expelled through the exhaust.

The downward stroke operates similarly to the upward stroke, but in reverse. Now, air is supplied to the upper cylinder instead. This air pressure forces the hammer to move downward back into the lower cylinder. As the hammer descends, the air that was originally in the lower cylinder is pushed out through the exhaust. This cyclical process of alternating air supply between the two cylinders allows for continuous hammering action.

Think of a seesaw on a playground. When one end goes up (the upward stroke), the other end must go down (the downward stroke). The action of pushing air into one cylinder causes the hammer to rise, while filling another cylinder causes it to descend, similar to how a seesaw works.

Most of the blow energy for both strokes is derived from steam energy. About 90% of the blow energy comes from the action of air or steam.

The operation of the double acting hammer relies predominantly on steam energy to create its blow energy. During both the upward and downward strokes, the energy generated is leveraged from the pressurized air or steam. This means that instead of requiring heavy weights for the hammer to perform effectively, the energy provided by the steam is sufficient, allowing the hammer to be lighter and more efficient.

Think of riding a bicycle. Instead of using your full body weight to push the bike forward (heavy weights), you use smooth pedaling (steam energy) to keep the bike moving. Just as a cyclist relies on their pedaling efficiency rather than just their body weight, the hammer uses steam energy for its operation.

Double acting hammers are designed for lighter conditions, suited for light to medium weight piles and soils with normal frictional resistance. They are not suitable for concrete piles due to their high blow rate.

The design of double acting hammers accommodates lighter conditions, making them appropriate for driving light to medium weight piles into normal soils. However, they are not recommended for use with concrete piles, as their high blow rate—ranging from 95 to 300 blows per minute—can lead to damage. The significant force generated can compromise the integrity of concrete structures, making these hammers more suitable for other applications.

Think about using a small hammer versus a large sledgehammer. A small hammer (double acting hammer) can be great for lightweight tasks like fixing a picture frame, but using it to break a concrete wall (heavy load) would be ineffective. Therefore, picking the right tool for the right material is crucial.

These hammers can efficiently drive steel piles but should not be used on tough soils like hardened clay or concrete where resistance is too high.

Double acting hammers are particularly effective in driving steel piles into soil with typical frictional resistance. However, their usage is limited in tough soil conditions such as hardened clay or when dealing with concrete piles. The resistance offered by these tougher materials would exceed the capacity of the hammer, making it ineffective and potentially damaging during operation.

Consider a car trying to drive on both a smooth road and a muddy patch. On the smooth road, it moves easily (capacity of the hammer), while on the muddy patch, the car struggles to move forward due to increased resistance (unsuitable conditions for the hammer).

--